Patent GB-1324675-A (GB)
Title: Automatic motorway driving system for motor vehicles
IPC: G05D1/02
Filed: 1972-01-25
Abstract: 1324675 Leader gear systems; inductive signalling FIAT SpA 25 Jan 1972 [29 Jan 1971] 3493/72 Heading H4U In a system for automatically controlling motor vehicles along a highway by means of energized inductive loops spaced along the highway which co-operate with pick-up means on the vehicle, the vehicle is provided with an A.C. generator and means for coupling the output of the generator into the inductive loops to provide the energization thereof. As shown in Fig. 1, a carriageway 1 of a motorway is provided with inductive loops 7, 7<SP>1</SP> which are spaced at regular intervals P in the normal driving lane and buried. Loops 8, 8<SP>1</SP> are similarly arranged in the passing lane and are provided with portion 9, 9<SP>1</SP> which fill the gaps p. The vehicle is provided with a low-frequency generator G, Fig. 4, connected to a coupling coil T on the front of the vehicle which induces an E.M.F. into the loop 7 over which the vehicle is located, this voltage being arranged to increase progressively in frequency as the vehicle passes from the start to the end of each loop. This signal is picked up by a pair of coils R1, R2, at the rear of the vehicle, symmetrically spaced about its longitudinal axis, and is supplied via amplifiers 10, 12, narrow band filters 14, 16, rectifiers 18, 20 and low pass filters 19, 23 respectively to the two inputs of a differential amplifier 22 controlling via amplifier 24 the steering servomechanism 26 to keep the vehicle on its course N. The filters 14, 16 include, for example, varactor diodes, controlled by the output of generator G so that they are always tuned to the instantaneous frequency from the generator. The repetition frequency of the pulses generated by the interaction of the vehicle with the series of loops 7, 7a, provides a measure of the speed, this train of pulses being taken from the output of rectifier 20, converted to a corresponding voltage at 28 and compared in a differential amplifier 32 with a reference voltage from source 36, representing the desired speed. The output of amplifier 32 controls via amplifier 38 servomechanism 40 operating the throttle, and also via OR gate 49, amplifier 50 and servomechanism 52, controls the brakes. The output of rectifier 20 is inverted at 42 to trigger the generator G and initiate the frequency scanning operation. When two vehicles are located over the same coil, the vehicle following receives its own frequency and a higher frequency emitted by the preceding vehicle and this effect is used to ensure that the vehicles are spaced at a safe distance apart by supplying the output of amplifier 12 to a diode 44 and extracting the difference frequency via a filter 45. The output of filter 45 will have a frequency proportional to the distance between the vehicles and this frequency is converted into a corresponding voltage at 46, inverted at 47 and supplied via gate 48, OR gate 49 and amplifier 50 to control the brake servomechanism 52. To ensure that the gate 48 only opens when the additional frequency picked up is higher than that of generator G, the output of amplifier 10 is supplied via a filter 62, which is controlled by the output of generator G to block the frequency transmitted by the loop T, to a frequency-tovoltage converter 64. The output of converter 64 is compared at 66 with the output of filter 14 similarly converted to a voltage at 68, the output of the differential amplifier 66 being positive if the frequency from filter 62 is higher than that from filter 14 and negative in the opposite case. A detector 70 provides an output only if its input is positive and this output enables the gate 48. Where it is desired to reduce the speed to lower values than the safe maximum speed, e.g. on corners, the buried loops are of reduced length to provide a higher pulse repetition frequency from rectifier 20. A warning of a vehicle about to overtake is provided by pick-up coil R2 receiving signals from the supplementary loops 9, 9<SP>1</SP> in normally blank periods. The output of amplifier 12 is rectified at 54 and supplied via a gate 56 to operate an indicator 58. A bi-stable 60 is set by the output of inverter 42, indicating the end of a loop 7 and reset by the leading edge of the pulses from rectifier 20, indicating the start of a loop 7 and the gate 56 is enabled only when the bi-stable is set.