A NOVEL DESIGN OF AN ELECTRIC POWER-ASSISTED BIKE BASED ON HELICAL GEARS

Abstract

An electric power-assisted bike (EPAB) is a bicycle with an attached electric motor to assist with human pedaling, where the electric power output of the motor is provided in accordance with the pedaling-force. This makes the pedaling-force sensor (PFS), which is used to sense the human pedaling force, the critical device in the EPAB. Accordingly, the present study proposes a novel design for the PFS, comprising of a helical gear system and an annular magnet device. The study then develops a mathematical model for the force distribution on the helical gears, and provides a general design rule to determine the parameter values of the PFS which will prevent a self-lock situation. A prototype is produced to verify and demonstrate the proposed approach.