Something about controller
- Two different types of controllers are designed to match brushed or brushless motors. As controller costs continue to decrease, brushless motors are becoming more common. (See the DC Motors page, which covers the differences between the two types.)
Controllers for brushless motors: Electric bicycles require higher initial torque, so models using brushless motors often have Hall sensor commutators for speed and angle measurements. The electronic controller assists based on sensor inputs, vehicle speed and required force. Controllers typically allow input via protective logic such as potentiometers or Hall-effect twist handles (or thumb-operated lever throttles), closed-loop speed control (for precise speed regulation), overvoltage, overcurrent, and thermal protection. Bicycles with pedal assist feature usually have a disc on the crankshaft with a magnetic ring and a Hall sensor that generates a series of pulses whose frequency is proportional to the pedal speed. The controller uses pulse width modulation to regulate the power of the motor. Sometimes support for regenerative braking is provided, but braking is not frequent, and the quality of the bicycle is very low, limiting the energy recovered. One implementation is described in an application note for a 200 W, 24 V brushless DC (BLDC) motor. [44]
Controllers for brushed motors: Brushed motors are also used in electric bicycles, but have become less common due to their inherent inefficiency. However, since controllers for brushless motors do not require Hall sensor feedback, they are generally simpler and cheaper, and are usually designed as open-loop controllers. Some controllers can handle multiple voltages.