Energy-Efficient Power Assist Control with Periodic Disturbance Observer and Its Experimental Verification Using an Electric Bicycle

Abstract

: This paper addresses the problem of energy-efficient power assist control for quasiperiodic motions. The simplest assist method would be to apply additional torque in proportion to the instantaneous value of torque generated by a user. In our previous study, it was shown that energy efficiency improves by flattening the torque pattern. To cope with the frequency fluctuation of our motion, we introduce a periodic disturbance observer with a frequency estimator and suppress the pulsation of the human torque based on a disturbance observer framework. The effectiveness of the proposed method is evaluated through numerical simulations and experiments with an actual electric bicycle being pedaled by a human.

Sensorless Pedalling Torque Estimation Based on Motor Load Torque Observation for Electrically Assisted Bicycles

“…In Figure 3, the pedalling torque generated by a pedalling force applied in a generic direction is shown. Due to the design of the crankset, a typical pedalling torque presents a quasi-periodic profile which is close to a sinusoidal profile plus an offset [15,[36][37][38]. The pedalling torque reaches its maximum and minimum twice during a pedalling cycle.…”

Experimental verification of torque sensorless control for electric power-assisted bicycles on sloped environment

“…Xuan and Tomizuka proposed a robust disturbance observer based power-assist scheme to provide flexible assistive power even in uphill conditions [1]. Hatada et al proposed a power assist control method using a periodic disturbance observer that viewed the pedaling torque generated by a human as a periodic disturbance [2]. Their control method achieved a high energy efficiency compared with a general method for commercial electric power-assisted bicycles.…”