Patent GB-975493-A (GB)
Title: Control system for railway trains
IPC: B60L15/40
Filed: 1963-07-26
Abstract: 975,493. Control of D.C. motors. GENERAL SIGNAL CORPORATION. July 26, 1963 [Sept. 14, 1962], No. 29701/63. Heading H2J. [Also in Division G3] A system for automatically controlling a railway locomotive of the diesel-electric type comprises means for computing the power required to be exerted by the vehicle to adjust the speed to a desired value, and means for adjusting the power exerted by the vehicle to equality with said computed power. The rails are energized at various pulse rate codes selected in accordance with predetermined desired speeds for the train. When a medium speed track code rate is received by coils RC, relay 120R is picked up to energize relay 120RP, and relay START, a relay DIST ensuring that the entire train is moving before the higher throttle settings are called for. Resistor 51 is present to call for the third throttle power setting, the voltage developed thereacross being applied through wire 28 to positioner MP1, the wire being earthed until the brakes are released. Relay EPVR-L is energized so that valve EPV-L releases the vehicle brakes, the positioner MP1 causing reversible motor RM1 to operate arm 26 towards the + 3 position on resistor 27. When the arm 26 reaches the + 1 position, its advance is delayed by relay ODD-BP which has a slow release due to capacitors C1-C3 which are associated with its coil. However, if the speed of the train is above a predetermined value, the delay time of the relay OCC-BP is reduced. Similarly, the arm 26 is delayed at the + 2 position of control resistor 27. During movement of the arm 26, the throttle power setting is gradually increased due to selective operation of cam switches TCC-TC7, the control wires WEX, WAV, WCV being energized in sequence, and resistor LRR being adjusted to increase the excitation of field winding BF of traction generator MG. The train speed is detected by axle-driven frequency generator ADFG, converter 75 providing a voltage analogue of the speed for picking up relay DIST when the integrated voltage exceeds a predetermined value. When relay DIST picks up, relay START drops to change the demand speed from two to twenty-five miles per hour. The demand speed is pre-set at two miles per hour by connecting torque motor TM to a tapping on resistor 80, the analogue of the actual speed being connected to the other side of the torque motor. A plurality of cam switches D + “-D-4 are operated by the torque motor selectively in accordance with the magnitude of the deviation between the actual and demand speeds. When the demand speed is increased, motor RM1 moves the arm 26 towards the + 8 position on resistor 27, the throttle being advanced. The rate of advance is controlled by speed-registering relays 2.5 SR-20 SR associated with motor control wires WAV-WDV, the relays being selectively energized by cam switches CS3. The selective energization of the speed-registering relays is effected by comparing the voltage representing the actual speed with a reference voltage from potentiometer 93 at positioner MP4 associated with motor RM4. The horse-power developed by the traction motors is detected by measuring the voltage and current outputs from main generator MG, and applying appropriate signals to multiplier 108 associated with amplifier 109, the voltage derived from tap 111 being an analogue of the actual horse-power. The voltage appearing across resistor 116 is proportional to the quotient of the actual horse-power and speed, the voltage analogue of the actual tractive effort being applied to adder 119 which also receives a signal representing the inertial force of the train, i.e. the product of mass and acceleration. The acceleration is detected by differentiating the speed analogue voltage in circuit 120 associated with amplifier 122 whose output represents the inertial force, a sign chamber 125 being provided. The output of adder 119 represents the rolling resistance of the train and is applied to multiplier 128 which also receives a voltage proportional to the demand speed multiplied by a constant relating hose-power to tractive effort. The output of multiplier 128 is a voltage analogue of the horse-power necessary to maintain the train at the desired speed, and is used to control motor RM1 to call for the proper throttle setting or dynamic braking necessary to maintain the desired speed. The load regulator LRR attempts to maintain a constant generator load on the diesel engine for a given throttle setting. When the train speed exceeds the demand speed by one-quarter miles per hour, relay D + “R opens to energize over-riding solenoid ORS to adjust the regulator LLR towards the minimum field position until the overspeed condition is removed. If the actual speed stays excessive, the throttle setting is altered. Similarly, if the train speed drops below the demand value, the regulator LRR is adjusted to increase the generator voltage, followed by advance of the throttle, if necessary. If the computed horsepower calls for dynamic braking, the arm 26 is operated downwardly on resistor 27 to positions -1 to -5 wherein contactors DB1-DB2 are operated. Resistors DG are connected across motor armatures TMA, and resistor DBR is connected to supply selected voltages to field winding BF. The motor field windings are now supplied from generator MG. If the actual speed exceeds the demand speed by a certain amount, a service application of the air brakes is initiated, the motor RM1 being returned to the " idle " position. An emergency application of the brakes is provided if the service brake application is not effected within a set period. Oscillator 178 provides an output signal to amplifier 179 which passes a signal under over-speed conditions to apply the emergency brake. When the train is travelling at fifty miles per hour and the code rate received by coils RC calls for a reduction to twenty-five miles per hour, a thirty miles per hour over-speed filter is connected to amplifier 179 so that relay C drops followed by dropping of relays D + “R - D + 4R. This initiates a service application of the air brakes which are released substantially at the same time as the speed reaches twentyfive miles per hour. If the demand speed is decreased to zero, the brakes are applied and the throttle returned to the " idle " position. Below a certain speed, the air brakes are released and an independent locomotive brake is applied.