Patent GB-1168079-A (GB)
Title: Motion Control System for Rapid Transit Vehicles
IPC: B61L3/12
Filed: 1966-12-13
Abstract: 1,168,079. Automatic train control. WESTINGHOUSE AIR BRAKE CO. 13 Dec., 1966 [15 Feb., 1966], No. 55705/66. Heading B7N. [Also in Division G3] In an automatic train control arrangement, the speed of the train is controlled in response to speed commands received from the wayside and in response to a stop command the train is braked in accordance with a distance/speed curve generated on the train. In response to a dispatch signal at terminal 63, a relay 14t is picked up to open the circuit to a door unit 68 to close the train doors and to apply battery to the contacts of the relays of relay bank 12. At this time a speed command signal is received from the track and applied at terminal 23 as a negative speed limit analogue signal. This signal is applied via diode 72 to the input of a desired velocity operational amplifier 7 which supplies a positive output signal at terminal 37. This is applied via line 74 to the input of a second operational " error " amplifier 10 which in turn supplies a negative signal which is a function of the difference between the limit speed and actual speed to the circuit 11. This circuit comprises a number of resistors and three amplifiers 58-60 which operate to energize their respective relays 12a, 12r, 12p at different levels of input signal. Since on starting the output of error amplifier 10 is a negative maximum all three amplifiers and relays are energized so that the brake application circuit is opened at contact 12ac, the brake release circuit is energized at contact 12rc and the train propulsion circuit is energized at contact 12pc. As the train moves off a velocity pick up 1 and pulse generator 2 supply negative output pulses at a frequency which is a function of the train speed and these are supplied via line 40 and diode 41 to reduce the value of the desired speed positive voltage applied to the error amplifier from amplifier 7. As the speed increases the negative error voltage from amplifier 10 decreases to a value which de-energizes the amplifier 60 and associated propulsion relay 12p and cuts off the train drive. Subsequent energization and de-energization of relay 12p maintains the train speed at the desired value. Should a lower speed now be signalled so that all relays 12 release and the brakes are applied, a feedback signal, which is a function of brake pipe pressure, is applied from unit 42 to the input of the error amplifier. With increasing braking pressure level this voltage reduces the error to a value sufficient to operate relay 12a so that the brakes are switched to the lap condition. On further reduction of speed relay 12r picks up to release the brakes and the train coasts until its speed drops below that required when relay 12p picks up and maintains the speed as previously described. On approach to a station stop the train passes an induction coil on the track which induces a signal in unit W.S. This operates a latching relay 4 which applies, via contact 4a, the output of pulse generator 2 to an integrator circuit 5. This supplies at the input of unit 6 a positive voltage which increases with distance travelled by the train. Unit 6 includes a number of function generators each comprising three resistors e.g. resistor 26 in the feedback path of amplifier 7, resistor 27 in series with the output of integrator 5 and resistor 28 from negative supply c, connected via a diode 32 to the input of amplifier 7. The function generators, only one of which is operative at a time depending on the value of the output voltage from the integrator, develop a positive voltage at amplifier output 37 which decreases at an increasing rate depending on the distance travelled by the train. The control arrangement acts to follow this stopping profile and brings the train to a stop at the station.