Effects of power-assist and load torque on vibration characteristics of electric bicycles

Abstract

There is a growing demand for electric bicycles from environmental and health perspectives. The electric bicycles are power-assisted by electric motors. In order to increase their power output and performance, it is necessary to understand their effects on the vibration characteristics of electric bicycles. However, it is not clear how the vibration characteristics of the bicycle are affected by the electric motors' assist for various load torques. This presentation discusses the effects of power-assist on the vibration response of the electric bicycle for various load torques. By conducting experimental modal analyses and running tests of the bicycle under various conditions, the vibration components caused by the structural vibration mode of the bicycle and by the electromagnetic effects of the power-assist were identified. Frequency components related to the rotational frequency of the tire were observed. Also, regardless of the load condition, frequency components related to mechanical resonance, and sidebands of the switching frequency caused by the power-assist were observed. Moreover, as the load torque increases, the vibration acceleration also increases especially at the handlebar. Furthermore, when the assist is not activated, the vibration acceleration is proportional to the magnitude of the load torque in the ride comfort affected frequency range.