Patent GB-1490533-A (GB)
Title: Automatic vehicle operation system
IPC: B61L27/04
Filed: 1974-09-27
Abstract: 1490533 Railway control GENERAL SIGNAL CORP 27 Sept 1974 [28 Sept 1973] 42091/74 Heading B7N [Also in Division G3] In an automatic rail vehicle operation system vehicles are automatically controlled in response to speed and stopping signals transmitted from the wayside. The signals are transmitted to the vehicles by combinations of four signals of frequency F1-F4, the speed signals combining speed commands and speed limit, e.g. M/H representing a command of medium speed and a limit of high speed and the stopping signals are of two kinds commanding a stop from medium or low speed respectively. The signals are decoded in unit 100 and the command signals are transmitted to analogue speed selector 101. The selector 101 supplies a fixed voltage representing required speed to velocity command 102 for application to summing amplifier 104. Tachometer pulses from a generator on the vehicle are applied to compensate circuit 111 where their rate can be modified if necessary to compensate for wheel wear and the compensated pulse train, each pulse representing a predetermined amount of vehicle travel, is applied to a frequency voltage converter 110 producing a voltage output representing actual speed which is also applied to the summing amplifier. The actual speed signal is also applied to a rate circuit 106 which supplies a rate of change of speed signal to summing amplifier 107 which in addition receives an input from an accelerometer providing an output proportional to the total acceleration on the vehicle due both to the track grade and the rate of change of speed. The amplifier 107 supplies the grade acceleration signal as a third input to summing amplifier 104 which thus provides a speed error signal which is compensated for track grade and this is applied to limit circuit 103 serving to limit the amount of error signal. The output from the limit circuit which is a measure of required acceleration is applied to summing amplifier 105 with the output of the accelerometer. The amplifier supplies a signal equal to the required change in tractive effort to bring the actual speed into line with that required within allowable acceleration limits. This signal is applied to a jerk limit circuit which acts to limit the rate of change of tractive effort taking into account the vehicle weight and its output is applied via integrator 113 to the vehicle speed control apparatus in which, in dependence on its sense, it controls either the vehicle traction motor or the brakes. When one of the stop signals is received this is applied to stopping profile generator 109 to select a value of distance to go depending on whether the vehicle has to stop from medium or low speed. This distance to go is represented as a fixed number in a counter which is then decremented as the vehicle proceeds by the compensated tachometer pulses. The number in the counter is applied to a digital to analogue converter which supplies a distance to go voltage to velocity command 102 which interprets this as a velocity command. When this drops below the velocity command supplied from the analogue speed selector 101 it controls the vehicle speed as described to bring the vehicle to a halt.