GB2615371A

GB2615371A - Lift control

Info

Publication number: GB2615371A
Application number: GB2201615.8A
Authority: GB
Inventors: Johnson Brendan; Rishikeson Balasingham
Original assignee: Lester Control Systems Ltd
Current assignee: Lester Control Systems Ltd
Priority date: 2022-02-08
Filing date: 2022-02-08
Publication date: 2023-08-09
Anticipated expiration: 2042-02-08
Also published as: GB2615371B

Abstract

A lift car movement control system has a reference strip 118, such as a QR code strip, carrying positioning information extending along the lift shaft with first and second sensors 120 on the lift car reading the reference strip. A lift controller 100 determines, based on information received from the first sensor, a first parameter relating to the movement of the lift car in the lift shaft, and to control movement of the lift car based on the first parameter, and determine, based on information received from the second sensor, a second parameter relating to the movement of the lift car in the lift shaft, and to modify the movement of the lift car based on the second parameter. The lift controller may have a means for recording data relating to the floor positions in the shaft and based upon origin and destination floors may calculate a speed profile for the journey which may minimise jerk. A brake controller 900 has an actuator 902, which may actuate a pair of shoes on a sheave, activated using a switch BR and control loop 907, 908. The controller may also monitor the brake or an overspeed governor.

Description

Lift Control

Field of Invention

This invention relates to a lift control. More specifically, the invention relates to a lift control system and lift controller for controlling movement of a lift car in a lift shaft, and a brake controller for a braking system for a lift.

Background

Existing lift control systems require a number of components to be physically installed in the lift shaft. These include mechanical components, such as overspeed governors, and electromagnetic components, such as stepping vanes and speed check switches. These components are time consuming to install and increase the overall complexity of the systems.

Furthermore, due to the reliance on lift shaft components such as stepping vanes in existing lift systems, the floor-to-floor lift car trajectory can be jerky, resulting in increased floor-tofloor travel times can be high and poor ride quality for the passengers. In addition, the brake controllers in existing lift systems are energy inefficient in normal floor-to-floor operation.

The present disclosure seeks to ameliorate these problems. Summary of the Invention Aspects and embodiments of the present invention are set out in the appended claims. These and other aspects and embodiments of the invention are also described herein.

According to at least one aspect described herein, there is provided a lift control system for controlling movement of a lift car in a lift shaft, the lift control system comprising: a reference strip extending along the lift shaft, the reference strip carrying positioning information, preferably encoded positioning information; at least a first and a second sensor on the lift car arranged to read the reference strip; and a lift controller configured to: determine, based on information received from the first sensor, a first parameter relating to the movement of the lift car in the lift shaft, and to control movement of the lift car based on the first parameter; and determine, based on information received from the second sensor, a second parameter relating to the movement of the lift car in the lift shaft, and to modify the movement of the lift car based on the second parameter. -2 -

Preferably, the lift controller is configured to modify the movement of the lift car if the second determined parameter deviates from a calculated profile for that parameter, preferably if the deviation exceeds a threshold value.

Preferably, the second determined parameter is a speed of the lift car, and the lift controller is configured to modify the movement of the lift car if the determined speed of the lift car deviates from a calculated speed profile.

Preferably, the threshold value varies in dependence on the position and/or speed of the lift car.

Preferably, the lift controller is configured to modify movement of the lift car by: correcting the speed of the lift car to maintain a calculated speed profile; or to decelerate the lift car to a, preferably predefined, lower speed, preferably wherein the lower speed is between 0.06 to 0.1 m/s.

Alternatively, the lift controller may be configured to modify movement of the lift car by overriding the control of the movement of the lift car.

Preferably, the overriding the control of the movement of the lift car comprise calculating an updated speed profile based on the first and/or second determined parameter(s), and controlling movement of the lift car according to the updated speed profile.

Alternatively, the overriding the control of the movement of the lift car may comprise applying a brake, preferably to: stop the lift car; or decelerate the lift car to a, preferably predefined, lower speed, preferably wherein the lower speed is between 0.06 to 0.1 m/s.

Preferably, the positioning information is encoded on the reference strip. Preferably, the encoding is a machine-readable optical encoding.

Preferably, the at least two sensors are cameras configured to read the encoded positioning information from the reference strip.

Preferably, the cameras are infra-red cameras, preferably wherein the lift controller comprises an infra-red illumination device to illuminate the reference strip.

Preferably, the at least two sensors are offset from one another along the axis of the reference strip, preferably wherein the sensors read different parts of the reference strip.

Preferably, the at least two sensors are connected to the lift controller on separate channels of a controller area network (CAN). -3 -

Preferably, the lift controller is configured to control movement of the lift car according to a calculated speed profile by issuing speed commands to a motor, the motor arranged to drive movement of the lift car.

Preferably, the lift controller is configured to modify the movement of the lift car, based on the second determined parameter, by correcting or overriding the speed commands issued to the motor.

According to another aspect described herein, there is provided a method of controlling movement of a lift car in a lift shaft, the method comprising: reading, using at least a first and a second sensor mounted on the lift car, a reference strip extending along the lift shaft, the reference strip carrying positioning information, preferably encoded positioning information; determining, based on information received from the first sensor, a first parameter relating to the movement of the lift car in the lift shaft, and to control movement of the lift car based on the first parameter; and determining, based on information received from the second sensor, a second parameter relating to the movement of the lift car in the lift shaft, and to modify the movement of the lift car based on the second parameter.

Preferably, the first and/or second determined parameters comprises at least one of a position of the lift car; a speed of the lift car; an acceleration of the lift car; and a jerk of the lift car.

According to another aspect described herein, there is provided a lift controller for controlling movement of a lift car in a lift shaft, the lift controller comprising: means for recording information about the positions of floor levels in the lift shaft; and means for calculating a speed profile of the lift car from an origin floor direct to a destination floor using the recorded information about the positions of the origin floor and destination floor levels, wherein the lift controller is configured to drive the lift car along the lift shaft according to the calculated speed profile.

Preferably, to record the information about the positions of the floor levels in the lift shaft, the lift controller is configured to drive the lift car at least once along the length of the lift shaft, and to record a position measurement each time a floor level is detected, preferably wherein the floor level positions are detected from the positions of door zone vanes in the lift shaft.

Preferably, the magnitude of the jerk of the lift car during acceleration and/or deceleration of the lift car satisfies: Jerk PEAKJerk (0) = (1 cos(0)) -4 -where 9 = 180-tj or 3601 and where t is the time since the beginning of the jerk, t1 is the tJ total duration of the jerk, and JerkpEAK is the peak jerk.

Preferably, the magnitude of the acceleration of the lift car during acceleration and/or deceleration of the lift car satisfies:

APEAK

Acceleration (0) = (1 -cos(6)) where 0 = 180-during the phase where the lift car acceleration is increasing (preferably tA from zero) to a constant acceleration, and where 0 = 180 + [180 -] during the phase where tA the lift car acceleration is reducing from the constant acceleration (preferably to zero), and where t is the time since the beginning of the acceleration/deceleration phase, tA is the total 10 duration of the acceleration/deceleration phase, and APEAK is the peak acceleration/deceleration during the phase.

Preferably, the lift controller comprises means for receiving user input of at least one parameter to characterise the speed profile, and wherein the lift controller is configured to calculate the speed profile of the lift car based at least partially on the at least one 15 parameter.

Preferably, the at least one parameter relates to one or more of: an average acceleration or deceleration; a degree of rounding of the acceleration or deceleration phases of the speed profile; a jerk balance between the beginning and end of the acceleration and/or deceleration phases; a minimum time on high speed; a finish profile distance; and/or a finish profile correction.

According to another aspect described herein, there is provided a method of controlling movement of a lift car in a lift shaft, the method comprising: recording information about the positions of floor levels in the lift shaft; calculating a speed profile of the lift car from an origin floor direct to a destination floor using the recorded information about the positions of the origin floor and destination floor levels; and driving the lift car along the lift shaft according to the calculated speed profile.

According to another aspect described herein, there is provided a brake controller for a braking system for a lift, the braking system comprising at least one actuator arranged to actuate the brake between an applied state and a released state, the brake controller comprising: means for providing a power supply to the braking system to activate the at least one actuator; and means for controlling the power supplied to the at least one actuator, -5 -wherein the brake controller is configured to control the power supplied to the at least one actuator: at a lift power to actuate the brake from the applied state to the released state; and at a hold power to retain the brake in the released state, wherein the hold power is lower than the lift power.

Preferably, the brake controller comprises a varistor connected, in use, in parallel with the at least one actuator.

Preferably, the brake controller comprises a rectifier, preferably a full wave rectifier, for converting an alternating current power supply to a direct current power supply to the braking system.

Preferably, the brake controller comprises a second varistor connected, in use, in parallel with the direct current output of the rectifier.

Preferably, the means for controlling the power supplied to the at least one actuator is a means for controlling the voltage or current of the power supply, preferably the voltage of the power supply, preferably wherein the means for controlling the power supplied to the at least one actuator is a potentiometer.

Preferably, the brake controller is configured to control the voltage or current (preferably voltage) of the power supply: at a lift current or voltage (preferably voltage) to actuate the brake from the applied state to the released state; and at a hold current or voltage (preferably voltage) to retain the brake in the released state, wherein the hold voltage or current is lower than the lift voltage or current.

Preferably, the at least one actuator is at least one solenoid.

Preferably, the solenoid is arranged to actuate the brake between an applied state and a released state by moving the brake between an applied position and a released position, preferably against a biasing force.

Preferably, the means for providing a power supply is for driving a current through the at least one solenoid.

According to another aspect described herein, there is provided a lift controller for controlling movement of a lift car, the lift controller comprising a brake controller as aforementioned.

Preferably, the lift controller comprises heatsink arranged to dissipate heat from the lift controller, and wherein the brake controller is in thermal contact with the heatsink. -6 -

According to another aspect described herein, there is provided a method of controlling a braking system for a lift, the braking system comprising at least one solenoid arranged to move the brake between an applied position and a released position, the method comprising: providing a power supply to the braking system to drive a current through the at least one solenoid; and controlling the voltage of the power supply: at a lift voltage to move the brake from the applied position to the released position; and at a hold voltage to retain the brake in the released position, wherein the hold voltage is lower than the lift voltage.

According to another aspect described herein, there is provided a lift controller for controlling movement of a lift car, the lift controller comprising: a monitoring unit for at least one solenoid of a lift brake or a lift overspeed governor, the monitoring unit comprising: at least one switch configured to move between an open and a closed position in dependence on the current through the at least one solenoid; and at least one relay configured to move between an open and a closed position in dependence on the position of the at least one switch, the relay configured to provide an input to a microprocessor of the lift controller wherein the lift controller is configured to control movement of the lift car in dependence on the input from the at least one relay.

Preferably, the monitoring unit is for two solenoids of a lift brake, the monitoring unit comprising two switches, each switch corresponding to one of the solenoids, and each switch configured to move between an open and a closed position in dependence on the current through its corresponding solenoid.

Preferably, the lift controller comprises two relays, each relay corresponding to one of the switches, and each relay configured to move between an open and a closed position in dependence on the position of the corresponding switch.

Preferably, each relay is configured to provide an input to the microprocessor of the lift controller, and wherein the lift controller is configured to control movement of the lift car in dependence on a comparison of the inputs from the two relays.

Preferably, the monitoring unit further comprises means for monitoring the operation of the at least one relay, and to provide an input to a microprocessor of the lift controller.

Preferably, the lift controller is configured to control movement of the lift car in dependence on input from the means for monitoring the operation of the at least one relay.

Preferably, the control of the movement of the lift car by the lift controller comprises preventing movement of the lift car. 7 -

According to another aspect described herein, there is provided a lift control system comprising the lift controller as aforementioned.

According to another aspect described herein, there is provided a lift system comprising a lift car and the lift control system as aforementioned, the lift control system configured to control movement of the lift car.

According to another aspect described herein, there is provided a system comprising two or more of: the lift control system as aforementioned; the lift controller as aforementioned; and/or the brake controller as aforementioned.

As used herein, the term "lift" may be exchanged with the equivalent term "elevator".

As used herein, the term "speed profile" is used to mean the speed of the lift car as a function of time, or as a function of position, and is used to refer to the variation of the speed of the lift car over the course of a journey.

As used herein, the term "parameter relating to the movement of the lift car" (or similar) preferably refers to a measure of a characteristic of the movement of the lift car in the lift shaft. In particular, this term is used to refer to the position (i.e. location or displacement) of the lift car in the lift shaft, or to time-derivatives of that position, such as the speed, acceleration, jerk, etc. of the lift car in the lift shaft.

Angles expressed herein in degrees could equally be expressed in radians, or another equivalent unit, and vice versa Any apparatus feature as described herein may also be provided as a method feature, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. Furthermore, any, some and/or all features in one aspect can be applied to any, some and/or all features in any other aspect, in any appropriate combination. It should also be appreciated that particular combinations of the various features described and defined in any aspects of the invention can be implemented and/or supplied and/or used independently.

The invention also provides a computer program or a computer program product for carrying out any of the methods described herein, and/or for embodying any of the apparatus features described herein, and a computer readable medium having stored thereon a -8 -program for carrying out any of the methods described herein and/or for embodying any of the apparatus features described herein.

The invention also provides a signal embodying a computer program or a computer program product for carrying out any of the methods described herein, and/or for embodying any of the apparatus features described herein, a method of transmitting such a signal, and a computer product having an operating system which supports a computer program for carrying out the methods described herein and/or for embodying any of the apparatus features described herein.

Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus aspects, and vice versa. As used herein, means plus function features may be expressed alternatively in terms of their corresponding structure, such as a suitably programmed processor and associated memory.

Furthermore, features implemented in hardware may generally be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly.

The invention extends to methods, system and apparatus substantially as herein described and/or as illustrated with reference to the accompanying figures.

One or more aspects will now be described, by way of example only and with reference to the accompanying drawings having like-reference numerals, in which: Figure 1 is a block diagram showing the mean components of the lift control system; Figure 2a is speed profile graph for a floor-to-floor trajectory for a lift car of existing lift systems; Figure 2b is speed profile graph for a for a floor-to-floor trajectory for a lift car according to

the lift control system of the present disclosure;

Figure 3 shows speed, acceleration, and jerk profile graphs for the acceleration phase of the lift car trajectory; Figures 4a, 4b, and 4c are speed profile graphs for floor-to-floor trajectories having differing acceleration and deceleration parameter settings; Figures 5 is speed profile graph for floor-to-floor trajectories having differing s-curve rounding parameter settings; -9 -Figures 6a, 6b, and 6c are speed profile graphs for floor-to-floor trajectories having differing jerk balance parameter settings; Figures 7 is speed profile graph for floor-to-floor trajectories having differing minimum time on high speed parameter settings; Figures 8a and 8b are speed profile graphs for finish profile of the deceleration phase of the lift car trajectory; Figures 9a and 9b are circuit diagrams showing the components of the brake controller of the present disclosure; and Figure 10a and 10b are circuit diagrams showing the components of the monitoring unit for the lift controller.

Detailed description

The present disclosure relates to a lift control system for controlling movement of a lift car in a lift shaft. The lift control system is described in overview with reference to Figure 1. The lift control system can be used to provide an improved safety process for monitoring the speed of a lift car and for preventing a lift from travelling too fast at the upper and lower limits of the lift shaft (known as 'slowing limits' control), as described below with reference to Figure 1. The lift control system can also be used to provide an improved process for controlling the lift car as it travels along the lift shaft to improve ride quality and reduce floorto-floor travel times. An example lift car trajectory of an existing system is described with reference to Figure 2a, and exemplary lift car trajectories using the lift control system of the present disclosure are described with reference to Figures 2b to 8b. The present disclosure also includes a brake controller which achieves significant energy savings as compared with existing brake controllers. This improved brake controller is described with reference to Figures 9a and 9b. Lastly, the lift control system of the present disclosure can be used to provide protection against uncontrolled movement of the lift car, as is described with reference to Figures 10a and 10b.

Lift control system Figure 1 shows a block diagram of the main components of the lift control system. The lift control system comprises a lift controller 100 and a drive system 102. The control system is configured to control movement of a lift car 106 along a lift shaft, the lift car 106 being coupled to a counterweight 108 by cables over a sheave 110.

-10 -The motor system 102 is arranged to control movement of the lift car 106, which in this example is achieved by the motor system 102 driving rotation of the sheave 110 to move the lift car 106 and the counterweight 108 along the lift shaft in opposite directions. The lift controller 100 is communicatively connected to the motor system 102 such that the lift controller 100 is able to send commands to the motor system 102 thereby to control movement of the lift car 106.

The lift controller 100 comprises a printed circuit board (PCB) with, amongst other components, a mulficore microprocessor. The microprocessor has a first core dedicated controlling the safety aspects of the lift system. This first core controls the safety componentry (such as the lift brake) and is connected to the inputs and outputs of those components. The microprocessor also has a second core which controls a thin film transistor (TFT) liquid crystal display (LCD) which forms part of an interface to enable an engineer to adjust settings of the lift controller 100, and a third core which controls non-safety related componentry, and which is connected to the inputs and outputs of those components. The microprocessor is preferably a lockstep microprocessor, more preferably an lnfineon Tri Core Lockstep Micro-Controller.

The motor system 102 comprises a motor controller 112 which is communicatively connected to a motor 114 such that the operation of the motor 114 is controlled by the motor controller 112 (based on control from the lift controller 100). The motor 114 is coupled to the sheave 110 thereby to drive rotation of the sheave 110 to move the lift car 106 and counterweight 108 along the lift shaft. In other examples, the motor may drive movement of the lift car in an alternative way, such as by actuation of a piston connected to the lift car rather than by rotation of a sheave (e.g. in hydraulic lifts).

The lift control system also comprises a position encoder 104 and a motor encoder 116 (the latter being part of the drive system 102). The lift controller 100 is communicatively connected to the position encoder 104 such that the lift controller 100 is able to receive information about the position and/or speed of the lift car 106 in the lift shaft from the position encoder 104. The motor controller 112 is communicatively connected to the motor encoder 116 such that the motor controller 112 is able to receive information about the speed of the motor 114 (e.g. the revolutions per minute) from the motor encoder 116.

The motor 114 is communicatively connected to a motor encoder 116, which in turn is communicatively connected to the motor controller 112 such that the motor controller 112 is configured to receive information about the speed of the motor 114 via the motor encoder 116. While the lift controller 100 and the motor controller 112 are shown as separate features in Figure 1, in practice these features may alternatively be provided by a single item of software and/or hardware; for example the lift controller 100 may directly control the motor 114 rather than via a motor controller 112, and the motor encoder 116 may send information about the speed of the motor 114 to the lift controller 100.

Therefore, the system comprises two separate feedback loops: one lift car position feedback loop using the position encoder 104 to measure the position and speed of the lift car 106 and to control movement of the lift car 106 between positions in the lift shaft by instructions from the lift controller 100 to the motor system 102; and another motor speed feedback loop to measure the speed of the motor 114 using the motor encoder 116 to modify the motor 114 speed by instructions from the motor controller 112 to the motor 114 so that the motor 114 accurately maintains the speed at which it is instructed to operate, or slows if it is travelling too fast.

The lift controller 100 is connected to the position encoder 104 via a wired Controller Area Network (CAN) connection. Via this CAN connection, mainly speed and position information are sent back to the lift controller 100 from the position encoder 104. The lift controller 100 is connected to the motor system 102, specifically the motor controller 112, via a serial communication link, preferably a wired RS422 connection. The lift controller 100 also comprises an output port, preferably a RS232 port, which can be accessed by an engineer to monitor to position encoder 104 and the motor system 102, for example for fault detection and maintenance.

A code tape 118 is mounted in the lift shaft and runs vertically along the lift shaft, preferably along the entire operable length of the lift shaft (that is, along the entire section of the lift shaft that is travelled by the lift car in normal operation). The code tape 118 is an elongate strip of material which carries an encoding on at least one side of the strip, preferably both sides of the strip. In this example, the encoding is a two-dimensional optical encoding, similar to a Quick Response (OR) code extended along the code tape 118. In other examples, the position information is encoded differently, for example as a magnetic encoding on a magnetic strip. The optical encoding is non-repeating along the length of the code tape 118. At least one sensor 120 is mounted on the lift car 106 for reading the encoding. In this example, the sensor is a camera, preferably an infra-red camera, for reading the optical encoding on the code tape 118. The sensor 120 also comprises at least one illumination device (such as one or more light emitting diodes) for illuminating the code tape 118 such that it can be read by the sensor 120. In this example, the illumination device preferably emits infra-red radiation which is reflected off of the code tape 118 to the sensor 120.

-12 -The code tape 118 is stationary in the lift shaft, while the sensor 120 travels with the lift car 106 along the lift shaft relative to the code tape 118. As the optical encoding on the code tape 118 is non-repeating, the optical encoding at any given position along the code tape 118 is unique and can thus be used to determine the location of the sensor along the length of the code tape 118. As the code tape 118 is fixed in the lift shaft, and the sensor is mounted on the lift car 106, this location represents an absolute position of the lift car 106 in the lift shaft. The code tape 118, sensor 120 and position encoder 104 are occasionally referred to collectively as the positioning system.

The position encoder 104 is communicatively connected to the sensor 120 to receive data from the sensor 120. The position encoder 104 is configured to de-code the reading of the code tape so as to determine the position of the lift car 106 in the lift shaft. The position encoder 104 is also configured to determine the speed of the lift car 106 by frequently sampling the position of the lift car 106 continuously over time (preferably every 10 ms) and determining the speed of the lift car 106 by calculating the rate of the change of position over time. This position information is communicated from the position encoder 104 to the lift controller 100.

In this example, the motor encoder 116 is an optical encoder. The optical encoder comprises a disc (not shown) coupled to the motor 114 so that the disc rotates with the motor 114. The disc comprises an opening, with a light source and light sensor located on opposite sides of the disc and aligned with the opening so that, with each rotation of the disc, light from the light source is allowed through the opening and is detected by the sensor. The speed of the motor (i.e. in revolutions per minute) can be derived from the frequency of the detection of light by the light sensor. The motor encoder 116 is communicatively connected to the motor controller 112 such that information about the speed of the motor 114 -as determined by the motor encoder 116 -is communicated from the motor encoder 116 to the motor controller 112.

Slowing limits control The control system described above can be used to provide an improved safety process for monitoring the speed of a lift car and for preventing a lift from travelling too fast at the upper and lower limits of the lift shaft.

In existing lift systems, a number of mechanical switches are located in the lift shaft to monitor the speed of a lift car and to ensure that a lift is reducing its speed as expected as it approaches the end of the lift shaft. Typically, these switches are located at the extremities -13 -of a lift shaft (i.e. at the very top and very bottom of a lift shaft) to ensure that the lift car has started to decelerate as it approaches the limits of the lift shaft.

Typically, existing systems use three types of electromechanical switches: slow down check switches; stopping switches; and final limit switches. Each of these types of switches are located progressively further towards the limits of the lift shaft. Slow down check switches are located in the operable part of the lift shaft (i.e. in the part of the lift shaft travelled by the lift car in normal use) but near the top and bottom of the lift shaft and they are responsible for checking that the lift car is slowing down as it nears these areas in order to avoid high speed crashes. Stopping switches are located at the top and bottom ends of the operable part of the lift shaft and they are responsible for checking that the lift has stopped correctly at the top and bottom, i.e. not over travelled. The switches are set typically 10mm above and below floor level respectively. Final limit switches are located beyond the top and bottom ends of the operable part of the lift shaft, and act as the final backup safety systems which cut off the electrical power to the lift should it breach the upper or lower limits of the operable part of the lift shaft.

In addition to these electromechanical switches, existing lift systems use an array of further safety equipment such as an overspeed governor (which is a device which acts as a stopping mechanism in case the elevator runs beyond its rated speed and is typically actuated by mechanical means such as centrifugal flyweights) mounted on the lift shaft that is activated during emergencies to stop the lift car.

These traditional components provide checkpoints along the lift shaft to ensure the lift has started to reduce its speed as it approaches the top or bottom floors. If the speed check fails at one of these checkpoints, then the lift is forced to decelerate quickly to a pre-determined slow speed (usually 0.06 to 0.1 metres per second). For example, if the lift is approaching the bottom floor and the remaining distance to the bottom floor is approximately 4 metres, then the lift speed must be travelling at less than 2.2 metres per second in order for the lift car to be able to decelerate in time to stop at the bottom floor. If a speed check (carried out by one of the electromechanical switches located 4 metres above the bottom floor) determined that the lift car is exceeding this speed, a brake is applied to force the lift car to decelerate to a slow speed (e.g. 0.06 to 0.1 m/s).

These lift shaft switches and other components increase the overall complexity of the lift system by increasing the number of separate components that must be installed into the lift shaft, connected with other components, and routinely safety tested. The presence of these components also increases the setup time required when installing a new lift system within a lift shaft. It is therefore advantageous to reduce the number and complexity of the physical -14 -components required in these safety systems, particularly those that must be built into the lift shaft.

The present disclosure, specifically the lift control system described above, provides an alternative safety system for monitoring the speed of the lift car and for preventing a lift car from travelling too fast at the upper and lower limits of the lift shaft, while simplifying the components required within the lift shaft. This is achieved in the present disclosure by providing two separate sensors as part of the sensor 120 which are respectively used with the position encoder 104 to control the position and speed of the lift car 106, and to carry out slowdown checks to ensure that the lift car 106 is decelerating appropriately when instructed to do so. In this example, the two sensors are two cameras (preferably infrared cameras).

The first, or primary, camera is communicatively coupled to the position encoder 104 and is used to enable the lift controller 100 to calculate a trajectory to move the lift car 106 along the lift shaft from an origin position to a destination position (for example, if the lift car 106 has been called to another floor) under normal operating conditions. The first camera takes a reading of the code tape 118 and transmits data to the position encoder 104 which de-codes the reading to determine the absolute position of the lift car 106 within the lift shaft as described above. This determined position is transmitted to the lift controller 100, and the lift controller 100 calculates a speed profile for the lift car 106 (as is described in more detail below) from its current position to its destination position. Based on this profile, the lift controller 100 issues commands to the motor system 102, specifically to the motor controller 112, and the motor controller 112 in turn controls the motor 114 to turn the sheave 110 so as to move the lift car 106 according to the calculated speed profile. This process is then repeated, with new measurements of the code tape 118 being taken by the primary camera, and the lift controller 100 continually updating the instructions to the motor controller 112 based on the new measurements.

Under normal operating conditions, this continuous process of reading the code tape 118 by the primary camera, controlling the motor 114 to move the lift car 106, and re-reading the code tape 118 by the primary camera, is sufficient to control the lift car 106 as it moves between floors to pick up and drop off passengers.

The second, or secondary, camera is used to carry out slowdown checks -analogous to the slowdown checks carried out by the traditional electromechanical switches described above -to check that the lift car is decelerating as it should according to the calculated speed profile. This increases the safety integrity of the system in the event that the primary camera malfunctions or fails, or if the motor 114 malfunctions, by providing a backup safety control system using the second camera.

-15 -The secondary camera is used to check whether, and how closely, the speed of the lift car 106 corresponds to the command given to the motor 114 by the lift controller (via the motor controller 112). The second camera performs this check by taking another, separate reading of the code tape 118 (separate from the reading of the first camera) and transmits information about the reading to the position encoder 104 which de-codes the reading -separately from the decoding of the reading taken by the first camera -in order to determine a second value for the position and/or speed of the lift car 106 and transmit this information to the lift controller 100.

The lift controller 100 determines whether the position or speed of the lift car 106 (as determined from the measurements of the code tape 118 by the secondary camera) has deviated from the calculated speed profile (as calculated based on the measurements of the code tape 118 by the primary camera), either by travelling faster or slower than it should be. This determination is made by comparing the speed of the lift car 106 at an instant in time (as determined based on the measurements of the second camera) against the expected speed at that instant according to the calculated speed profile (as calculated based on the measurements of the primary camera). The lift car is determined to have deviated from the calculated speed profile if its actual speed differs from the expected speed (according to the calculated speed profile) by an amount exceeding a threshold value. The threshold value may vary depending on the speed or position of the lift car. For example, if the lift car is near its destination floor level, or near the limits of the lift shaft, the threshold value may be small since there is more danger associated with an incorrect speed. Similarly, if the lift is far from its destination floor and far from the limits of the lift shaft, the threshold may be larger since there is more time for the lift controller to make appropriate corrections to the speed to avoid danger. Furthermore, at lower speeds the threshold may be lower, and at higher speeds the threshold may be higher, for example the threshold may vary in proportion with the speed of the lift car. At very low speeds the threshold may be ignored as it might cause false triggering.

If the lift car 106 is travelling faster (or slower) than expected according to the calculated speed profile, the motor controller 112 adjusts its instructions to the motor 114 accordingly so that the lift car 106 decelerates (or accelerates) so that is maintains its intended speed.

Alternatively, the motor controller 112 may force the lift car to stop if the lift car 106 has exceeded a safe speed, particularly at the limits of the lift shaft. In particular, when the lift car 106 is decelerating (e.g. to arrive at a floor level) the speed of the lift car is constantly checked (using the second camera) to confirm whether the intended slowdown is being achieved. If not, then the lift car is forced to decelerate to a slow speed (typically 0.06 -0.1 m /s).

-16 -For example, if the lift is approaching the bottom floor and the remaining distance to the bottom floor is approximately 4 metres, then the lift speed must be less than 2.2 metres per second in order for the lift car to be able to decelerate in time to stop at the bottom floor. If the lift car 106 has not begun to decelerate or has not decelerated sufficiently (as determined by the motor encoder 116 based on data from the secondary camera of the sensor 120), a brake is applied to force the lift car to apply an increased deceleration profile to the lift car 106.

In the present example, the first and second cameras of the sensor 120 are connected to two separate channels of the CAN (to which the position encoder 104 and lift controller 100 are also connected). The sensor 120 thus uses the first channel to communicate data from the first camera to the position encoder (which then provides position and/or speed information to the lift controller for calculation of a speed profile) and uses the second channel to communicate data from the second camera to position encoder (which then provides position and/or speed information to the lift controller which is used to perform a slowdown check). The measurements of the first and second cameras are of the same nature, that is, they are both measurements of the code tape 118 used to determine the position and/or speed of the lift car 106.

This control system therefore provides a backup to the electromechanical switches and other componentry which have traditionally been used to perform a secondary check on the speed of the lift car to ensure that the lift car is not travelling faster than intended. Instead of these electromechanical components, the secondary speed check in the control system of the present disclosure is performed by the secondary camera.

The implementation in the present disclosure gives rise to a number of advantages over the existing systems described above.

First, the use of two cameras, one to control the movement (i.e. position and speed) of the lift car 106 in the lift shaft, and the other to check whether the true position and/or speed of the lift car 106 matches the intended position and/or speed, provides a dual safety check on the speed of the lift car 106 so that it always maintains the intended speed and cannot exceed a safe speed. This reduces reliance on the traditional switches and other mechanical components (e.g. overspeed governors) described above, that are typically used to perform this safety function, because these safety functions can be carried out by the components of the lift control system disclosed above. In future, these traditional components could no longer be necessary, which in turn means that the time required to install the lift control system of the present disclosure is much reduced because there would -17 -be no need to install the traditional electromechanical componentry (switches and overspeed governors, etc.) into the lift shaft.

Second, the use of two cameras means that the system has in-built redundancy so that even if one of the cameras fails, or if the calibration of one of the cameras is faulty, the system can rely on the other camera to guide the lift to a safe position (e.g. to the nearest floor, or to the ground floor) until the camera can be checked and repaired. This means that the system is more robust against potential malfunctions than the existing systems because, in the existing system, if one of the switches fails, the over-speeding lift car will only be slowed once it reaches the next switch along in the lift shaft, by which point it might be more difficult to decelerate the lift car safely.

Direct approach control The control system described above can be used to provide an improved process for controlling the lift car as it travels along the lift shaft to improve ride quality and reduce floorto-floor travel times.

Figure 2a shows a graph indicating a typical speed profile of a lift car in existing lift systems.

The graph shows (on the y-axis) the speed of the lift car along the lift shaft as a function of time (on the x-axis) for the duration of a single floor-to-floor journey. As shown in Figure 2a, as the lift car accelerates towards its destination, the acceleration increases from an initial acceleration until it reaches a constant acceleration (as indicated by the constant gradient part of the increase in speed over time). As the lift car approaches its target travel speed, the acceleration is reduced until the lift travels at a constant speed towards its destination. This is the maximum speed reached by the lift car over the journey and is called the 'high speed' (although it is not necessarily the top speed of the lift car). VVhen the lift car approaches the destination floor, the lift car decelerates down to a constant low speed called a 'levelling speed'. This low levelling speed is maintained for a time (to in Figure 2a) until it is detected that lift car is at the destination floor, at which point the lift is braked sharply (over a time ti in Figure 2a) to stop the lift at the floor.

These existing systems have a number of disadvantages. Firstly, these systems rely on detecting when the lift is approaching the destination floor which is achieved using vanes distributed throughout the lift shaft. Vanes are magnetic strips located in the lift shaft at every door zone ('door zone vanes') and along the approach to a door zone ('stepping vanes'). The lift cars of existing systems comprise magnetic sensors to detect the presence of the stepping vanes (which are used to determine when to decelerate the lift car from its high speed to its levelling speed) and door zone vanes (which are used to determine when -18 -to decelerate the car from its levelling speed to a stand-still). This means that a large number of vanes must be installed throughout a lift shaft (multiple stepping vanes and a door zone vane for every floor) which increases the time required to install the lift systems.

Secondly, because the door zone vane is located at the floor level, the lift car must be stopped almost immediately as soon as the vane is detected otherwise the lift car would overshoot the door zone. Therefore, the final deceleration of the lift car (i.e. during time ti in Figure 2a) is sudden which results in a jerky ride for the passengers.

Lastly, due to the reliance on stepping vanes and door zone vanes, it is necessary to decelerate the lift car to a slow levelling speed (i.e. during time to in Figure 2a) so that the lift car is not travelling so fast that it cannot be stopped before the destination floor when the door zone vane is detected. This means that significant time is wasted during the journey while the lift slowly approaches its destination floor.

In the present disclosure, the lift control system described above can be used to control the movement of the lift car 106 to achieve a direct approach to a destination floor without the need for the lift car 106 to decelerate to a levelling speed as it approaches the destination floor.

In the lift system of the present disclosure, the floor levels of a lift shaft are determined automatically using the positioning system (i.e. the code tape 118, sensor 120, and position encoder 104) in combination with the lift controller 100, during the course of a learning run along the lift shaft. During a learning run, the lift car 106 travels from the bottom of the lift shaft to the top of the lift shaft, and back again, at reduced speed. The learning runs begins with the lift car 106 stationary at the bottom of the lift shaft, aligned with the door zone vane for the bottom floor. As the lift travels past the floor levels the door zone vanes are detected and a position reading is recorded. It should be understood that other means for identifying and detecting the door zones could equally be used in place of door zone vanes, for example mechanical switches that are tripped by the lift car, or optical labels that are read by the cameras of the sensor.

In this way, the lift system learns and stores information about the absolute positions of all floor levels in the lift shaft, which information can be used to enable the lift to approach a floor level directly without the need for the lift to slow to a levelling speed before stopping.

The bottom floor, at which the learning run is started, is recorded as the first learned floor level.

-19 -The lift controller 100 comprises a user interface (which in this example is program running on a personal computer connected to the lift controller 100, preferably via the RS232 port) by which an engineer can instruct the lift controller 100 to perform a learning run, and by which a engineer can view the results of the learning run, which is a stored list of all floor level positions. The engineer can make manual adjustments to the floor level positions in the event that the door zone vanes in the lift shaft are not calibrated exactly for the floor level. For example, if the door zone vane on one floor is located 15 mm higher than the actual floor level, the learning run will record the position for that floor 15 mm higher than the actual floor; an engineer can manually reduce the position recording for this level by 15 mm if it is found that the lift car is stopping 15 mm above the floor level.

The learning run also provides an opportunity to calibrate the motor. As the lift car 106 travels at a set speed during the learning run (typically set at 0.2 m/s), the sensor of the positioning system can be used to verify whether or not the lift car 106 in travelling at the intended speed. If the lift car 106 is travelling faster or slower than expected, the motor is re-calibrated (i.e. the power supply to the lift motor is calibrated) so that the lift car 106 travels at the intended speed. Therefore, when the lift is in operation after the learning run is complete, the lift will travel at the intended speed.

Once the learning run has been completed, and the floor level positions have been recorded, the lift controller 100 uses this position information to calculate a trajectory for the lift car 106 from an origin floor direct to a destination floor. Figure 2b depicts the speed profile of an exemplary floor-to-floor of a lift car 106 over the course of a single journey from an origin floor to a destination floor using the lift control system of the present disclosure. The trajectory of the lift car 106 has three phases: an acceleration phase (where the lift car 106 accelerates from stationary to its maximum speed, between to and ti in Figure 2b), a high-speed phase (where the lift car 106 travels steadily at its high speed, between ti and t2 in Figure 2b) and a deceleration phase (where the lift car 106 decelerates from its high speed, between t2 and to in Figure 2b, to arrive and stop directly at a lift floor, at to in Figure 2b). The acceleration and deceleration phases of the journey have 's-curve' profiles (that is, the acceleration speed profile has a convex gradient at its beginning and a concave gradient at its end, with a substantially constant gradient between, and vice versa for the deceleration profiles). These s-curve profiles are calculated by the lift controller 100 as described below.

A direct approach to the destination floor is made possible by the recording of the lift floor positions during the learning run and by using the positioning system (i.e. the sensor 120, code tape 118, and position encoder 104) to provide an accurate measurement of the lift car's current position, from which the distance to the destination floor can be calculated, and -20 -a measurement of the speed of the lift car 106 can be taken. These distance and speed measurements can be used by the lift controller 100 to calculate the average deceleration needed to bring the lift car 106 to a stop exactly at the destination floor level, and thus the lift controller 100 can generate a deceleration profile which provides this average deceleration.

Or, if an average acceleration and deceleration is set (e.g. by an engineer), the lift controller can calculate the position at which the lift car 106 will need to begin decelerating in order to stop exactly at the position of the destination floor level, and a deceleration profile which provides this selected average deceleration.

Figure 3 shows three graphs depicting the speed, acceleration, and jerk profiles of the lift car 106 over the course of the acceleration phase of the speed profile shown in Figure 2b. The bottom graph shows the speed profile, the middle graph shows the acceleration profile (i.e. the rate of change of the speed), and the top graph shows the jerk profile (i.e. the rate of change of the acceleration). As can be seen from Figure 3, the acceleration phase of the lift car 106 journey itself comprises three phases: a first phase (to to t1 in Figure 3) where the acceleration is increasing from zero to a constant value, a second phase (t1 to t2 in Figure 3) where the acceleration is constant, and a third phase (t2 to to in Figure 3) where the acceleration decreases from the constant value to zero. As the acceleration changes with respect to time in the first and third phase, there are two jerks: one positive jerk corresponding to the first phase and one negative jerk corresponding to the third phase.

Typically, s-curve motion profiles for elevators are calculated using high order polynomial equations to model the jerk, usually 3, 41h, or even 5th order polynomials which are complex and computationally time consuming to calculate. The inventors have found that the s-curve motion profile can be calculated more simply, and with improved results, using a trigonometric function to model the jerk. In the lift system of the present disclosure, the lift controller 100 calculates the s-curve motion profiles for the acceleration and deceleration phases using the following jerk function: Jerk (0) =Jerk2pEAK ( cos(0)) [1] In equation 1, JerkPEAK is the maximum jerk over the over the course of the acceleration phase of the trajectory and is a constant value which is fixed to limit the maximum jerk the lift controller 100 can exert. When the acceleration is increasing (between to and ti) JerkpEAK -is a constant positive value, and when the acceleration is decreasing (between t2 and to) JerkpEAK is a constant negative value.

The argument 0 is a function of time and is scaled so as to map the duration of the jerk to a part of the period of the 1 -cos(0) function (e.g. to a half-period or a full-period of the -21 -function). As an example, to model the jerk using a half-period of the 1 -cos(0) function, the argument 0 is a function of time (t) as follows: t-to = 180 [2a] ti-to o = 180 [2b] t3-t2 where equation 2a is applicable when the lift car is accelerating from stationary to a constant acceleration, and where equation 2b is applicable when the lift car acceleration is reducing from a constant acceleration to zero.

As another example, to model the jerk using a full-period of the 1 -cos(0) function (as is shown in Figure 3), the argument 0 is a function of time (t) as follows: 10= 360 t-ro [3a] ti-to = 360 t t2 [3b] r3-r2 where equation 3a is applicable when the lift car is accelerating from stationary to a constant acceleration, and where equation 3b is applicable when the lift car acceleration is reducing from a constant acceleration to zero.

In other words, equations 2a and 3a show 9 for the first phase of acceleration (i.e. between to and ti) and equations 2b and 3b the third phase of acceleration (i.e. between t2 and t3) respectively. In these equations, t is the current time, to and t1 are the start and end times of the first phase of acceleration, and t2 and t3 are the start and end times of the third phase of acceleration. Thus, t -to and t -t2 are a measure of the time since the start of the first and third acceleration phases respectively, while t1 -to and t3 -t2 are measures of the duration of the first and third phases of acceleration. Therefore, t t° and t t2 represent the ti-to t,-t2 current time as a fraction of the total duration of the first and third phases of the acceleration respectively. This fraction is scaled by 180° (or 360°) so that 9 takes a value between 0° and 180° (or 0 and 360°) over the course of each of the first and third acceleration phases.

The argument 0 may be written more generally as 180-(to model the jerk using a half-tj period of the cos function) or 360-ti (to model the jerk using a full-period of the cos function) with t being the time since the beginning of the jerk, and t1 is the total duration of the jerk.

-22 -Therefore, 0 effectively scales the duration of the first and third acceleration phases between 0° and 180° (or between 0° and 360°, as in the example shown in the jerk graph in Figure 3) such that these phases are represented by one half period (or one full period, as in the example shown in Figure 3) of the 1-cos(()) function in the jerk model of equation 1.

Since cos(0) takes a value between 0 and 1, and the jerk function takes a value between zero and JerkpEAK (between which the function varies according to 1-cos(0).

In an alternative example, this trigonometric model can be used to model the acceleration of the lift car over time (instead of the jerk). In this case, the lift controller 100 calculates the s-curve motion profiles for the acceleration and deceleration using the following function: Acceleration (0) = APEAK (1 -cos(0)) [4] In equation 4, A PEAK is the maximum acceleration over the course of the acceleration phase of the trajectory. The argument 0 is a function of time and is scaled so as to map the duration of the acceleration to a half-period of the 1-cos(0) function. In particular, the first phase of the acceleration (between to and t] in Figure 3, where the acceleration is increasing from zero to a constant value) is mapped to the first half of the 1 -cos(0) function, while the third phase of the acceleration (between t2 and t3 in Figure 3, where the acceleration decreases from the constant value to zero) is mapped to the second half of the 1 -cos(0) function. Thus, to model the acceleration using this method the argument 0 is a function of time (t) as follows: (-to = 180 [5a] ti-to = 180 + [180 ttct22] [5b] where equation 5a shows B for the first phase of acceleration (i.e. between to and ti when the lift car is accelerating from stationary to a constant acceleration) and equation 5b shows 0 for the third phase of acceleration (i.e. between t2 and to when the lift car acceleration is reducing from the constant value to zero). Equation effectively 5a scales the duration of the first acceleration phase between 0° and 180°, such that this phase is represented by the first half of the 1 -cos(B) function in the acceleration model of equation 4. Equation 5b scales the duration of the third acceleration phase between 180° and 360°, such that this phase is represented by the second half of the 1 -cos(0) function in the acceleration model of equation 4.

-23 -Equations 5a and 5b can be simplified as 9 = 180-t and 9 = 180 + [180-t respectively, tA tA where t is the time since the beginning of the acceleration/deceleration phase, tA is the total duration of the acceleration/deceleration phase, and APEAK is the peak acceleration/deceleration.

The jerk and acceleration models have been described above with reference to the acceleration phase of the lift car 106 floor-to-floor trajectory. However, the same applies mutatis mutandis to the deceleration phase of the trajectory, which mirrors the acceleration phase but in the opposite direction (i.e. the acceleration and jerk profiles would be mirrored across the x-axis for the deceleration phase).

The inventors have found that modelling the jerk or acceleration using this trigonometric method provides for an s-curve motion profile that is as smooth as that provided by the 5th order polynomial alternative, and yet is as computationally simple as a 3rd order polynomial. A smooth jerk profile means that the ride quality as experienced by a user of the lift car 106 is improved.

Using these models, a number of parameters of the s-curve generation can be adjusted to suit different implementations of the lift system. These parameters are usually adjusted and set upon installation of the lift system by a lift engineer.

-Average acceleration and deceleration The average acceleration and/or deceleration can be adjusted according to whether a smoother ride of a faster ride is preferred.

Figures 4a, 4b and 4c show various speed profiles for floor-to-floor journeys where the acceleration and deceleration has been set to different values in each figure. The dashed line in each figure represents the average (i.e. constant) acceleration and deceleration from/to stationary to/from the high speed in each speed profile, whereas the solid line represents the actual speed profile of the lift car 106 as calculated by the lift controller 100 according to the jerk model described above. The actual speed profile of the lift car 106 is an s-curve calculated to provide the selected average acceleration or deceleration.

In Figure 4a the average acceleration and deceleration are set at 0.6 m/s'. This acceleration and deceleration will suit most lift applications. In Figure 4b the average acceleration and deceleration are set to 0.25m/s2. This reduced acceleration and deceleration result in a reduced jerk when starting and finishing the acceleration or deceleration phase. The result is a smoother and less jerky ride; however the floor-to-floor travel times will be increased -24 -because more time is needed for the lift car 106 to reach its maximum speed. In Figure 4c the average acceleration and deceleration are set to 1m/s2. This increased acceleration and deceleration result in an increased jerk when starting and finishing the acceleration or deceleration phase. The result is a "harsher" ride with more noticeable jerk; however the floor-to-floor travel times will be reduced because the lift car 106 will reach its maximum speed sooner in the journey and will spend longer at that speed before decelerating.

-Acceleration and deceleration rounding The rounding of the s-curve can be adjusted to reduce the jerk, and hence the vibration, when changing from a constant speed value to a varying speed (i.e. at the start and end of s-curve, which is the start and end of the acceleration and deceleration phases of the journey). The more rounding, the smoother (i.e. less jerky) is the transition from a constant speed (e.g. 0 or the high speed) to a varying speed.

Figure 5 shows a speed profile for a floor-to-floor journey showing three different s-curves each with different degrees of rounding. S-curve 502 has the most rounding, whilst s-curve 504 has the least rounding. If the rounding it set to zero, the result will be a straight line (i.e. constant acceleration and deceleration, as indicated by the dashed line in Figure 5).

While the rounding of the s-curve smooths the transition from a constant speed to a varying speed at the beginning and end of the acceleration and deceleration phases, the rounding increases the peak acceleration and deceleration (i.e. in the middle of the acceleration and deceleration phases) as indicated by the steeper gradients of s-curve 502 in Figure 5 for which these is the most rounding. For example, for an average acceleration or deceleration of 0.6 m/s2 over the course of the acceleration or deceleration phase, the peak acceleration or deceleration may be up to 1.3 times (0.78 m/s2) when the rounding is set to full. If an increased peak acceleration or deceleration is not desirable, it is preferably to reduce the overall acceleration or deceleration rate, rather than reduce the rounding, because too little rounding may cause vibrations.

-Jerk balance The s-curve can be adjusted to control the balance between the jerk at the start and the end of the acceleration or deceleration phase of the trajectory.

Figures 6a, 6b and 6c show various speed profiles for floor-to-floor journeys where the jerk balance has been set to different values in each figure. The dashed line in each figure represents the average acceleration and deceleration from/to stationary to/from the high speed in each speed profile, which is the same for each profile. The solid line represents the -25 -actual speed profile of the lift car 106 as calculated by the lift controller 100 according to the jerk model described above. The actual speed profile of the lift car 106 is an s-curve calculated to provide the selected average acceleration or deceleration. Adjusting the jerk balance allows adjustment of the rounding of the s-curve at the start of the acceleration or deceleration phase relative to the rounding of the s-curve at the end of the acceleration and deceleration phase.

Figure 6a shows a speed profile with the jerk balance set to 0. This means that the rounding at the start of the s-curve is identical to the rounding at the end of the s-curve, meaning that the solid line (the actual speed profile) crosses the dashed line (the average deceleration line) exactly halfway along the dashed line. This means that the passenger in the lift will feel an equal (but opposite) jerk at the start and end of the acceleration phase, and at the start and end of the deceleration phase.

Figure 6b shows a speed profile with the jerk balance set to -2. This means that the rounding is increased at the low-speed ends of the acceleration and deceleration s-curves and decreased at the high-speed ends of the s-curves. Therefore, the acceleration/deceleration of the lift car 106 at the low-speed ends of the s-curves is more gentle than in the speed profiles of Figure 6a, as indicated by the solid line (the actual speed profile) crossing the dashed line (the average acceleration/deceleration line) after the halfway point of the dashed line in the acceleration phase, and before the halfway point of the dashed line in the deceleration phase. Thus, when setting off and stopping the passenger will feel a reduced jerk as compared to the profile in Figure 6a, but an increased jerk as compared to the profile in Figure 6a when approaching high speed and when decelerating from high speed.

Figure 6c shows a speed profile with the jerk balance set to +2. This means that the rounding is decreased at the low-speed ends of the acceleration and deceleration s-curves and increased at the high-speed ends of the s-curves. Therefore, the acceleration/deceleration of the lift car 106 at the low-speed ends of the s-curves is higher than in the speed profile of Figure 6a, as indicated by the solid line (the actual speed profile) crossing the dashed line (the average acceleration/deceleration line) before the halfway point of the dashed line in the acceleration phase, and after the halfway point of the dashed line in the deceleration phase. Thus, when approaching high speed and when decelerating from high speed the passenger will feel a reduced jerk as compared to the profile in Figure 6a, but an increased jerk as compared to the profile in Figure 6a when setting off and stopping.

-26 -This jerk balance setting can be adjusted to reduce vibrations or improve ride quality in specific parts of the lift car 106 journey.

-Minimum time on high speed The minimum time on high speed can be adjusted to ensure that the lift car 106 spends at least a certain length of time at the high speed (that is, the maximum speed along the journey). Increasing the length of time spent at high speed means that the lift car 106 will settle for longer on the high speed which will improve the ride quality for the passenger.

For long distance multi-floor journeys this parameter will not noticeably affect the passenger's ride because the lift car 106 will reach its normal high speed and spend a long time at that top speed due to the long distance. Therefore this setting applies mainly to floor to floor journeys where the normal high speed cannot be reached because doing so would involve exceeding a maximum jerk or acceleration/deceleration.

Figure 7 shows a three speed profiles for a short floor-to-floor journey with different settings for the minimum time on high speed. The middle profile 702 corresponds to the default setting for this parameter, which is a minimum of 1 second spent on high speed. The lower profile 704 corresponds to a minimum of 2 seconds spent on high speed. The higher profile 706 corresponds to a minimum of 0.2 seconds spent on high speed. In these examples, the journey time is too short for the lift car 106 to reach its normal high speed speed, therefore the highest speed reached by the lift car 106 on the journey depends on the setting of this minimum time at high speed parameter.

For profile 704, the time spent on high speed is long meaning that there is less time available at the start and end of the profile for acceleration and deceleration, meaning that only a low speed is possible (without exceeding a maximum jerk or acceleration or deceleration) which results in increased floor-to-floor travel times. Conversely, for profile 706, the time spent on high speed is short meaning that there is more time at the start and end of the profile for acceleration and deceleration, meaning that a higher speed is possible. However, the shorter the time spent at high speed, the more unsettled the ride will feel for the passenger. A setting of 1 second spent on high speed results in good compromise between ride quality and travel time.

-Finish profile: finish distance and finish correction The finish distance and finish correction parameters may be adjusted to tweak the speed profile at the very end of the deceleration phase of the lift car 106 journey. Adjustment of these parameters means that the lift car 106 deviates from the normal deceleration s-curve -27 -slightly in the very final stages of deceleration so that the approach to a floor is more gradual which gives a smoother and more controlled stop for the passenger.

When the 'finish distance' parameter is activated, the very last part of the deceleration profile is adjusted to provide a gentler deceleration to the stopping point. The finish distance parameter can be adjusted by an engineer to control at which point in the deceleration of the lift car 106 deviates from the normal s-curve. A typical value for this parameter is 15 mm, meaning that the lift car 106 trajectory deviates from the normal s-curve only in the last 15 mm of the journey.

Figure 8a shows the deceleration phase of a speed profile for a lift car 106 journey with the finish distance parameter activated. The dashed line indicates the normal deceleration s-curve, and the solid line indicates the adjusted deceleration curve within the finish distance (of 15 mm). Between to and ti the deceleration profile is the normal s-curve profile. Between ti (when the lift car 106 is within 15 mm of the destination floor level) and t2, the profile deviates from the normal s-curve profile by flattening sooner and decelerating to a stop over a longer period of time than the normal deceleration s-curve. Between t2 and to the lift car 106 is controlled to adopt a 'profile finish speed' which can be set by an engineer. The profile finish speed (PFS) is used to provide the absolute finishing speed of the speed profile which will only be applied for the last few millimetres of travel. A typical setting for the PFS parameter is 2 mm/s. After to the lift car 106 comes to a stop, which will be a gentle stop (almost unnoticeable by the passengers) due to the fact that the lift is stopping from such a low speed.

To avoid overshooting the destination floor level, due to decelerating more slowly than in the normal s-curve, a correction may be required as the lift car 106 enters the final stages of the deceleration. Figure 8b shows the deceleration phase of a speed profile for a lift car 106 journey with the finish correction parameter activated. The upper dashed line 802 indicates the s-curve travelled by the lift car 106 as it decelerates normally between to and ti. When the lift car 106 enters the finishing distance at ti (which depends on the finishing distance parameter setting, as described above, but will usually be 15 mm from the destination floor level) the lift car 106 enters the finishing profile. At ti a check is performed by the lift controller 100 (using the positioning system) as to whether the lift car 106 will overshoot the destination floor level if the finishing profile is implemented (i.e. if the lift is controlled to decelerate more gently to the profile finish speed (PFS) before stopping). If the lift controller 100 determines that the destination floor level would be overshot, a correction 802 is applied at t1 to decelerate the lift car 106 briefly before the finish profile is implemented. The -28 -correction has the effect of dropping the lift car 106 trajectory from an overshoot trajectory 804 to a corrected trajectory 806.

-Advance distance The deceleration profile is calculated to take the lift directly to the destination floor position.

To ensure this happens, the profile is tracked and corrected periodically (i.e. every 10 ms by the dual cameras and position and speed feedback control loops of the positioning system as described above) so that the speed applied for the distance remaining to the destination floor is true to the intended profile. Nonetheless, to ensure that the lift controller 100 can correct for any position overshoots in the finishing profile, an 'advance distance' parameter is provided. The advance distance parameter effectively provides an offset of the destination floor level, meaning that the profile will effectively finish before floor level is reached, by the offset selected. This allows compensation for any overshoot. The advance distance parameter works together with the finish distance parameter to provide the accurate finishing profile. The finish distance parameter should be greater than the advance distance parameter. A typical value for the finish distance is 15 mm, and a typical value for the advance distance is 5 mm.

In addition to the parameters mentioned above, the lift system also provides a number of other parameters that can be adjusted to customise the speed profiles for floor-to-floor journeys. These parameters include the following: Drive Contract Speed: this parameter sets the maximum top speed for the lift car 106 Drive High Speed: this parameter sets the value for 'high speed' which is the speed travelled by the lift car 106 between its acceleration and deceleration phases Drive Medium Speed / Drive Level Speed: these parameters set the values for the speed for a specific floor-to-floor journey or for all journeys to or from a specific floor. This is because it may be desired for one particular floor-to-floor journey to have a lower speed than the default high speed (e.g. to or from the operating floor in a hospital as the lift is likely carrying patients) Learning Run Speed: this is the speed the lift will travel at during a learning run of the shaft. If the speed is set too high errors may occur learning the data. A typical setting for this is 0.2m/s, with a maximum setting of 0.5m/s * Within Floor Level Distance: this parameter sets the distance above or below floor level within which the lift car 106 is deemed to be at the floor level. A typical setting for this parameter is 6 mm * * * * -29 -This lift control system of the present disclosure gives rise to a number of advantages over the existing systems described above.

First, as the absolute positions of the floor levels are recorded during the learning run, it is no longer necessary to instal stepping vanes to indicate when the lift car is approaching a floor level. This reduces the number and complexity of the components that need to be installed in the lift shaft meaning that the set up time for the lift system of the present disclosure is reduced as compared to existing systems.

Second, as the control processes described above enable a direct approach to the destination floor level (i.e. a deceleration directly to the floor level) rather than decelerating to a levelling speed before the floor level until the door zone vane is detected, floor-to-floor travel times are significantly reduced (since a longer portion of the travel time is spent at high speed as compared to the speed profiles of existing system) which also reduces the wait times for other passengers and increases the capacity of the lift system as the lift cars can complete more journeys in a given time interval.

Last, the direct approach to the lift floors provides an improved ride quality for passengers as compared to existing systems because the lift car gradually decelerates direct to the floor level with a controlled jerk rather than decelerating to a levelling speed then suddenly stopping as soon as the door zone vane is, as in the existing systems described above. This ride quality is further improved by the trigonometric jerk model described above, which provides for a smoother journey as compared to the existing systems.

Brake controller The present disclosure also provides an improved brake controller which achieves significant energy savings as compared with existing brake controllers.

The primary brake of most lift systems is coupled to the sheave and comprises a pair of brake shoes which independently contact the sheave in order to impede its rotation thereby to brake the lift car. The brake shoes are mechanically biased (e.g. via a spring) into contact with the sheave such that, in the absence of other forces, the brake shoes are forced into contact with the sheave to hold it, and thus the lift car, stationary. In order to release the brake, a force must be applied to separate the brake shoes from the sheave so that it can turn freely. This is typically achieved by applying an appropriate current through a pair of solenoids (one solenoid for each brake shoe) to generate an electromagnetic force which acts against the mechanical biasing of the brake shoes to release the brake.

-30 -Figure 9a shows a circuit diagram illustrating the operation of the brake controller 900 of the present disclosure. In this example, the lift brake comprises at least one solenoid 902 which is used to release the lift brake as described above. When an electric current is passed through the solenoid, an electromagnetic force is generated which forces the brake shoes (not shown) apart from the sheave against the mechanical biasing to release the brake.

A power supply (not shown) is provided to power the brake controller, and thus provides a means for driving a current through the solenoids. The power supply could be part of the brake controller 900, but in this example it is external to the brake controller, and the brake controller has means for connecting to the power supply which in this example is a live power line (L). A neutral line (N) and earth line (E) are also provided. The power supply is this example is a 240 V power supply. The brake controller 900 controls the voltage provided across the solenoid 902 to control release of the lift brake as described below.

The brake controller 900 is connected to the lift controller 100 by a screened cable 904 (which comprises a surrounding screen 906a to reduce noise and interference in the cable).

The cable 904 provides a serial CAN input and output connection between the lift controller and the brake controller 900, and comprises CAN low (CL) and CAN high (CH) communication channels, 5 V and 0 V power lines, and a connection for the cable screen 906 (SON).

A first switch (BR) is located along the live power line (L). The switch comprises a contact that is normally open thus breaking the connection between the brake controller 900 and the external power supply in normal operation. In order for power supply to reach the brake controller 900, the first switch (BR) must be actuated to close the contact. When this contact is closed, and power is supplied to the brake controller from the live power line (L), the brake controller supplies power to a control loop circuit 907 which runs between two terminals (+OUT and +IN) of the brake controller 900. The control loop 907 comprises a set of two second switches (UP and ON). The two second switches are connected in parallel with one another in the control loop circuit, and both of the second switches comprise contacts that are normally open thus breaking the control loop circuit. In order to close the control loop circuit, at least one of the switches (UP or ON) must be actuated to close its contact. One of the second switches (UP) is actuated when the lift controller releases the brake to move the car upwards in the lift shaft, while the other the second switches (DN) is actuated when the lift controller releases the brake to move the car downwards in the lift shaft. The control loop 907 also comprises a third switch (CEB) which is connected in series in the control loop circuit. The third switch comprises a contact that is normally open thus breaking the control loop circuit. In order to close the control loop circuit, the third switch (CEB) must be actuated -31 -to close its contact. These switches (BR, UP, DN and CEB) are 'normally open' in the sense that their contacts are biased (e.g. by a spring) to an open position, and some external input is required to overcome the biasing to close the contact. The switches may be contactors or relays for example.

Thus, in order to release the brake, three separate switches must be actuated: the first switch (BR) to provide power to the brake controller; and at least one second switch (UP or DN) and a third switch (CEB) to close the control loop circuit 907. Therefore these switches provide safety integrity in the braking system, by preventing release of the brake unless the lift controller correctly actuates all necessary switches; in this way the switches provide a safeguard against accidental or uncontrolled release of the brake. The switches are actuated between open and closed positions by the lift controller 100 when the lift controller moves the lift car, for example when the lift is called between floor levels by a user.

Alternatively or additionally, at least one of the switches may be actuated based on the position of one of the other switches; in particular the third switch (CEB) may be actuated based on the positions of the two second switches (UP and DN). For example, the third switch may be configured to close its contact only when one of the second switches is actuated (so that the contact of the third switch remains open if none or both of the second switches are actuated, such as might indicate a malfunction of the seconds switches) -in this way, the third switch effectively provides a means for monitoring the second switches for potential malfunctions, and prevents release of the brake in the case of such a malfunction.

When the control loop 907 forms a closed circuit, current is enabled to flow along a brake loop circuit 908 and through the solenoid 902 thus generating an electromagnetic force releasing the brake. The brake loop 908 is connected between terminals of the brake controller (B+ and B-). The brake loop 908 also comprises screening 906b to reduce interference and noise in the brake loop.

The brake controller 900 also comprises means for varying the voltage supplied across the solenoid 902. In this example, this means is a potentiometer which receives an input of the fixed voltage power (240 V) from the external power supply, and provides an output which is a variable voltage across the solenoid 902 between the brake loop terminals of the brake controller (B+ and B-). In operation, when the braking system of the present disclosure is used to release the brake of the lift car 106, the lift controller 100 is configured to send an instruction to the brake controller 900 to provide a voltage across the solenoid 902 to drive a current through the solenoid 902. The brake controller 900 then increases, using the potentiometer, the voltage supplied across the solenoid 902 until it is sufficient to drive a large enough current through the solenoids 902 to generate an electromagnetic force that is -32 -large enough to overcome the mechanical biasing of the brake shoes in order to force the brake shoes apart from the sheave to release the brake. This voltage is called the 'lift voltage' (or lift power') and is the voltage (or power) required to lift the brake shoes off of the sheave, against the mechanical biasing, to release the brake.

The inventors have realised that once the energy has been expended to overcome the mechanical biasing of the brake shoes, and thus force the brake shoes apart from the sheave, a lower electromagnetic force is required then to hold the brake shoes stationary in the separated position (i.e. the hold the brake in the released position). Thus, in operation, once the brake shoes have been separated to release the brake, the lift controller 100 instructs the brake controller 900 to reduce, using the potentiometer, the voltage across the solenoid 902 to a 'hold voltage' (or 'hold power'). The hold voltage is lower than the lift voltage, but still sufficiently large to drive a current that is sufficiently large to generate an electromagnetic force that balances the mechanical biasing force thereby to hold the brake shoes stationary and maintain the brake in its released position. This reduced voltage (or power) which holds the brake shoes stationary, apart from the sheave, is called the 'hold voltage' (or 'hold power').

This method of operation, in which the hold voltage is lower than the lift voltage, is in contrast to existing braking systems in which the same voltage is applied while the brake shoes are being separated and also while they are held stationary in their separated position (i.e. in existing systems, to release the brakes a power supply is simply turned on to separate the brake shoes and hold them apart, and to re-apply the brakes the power supply is simply turned off so that the brake shoes contact the sheave under the mechanical biasing). These existing systems are inefficient because an unnecessarily large voltage is applied while the brake shoes are held in their separated position.

The use of a reduced hold voltage in the brake controller of the present disclosure provides significant power saving advantages; in particular the inventors have achieved energy savings of 76% by reducing the brake power from 0.60 kW (when using known brake controllers where the same hold and lift voltages are applied) to 0.14 kW (when using the brake controller of the present disclosure where a lower hold voltage is provided compared to the lift voltage).

During operation, when the brake controller 900 reduces the voltage supplied to the solenoid 902 from the higher lift voltage to the lower hold voltage, an electrical spike (i.e. a voltage/current spike) and/or electrical noise or interference can occur as a result of the sudden change in the voltage. Therefore, the brake controller 900 also comprises a suppression circuit, comprising a varistor connected in parallel with the solenoid 902. The -33 -varistor has an electrical resistance that varies with the applied voltage, in particular, the varistor has an electrical resistance that decreases as the applied voltage increases. This varistor has the effect of smoothing the transition from the higher lift voltage down to the lower hold voltage, by decreasing the rate of the reduction of the voltage. This varistor therefore supresses the electrical spike and electrical noise sent back through the circuitry.

If the external power supply is an alternating current (AC) power supply, a rectifier, preferably a full wave rectifier, is provided to convert the AC power supply to a direct current (DC) power supply. In this case, a further varistor may be connected across the DC current output terminals of the rectifier to provide further suppression of electrical spikes.

Figure 9b is a circuit diagram showing of the brake controller 900 of the present disclosure, as used for a hind-winding operation. The term "hand-winding" refers to the case where some part of the lift system (such as the lift controller) fails, and the lift cables must be wound manually by an operator in order to move the lift car along the lift shaft to a floor level. If the lift controller 100 fails, the lift controller cannot actuate the switches of the brake controller circuity, meaning that the contacts of these switches will remain open, preventing power supply to the solenoid 902 thus preventing release of the brake. It is not possible for an operator to hand-wind the lift cables while the brake is applied (because the lift car would not move). To solve this problem, a pair of hand-winding switches (HW1) and (HW2) are provided which respectively bypass the first switch (BR) on the live power line (L) and the second and third switches (UP, DN, and CEB) in the control loop circuit 207. In this example, the hand-winding switches (HW1 and HW2) are push switches which are actuated manually by a user. When actuated, contacts in these switches (HW1 and HW2) are closed to provide bridges that allow current to bypass the broken first, second and third switch contacts thus providing a power supply to the solenoid 902 to release the brake. A further switch (HW1) is a hand-winding input to the lift controller 100 to set the lift controller 100 to hand-winding operation mode so that the lift controller 100 does not interfere with the hand-winding operation.

In order to prevent the brake from remaining released for too long (which can cause the lift to run away along the lift shaft under the force of the counterweight), the brake controller is configured to limit the duration for which power is supplied to the brake solenoid 902 in hand-winding operation. In this example, in hand-winding operation the brake controller is configured to provide a first voltage pulse (at the higher "lift voltage") across the solenoid 902 followed by a second voltage pulse (at the lower "hold voltage") across the solenoid 902, and to limit the total combined time duration of the two pulses so that it does not exceed 20 seconds. This total time duration can be set by a user, up to the 20 second maximum value, with a preferably value being 8 seconds. When the pulse duration time expires, the voltage -34 -is reduced to zero such that the brake is reapplied. The level of the voltage provided across the solenoid 902 in both pulses is controlled using a potentiometer as described above.

The brake controller circuitry shown in Figures 9a and 9b must be connected to the lift controller 100 such that the lift controller can operate the brake (via the brake controller 900) to control movement of the lift car 106 along the lift shaft. However the brake controller generates significant heat due to the high electrical power required to release the brake, which can be problematic if the brake controller 900 is mounted on the same printed circuit board (PCB) as the lift controller 100. To ameliorate this problem, the brake controller is physically connected to the lift controller 100 via a heat sink situated between the brake controller 900 and the lift controller 100. The heat sink is preferably integrated into a backplate of the lift controller, with the brake controller mounted to the lift controller in contact with the heat sink such that the heat sink conducts heat away from both the lift controller and the brake controller simultaneously. In this way, a single heat sink is provided for both the lift controller and the brake controller which provides a more compact overall controller.

Uncontrolled movement detection The control system of the present disclosure can be used to provide protection against uncontrolled movement of the lift car by providing means for detecting uncontrolled movement so that it can be rectified. In particular, the present disclosure provides means for monitoring a lift brake and an overspeed governor so as to detect uncontrolled operation of these components.

-Brake monitoring The motor of a typical traction lit must have at least two brakes (i.e. two brake shoes), so as to provide redundancy in the event that one of the brakes fails. The two brakes preferably operate on opposite sides of the sheave to impede rotation of the sheave. Figures 10a and 10b show the components of a brake monitoring circuit for monitoring the two brakes of a typical traction lift to detect faults and uncontrolled operation of the brakes.

Referring to Figure 10a, two brake monitoring switches (1002a, 1002b) are provided, one for each of the brakes. These switches are normally in their closed position but are opened when the brake is energised (i.e. when a current is driven through the brake solenoids to release the brake as described above) so that the electrical contact controlled by the switch is broken. When the brakes are de-energised (i.e. when the current is removed, and the two -35 -brakes shoes are re-applied under the mechanical biasing force as described above) the brake switches (1002a, 1002b) are closed so that the contacts are re-made.

When the lift car is stationary, with the brakes de-energised (i.e. applied), the brake switches (1002a, 1002b) are closed, and the electrical contacts are made. When the electrical contacts are made, current flows through the brake switches (1002a, 1002b) to two relays (BM1, BM2). The first relay (BM1) corresponds to the first switch (1002a) which corresponds to the first brake, and the second relay (BM2) corresponds to the second switch (1002b) which corresponds to the second brake.

Referring to Figure 10b, the relays (BM1, BM2) shown in Figure 10a provide two inputs to the microprocessor of the lift controller 100. The first relay (BM1) corresponding to the first brake provides a first input (1004a) to the microprocessor of the lift controller 100, and the second relay (BM2) corresponding to the second brake provides a second input (1004b) to the microprocessor of the lift controller 100. The lift controller 100 comprises two light emitting diodes (LEDs) corresponding to the relays (BM1, BM2) which are illuminated when the relays are closed, to indicate the operational status of the switches. Both LEDs must be on when the lift is stationary so indicate that the brake is applied (and thus switches 1002a, 1002b are closed) When the lift car is controlled to move, a current is driven through the brake solenoids simultaneously and if both brakes operate successfully both brake switches (1002a, 1002b) will open, thus breaking the contact, and both inputs (1004a, 1004b) from the relays (BM1, BM2) to the microprocessor of the lift controller 100 will be off. If one or both of the inputs (1004a, 1004b) from the relays (BM1, BM2) fails to go off then a brake fault is deemed to have occurred and the microprocessor will log a "UMD FAULT". This is detected by the microprocessor comparing the inputs (1004a 100b); if the two inputs to not match (either because one is on while the other is off, or vice versa) this is indicative of a fault of one of the brakes. In order to prevent nuisance tripping this start fault can occur up to a maximum of 4 consecutive attempts before the microprocessor will stop any further lift operations, park the lift car with the doors open, and require a competent person to reset the fault using the lift controller menu.

When the lift car is controlled to stop, the current through the brake solenoids is reduced and if both brakes operate successfully both brake switches (1002a, 1002b) will close, thus making the contact, and both inputs (1004a, 1004b) from the relays (BM1, BM2) to the microprocessor of the lift controller 100 will turn on. If one or both of the inputs (1004a, 1004b) from the relays (BM1, BM2) fail to turn on within a pre-defined time after the lift has stopped at a floor level, this indicates that one or both of the brakes has failed to be applied -36 -and a "UMD FAULT" will be logged and no further operations are allowed. This is again detected by the microprocessor comparing the inputs (1004a 100b). An engineer can adjust the length of the pre-defined time within which an input from the relays must be detected to avoid a fault.

In addition to the microprocessor monitoring of the inputs (1004a, 1004b), the two relays (BM1, BM2) are also connected into an electrical starting circuit (that is, the circuit responsible for starting movement of the lift car when instructed by the lift controller 100). If the relays (BM1, BM2) fail to close when the brake is applied (which indicates that at least one of the brake solenoids is malfunctioning), the starting circuit will be broken so as to prevent the next start of the lift.

-Overspeed governor monitoring Overspeed governors typically incorporate an electromagnetic solenoid which is coupled to a mechanical pin which rests on a safety gear operating rope. The electromagnetic solenoid's function is to actuate the pin so that it is clear of the safety gear rope during normal lift movement. If the pin is left in the resting position and lift movement occurs, it will cause the safety gear to engage and prevent further movement of the lift car. Thus, the pin must be actuated clear of the safety rope to allow movement.

For monitoring purposes, the solenoid has an overspeed governor solenoid monitoring switch (i.e. a contact) which is closed (i.e. the contact is made) when the solenoid is energised (i.e. when the solenoid is in the lifted position by a current being driven through the solenoid) but open (i.e. the contact is broken) when the solenoid is de-energised.

With the lift car stationary, the overspeed governor solenoid will be de-energised and the pin will be in a position to engage the lift safety gear. Upon the start of lift car travel, a current is driven through the overspeed governor solenoid which in turn actuates the mechanical pin (via an electromagnetic force) clear of the safety gear operating rope so as to permit movement of the lift car. Accordingly, the overspeed governor solenoid switch is simultaneously moved to the closed position to make the contact so that lift movement can occur.

During normal high speed movement, the overspeed governor solenoid is time delayed in order to ensure that the solenoid does not immediately de-energise in the event of any emergency stop operation or loss of mains power supply and thus engage the lift safety gear (which might interfere with other emergency control procedures). The time delay is removed -37 -when the lift car is detected to be in the target door zone so as to minimise the amount of lift car movement if uncontrolled movement occurs.

In order to remove the time delay are the correct time, the lift controller 100, using the positioning system described above, identifies when the lift car has arrived at a target floor level, and, via the microprocessor, turns off the power supply to the overspeed governor solenoid (via a power control relay). The first relay status is monitored using a microprocessor input to ensure that the relay is operating correctly. The overspeed governor solenoid monitoring switch is also monitored by the microprocessor (via a solenoid monitoring relay). In addition to the microprocessor monitoring of the inputs, the solenoid monitoring relay is included in the electrical starting circuit so as to break the starting circuit to prevent the movement of the lift if the overspeed governor solenoid switch fails to open when the lift has stopped.

The monitoring of the solenoid monitoring relay confirms whether the solenoid is energised when the lift is running and de-energised when the lift is stationary. In addition, the operating status of solenoid monitoring relay is itself monitored using a normally-closed contact in the electrical safety starting circuit. If the solenoid does not energise and de-energised as expected, or if there is a failure of the solenoid monitoring relay to de-energise when the lift has stopped, the microprocessor will stop the lift operation and display or record "UM D FAULT". Wien a UMD fault occurs, the lift is out of service and will need resetting by a competent person. will prevent any further operations.

In order to prevent nuisance tripping when starting a lift journey, a maximum of 4 consecutive attempts are made before the microprocessor will stop any further lift operations, park the lift car, and require a competent person to reset the fault using the lift controller menu.

It will be understood that the invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention. Each feature disclosed in the description, and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination. Reference numerals appearing in the claims are by way of illustration only and shall have no limiting effect on the scope of the claims.

Claims

-38 -Claims 1 A lift control system for controlling movement of a lift car in a lift shaft, the lift control system comprising: a reference strip extending along the lift shaft, the reference strip carrying positioning information, preferably encoded positioning information; at least a first and a second sensor on the lift car arranged to read the reference strip; and a lift controller configured to: determine, based on information received from the first sensor, a first parameter relating to the movement of the lift car in the lift shaft, and to control movement of the lift car based on the first parameter; and determine, based on information received from the second sensor, a second parameter relating to the movement of the lift car in the lift shaft, and to modify the movement of the lift car based on the second parameter.
2 A lift control system according to Claim 1, wherein the lift controller is configured to modify the movement of the lift car if the second determined parameter deviates from a calculated profile for that parameter, preferably if the deviation exceeds a threshold value.
3 A lift control system according to Claim 2, wherein the second determined parameter is a speed of the lift car, and the lift controller is configured to modify the movement of the lift car if the determined speed of the lift car deviates from a calculated speed profile.
4. A lift control system according to Claim 2 or 3, wherein the threshold value varies in dependence on the position and/or speed of the lift car.
A lift control system according to any preceding claim, wherein the lift controller is configured to modify movement of the lift car by: correcting the speed of the lift car to maintain a calculated speed profile; or to decelerate the lift car to a, preferably predefined, lower speed, preferably wherein the lower speed is between 0.06 to 0.1 m/s.
6. A lift control system according to any of Claims 1 to 4, wherein the lift controller is configured to modify movement of the lift car by overriding the control of the movement of the lift car.
-39 - 7 A lift control system according to Claim 6, wherein the overriding the control of the movement of the lift car comprise calculating an updated speed profile based on the first and/or second determined parameter(s), and controlling movement of the lift car according to the updated speed profile.
8 A lift control system according to Claim 6, wherein the overriding the control of the movement of the lift car comprises applying a brake, preferably to: stop the lift car; or decelerate the lift car to a, preferably predefined, lower speed, preferably wherein the lower speed is between 0.06 to 0.1 m/s.
9. A lift control system according to any preceding claim, wherein the positioning information is encoded on the reference strip.
10. A lift control system according to Claim 9, wherein the encoding is a machine-readable optical encoding.
11. A lift control system according to Claim 9 or 10, wherein the at least two sensors are cameras configured to read the encoded positioning information from the reference strip.
12. A lift control system according to Claim 11, wherein the cameras are infra-red cameras, preferably wherein the lift controller comprises an infra-red illumination device to illuminate the reference strip.
13. A lift control system according to any of Claims 9 to 12, wherein the at least two sensors are offset from one another along the axis of the reference strip, preferably wherein the sensors read different parts of the reference strip.
14. A lift control system according to any preceding claim, wherein the at least two sensors are connected to the lift controller on separate channels of a controller area network (CAN).
15. A lift control system according to any preceding claim, wherein the lift controller is configured to control movement of the lift car according to a calculated speed profile by issuing speed commands to a motor, the motor arranged to drive movement of the lift car.
-40 - 16. A lift control system according to Claim 15, wherein the lift controller is configured to modify the movement of the lift car, based on the second determined parameter, by correcting or overriding the speed commands issued to the motor.
17 A method of controlling movement of a lift car in a lift shaft, the method comprising: reading, using at least a first and a second sensor mounted on the lift car, a reference strip extending along the lift shaft, the reference strip carrying positioning information, preferably encoded positioning information; determining, based on information received from the first sensor, a first parameter relating to the movement of the lift car in the lift shaft, and to control movement of the lift car based on the first parameter; and determining, based on information received from the second sensor, a second parameter relating to the movement of the lift car in the lift shaft, and to modify the movement of the lift car based on the second parameter.
18. A lift control system or method according to any preceding claim, wherein the first and/or second determined parameters comprises at least one of: a position of the lift car; a speed of the lift car; an acceleration of the lift car; and a jerk of the lift car.
19 A lift controller for controlling movement of a lift car in a lift shaft, the lift controller comprising: means for recording information about the positions of floor levels in the lift shaft; and means for calculating a speed profile of the lift car from an origin floor direct to a destination floor using the recorded information about the positions of the origin floor and destination floor levels, wherein the lift controller is configured to drive the lift car along the lift shaft according to the calculated speed profile 20 A lift controller according to Claim 19, wherein, to record the information about the positions of the floor levels in the lift shaft, the lift controller is configured to drive the lift car at least once along the length of the lift shaft, and to record a position measurement each time a floor level is detected, preferably wherein the floor level positions are detected from the positions of door zone vanes in the lift shaft.21. A lift controller according to Claim 19 or 20, wherein the magnitude of the jerk of the lift car during acceleration and/or deceleration of the lift car satisfies: -41 -Jerk PEAKJerk (0) = (1 cos(0)) where 0 = 180-t, and where t is the time since the beginning of the jerk, tj is the tj total duration of the jerk, and JerkpEAK is the peak jerk.22. A lift controller according to any of Claims 19 to 21, wherein the lift controller comprises means for receiving user input of at least one parameter to characterise the speed profile, and wherein the lift controller is configured to calculate the speed profile of the lift car based at least partially on the at least one parameter.23. A lift controller according to Claim 22, wherein the at least one parameter relates to one or more of an average acceleration or deceleration; a degree of rounding of the acceleration or deceleration phases of the speed profile; a jerk balance between the beginning and end of the acceleration and/or deceleration phases; a minimum time on high speed; a finish profile distance; and/or a finish profile correction.24 A method of controlling movement of a lift car in a lift shaft, the method comprising: recording information about the positions of floor levels in the lift shaft; calculating a speed profile of the lift car from an origin floor direct to a destination floor using the recorded information about the positions of the origin floor and destination floor levels; and driving the lift car along the lift shaft according to the calculated speed profile.A brake controller for a braking system for a lift, the braking system comprising at least one actuator arranged to actuate the brake between an applied state and a released state, the brake controller comprising: means for providing a power supply to the braking system to activate the at least one actuator; and means for controlling the power supplied to the at least one actuator, wherein the brake controller is configured to control the power supplied to the at least one actuator: at a lift power to actuate the brake from the applied state to the released state; and at a hold power to retain the brake in the released state, wherein the hold power is lower than the lift power.-42 - 26. A brake controller according to Claim 25, comprising a varistor connected, in use, in parallel with the at least one actuator.27. A brake controller according to Claim 25 or 26, comprising a rectifier, preferably a full wave rectifier, for converting an alternating current power supply to a direct current power supply to the braking system.28. A brake controller according to Claim 27, comprising a second varistor connected, in use, in parallel with the direct current output of the rectifier. 10 29 A brake controller according to any of Claims 25 to 28, wherein the means for controlling the power supplied to the at least one actuator is a means for controlling the voltage or current of the power supply, preferably the voltage of the power supply, preferably wherein the means for controlling the power supplied to the at least one actuator is a potentiometer.A brake controller according to any of Claims 25 to 29 wherein the brake controller is configured to control the voltage or current (preferably voltage) of the power supply: at a lift current or voltage (preferably voltage) to actuate the brake from the applied state to the released state; and at a hold current or voltage (preferably voltage) to retain the brake in the released state, wherein the hold voltage or current is lower than the lift voltage or current.31. A brake controller according to any of Claims 25 to 30, wherein the at least one actuator is at least one solenoid.32. A brake controller according to Claim 31, wherein the solenoid is arranged to actuate the brake between an applied state and a released state by moving the brake between an applied position and a released position, preferably against a biasing force.33 A brake controller according to Claim 31 or 32, wherein the means for providing a power supply is for driving a current through the at least one solenoid.34. A lift controller for controlling movement of a lift car, the lift controller comprising a brake controller according to any of Claims 25 to 33.-43 - 35. A lift controller according to Claim 34, wherein the lift controller comprises heatsink arranged to dissipate heat from the lift controller, and wherein the brake controller is in thermal contact with the heatsink.36 A method of controlling a braking system for a lift, the braking system comprising at least one solenoid arranged to move the brake between an applied position and a released position, the method comprising: providing a power supply to the braking system to drive a current through the at least one solenoid; and controlling the voltage of the power supply: at a lift voltage to move the brake from the applied position to the released position; and at a hold voltage to retain the brake in the released position, wherein the hold voltage is lower than the lift voltage.37 A lift controller for controlling movement of a lift car, the lift controller comprising: a monitoring unit for at least one solenoid of a lift brake or a lift overspeed governor, the monitoring unit comprising: at least one switch configured to move between an open and a closed position in dependence on the current through the at least one solenoid; and at least one relay configured to move between an open and a closed position in dependence on the position of the at least one switch, the relay configured to provide an input to a microprocessor of the lift controller wherein the lift controller is configured to control movement of the lift car in dependence on the input from the at least one relay.38. A lift controller according to Claim 37, wherein the monitoring unit is for two solenoids of a lift brake, the monitoring unit comprising two switches, each switch corresponding to one of the solenoids, and each switch configured to move between an open and a closed position in dependence on the current through its corresponding solenoid.39. A lift controller according to Claim 38, comprising two relays, each relay corresponding to one of the switches, and each relay configured to move between an open and a closed position in dependence on the position of the corresponding switch.-44 - 40. A lift controller according to Claim 39, wherein each relay is configured to provide an input to the microprocessor of the lift controller, and wherein the lift controller is configured to control movement of the lift car in dependence on a comparison of the inputs from the two relays.41. A lift controller according to any of Claims 37 to 40, wherein the monitoring unit further comprises means for monitoring the operation of the at least one relay, and to provide an input to a microprocessor of the lift controller.42. A lift controller according to any of Claims 41, wherein the lift controller is configured to control movement of the lift car in dependence on input from the means for monitoring the operation of the at least one relay.43. A lift controller according to any of Claims 37 to 42, wherein the control of the movement of the lift car by the lift controller comprises preventing movement of the lift car.44. A lift control system comprising the lift controller of any of Claims 19 to 23, 34, 35, or 37 to 43.45. A lift system comprising a lift car and the lift control system according to any of Claims 1 to 16, 18, or 44, the lift control system configured to control movement of the lift car.46. A system comprising two or more of: the lift control system according to any of Claims 1 to 16, 18 or 44; the lift controller of any of Claims 19 to 23, 34, 35, or 37 to 43; and/or the brake controller of any of Claims 25 to 33.