Electric Bicycle - Controllers

Controllers

Control can be as simple as an on-off switch but more usually they are power-on-demand, where the motor is activated by a handlebar mounted throttle, and/or a pedelec (from pedal electric), also known as electric assist, where the electric motor is regulated by pedaling. These have a sensor to detect the pedaling speed, the pedaling force, or both. Brake activation is sometimes sensed to disable the motor as well.

There are two distinct types of electric bike controllers designed to match either a brush or brushless motor. Brushless motors are becoming more common as the cost of controllers continues to decrease. The page on DC motor covers the differences between the two types.

Electric bicycles require high initial torque and therefore models that use brushless motors typically have Hall sensor commutation for speed measurement. An electronic controller provides assistance as a function of the sensor inputs, the vehicle speed and the required force. The controllers generally provide potentiometer-adjustable motor speed, closed-loop speed control for precise speed regulation, protection logic for over-voltage, over-current and thermal protection. The controller uses pulse width modulation to regulate the power to the motor. Sometimes support is provided for regenerative braking but infrequent braking and the low mass of bicycles limits recovered energy. An implementation is described in an application note for a 200 W, 24 V Brushless DC (BLDC) motor.

Brush motors are also used in electric bikes but are becoming less common due to their intrinsic lower efficiency. Controllers for brush motors however are much simpler and cheaper due to the fact they don't require hall sensor feedback and are typically designed to be open-loop controllers.