DE2045034B2 - Automatic steering device for a vehicle - Google Patents

Description

pending signal and means for generating a reference signal which is substantially constant is. It is expedient that the scanning devices each have pairs of spaced apart from one another Have take-up spools.

A further development consists in that the first and the reference signal from the scanning devices are each fed into the rotor bonds of the angle resolver and that the output signals from stator windings of the angle resolver are derived. It is useful that the output signals are each fed from the stator windings into the inputs of a Phaser.detektors.

The invention is explained in more detail below using an exemplary embodiment with reference to the drawing will.

F i g. 1 schematically shows part of a vehicle with an automatic steering device according to the invention and

F i g. 2 shows the circuit of the automatic steering device according to the invention in connection with a top view of the in F i g. 1 shown part of the vehicle.

The present invention is preferably, but not exclusively, used in the automatic Steering device for container trolleys. A typical container hand truck has eight wheels, four on each side, to achieve effective "four-wheel steering". Every wheel is going through its own double-acting hydraulic servomotor via corresponding electro-hydraulic valves driven. The wheels are connected to each other on each side by articulated rods, which are the right one determine the relative rotation of the wheels. They are also by shafts, connecting rods and Lever connected across the top of the cart so that the wheels are curved on the outside Track can take a smaller angle than the wheels on the inside. The cart is used to transport containers within a dock complex and to set them down at storage locations, before loading takes place. It is necessary to have a number of containers after being set down is precisely aligned with one another, and if the cart is steered by Hard, it is a very slow one Speed required to ensure accurate regulation. An embodiment of the The present invention, which will now be described, is used to provide a suitable automatic Steering device that works together with a hydraulic steering device for a trolley.

F i g. 1 shows one of the front wheels of eight wheels of a container trolley below its chassis 2. A fork 7 is articulated to the chassis 2 and has a pair of brackets 3 and 4 and holds the radiator on its axis. A hydraulic device is attached to the chassis 2, which has a hydraulic cylinder 5 and a rod 6 connected to the piston in the Zylhider 5 is coupled and acts on the edge of the fork 7 and so a steering for the wheel 1 when bumped or pulling the rod 6 causes. A feed pipe 8 contains pressure oil for the hydraulic cylinder 5. The rest of the chassis, other wheels, hydraulic controls, shafts, etc. are off Not shown for the sake of clarity, since in the present exemplary embodiment the regulation the steering is only effected on one front wheel, while the other wheels have a position as determined by the waves, etc.

The means for sensing the error in the steering of the wheels from a desired track is used now described. A wire 14 is buried in the ground and carries an alternating current. A pair of Coil assemblies 12 and 13 are mounted on a plate 11 at the end of parts 9 and 10, the extend from the brackets 3, 4. Each coil assembly contains a pair of coils, and the four Coils are wound to produce signals that are the sum and difference of the Wire 14 is intercepted signals. This is explained in detail on the basis of F1 g. 2 explained. The difference signal is thus representative of the lateral offset of the center of the plate 11 from the wire 14, and the sum signal is essentially constant. A rotor IS of an angle resolver is at the end a rod .16 attached, which is coupled to the fork 7 via bellows 17, so that it is with the RaJ 1 turns. The bellows 17 allow a vertical movement of the wheel 1. The staton windings of the resolver are located within the chassis 2, but are not shown. The rotor 15 and the The stator of the angle resolver and the circuitry associated with the coils will now be referred to by reference on F i g. 2 will be described.

The coil assemblies 12 and 13 each have pairs of coils 18 and 19 and 20 and 21, which are coupled so that the coils 18 and 19 are connected to one another in phase opposition and the difference signal generate while the coils 19 and 21 are connected in phase with each other and that Generate sum signal. The sum signal from the live end of the coil 19 is to one Preamplifier 23 out for the sum signal and the difference signal from the live The end of the coil 18 is led to a preamplifier 22 for the difference signal. The output signals of the Preamplifiers 22 and 23 are associated with corresponding windings 24 and 25 of the rotor 15 of the angle resolver guided. In Fig. 1, the preamplifiers 22 and 23 are arranged within the plate 11. That from a stator winding of the angle resolver captured signal is via an amplifier 28 to a Out of phase detector 30 and the signal picked up by a stator winding 27 is via an amplifier 29 supplied to the phase detector 30 as a reference signal. The output of the phase detector 40 is thus a signal, the phase of which is the direction and the magnitude of which is the amount of the lateral displacement of the center of the plate 11 represented by the wire 14. The error signal is in an amplifier 31 amplified and an electro-hydraulic control signal Valve 32 supplied which causes the hydraulic cylinder 5 to retract the rod 6 either or extend it and so steer the radiator to an angle that will reduce the error seeks. Turning the wheel 1 causes a rotation of the rotor 15, with the result that a A lower control signal is generated and a lower subsequent angular rotation signal is generated by the control system is required. In this way, the wheel is caused to follow wire 14, and it does so in one go Manner in which the angle of rotation of the control signal is substantially proportional to the lateral offset

is. At rest or when moving, a stable situation is achieved if the ratio of the difference and the total voltage is equal to the tangent of the angle of deflection of the front wheel. If the vehicle follows a curve, the wire 14 is thus offset with respect to the center line of the plate 11. The servo loop between the angle resolver and the hydraulic cylinder can thus be simpler Post-control servo. If this servo had a perfect quality, the entire servo loop would have a forward open loop transfer function of the form:

-v = arc tan

K _C AE \

In it is

<x = steering angle,
K _c = gain constant of the differential signal coils in volts / meter,

A = the ratio of the gain of the differential to sum amplifiers,
S = voltage at the buzzer signal coils,

the lateral offset of the center line
Plate 11 from wire 14.

The constants Kc and 5 depend on the design of the coil pairs, their geometrical relationship to the wire 14 and the excitation frequency of the wire 14.

For small error angles, the voltage coming from the stator winding 26 is proportional to the

ίο the total voltage impressed on the resolver. the Loop gain therefore varies with the height of the coil pairs. This difficulty can be substantial can be avoided by using an automatic amplification system that reduces the amplification of the Differential amplifier changes inversely proportional to the sum signal.

An embodiment is also possible which is designed similar to that mentioned above, in the case of dei However, the sum and difference signals are fed into the stator windings of the resolver and the dem Phase detector removed from the rotor windings for supplying the control signal supplied signals are.

For this 1 sheet of drawings

Claims (5)

1 2 to get the vehicle back on the desired route. The corrective torque is supplied by the steering motor with a variable 1. Automatic steering device for driving that is proportional to the error. That means, stuff, with a current-carrying electrical 5 that the correction variable is proportional to the error size Guide cable that is the desired route. This arrangement operates with the vehicle forward Vehicle and with driving speeds of up to a few kilometers per provided scanning devices, the Si hour satisfactory. The vehicle in which the signals as a function of the magnetic automatic steering device according to the aforementioned Generate field of guide cable, which is used in the British patent specification, is marked for a that the scanning speed of about 3 to 4 km per hour devices (12, 13) output signals designed in. Is the correction variable proportional to the an angle resolver (24, 25, 26, 27) can be fed in. The output signals generated by an upward speed of the vehicle but unsta-deflection angle of the vehicle from the bil. Desired route depend and in a single case known from the British patent direction (32, 8, 5, 6) can be fed, the device is the steering via a direct Steering device (1, 7) of the vehicle has a mechanical steering connection that can cause the same problem angle correction signal, which the vehicle can also occur with hydraulic steering, returns to the desired route. ₂₀ in which a substantial compliance due 2. Steering device according to claim 1, characterized in that duct elasticity is present. Also marked, that the scanning devices (12, which usually act to control the hydraulic 13) Means (18, 20) for generating a first, see steering device used electro-hydraulic the size and direction of the deviation, valves see speed changes, the prodes Vehicle from the desired route 25 are proportional to the error. Is thus the steering dependent signal as well as means (19, caused automatically by a signal of a vehicle, 21) to generate a reference signal that represents the error in the steering and that is essentially constant. is fed to an electro-hydraulic valve, 3. Steering device according to claim 1 or 2, so the resulting control loop tends to unsteady characterized in that the scanning device ₃₀ bilität when the correction variable to the error proportions (12, 13) is each pairs of tional at a distance. mutually arranged take-up reels (20, The invention is based on the object of providing a 21 and 18, 19). to create an automatic steering device that 4. Steering device according to claim 2 or 3, significantly greater vehicle speeds, characterized in that the first and the ₃₅ is stable. Reference signal from the scanning devices (12, 13) The object on which the invention is based in each case in rotor windings (24, 25) of the Winkeire- is solved in that the scanning device solvers (15) can be fed and that the outputs emitted signals in an angle resolver output signals from stator windings (26, 27) can be fed in that generates output signals that Angular resolvers are derived. ₄₀ from a deflection angle of the vehicle 5. Steering device according to claim 4, characterized in that it depends on the desired travel path and characterized in that the output signals from the can be fed into a device, that of the steering stator windings (26, 27) a steering angle correction one in each case to the input device of the vehicle Phase detector (30) can be fed. signal that the vehicle on the desired 45 th route back. In the case of an automatic steering device, the invention measured the scanning device that the vehicle from its predetermined route deviates, the angle resolver determines that the 50 deviation corresponds to a certain angle. The invention relates to an automatic steering mechanism. This angle signal then causes the direction to be rotated for a vehicle, with a current-flowing steering system by the respective angle. If, for example, the electrical guide cable that determines the angular resolver determines that the scanned deviation defines the desired travel path of the vehicle and corresponds to an angle of 5 ~, then the steering devices provided on the vehicle are used. 55 wheels turned by 5 ^: As the vehicle returns to the signals depending on the magnetic travel path desired, the guide cable generating field decreases. The angle signal from the angle resolver until it, by British patent specification 1 097 141, a steering device that automatically returns when the vehicle is on its way back is known, which is a driving, and the steering angle is also zero on a predetermined route that leads 60 is. Thus, the correction itself is proportional to the error de- fect by a guide cable on or in the ground and not the value with which the correction is fin- ished and through which an alternating current flows. That is effected. This results in a substantially magnetic field of the guide cable, which induces a more stable automatic steering device at substantially voltage levels in a pair of pick-up coils. higher forward speeds of the vehicle.
If the vehicle deviates from the desired route 65. A further development of the invention consists in the fact that the scanning devices in the two pick-up coils for generating a voltage are different, and that differ from the size and direction of the deviation The differential signal then feeds a steering motor that diverts the vehicle from the desired route.