Motor speed controller

A system for controlling the electrical power applied to a DC drive motor for an electric vehicle, comprising:

• an operator controlled accelerator operative to provide an output electrical signal proportional to the accelerator position which is continuously variable between limiting values;
• a multi-vibrator having the output of the accelerator as its input and being operative to provide a periodically cycling bi-stable output wherein the ratio of on-time to off-time is a function of the signal received from the accelerator;
• a power switching device connected in series with the motor and battery;
• means for deriving an electrical signal having a value which is a direct function of the instantaneous current passing through the motor;
• comparator means operative to receive said instantaneous current signal and a reference value and to provide an output signal at such time as the current passing through the motor exceeds the reference value;
• and a gate for controlling said switching device, to pass current from the battery to the motor only and at all times when the output of the multi-vibrator is in an "on" state and a signal representative of the instantaneous value of the current passing through the motor does not exceed said reference signal.