GESCHWINDIGKEITSREGELSYSTEM

摘要

A speed control system for a DC motor (10) receives inputs from devices (38, 40) for sensing motor current and motor voltage, and has a microprocessor (32) for deriving from the sensed motor current and motor voltage a value for a parameter related to the speed of the motor (10), for comparing the derived value of the parameter with a reference value of the parameter corresponding to a predetermined motor speed, and controlling the motor voltage in response to the comparison, for example through a chopper control switch (20), to control the motor speed. In one form of the invention, the parameter is related to the motor voltage, and the microprocessor derives from the value of the sensed motor current a value for the parameter which would correspond to the motor current at the predetermined speed, using data stored in a look-up table in a memory (42) linked to the microprocessor, and compares the derived value with the sensed motor voltage. In another form of the invention, the parameter is the actual speed of the motor, and the microprocessor calculates the motor speed from the sensed motor current and motor voltage and from data stored in the memory (42) representing the variation with motor current of a parameter related to the magnetic flux of the motor. This enables the value of the speed to be derived using a simple calculation, so that an inexpensive microprocessor can be used. The control system can be used to control the traction motor of an industrial vehicle to provide a speed limit for the vehicle.