Patent GB-1465195-A (GB)
Title: Counteraction of wheel slip and skidding in motor-driven rail vehicles
IPC: B60T8/17
Filed: 1974-04-04
Abstract: 1465195 Automatic control of vehicle acceleration and deceleration ASEA AB 4 April 1974 [6 April 1973] 14921/74 Heading G3N A motor-driven rail vehicle having at least one driving wheel driven by a driving motor is provided with means for preventing wheel slip or locking and comprises means for sensing angular acceleration of the wheel and means for controlling the torque of the motor, the sensing means effecting control on the torque controlling means whereby when an acceleration occurs, the absolute value of which is greater than a predetermined first value, the torque controlling means is arranged to reduce the torque at a particular rate, to continue to reduce the torque at a lower rate when a predetermined low first torque value has been reached and when the acceleration has decreased to a predetermined second value the torque is increased. As shown, a D.C. motor M is supplied via controlled rectifier SR. The desired speed n of the wheel is set at potentiometer P1 which supplies a voltage to a summing device S1 where a subtraction of the actual speed of the wheel as sensed at tachogenerator TG is made and the result of this subtraction is applied to a speed regulator NR. The output of this regulator constitutes a current reference signal which is applied to a second summing device S2 for subtraction with the actual motor current sensed at I. This difference is applied to a current regulator IR to control the output voltage of converter SR. Two limiting amplifiers BF1, BF2 affect the current reference signal such that this signal cannot exceed the value BI1, BI2 applied to the amplifiers respectively. Signal BI1 is taken from a potentiometer P2 to set I max , and the signal BI2 is derived from acceleration sensing circuitry. The output of tachogenerator TG is differentiated at DK to provide dn/dt and after filtering, this is applied to two bi-stable devices NV1, NV3. The outputs of these devices are rectified at D1, D3 and passed to a sign-reversing integrator IN, the output c of which constitutes the signal BI2. The signal I ref  is also applied as input to a bi-stable device NV2 which is also connected via diode D2 to the integrator input. In operation without wheel slip, no signals will be present across resistors R1 and R2 and a constant negative voltage across R3 ensures that signal BI2 is at its maximum positive value. In the event of slip under acceleration, differentiator DK provides a sudden large signal which causes bi-stable NV1 to switch to a positive output and to drive the output of integrator IN rapidly downwards, thereby reducing I ref  and the armature current of motor M. When the current I ref  signal is reduced to about 10% of maximum, bi-stable NV2 switches to provide a negative output to the integrator IN to slow the rate of decrease of signal BI2. When the acceleration reaches substantially zero the output at NV 1 changes to a negative value and is blocked at Dl and the output of the integrator is increased by the negative signal from NV2. When the signal I ref  attains approximately 75% of maximum value, bi-stable NV2 changes state and the value of BI2 rises to maximum exponentially with the input at R3.