Patent GB-1162371-A (GB)
Title: Improvements in or relating to Positioning Apparatus
Inventor: HARTLEY FREDERICK WALTER
IPC: G05D3/20
Filed: 1965-09-15
Abstract: 1,162,371. Inductive control of vehicles. ELECTRIC & MUSICAL INDUSTRIES Ltd. 15 Sept., 1966 [15 Sept., 1965], No. 39303/65. Heading H4U. Apparatus for positioning a movable member, e.g. a vehicle or crane, at a selected one of a number of stations arranged along a path, comprises at least one conductor supplied with periodically varying current and arranged to provide in predetermined relationship with said stations regions in which there is a predetermined change in the direction of a periodically varying magnetic field, sensing means including a pair of spaced coils mounted on the movable member and connected so that a predetermined control signal is obtained when the coils bridge one of said regions and means including a reversible counter responsive to said control signals to position the movable member at the required station. The apparatus is described in relation to vehicles which are automatically guided to storage bins along a route in a warehouse. The vehicles may be mounted on rails or arranged to follow a leader cable. A conductor 1, Fig. 1, is laid along the path X X<SP>1</SP> of the vehicle and supplied by a generator 2. The conductor is arranged in loops with common boundaries A, B &c. and at these boundaries the current flows alternately in opposite direcdirections. Sensing coils 3, 4 are mounted one in front of the other on the vehicle so that their axes lie transverse to the path XX<SP>1</SP> and are connected in series so that the resultant output is zero when both coils are in the same magnetic field, as at 7. However, when the vehicle moves so that coils 3 and 4 bridge the region B the coil outputs will add and provide an alternating voltage at terminals 5, 6. When the coils bridge region A<SP>1</SP> a voltage of opposite phase will appear at terminals 5, 6. As described, only the signals at regions B are utilized and these are selected by comparison in a phase detector 8 with a reference voltage of the same frequency, picked up by a coil 9, Fig. 2, from a separate cable spaced to one side of the path X X<SP>1</SP>. The resulting output pulses are fed via a unidirectional limiter 10 to a reversible counter 11 which counts the pulses as the sensing head passes the points B the direction of the count being dedependent on whether the vehicle is travelling forward or in reverse. A signal representing the count corresponding to the destination of the vehicle together with the commands for the operation to be performed is either fed via terminal 17 into a store 18 or is introduced into the store as punched cards or the like. This information is transferred to detector 16 which detects the direction in which the vehicle must travel in order to reach the destination count and feeds a direction signal to a forward/ reverse selector 13 of the motor controller 14 to reduce the difference between the count registered at 11 and that supplied by store 18. When there is a difference between the two counts a " start " contactor 22 is operated to drive the motor 20 and when the counts become equal a signal from detector 16 causes the motor 18 to be stopped. Circuit 22 is then operated by a signal from store 18 to carry out the desired operation. When the bin operation is complete a signal is fed back to the store 18 so that the next destination may be presented to the detector 16.