GB886166A - A system of automatically controlling road vehicles - Google Patents

Abstract

886,166. Automatic position and speed control systems. GENERAL MOTORS CORPORATION. Aug. 10, 1959 [Aug. 25, 1958], No. 27203/59. Class 38 (4). [Also in Group XL (c)] In an automatic control system for a road vehicle a pair of electric conductors are spaced in a regularly recurrent pattern along a desired course and a control apparatus in the vehicle detects the magnetic field due to an alternating current in the conductors. As shown, Fig. 3, a pair of conductors 22, 24 buried in a roadway are energized from an alternating-current generator 28. The magnetic field along the centre-line of the conductors is at a minimum where the conductors cross and the field in each loop 30 is reversed relative to the field in adjacent loops. Pick-up coils 34, 36 are mounted on the vehicle and the voltages induced are applied to capacitors 42, 44 through rectifiers 38, 40. The voltages across the capacitors are in opposition and are equal when the coils are symmetrically situated above the conductors. When the road vehicle is off-course, the voltage across the capacitors represents in magnitude and sign the deviation, and controls a steering servo 46 so as to correct the deviation. The recurrent pattern of the conductors causes the voltages induced in the coils 34, 35 to be modulated at a frequency dependent on the speed of the road vehicle, and by a demodulator 48, responsive to the modulation frequency, a speed-dependent voltage is derived and compared with a reference voltage from a demodulator 50 responsive to the frequency of the generator 28. The difference between the speed and reference voltages actuates a throttle servo 52 so as to maintain the vehicle speed constant. In another embodiment, Fig. 8, the conductors 66, 70 are disposed as shown and pick-up coils 76, 78 are positioned one loop length apart along the length of the vehicle and the voltage used in either coil is used to control the vehicle speed. The sum of the induced voltages in coils 76, 78 is substantially constant and can be used to transfer information, such as a voice signal or a command speed signal, to the vehicle. The command signal may be derived from a third cable laid in the road.