ES357289A1 - Apparatus for driving a vehicle - Google Patents

Abstract

Apparatus for providing a signal dependant upon the speed of a vehicle moving along a fixed path comprises means providing gauging signals at points along the path means providing a reference signal of frequency much greater than the gauging signals and means for counting the number of periods of the reference signal between successive gauging signals, the counting means issuing a signal indicative of the count therein and being reset to zero at the occurrence of each gauging signal. In an automatic speed control system particularly for underground trains, a counter carried by the train counts clock pulses over predetermined lengths of track, trains being braked, driven or allowed to run on under headway according to whether the count is greater than, less than or equal to a fixed base number. A piloting cable is laid between the rails 10b with straight portions 11 separated by discontinuities 12 the cable carries an A.C. signal. The train carries three pick-up coils R, A, B. Coil R picks up the A.C. signal continuously and feeds it to a Schmitt trigger circuit 103 to generate the clock pulses. The coils A, B feed phase discriminator and shaping circuits to provide a reset pulse every time the coils pass over a discontinuity 12 in the cable. The reset pulses control a gate P which allows decade counters D1-D2 to count the clock pulses from the end of each pulse. During the pulse the counters are read and then reset. The reading is applied through decoders to a programme matrix MP which energizes an appropriate one of a set of memory cores MT 3 -MF 3 corresponding respectively to individual braking or traction steps on a controller (not shown). The speed of the train over particular portions of track (e.g. bends or stations) may be varied by varying the spacing between the discontinuities 12 or by supplying different frequency A.C. signals to that portion of the cable. When it is necessary to alter the speeds of all trains in the system (e.g. during rush hours) the frequency of the signals is changed. In an alternative arrangement, not requiring the cable, the reset pulses may be derived from a generator driven from the wheels of the train, the lengths of track then being all equal to the circumference of a wheel. The speed is controlled by altering the frequency of the A.C. signal which may be obtained from a straight cable along the track or from a clock pulse generator on the train whose frequency is altered by trackside units at suitable points.