Patent GB-1160441-A (GB)
Title: Improvements in and relating to Automatic Control Systems for Vehicles.
Inventor: WELCH BRIAN RICHARD
IPC: G05D1/02
Filed: 1966-03-25
Abstract: 1,160,441. Leader gear systems. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 17 March, 1967 [25 March, 19661, No.13411/66. Heading H4U. A system in which a self-propelled automatically-steerable vehicle is caused to follow automatically a path defined by an electrically energized guide wire comprises one or more guide wires defining intersecting paths for the vehicle, and means for providing a signal at a predetermined position of a vehicle travelling along one of two paths towards an intersection to initiate a predetermined operation of the vehicle steering to turn the vehicle from a direction along said one path to a direction along the other path. The system is described in relation to a tractor drawing an implement, a land area to be worked being laid with a parallel system of field guide wires 1 to 8, Fig. 2, which are connected at one end to a first headland guide wire HW1 and at the other end to a field controller FC for selectively energizing the field guide wires. At this end a second headland wire HW2 is laid as shown and a signal wire TW crosses each of the wires 1 to 8 at two positions. In the field controller, Fig. 3, the field guide wires 1 to 8 are connected to a loop selector LS controlled via receiver R by a signal from the tractor and are selectively energized from an oscillator GO via switches S1, S2. The headland wire HW2 is also energized by the oscillator GO. The field guide wires can also be energized by an oscillator TO under the control of bi-stable BS controlled by a signal from the tractor via receiver R. An oscillator SO energizes the signal wire TW. On the tractor, Fig. 4, three sensing heads are mounted, one SS causing the tractor to follow a field guide wire by controlling the steering, a second TS responsive to energization of the signal wire TW to initiate a predetermined operation to cause the tractor to turn away from a field guide wire and into line with a headland wire HW1 or HW2, and a third GS for sensing the energization of a field guide wire while the tractor is following a headland wire, to initiate a turn from the headland to the field guide wire. The head TS also controls the tractor-drawn implement so that it is raised while the tractor is on the headland. The output of head SS is supplied to a phase detector PD which via a switch SW1 and circuit SCC controls valves SCV operating the steering. An output from the head TS is detected at TD and supplies a counter CC counting the number of times the head TS is energized, which is connected. to a circuit SPC controlling the lateral displacement of the head SS. The counter also supplies a circuit FWC which supplies a signal to a transmitter T to provide via receiver R a signal to cause the controller, Fig. 3, to change the guide wire or wires energized after a predetermined count. The detector TD is also connected via a delay TDC and an OR gate to trigger the switching circuit SW2 which also has a control input from head SS so that a signal from either head GS or TS operates switch SW2 to allow a signal from head SS to pass via a null detector ND to control the reset of switch SW1 and also to provide an input for the transmitter T. Signals from head GS are detected at GD, counted at GC and after a predetermined count an output is supplied via the OR gate so that a voltage FLV causing full lock is applied to the steering circuit until a reset signal from detector ND restores SW1 to the normal position. Control circuit SCC via contacts C2, C3 also effects differential braking of the rear wheels through valves BCV. In operation, assuming that the tractor is proceeding along guide wire 1 towards headland H1 (the loop being completed by guide wire 5), when the head TS approaches wire TW the circuit 1CC initiates the lifting of the implement and after a delay at TDC the switch SW1 is triggered so that voltage FLV is applied and turning and differential braking effected. After a further delay at DC the switch SW2 is operated, the tractor having turned away from the guide wire so that there will be no signal from head SS. When the tractor has turned sufficiently the signal from headland wire HW1 via head SS and null detector ND resets switch SW1 so that the tractor proceeds along the headland wire and also sends a signal, via transmitter T to the controller to cause it to energize temporarily the guide wire 4 from oscillator TO. When head GS approaches guide wire 4 a similar turning operation is initiated turning the tractor into the path of guide wire 5 the signal wire TW then causing the implement to be lowered. On completion of the turn a signal is sent back to the controller to terminate the energization of wire 4. Alternatively all the guide wires between the pair in use may be energized temporarily and the tractor provided with a counter for counting the successive signals as the tractor passes along a headland. Means may be provided to enable the tractor to reverse on a headland. The sensing heads TS, GS may be replaced by a single head and the appropriate control signals provided by modulating a carrier with two audio frequencies which are selected by filters after demodulation. The transmitter T and receiver R may operate by radio or by inductive coupling.