Force-Sensorless power assist control design for electric bicycles

Electric power-assist systems help vehicle operators to achieve the same speed with less effort, as compared to the situation when the vehicle is driven purely by human power. That is, the electric power-assist systems act only to assist pedaling torque, rather than replace it. Conventional power-assist controllers need force sensing, and only focus on the amplification of the force. But force sensing is replaced by a PI-type closed-loop torque observer (PICTO) in this research, where a force sensor free power assistive system is proposed. Prior to the development of power assist control design, parameter identification of a brushless dc (BLDC) motor was performed. The effectiveness of the proposed scheme is demonstrated through experimental studies of BLDC motor drives.