Patent GB-1487804-A (GB)
Title: Control system for a vehicle driven by an electric motor
IPC: B60L11/18
Filed: 1975-04-16
Abstract: 1487804 Control of D.C. motors DEUTSCHE AUTOMOBIL GmbH 16 April 1975 [25 April 1974] 15680/75 Heading H2J [Also in Division F2] A control system for a vehicle driven by a D.C. motor 2 through a clutch 11, gear-box 13 and axle 15, comprises a controller 36 supplying current to the motor field winding 5 and receiving a desired value of field current from a controller 35 to which is fed the actual value of the armature current and a desired value which, when the clutch 11 is engaged, is determined by the vehicle accelerator or brake pedal setting and which, when the clutch 11 is disengaged, is determined by an automatic synchronizing controller 34 or is set to zero, the vehicle speed being adjusted by field current variation and by the gear-box 13 which has at least two speeds in the forward direction. The armature is connected to a battery 1 through three parallel circuits consisting of a braking diode 4, main contacts 22a and the series combination of auxiliary contacts 23a and a resistor 3. The system operates in the following ways: (1) The accelerator pedal 24 adjusts a potentiometer 25 whose output signal passes through relay contacts 20a, junction 32 and relay contacts 21a for combination with a signal at terminal 8 representative of the actual armature current, the resultant signal being applied to controller 35 which emits a desired field current signal for combination with a signal at terminal 7 representative of the actual field current, the resultant signal being applied to controller 36. (2) The brake pedal 26 adjusts a potentiometer 28 and opens a switch 27 to de-energize a relay 20, whose contacts 20a, 20b and 20c open to respectively disconnect the potentiometer 25 and de-energize relays 22, 23 to open contacts 22a, 23a, the signal from potentiometer 28 being transmitted and combined as described for the signal from potentiometer 25, whereby the motor is regeneratively braked through the diode 4 until a speed is reached when the motor voltage becomes less than that of the battery 1 without clutch 11  having been operated. (3) The clutch pedal 29 is operated to disengage the clutch 11 prior to a gear change, the pedal 29 closing a switch 30 to energize a relay 21 whose contacts 21a changeover to apply to the controller 35 either the output of controller 34 or a zero signal. In the former case tachometers 10, 11 respectively detect the speed of the motor and gear-box to produce signals at 17, 18 for combination and supply to the controller 34, whose signal is transmitted and combined as before to cause controller 36 to accelerate or brake the motor, according to whether the gear change is down or up, so that the motor and gear-box speeds are equalized before the clutch is engaged after the gear change. Closure of switch 30 also energizes relay 20 via diode 31 to ensure that contacts 22a, 23a remain closed. If changeover of relay contacts 21a causes a zero signal to be supplied to controller 35, members 10, 12 and 34 are omitted and the motor is controlled to produce no torque during a gear change, engagement of the clutch 11 causing the motor to be mechanically accelerated or braked to match the new speed set by the gear change. Relay 22 is also controlled by a trigger stage 37 responsive to the signal from tachometer 10, whereby relay 22 is not energized until a predetermined speed is reached and the motor is supplied through members 3, 23a when starting. Likewise the stage 37 operates to open contacts 22a when the motor speed falls during an overload condition, the resistor 3 again limiting the motor current to a safe value. The clutch pedal 29 may be omitted and the clutch and switch 30 operated simultaneously by the gear lever.