WO2023111968A1

WO2023111968A1 - Improvements relating to laundry apparatus and/or their control

Info

Publication number: WO2023111968A1
Application number: PCT/IB2022/062341
Authority: WO
Inventors: Christopher Harold MATULIS; Jamal Azhar KOYA; Ethan Russell BOS
Original assignee: Fisher & Paykel Appliances Limited
Priority date: 2021-12-16
Filing date: 2022-12-16
Publication date: 2023-06-22
Also published as: CN116265640A; EP4448859A1; US20250084579A1; EP4448859A4

Abstract

A method of mitigating an out of balance washing load in a washing machine with a horizontal axis drum comprising: determining an indication of an angular position, and optionally a radial position, of a OOB mass of the washing machine drum, and controlling rotational speed of the drum so that, as the drum and OOB mass rotates, a rotational speed of the drum is varied relative to a usual speed based on the OOB mass so that an outward radial force on the washing load reduces below the inwards radial force and/or of gravity.

Description

IMPROVEMENTS RELATING TO LAUNDRY APPARATUS AND/OR THEIR CONTROL

FIELD OF THE INVENTION

The present disclosure relates to a method and apparatus for mitigating an out of balance mass in a laundry apparatus.

BACKGROUND

Typically a laundry machine (laundry apparatus) operates in one of two modes.

1. A cleaning mode in which a laundry apparatus drum rotates relatively slowly to tumble and/or agitate the laundry load (that is, laundry e.g. clothes, linen, and the like) and wash liquid inside the drum such that the washing load is cleaned by mechanical action.

2. A spin mode (also termed "spin cycle") in which the drum rotates at a relatively high speed ("spin speed") to remove liquid from the washing load by centrifugal force (for example to remove suds after the cleaning phase, to saturate washing load during the rinse phase, or to remove as much water as possible during the dehydrating phase).

During the spin mode, forces can cause the laundry load can to adhere to the inner surface of the drum and to rotate with it. This can cause an out of balance (OOB) condition where the mass of the laundry load is not evenly distributed about the centre of rotation of the drum while the laundry apparatus is operating in spin mode. This is undesirable. Spinning the drum in the out of balance condition can cause undesired vibrations and resonances that result in noisy operation and potential damage to the drive and suspension systems of the machine.

It is therefore an object of the present invention to provide an improved method and/or apparatus for mitigating an out of balance laundry load in a laundry apparatus which goes at least some way toward addressing one or more of the problems mentioned above and/or at least provides the public with a useful alternative. SUMMARY OF INVENTION

It is an object of the present invention to provide a method and/or apparatus for mitigating an out of balance mass in a laundry apparatus.

The present invention may be said to comprise a method of mitigating an out of balance washing load in a washing machine with a horizontal axis drum comprising : determining an indication of an angular and optionally a radial position of a OOB mass of the washing machine drum, and controlling rotational speed of the drum so that, as the drum and OOB mass rotates, a rotational speed of the drum is varied relative to a usual speed based on the OOB mass so that an outward radial force on the washing load reduces below the inwards radial force and/or of gravity.

Optionally the rotational speed of the drum is varied for less than a revolution of the drum.

The present invention may be said to consist in a method of mitigating an out of balance washing load in a washing machine with a horizontal axis drum comprising : determining an indication of an OOB mass of the washing machine drum, and controlling rotational speed of the drum so that, as the drum and OOB mass rotates, a rotational speed of the drum is varied, within one revolution of the drum, relative to a usual speed based on the OOB mass so that an outward radial force on the washing load reduces below the inwards radial force and/or of gravity.

Optionally determining an indication of an OOB mass comprises determining an angular position of the OOB mass.

Optionally wherein the rotational speed of the drum is varied based on an angular position of the OOB mass and/or washing load.

Optionally the angular position of the OOB mass and/or washing load is determined based on : a time, and/or an angular position of the drum, as the drum rotates.

Optionally the rotational speed of the drum is reduced also based on the radial position of the OOB mass. Optionally the rotational speed of the drum is controlled using a control signal with a profile that varies from a normal control signal.

Optionally the control signal varies based on: a time, and/or an angular position of the drum, as the drum rotates.

Optionally the control signal varies based on the angular position of the OOB Mass and/or washing load as the drum rotates.

Optionally the control signal to control a rotational speed of the drum comprises: o Angular start position/angular span/angular stop position of the rotational speed reduction o Slope of the control signal can determine among other things how quickly the speed reduces and/or the radial extent of the target region. o Magnitude of the control signal can determine how large the speed reduction is and/or the radial extent of the target region.

Optionally the control signal profile creates a rotational speed profile of the rotating drum that creates a target region which redistributes an OOB mass and/or washing load in the target region.

Optionally the target region comprises and angular span and a radial extent.

In another aspect the present invention may be said to comprise a laundry apparatus comprising : a drum, a motor to rotate the drum, one or more sensors, and a controller that receives input from the sensors and controls the motor to rotate the drum, wherein the controller is configured to mitigate an out of balance washing load according one or more methods set out herein.

In another aspect the present invention may be said to comprise in a method of mitigating an out of balance laundry load in a laundry machine with a horizontal axis drum, comprising the steps of: spinning the drum above a satellisation speed of the laundry load (which speed is optionally a constant speed); and within a single revolution of the drum, varying the drum speed by sequentially decreasing and then increasing the drum speed below and then above satellisation speed, to selectively cause laundry load in the drum to drop under gravity.

Optionally the rate at which drum speed is decreased to a speed below satellisation speed is more rapid than the rate at which drum speed is subsequently increased to a speed above satellisation speed.

Optionally the method further comprises the step of: determining a position (which is optionally an angular position) of an out of balance mass of the out of balance laundry load.

Optionally the step of varying the drum speed coincides rotation of the drum below satellisation speed with the position of the out of balance mass being at, near, or passing through, a high point in its rotation about the horizontal axis of the drum.

Optionally the method further comprises the step of: determining a target zone with an angular extent relative to the angular position of the out of balance mass, and optionally with a radial extent relative to the radius of the drum; and wherein, within a single revolution of the drum, drum speed is varied by sequentially decreasing and then increasing the drum speed below and then above satellisation speed, to selectively cause laundry load located within the target zone to drop under gravity.

Optionally the angular extent of the target zone is between about 0 - 90 degrees in either direction relative to the position of the out of balance mass; or optionally between about 0 - 45 degrees, about 0 - 30 degrees, about 0 - 15 degrees, or about 0 - 5 degrees in either direction relative to the position of the out of balance mass. Optionally the radial extent of the target zone is between about 25 - 100 percent of the radius of the drum; or optionally between about 40 - 100 percent, about 60 - 100 percent, about 80 - 100 percent, or about 90 - 100 percent of the radius of the drum.

Optionally one or more selected from the following are used as inputs from which to determine the position of the out of balance mass. a. motor torque, power, current, speed, or voltage; and/or b. a time (relative to a reference time point); and/or c. drum speed, drum angular position, drum linear acceleration and/or drum angular acceleration.

Optionally the position of the out of balance mass is determined using : d. sensor data, optionally selected from one or more of data from an accelerometer or gyroscope; and/or e. motor data, optionally selected from one or more of motor torque, power, current, speed or voltage.

Optionally the position of the out of balance mass is determined using only motor data.

Optionally, during the step of varying the drum speed by sequentially decreasing and then increasing the drum speed below and then above satel lisation speed, the rotational speed of the drum is controlled using a control signal with a profile that varies from a previous normal and/or constant control signal profile, and optionally has a pulsed profile.

Optionally the control signal varies based on one or more selected from: f. motor torque, power, current, speed, or voltage; and/or g. a time (relative to a reference time point); and/or h. drum speed, drum angular position, drum linear acceleration and/or drum angular acceleration; and/or i. the mass of the laundry load; and/or j. the size/diameter of the drum; Optionally the control signal comprises one or more selected from: k. an angular start position/angular span/angular stop position of rotational speed decrease and subsequent speed increase; l. a time (relative to a reference time point) at which rotational speed decrease and subsequent speed increase is initiated and/or concluded; m. a slope or rate of rotational speed decrease and subsequent speed increase; and/or n. a magnitude or amplitude of rotational speed decrease and subsequent speed increase.

Optionally the control signal profile creates a rotational speed profile of the rotating drum that selectively causes laundry load in the drum to drop under gravity; and optionally wherein the control signal profile creates a rotational speed profile of the rotating drum that selectively causes laundry load in the target zone to drop under gravity.

In another aspect the present invention may be said to comprise in a laundry apparatus comprising : a drum, a motor to rotate the drum, optionally one or more sensors, and a controller that receives inputs from the motor and/or sensors (if present) and controls the motor to rotate the drum, wherein the controller is configured to mitigate an out of balance washing load according to one or more methods set out herein.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7).

The term "comprising" as used in this specification means "consisting at least in part of". Related terms such as "comprise" and "comprised" are to be interpreted in the same manner. This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments will be described with reference to the following drawings, of which: Figures 1A, IB and 1C depict, schematically, the drum of a laundry apparatus in an Out of Balance (OOB) condition.

Figure 2A, 2B depicts a representation or model of the drum of a laundry apparatus in an OOB condition as shown in any one of Figures 1A, IB or 1C.

Figure 3 shows, schematically, a laundry apparatus for carrying out a method of the present embodiments.

Figure 4 shows an exemplary laundry apparatus for carrying out a method of the present embodiments, with a section taken through the cabinet of the laundry apparatus.

Figure 5 shows a cross section taken through the drum and driving motor assembly of an exemplary laundry apparatus for carrying out a method of the present embodiments.

Figures 6A to 6E show various relative angular positions of an OOB Mass of a satellised laundry load.

Figure 7 shows an exemplary cyclic variation over time in the driving torque of a motor rotating the drum of a laundry apparatus.

Figure 8 shows an exemplary angular spin speed profile of a laundry drum during the spin cycle.

Figures 9A to 17 show various motor speed/torque variations and OOB Mass positions to mitigate out of balance laundry loading in a laundry apparatus.

Figure 18 is a flow diagram showing a method of mitigating OOB laundry loading in a laundry apparatus.

Figures 19 to 22 show various washing load distributions and relative target zones. Figure 23 shows typical improvement in the OOB Condition by executing speed dips to redistribute laundry load mass inside the drum. DETAILED DESCRIPTION

Various embodiment of a laundry apparatus will be describe for assessing and mitigation out of balance (OOB) washing loads.

1. Out of Balance explanation

First, and explanation of out of balance washing loads in a laundry apparatus (also termed "laundry machine" or "washing machine", which can be used interchangeably) will be provided.

Typically a laundry machine (laundry apparatus) 1 operates in two distinct modes during its cycle: a) A cleaning mode in which a laundry apparatus drum 11 rotates relatively slowly to tumble and/or agitate the laundry load (that is, laundry e.g. clothes, linen, and the like) and wash liquid inside the drum such that the washing load is cleaned by mechanical action. In this mode there is relative movement between the washing load and the inner surface of the drum; and b) A spin mode (also termed "spin cycle") in which the drum 11 rotates at a relatively high speed ("spin speed") to remove liquid from the washing load by centrifugal force (for example to remove suds after the cleaning phase, to saturate washing load during the rinse phase, or to remove as much water as possible during the dehydrating phase). In this mode the drum 11 reaches a satellisation speed where the centrifugal force is sufficient to overcome gravitational forces on the laundry load, such that the laundry load is caused to adhere to the inner surface of the drum 11 and to rotate with it (also termed "plastered" or "satellised" condition of the laundry load - -see, e.g. Figure IB). It will be appreciated that "spin speed" and "speed" in this context relates to angular speed, and any reference to spin speed, angular speed (or angular velocity), rotational speed can be used interchangeable to described the rate of rotation (spin).

Referring to Figures 1A, IB and 1C, an out of balance (OOB) condition occurs when the mass of the laundry load 2 is not evenly distributed about the centre of rotation of the drum 11 while the laundry apparatus is operating in spin mode. Note, Figures 1A to 1C show diagrammatically a non-limiting example of the actual distribution of laundry that might cause OOB. Spinning the drum 11 in the out of balance condition can cause undesired vibrations and resonances that result in noisy operation and potential damage to the drive and suspension systems of the machine. In some cases, the vibration may be of such magnitude that the drum 11 is caused to strike a cabinet 12 of the washing machine.

In order to resolve or improve (more generally "mitigate") the OOB condition, the washing load may be redistributed more evenly about the centre of rotation. For example:

• Figure 1A shows an OOB condition wherein the mass of the washing load 2 is not evenly distributed about the periphery of the drum, but rather is concentrated at one circumferential region of the drum. In this case the OOB condition could be resolved or improved (together "mitigated") by shifting some of the load away from the region of mass concentration, so that there is a more even layer of washing plastered about the circumference of the drum;

• Figure IB shows an OOB condition wherein at one circumferential region of the drum there is no washing load mass 2 at all. In this case the OOB condition could be resolved or improved by shifting some of the washing load into the region of no mass;

• Figure 1C shows an OOB condition wherein a single item of the washing load (say a sheet or a towel) is rolled or bunched at a particular circumferential region of the drum 11. In this case the OOB condition could be resolved or improved by shifting the item in a way that causes it to unroll, unbunch or otherwise redistribute , and to lie more evenly about the circumference of the drum.

In the present embodiments, each of the OOB conditions shown in Figures 1A, IB and 1C can be represented/modelled, as shown in Figure 2A, 2B, as a point mass (OOB Mass) 4 acting through a centre of mass of the out of balance washing load. The mass is pressed radially outward by centrifugal force F as the drum spins at speed w. The higher the speed w, the greater the centrifugal force.

The OOB mass 4 is a notional mass with a notional position (a position that can change over time) that is not a mass of a real washing load 2 or its distribution, but provides a model/representation of such a real mass 2. Rotation of the out of balance washing load (e.g. as represented by rotation of the OOB mass) causes an oscillatory excitation of the drum (which is suspended upon springs inside of the laundry apparatus) and thus an oscillatory motion of the drum in a plane orthogonal to the axis of rotation, here represented by the arrows X and Y. The purpose of resolving or improving (mitigate) the OOB condition is, at least in part, to reduce the magnitude of this motion.

2. Washing machine apparatus with OOB functionality

An exemplary apparatus for carrying out the method of the present embodiments is described in relation to Figures 3 to 5.

In general terms, as shown in diagrammatic form in Figure the 3 laundry apparatus 1 (in this case a horizontal axis/front-loader laundry apparatus) has a motor 10, a horizontal axis internal drum 11 and an outer drum 5 suspended (e.g. by springs 18) in an outer cabinet ("housing") 12, a weight sensor 14, and a motor sensor 15. The motor drives the drum to rotate and rotationally oscillate in the axial direction along the x axis (see insert Figure 1). The output signals of the weight sensor 14 can be used to derive information representative of the load size (mass). The laundry apparatus also has an accelerometer 17 ("movement sensor") for detecting movement of the drums 5, 11. The output signals of the motor sensor 15 (which could be an angular position sensor, or an angular velocity sensor), weight sensor 14 and/or accelerometer 17 can be used to derive information representative of the drum 11 motion due to an OOB condition. Note, the weight sensor 14 and motor sensor 15 are optional and instead it is possible to determine load mass and motor speed "sensorlessly" via the motor current/torque (e.g. from output from a motor controller). A controller 16 controls the motor 10 to drive the drum 11 according to the present method.

Referring to Figure 3, the controller is connected to the motor 10 and/or motor sensor 15, accelerometer (or other movement sensor) 17, weight sensor 14 and any other sensors (e.g. water pressure sensors) of the laundry apparatus. (Note, these could also be provided in the example embodiment of Figure 4). The controller 16 can provide signals to drive the motor 10, which in turn drives rotation of the internal drum 11. The controller 16 is programmed among other things to receive input data, make a determination of OOB output parameters (OOB assessment - to be described later) in order to characterise the OOB condition, and then take appropriate action to resolve or improve (mitigate) the OOB condition (OOB mitigation). The accelerometer 17 (if used), weight sensor 14 (if used), motor speed 15 (if used) and/or position sensor (if used) and any other component that provides information from which the OOB condition can be characterised is termed an "OOB sensor". The OOB sensors might be used for other assessment and control also, in addition to OOB assessment and OOB mitigation. As described previously, the motor 10 itself can be used as an OOB sensor, to the extent that data from the motor (such as current, torque, position, speed and temperature) can be processed to provide information which may alone, or in combination with other information, enable the OOB condition to be characterised.

For example, the controller 16 could be programmed to take one or more of the following actions to resolve or improve (mitigate) the OOB mass 4, thereby to resolve or improve (mitigate) the OOB condition:

• stop or slow rotation of the drum;

• speed rotation of the drum;

• maintain the current speed of rotation of the drum;

• reverse the direction of rotation of the drum, or cause an oscillation of the drum in alternate rotational directions;

• execute a dip in the rotational speed of the drum, which causes at least some of the washing load to be redistributed and satellised at a new location; and

• alter the spin speed profile over the course of a drum rotation revolution so that, for example, there is a lengthening or shortening of the time period for which the drum spins at certain speeds.

Preferably the actions mitigate (e.g. eliminate or at least reduce) the OOB condition/mass 4 within one spin revolution of the drum, or within a small number of revolutions. Taking the actions can redistribute the real washing load mass 4, which can mitigate the OOB mass 4, thus mitigating the OOB condition. Reference to redistribution means some movement of real washing load. This can happen due to e.g. slowing the rotation such that redistribution happens due to gravity, friction, centrifugal action, bounciness or other forces.

Referring to Figure 4 a laundry apparatus 1 of the horizontal-axis (also termed "front-loading") variety is shown, as one example of a laundry apparatus as per the general laundry apparatus of Figure 2A, 2B. The front-loading machine includes an outer cabinet 12 with a front door 3 allowing access to a perforated rotatable inner drum 11 for holding a load of laundry such as clothing for washing, and mounted within the outer cabinet to rotate about a horizontal axis (x-axis). A generally cylindrical, fixed (non-rotating) outer drum 5 for containing washing liquid is mounted (suspended on springs 18) within the cabinet 12 around the rotating inner drum 11. A motor 10 is attached at the rear of the outer drum 5 to directly drive rotation of the inner drum 11 relative to the outer drum 5 about the horizontal axis.

Figure 5 shows, in cross section, the inner and outer drums 11 and 5, and motor 10, of the laundry apparatus of Figure 4. In Figure 5 the outer cabinet 2 is not shown. The stator 6 of an axial flux motor 7 is fixedly attached at the end of the (non-rotating) outer drum 5, for example by mounting to the bearing housing structure 21 which is held in the end wall 5a of outer drum 5. Rotor 8 external to the outer drum 5 is rotationally fixed to the outer end of a rotor shaft 9 which extends through a passage in the end of the outer drum 5 and engages with the rotating inner drum 11 at its other end. The rotor shaft 9 is mounted via at least one or more bearings 20 such as roller bearings, carried by the bearing housing component 16.

It will be appreciated that Figures 4 and 5 are examples only, and the method of the present embodiments could alternatively be carried out in a different laundry apparatus, such as one directly driven by some other type of electric motor (such as a radial flux motor), or in a machine that is not directly driven and is instead driven via a belt and/or gearbox. The laundry apparatus may be a horizontal axis machine, or a tilt-axis machine (for example a machine in which the drum 11 is inclined at a 45 degree angle).

3. Washing machine OOB method

A method of:

OOB assessment - that is, determining an OOB parameter (e.g. OOB condition and/or OOB mass), and then

OOB mitigation - that is OOB condition/OOB mass mitigation and/or washing load redistribution will be described, first in overview, then with examples. Together, these are referred to as the "OOB method"

3.1 OOB assessment/mitigation - overview

The method implemented by the controller can generally follow steps such as those shown in Figure 18.

The controller 16 starts the spin cycle of the washing machine 1, by operating the motor 10 to spin the drum 11, step 60. The controller 16 is configured to drive rotation of the drum during the spin cycle according to a (e.g. predetermined) angular speed profile. For example, the controller may operate the drum to spin according to a spin cycle speed profile as shown in Figure 8. This shows the spin speed over time, during the spin cycle 80. During the spin cycle, the spin speed has various stages, comprising ramp sections where the spin speed increases, and plateau sections where the spin speed stays constant for a period of time. For example, as shown in Figure 8, the spin speed profile comprises three stages 81, 82, 83, 84 the first stage comprising ramp section 81A and plateau portion 81B, the second stage comprising ramp section 82A and plateau portion 82B, the third stage comprising ramp section 83A and plateau portion 83B, and the third stage comprising ramp section 84A and plateau portion 84B . This is by way of example only, and other spin speed profiles could be used.

The OOB method of the present embodiments is implemented at one or more OOB decision points, a decision point typically being at (but not limited to) one of the speed plateaus, where the OOB Condition is substantially "steady". In this example, the method is performed at the first speed plateau 81B, which might typically be around about 93 rpm, but that is not limiting and is by way of example only. Alternatively, the method might be performed at a subsequent speed plateau e.g. 82B, 83B, 84B or a higher rotational speed. For example rotational speeds could be as high as 500 RPM (for example 100, 200, 300, 400 or 500 RPM). The spin speed is increased through at least the first resonant frequency of the suspended assembly and up to the first speed plateau 81B, by which point the load is centrifuged 43 so it is plastered 41 (due to centrifugal force) against the inside circumference of the drum 11, step 61. This can be termed as full "satellisation". Figure 8 shows the spin speed of the drum 11 over a traditional spin cycle 80. The internal drum 11 is driven through the speeds at which there is resonance of the suspended assembly (i.e. the drum, washing load and motor supported on springs inside of the cabinet), and then at a constant speed for periods of time, e.g. 81b, 82B, 83B, 84B. At the first period of constant speed, or speed plateau 81B, the washing load satellises 41. That is, the load is plastered relatively evenly in thickness and distribution to the inside surface of the drum 11 under centrifugal force. However as explained with respect to Figures 1A to 1C, some of the load might not be distributed evenly about the axis of rotation, and this can cause an OOB condition of the drum 11, that can be represented by a notional OOB mass 4 (as described above and with respect to Fig 2A), and the movement of which will be described next.

At a suitable point in the spin cycle 80 (such as at the first plateau 81B) , the controller 16 determines an out of balance (OOB) parameter (e.g. OOB Mass 4 and/or OOB condition), step 62. This could be information indicative of the position (e.g. angular position) and/or magnitude of a OOB Mass 4, and may additionally include information as to the distributed mass of the suspended assembly, and/or information about where the load mass is located along the axial direction of the drum. This OOB parameter can be determined in any of the methods known in the art for detecting and characterising out of balance loading in a laundry apparatus.

After determining the OOB parameter, the controller 16 determines if the OOB parameter (e.g. the OOB condition and/or OOB mass 4) is acceptable or, therefore whether redistribution is required, step 63. Again, there are various methods known in the art for determining whether the OOB parameter is acceptable, or whether the parameter exceeds certain thresholds above which vibration or movement of the drum is excessive or is predicted to become excessive at higher speeds. In general terms, if the OOB parameter is above a threshold or otherwise on the wrong side of a threshold, OOB condition is determined; and if the OOB parameter is below or otherwise on the correct side of a threshold, OOB condition is resolved. For example, such methods typically take into account whether the magnitude of the OOB Mass 4 exceeds a certain threshold, and the threshold to be exceeded may vary depending on where load mass is concentrated along the axial direction (with load mass concentrated near the front of the drum (distal-most from the bearings) considered to be more problematic than load mass concentrated near the rear of the drum and proximate to the bearings). If the OOB parameter is acceptable (e.g. OOB Mass is below the threshold), then the spin cycle is continued as per usual known to those skilled in the art, step 64. For example the spin speed may be advanced to the next speed plateau, where evaluation of the OOB parameter is repeated in the manner described above. However, if the OOB parameter is not acceptable, further action is taken to improve or resolve (that is, mitigate) the OOB Condition before increasing the drum speed.

The controller 16 then determines the angular position of the OOB Mass, step 65.

The OOB mass 4 and its movement is described further with reference to Figures 6A to 6D. These Figures show the 0, 90, 180 and 270 degree angular positions of the OOB Mass 4 during one revolution of the internal drum Il in the counter clockwise direction A (where the reference of a 0 degree angular position is set with the OOB Mass is at its lowest point of the revolution). In this reference system, the rotational bottom B is 0 degrees, 90 degrees is the right hand side R, the rotational top T is 180 degrees and 270 degrees is the left hand side L, but note the angular positions are a notional reference system for description purposes, and are not limiting. Any suitable frame of reference could be used.

In order to carry out the method of the present embodiments, the controller 16 determines the angular position of the OOB Mass 4 as the drum revolves, step 65. For example: a) accelerometer(s) (or other movement sensors) 17 attached to the internal and/or external drum 11 could be used to measure the amplitude of accelerations in the X and Y direction (as per Figure 2A, 2B) from which the angular position of the OOB mass 4 can be derived; and/or b) the angular position of the OOB Mass 4 may be determined by monitoring cyclic variations in the motor torque (or in some parameter indicative of or related to motor torque, such as current, amps or motor angular velocity or acceleration) which occur in response to a torque which the OOB Mass exerts on the drum. As shown in Figure 7, the motor torque reaches a maximum when the OOB Mass is at a 90 degree angular position, and thus, under gravity, exerts a negative torque in relation to the counter-clockwise motion of the drum. Conversely, the motor torque reaches a minimum when the OOB Mass is at a 270 degree angular position, and thus, under gravity, exerts a positive torque in relation to the counter-clockwise motion of the drum. The time at which the OOB mass reaches the 180 degree angular position (i.e. the highest point during a revolution) can be estimated as occurring roughly half-way between the occurrence of maximum and minimum motor torque.

The motor speed and/or position sensor 15 can be used for determining the angular velocity of the motor 10. For example a hall effect sensor or encoder could be used. However it is alternatively possible to use data from the motor, such as current, (or some other type of sensorless control methodology) to estimate the position and/or speed (that is, angular position and/or angular velocity) of the motor.

In at least some embodiments, in order to carry out the method of the present embodiments, the apparatus provides a method and/or apparatus by which to determine mass of the washing load 2. The weight sensor 14 can be used for determining the mass of the washing load. For example, the weight sensor 14 may be located in the feet 30 of the washing machine (see Figure 4), or attached at the suspension 18 (see Figure 3) in order to measure extension of the springs under the weight of the load. However it is alternatively possible to use data from the motor to estimate the mass of the washing load 2, for example, based on the torque required to accelerate the rotating inner drum from a first speed to a second speed, or based on the time that the motor spends coasting after briefly spinning the load in a dry condition.

So, based on the above, the controller 16 monitors the spinning drum 11 and determines and/or receives an OOB parameter, which indicates the presence/absence and/or severity of an OOB Condition/mass of the drum 11. As part of that the controller 16 may further determine and/or receive information indicative of the approximate position (that is, angular position relative to a datum, such as the rotational bottom/notional 0 degree angular position such as in Figures 6A to 6D) of the OOB Mass 4 as it spins with the drum 11.

It should be noted that while the specification refers to the angular position of an OOB mass 4, this OOB Mass is a notional point mass 4 at the circumference of the drum, that is a model/representation of the resultant force due to real OOB conditions (that is, due to a mass of a real washing load 2) in the drum. Thus there may not be an actual mass at the angular location of the OOB Mass 4 - for example, as shown in Figure 6E, there may be two real masses 2 in the vicinity of the OOB Mass 4, one at a positive angular location relative to the OOB Mass and one at a negative angular location relative to the OOB Mass. The method of the present invention proceeds on the assumption that at least some of the mass of the real washing load (real mass) 2 is likely to be within the vicinity of the OOB Mass 4, and thus taking action to redistribute items at or near the location of the OOB Mass 4 has a higher likelihood of improving or resolving the OOB Condition than can be achieved by redistributing items at random.

In general terms, to attempt to improve or resolve the OOB Condition, and attempt is made to redistribute the actual washing load (real mass) 2 so that the OOB Mass 4 is reduced or eliminated. The method and apparatus of the present disclosure determines a suitable variation of rotational speed and varies the rotational speed (also termed "angular speed") of the washing machine drum 11 at a target angular position of the drum rotation cycle, step 66. The variation of rotational speed is for less than/occurs within one revolution of the drum. Varying the rotational speed of the washing machine drum may redistribute the actual load, and as such the notional OOB Mass 4 is reduced or disappears. If the OOB Mass 4 reduces/disappears, it can be inferred that the actual washing load 2 has been at least partially redistributed which leads to an improvement or resolution of the OOB condition. At a general level, the method proceeds on the basis that by redistributing real washing load mass 4, which is modelled by the OOB Mass 4, there is a higher percentage chance of improving or resolving the OOB Condition.

The controller determines, step 66, an appropriate rotational speed variation to mitigate OOB based on the received information that:

A) indicates the size of the OOB Mass, and/or

B) indicates the radius R of the drum, and/or

C) indicates the angular speed of the drum/OOB Mass, and/or

D) indicates the angular position of the OOB Mass, and/or

E) indicates the size (volume and/or mass) of the washing load, and/or

F) indicates statell isation speed. The controller 16 controls, step 66, the rotational speed of the washing machine drum 11 by controlling the speed of the motor 10 based on the determined rotational speed based on the OOB condition/mass 4 that the controller 16 determines and/or receives input on.

For example, the rotation speed variation can be a speed profile ("mitigation speed profile"), that comprises a varying speed over time/angular position of the drum 11. In general terms, a speed profile could be as follows. During a revolution of the internal drum 11, as the angular position of the OOB Mass (while rotating with the drum) : a) approaches, b) is in the vicinity of, c) is at a target angular position, and/or d) leaves a target angular position 40 of the washing machine 10), the angular speed of the washing machine drum 11 is reduced. The angular speed is preferably reduced for less than one revolution of the drum, before it is returned to normal.

Preferably, the target angular position is at a point above halfway (e.g. above point R/90-degree angular position shown in Fig 6b) where the effect of gravity can pull mass 2 radially inwards/away from the drum, and/or cause laundry load to drop down to a lower part of the drum.. The speed is reduced to the extent that centrifugal force 43 on the OOB mass 4 is no longer sufficient to counteract the force of gravity G in order to keep the mass satellised during the top half of the rotation. Therefore the OOB mass is likely to drop under gravity G as deceleration occurs. Then, as the angular position of the OOB Mass 4 moves away from the position 40, or out of the vicinity of the position (e.g. a target zone, such as a wedge), the angular speed is increased and/or returned to normal so that the mass is once again satellised at the inner surface of the drum for subsequent rotations.

So, when the OOB mass 4 reaches a target angular position (or as the OOB mass approaches the target angular position), the drum 11 is decelerated to a second angular speed, and re-accelerated after leaving the target angular position back to its first or increased angular speed, causing a "speed dip" to be executed.

Deceleration of the drum to speed decreases the centrifugal force 43 on the laundry in the drum, allowing at least some of the laundry load mass 4 in the top half of the drum 11 to drop under gravity G and land at an alternate peripheral location of the drum. It is expected that the mass 2 may spread out as it falls and/or fall to a location where there was previously a localised area of low clothing mass (for example as shown in Fig IB), redistributing the mass of the clothing more evenly about the centre of rotation. The fallen mass will be satellised at the new location as the drum returns to its first speed or an increased speed. This will preferably occur within one revolution of the drum spinning, and with the drum continuing to spin at high speed after the speed dip has been executed.

Note, while an angular position of a OOB mass 4 is used as the reference point for changing speed, it could actually be a target region 70, such as described later with reference to Figure 20.

In some embodiments, the speed dip is executed so that the rate of deceleration is more rapid/occurs over a shorter time period than the subsequent rate of acceleration/time to return to satel lisation speed. For example, a drum spinning at approximately 93 RPM may be decelerated at a rate of around 1000 RPM per second, and then subsequently accelerated at a rate of around 50 RPM as it returns to satellisation speed.

In this regard it has been found advantageous to use the mass of the laundry load/drum to aid in execution of the motor speed dip, such that deceleration and acceleration during the speed dip may be synchronised with the rise and fall of the OOB mass during its rotation. For example, with reference to Figure SB and 7, it can be advantageous to decelerate as the OOB mass 4 is passing through the 90 degree position, at which point the negative torque exerted by the OOB mass 4 is at a maximum and can assist in a rapid deceleration of drum speed. Conversely, the torque exerted by the OOB mass as it falls from the top of the rotation (i.e. 180 degree position) to the bottom (i.e. 0 degree position) can be used to assist in accelerating the drum speed back to satellisation speed within a single revolution of the drum.

As one example (without limitation), during a spin cycle, the washing machine drum 11 is rotating at a first angular speed SI at which the washing load is fully satellised. Then, during a single rotational cycle, as the angular position of the OOB mass (while rotating with the drum) reaches a target angular position (see later for detail, but as an example this could be 90 degrees in Figure 6B), the drum is decelerated to a second angular speed S2, and re-accelerated back to its first angular speed (i.e. a "speed dip" is executed). In general terms, the drum is decelerated to speed S2 as the OOB Mass reaches, approaches or leaves a top 180- degree angular position (for example as shown in Fig 6C). The fallen mass will be satellised at the new location as the drum returns to its angular speed SI. This will preferably occur within one revolution of the drum spinning. More detail will be provided later with an example described in relation to Figures 9A, 9B.

Once the controller controls the motor to the speed profile, the controller 16 measures OOB mass 4/OOB condition again, step 62, and if not acceptable, step 63, determines and implements a rotational speed variation again; or if it is acceptable, step 63, continues with the normal spin profile, step 64. For example, After, or in parallel with, executing the "speed dip", the Out of Balance parameter will be monitored and determined again, step 62. If the speed dip has been effective in redistributing real load mass 2 such that the OOB Condition is resolved or improved to a level where the OOB parameter (e.g. OOB mass 2) is acceptable, then spinning can continue according to the usual profile 80, steps 63, 64. However, if the OOB parameter is unacceptable (indicating that a problematic OOB Condition still exists), step 63, the mitigation speed profile can be applied again to execute a further speed dip or series of speed dips. Of course, because of redistribution of the real load mass 2, the OOB Mass 4 may have changed in position, size and other parameters, and therefore the mitigation speed profile may also change such as the initiation timing, speed variation and/or target position/region for the new OOB Mass 2. However in some embodiments the mitigation speed profile is set (e.g. target position/region and corresponding speed variation), and the same mitigation speed profile is applied repeatedly with only the timing of the signal to be altered according to the angular position of the OOB Mass 2.

In more general terms, the varying of the rotational speed of the washing machine at target angular positions of the OOB mass 4 will, if necessary, be repeated until the controller 16 has determined that the OOB Condition/mass 4 has been sufficiently improved or resolved (e.g. OOB parameter is less than a threshold or otherwise on the correct side of a threshold), at which point rotation of the drum 11 will return to the predetermined angular speed profile of the spin cycle. For example, referring to Figure 8 and 18, the method might also be carried out multiple times, e.g. once at every spin speed plateau 81B, 82B, 83B. It is possible that even once a OOB mass/condition is mitigated at a first spin speed plateau, e.g. 81B, a new OOB mass/condition might occur as the spin speed ramps to a subsequent plateau, e.g. 82. Hence carrying out the method of Figure 18 at various times during the spin cycle can be done.

3.2 Spin speed variation example

Referring to Figure 9A, 9B, an example of determination and implementation of a mitigation speed profile will be described. Figure 9A shows a motor torque profile over time, with a variation at time Tl. Figure 9B shows an angular speed vs time (mitigation speed profile). By way of example, this will reference two spin speeds SI, S2 during a spin cycle. These are by way of example only and should not be limiting. Multiple speeds could be used, or ramping/varying speeds. In this case, SI, S2 refer to target speeds, and to get to those speeds the motor will pass through a range of speeds on the way.

In this case, by way of example, the OOB assessment can initially take place at the first spin speed plateau 81B, in Figure 8. Referring to Figure 18, step 66, and Figure 9B, the controller 16 determines mitigation speed profile that varies the motor angular speed between a spin speed SI and a lower speed S2 (that is, a motor speed dip), and controls the motor accordingly, through a control signal : a) SI typically coincides with the angular speed at a speed plateau of the predetermined speed profile of the wash cycle (for example, 81 of Figure 8). SI is above the speed required to satellise the washing load taking into account the radius R of the drum. Various methods are known in the art for determining satellisation speed (e.g. where F=mw2r, solving for w, where Mg>mw2r, and W < sqrt(g/r). b) Deceleration to S2 should effect a sufficient reduction in centrifugal force that at least some of washing load mass is allowed to fall under gravity G and land at an alternate peripheral location of the drum. S2 should, accordingly, be below the satellisation speed. In some embodiments S2 could be obtained empirically, noting that the time taken to effect the redistribution can be reduced by minimising the difference between SI and S2.

The controller 16 further determines a mitigation speed profile that will, by the desired time T1 (corresponding to a certain angular position of the OOB Mass 4), slow the drum 11 rotation to a speed S2 below the satellising speed, step 66, with the effect that real mass located within a "target zone" of the drum may fall under gravity G and be redistributed at an alternative peripheral location.

The mitigation speed profile varies the motor from the norm - the normal motor speed being one that rotates the drum at a constant rotational speed. The mitigation speed profile of this example has one or more of: a) a start time Ti and/or stop time, and/or a duration for motor speed reduction, and/or a target time Tl for arriving at speed S2, and/or a duration for staying at speed S2; b) slope or rate of acceleration and/or deceleration; and c) a magnitude determining the size of motor speed reduction, and/or a spin speed SI, and/or a target reduced speed S2.

As shown in Figures 9A and 9B, the control signal causes the drum to decelerate to S2 at a time Tl/180 degrees generally coinciding with the OOB Mass (or where used the target region) reaching, approaching or leaving a 180-degree angular position (for example as shown in Fig 6C, where the reference of a 0 degree angular position is set with the OOB Mass at its lowest point during the revolution). Various methods known in the art for determining the angular position of the OOB Mass are discussed above in relation to Figures 6A to 7.

By way of example, with reference to Figures 6A to 7, motor data can be used to determine the time at which peak motor torque occurs (Tmax), and this can be understood to reflect the time at which the OOB Mass reaches a 90-degree angular position. The time taken for the OOB Mass to complete a further quarter revolution to arrive at the 180-degree angular position (Tl) can then be estimated from the known angular speed (SI) of the drum. The control signal must therefore drive the drum to arrive at speed S2 approximately T1 seconds after Tmax. Because the deceleration is not instantaneous, the controller may cause the deceleration to be initiated at a time Ti which is prior to Tl. In some embodiments, the controller 16 may be configured to slow the drum as the OOB Mass reaches a certain angular position somewhat prior to, or after, reaching the 180-degree angular position, in which case Tl could be decreased or increased accordingly.

It will be appreciated that alternatively to driving the motor to vary rotational speed over certain time intervals, it is additionally or alternatively possible to drive the motor to vary rotational speed according to the angular position of the rotor of the motor itself (which is directly coupled to the laundry apparatus drum). In which case the control signal may include such parameters as a start and/or stop angular position, and/or a range of angular positions of the rotor over which rotational speed is varied, and/or a target angular position of the rotor for arriving at speed S2, and/or a range of angular positions of the motor during which the motor angular speed remains at S2. In general terms as skilled person will appreciate that determining to vary angular speed based on time or determining to vary angular speed based on angular position (of the drum) are interchangeable and just a matter of the control/sensor arrangement used. The examples herein are not limiting, and any manner of control that implements a speed variation at a suitable position/range of drum rotation can be used.

In this embodiment, the controller 16 determines the angular position of the OOB Mass, step 65.

At a general level, the OOB method proceeds on the basis that by redistributing real washing load mass 2 located at or near the OOB Mass 4, there is a higher percentage chance of improving or resolving the OOB Condition than can be achieved by randomly redistributing real load mass, or by redistributing real load mass that is distant from the OOB mass. That is, by decelerating the drum to S2 at about the same time that the OOB Mass reaches an 180-degree angular position, there is created a notional "target zone" 70 (see Figure 11, 12 or more generally Figure 20) about the OOB Mass, such that real washing load mass located within that target zone may be redistributed by the variation in drum speed. At its broadest level, the method will be effective if the "target zone" extends 90 degrees in either direction from the angular location of the OOB Mass, for example as shown by the shaded hemispherical region in Figure 11.

In this embodiment the motor speed control signal profile is specified so that it controls the motor drum 11 so the rotational speed reduction occurs at a range of angular drum rotation positions so that (at the radial and/or angular position of the OOB mass 4) the radially outward centrifugal force on the real mass 2 is less than the radially inward/gravitational force G on the real mass 2, so that the real mass 2 will de-satellise and fall away from the position it is in. It may fall directly down and/or tumble, in a manner that might redistribute the washing load and remove the OOB mass.

Referring to Figure 20, the drum speed reduction may occur during an angular span 71 creating a notional wedge shaped region (target region 70) , within which any real washing load mass located there will experience the reduced centrifugal force and may undergo redistribution. Typically, the speed profile will be such that the speed reduction occurs as the OOB mass 2 approaches, is in the vicinity of, and/or or is at the top 40 of the washing machine. However, this is not the full extent. The reduction could in fact take place at any point from between the halfway horizontal points 73A, 73B of the angular rotation, that is at any point within 180° angular rotation range - e.g. angles A, B, giving target region span C (= 180-A-B). The target region 70 will also have a radial extent R, determined by the rotational speed profile in the manner previously described.

So in general terms, the motor speed control signal can be varied, to alter the speed profile of the rotating drum, to create a target region 70 being defined by an angular span C and/or an angular start B and stop position A, and/or a radial span R being the radial extent from the centre of the target region.

It has been found that the angular extent of the target zone can be altered by manipulating the profile of the control signal as follows:

It can be appreciated that if the dip in motor speed is executed very rapidly, then there will be only a momentary reduction in centrifugal force as the OOB mass 4 passes the top of the drum 11, and only real washing mass located in the close vicinity of the OOB mass (for example mass located in the target zone (shaded region) in Figure 13) will fall and be redistributed. Thus it is possible to reduce the angular extent of the target zone by increasing the rates of deceleration and acceleration as parameters of the control signal. Figure 12 shows a control signal in which the rate of deceleration and acceleration has been increased (relative to the control signal shown in the preceding Figure 10). Figure 13 shows a resulting reduction of the angular extent of the target zone (compared to the target zone shown in the preceding Figure 11) so that the target zone extends only 40 degrees on either side of the OOB Mass. That is, the acceleration and deceleration parameters of the control signal may be chosen so that only real washing mass located in a target zone 40 degrees either side of the OOB Mass may be redistributed by the variation in drum speed, while mass outside of that target zone remains satellised.

Similarly, it is found that lengthening the amount of time spent at speed S2 could increase the angular extent of the target zone. However there is a limited time that can be spent at speed S2, seeing as the motor speed must return to SI (or at least to a speed at which the load is satellised) inside of the time taken for the drum to complete a single revolution, and preferably returns to SI (or at least above satelisation speed) within the time taken for the drum to complete a half revolution beyond Tl.

This is shown more generally in Figure 21, where a faster dip (see left hand side) has a lesser angle target range, and a slower dip (see right hand side) has a greater angle target range.

One reason that it may be desirable to alter the angular extent of the target zone on either side of the OOB Mass, is that, as explained in relation to Figure 6E, there is a chance that no real load mass 2 is actually located at the angular position of the OOB Mass 4. In this case, attempting to redistribute mass within the close vicinity of the OOB Mass 4 may not be successful (i.e. there is no real mass 2 there to redistribute) and the OOB Condition may not be resolved or improved. In this case, it may be desirable to repeat the "speed dip" with an increased angular extent of the target zone (right hand side Figure 21), in the expectation that real load mass not redistributed under the previous attempt may now be caught within the target zone and successfully redistributed.

It has further been found that the radial extent of the target zone can be altered by manipulating the profile of the control signal as follows:

Theoretically the angular speed needed to satellise the OOB Mass is dependent on the radius R of the drum (shown in Figure 15), and a value for S2 can be calculated accordingly. Alternatively a value for S2 can be derived empirically by satellising items at the periphery of the drum

However, if there is a full load of laundry in the drum 11, then not all of the real mass 2 will be located at the radius R of the drum. In this case the OOB condition may be improved or resolved by redistributing real mass located at a lesser radius R2 of the drum (for example, as shown in Figure 17). In order to redistribute load mass located at this lesser radius R2, it is not necessary to slow the drum as much as is required to redistribute mass located at the radius R.

Figure 16 shows a control signal in which the speed S2 has been increased (relative to the control signal shown in the preceding Figure 4). Figure 17 shows a resulting reduction of the radial extent of the target zone (compared to the target zone shown in the preceding Figure 15) so that the target zone extends to a radius R2, which is lesser than the radius R at which the OOB Mass is located. That is, the S2 parameter of the control signal may be chosen so that only real washing mass located in a target zone at a lesser radius than that of the OOB Mass may be redistributed by the variation in drum speed, while mass located outside the radial extent of that target zone remains satellised.

In one example, the mass of the washing load may be measured (by methods previously described), and a lesser radius R2 (compared to the maximum value of R) may be assigned if the measured load mass exceeds some threshold which is designated to indicate a "full" or large load. The lesser radial value R2 can be assigned because a more massive/full load is likely to have load mass located at a smaller radius R2 (for example, as shown in Fig 17) than a less massive/half load which is more likely to have load mass located near the periphery R of the drum (for example, as shown in Fig IB).

Therefore in the manner described above it is possible to calculate a control signal/speed profile that will slow the drum to a speed S2 below satellisation speed to effect redistribution of real mass within a defined target zone, the target zone being defined in terms of an angular and radial extent with respect to the angular position of the OOB Mass and the drum radius R.

Figure 22 shows some general control signal parameters, leading to mitigation speed profiles that lead to various target regions 70 for redistributing OOB that fall within the target region.

1.3.2 Example embodiment

An example of how an appropriate control signal profile is determined can be given in relation to a laundry washing machine with a washing load capacity of approximately 8kg and a drum radius of approximately 0.262m, spinning at the first speed plateau of the wash cycle spin speed profile at a rotational speed SI of around 93 RPM (9.7 rad/sec). Prior to beginning the spin cycle, it has been determined that the mass of the washing load is around 6kg : a) The satellisation speed for real washing load mass located just inside the radial periphery of the drum can be calculated as sqrt(G/.262) = 6.11 rad/sec or 58 RPM, speed S2 is set at approximately 58 RPM accordingly. b) Since the washing load of 6kg is % of the washing capacity of the machine, it can be determined that the load is large. In the case of a large load it is not desirable to target, for redistribution, real washing load mass located just inside the radial periphery of the drum - it is instead desirable to target real washing load mass located at a lesser radial distance R2. Speed S2 is accordingly modified (i.e. increased somewhat) to lessen the radial extent of the target zone, and S2 becomes 6.3 rad/sec or approximately 60 RPM. c) The time, Ttorque_max, which can be taken as the time that the OOB Mass reaches an angular position of 90 degrees, is determined from motor data indicative of the peak torque during each revolution. The time taken for the drum to spin a further quarter revolution at 93 RPM can be calculated as 0.166 secs, which is about the time that the OOB Mass will take to reach an angular position of 180 degrees. The controller determines a speed profile such that the drum will decelerate to S2 at a time Tl, about 0.166 secs after time T_torquemax. d) The control signal may be initiated at a time Ti just prior to Tl, for example time Ti may be approximately 0.15 secs after Ttorque_max. Rates of deceleration are determined in order to give the necessary reduction in angular speed from SI at time Ti, to S2 at time Tl, and a roughly equal rate of acceleration may be determined to increase angular speed back to SI. Because the rates of deceleration and acceleration are sharp, it is only real load mass located within the vicinity of the OOB Mass (i.e. within 40 degrees either side of the angular position of the OOB Mass) that is caught within the "target zone" for redistribution. Preferably the deceleration and reacceleration is completed within 0.33 secs of Ttorque_max (which is the time it would take the OOB Mass to travel a half revolution, at 93 RPM, from an angular position of 90 degrees to 270 degrees).

However, as previously explained, deceleration of the drum to speed S2 may occur slightly before or after the time Tl at which the OOB Mass is estimated to reach its 180 degree angular position. Experiments have found that initiating the control signal at a time Ti of between 0.15 - 0.2 seconds after time Ttorque_max can result in an improved chance of resolving or improving the OOB Condition by redistributing items located within the vicinity of the OOB Mass (compared to redistributing the laundry load at random).

Performing several speed dips in series may increase the chance that the OOB Condition is sufficiently resolved or improved by the time that steps 62 and 63 are repeated. As steps 62 and 63 take some time to perform, it is desirable to minimise the number of times that they must be performed during the redistribution process. For example, in some laundry apparatus, it has been found that using the above-described method for redistribution, OOB laundry loading can be acceptably improved or resolved inside of an average time of around 65 seconds.

Figure 23 shows typical improvement in the OOB Condition by executing speed dips to redistribute the load mass inside the drum. Here the "BE" value on the vertical axis is correlated to the drum energy due to wobble caused by OOB loading, and is an indication of the severity of the OOB Condition. As an increasing number of speed dips are performed, the BE value drops, indicating that the OOB Condition is being improved by the redistribution of real load mass within the drum.

In some embodiments, the OOB parameter is monitored/determined and assessed for acceptability (i.e. steps 62 and 63 are repeated) after every time that a speed dip (steps 65 and 66) is performed. However, in some embodiments, a series of speed dips may be performed (i.e. steps 65 and 66 are repeated several times over several different revolutions of the drum) before steps 62 and 63 are repeated. Where several speed dips are performed in series, the angular speed of the drum may each time return to its original angular speed of SI, or optionally at least to a speed which is above the satellisation speed and which might, for example, be a slightly slower speed than SI.

Claims

1. A method of mitigating an out of balance laundry load in a laundry machine with a horizontal axis drum, comprising the steps of: spinning the drum above a satell isation speed of the laundry load (which speed is optionally a constant speed); and within a single revolution of the drum, varying the drum speed by sequentially decreasing and then increasing the drum speed below and then above satellisation speed, to selectively cause laundry load in the drum to drop under gravity.

2. The method of claim 1 wherein the rate at which drum speed is decreased to a speed below satellisation speed is more rapid than the rate at which drum speed is subsequently increased to a speed above satellisation speed.

3. The method of claim 1 or claim 2 further comprising the step of: determining a position (which is optionally an angular position) of an out of balance mass of the out of balance laundry load.

4. The method of claim 3 wherein the step of varying the drum speed coincides rotation of the drum below satellisation speed with the position of the out of balance mass being at, near, or passing through, a high point in its rotation about the horizontal axis of the drum.

5. The method of claim 3 or claim 4 further comprising the step of: determining a target zone with an angular extent relative to the angular position of the out of balance mass, and optionally with a radial extent relative to the radius of the drum; and wherein, within a single revolution of the drum, drum speed is varied by sequentially decreasing and then increasing the drum speed below and then above satellisation speed, to selectively cause laundry load located within the target zone to drop under gravity.

6. The method of claim 5 wherein the angular extent of the target zone is between about 0 - 90 degrees in either direction relative to the position of the out of balance mass; or optionally between about 0 - 45 degrees, about 0 - 30 degrees, about 0 - 15 degrees, or about 0 - 5 degrees in either direction relative to the position of the out of balance mass.

7. The method of claim 5 or claim 6 wherein the radial extent of the target zone is between about 25 - 100 percent of the radius of the drum; or optionally between about 40 - 100 percent, about 60 - 100 percent, about 80 - 100 percent, or about 90 - 100 percent of the radius of the drum.

8. The method of any one of claims 2 to 7 wherein one or more selected from the following are used as inputs from which to determine the position of the out of balance mass. a. motor torque, power, current, speed, or voltage; and/or b. a time (relative to a reference time point); and/or c. drum speed, drum angular position, drum linear acceleration and/or drum angular acceleration.

9. The method of any one of claims 2 to 8 wherein the position of the out of balance mass is determined using : a. sensor data, optionally selected from one or more of data from an accelerometer or gyroscope; and/or b. motor data, optionally selected from one or more of motor torque, power, current, speed or voltage.

10. The method of claim 9 wherein the position of the out of balance mass is determined using only motor data.

11. The method of any one of claims 1 to 10 wherein, during the step of varying the drum speed by sequentially decreasing and then increasing the drum speed below and then above satellisation speed, the rotational speed of the drum is controlled using a control signal with a profile that varies from a previous normal and/or constant control signal profile, and optionally has a pulsed profile.

12. The method of claim 11 wherein the control signal varies based on one or more selected from: a. motor torque, power, current, speed, or voltage; and/or b. a time (relative to a reference time point); and/or c. drum speed, drum angular position, drum linear acceleration and/or drum angular acceleration; and/or d. the mass of the laundry load; and/or e. the size/diameter of the drum;

13. The method of claim 11 or claim 12 wherein the control signal comprises one or more selected from: a. an angular start position/angular span/angular stop position of rotational speed decrease and subsequent speed increase; b. a time (relative to a reference time point) at which rotational speed decrease and subsequent speed increase is initiated and/or concluded; c. a slope or rate of rotational speed decrease and subsequent speed increase; and/or d. a magnitude or amplitude of rotational speed decrease and subsequent speed increase.

14. The method of any one of claims 11 to 13 wherein the control signal profile creates a rotational speed profile of the rotating drum that selectively causes laundry load in the drum to drop under gravity; and optionally wherein the control signal profile creates a rotational speed profile of the rotating drum that selectively causes laundry load in the target zone to drop under gravity.

15. A laundry apparatus comprising: a drum, a motor to rotate the drum, optionally one or more sensors, and a controller that receives inputs from the motor and/or sensors (if present) and controls the motor to rotate the drum, wherein the controller is configured to mitigate an out of balance washing load according to the method of any one of claims 1 to 14.

16. A method of mitigating an out of balance washing load in a washing machine with a horizontal axis drum comprising : determining an indication of an angular position, and optionally a radial position, of a OOB mass of the washing machine drum, and controlling rotational speed of the drum so that, as the drum and OOB mass rotates, a rotational speed of the drum is varied relative to a usual speed based on the OOB mass so that an outward radial force on the washing load reduces below the inwards radial force and/or of gravity.

17. A method according to claim 16 wherein the rotational speed of the drum is varied for less than a revolution of the drum.

18. A method of mitigating an out of balance washing load in a washing machine with a horizontal axis drum comprising : determining an indication of an OOB mass of the washing machine drum, and controlling rotational speed of the drum so that, as the drum and OOB mass rotates, a rotational speed of the drum is varied, within one revolution of the drum, relative to a usual speed based on the OOB mass so that an outward radial force on the washing load reduces below the inwards radial force and/or of gravity.

19. A method according to claim 18 wherein determining an indication of an OOB mass comprises determining an angular position of the OOB mass.

20. A method according to any one of claims 16 to 19 wherein the rotational speed of the drum is varied based on an angular position of the OOB mass and/or washing load.

21. A method according to claim 20 wherein the angular position of the OOB mass and/or washing load is determined based on : a time, and/or an angular position of the drum, as the drum rotates

22. A method according to any one of claims 16 to 21 wherein the rotational speed of the drum is reduced also based on the radial position of the OOB mass.

23. A method according to any one of claims 16 to 22 wherein the rotational speed of the drum is controlled using a control signal with a profile that varies from a normal control signal.

24. A method according to claim 23 wherein the control signal varies based on: a time, and/or an angular position of the drum, as the drum rotates.

25. A method according to claim 23 or 24 wherein the control signal to control a rotational speed of the drum comprises: o Angular start position/angular span/angular stop position of the rotational speed reduction o Slope of the control signal can determine among other things how quickly the speed reduces and/or the radial extent of the target region. o Magnitude of the control signal can determine how large the speed reduction is and/or the radial extent of the target region.

26. A method according to any one of claims 23 to 25 wherein the control signal profile creates a rotational speed profile of the rotating drum that creates a target region which redistributes an OOB mass and/or washing load in the target region.

27. A method according to claim 26 wherein the target region comprises and angular span and a radial extent.

28. A laundry apparatus comprising: a drum, a motor to rotate the drum, one or more sensors, and a controller that receives input from the sensors and controls the motor to rotate the drum, wherein the controller is configured to mitigate an out of balance washing load according any one of claims 16 to 27.