Design of Flux-Switching Actuators with Auto-locking Function for Power Assist Devices

Abstract

This research aims to design a flux-switching actuator with an auto-locking function for power assist devices Traditional actuators used in situations of brief travel and discontinuity such as power assistive devices usually need to stop at a position for a long time but still require electric power supply to maintain sufficient electromagnetic force This research presents a new flux switching device (FSD) based on the design concept of dual gap permanent magnet motors (PM motors) and magnetic bases Applications of this device include incorporation with direct-drive motors or motors with gear ratios which further enable high/low cogging torque switching ability by modifying the flux path When the proposed actuator is operated in low cogging torque mode it functions as the traditional device; however when the actuator needs to maintain the same position the cogging torque is adopted automatically and alternates to electromagnetic force in high cogging torque mode This feature can improve the safety of users and products In order to widen FSD applications this research also presents two improved actuator designs The first improvement starts with investigations of the rotor structure and output characteristics of line start permanent magnet motors (LSPMMs) Moreover the open angle of V-shaped magnets which possesses better efficiency is designed such that the prototype efficiency can reach 90% With this investigation this research integrates the rotor structure of LSPMMs into the actuator design and presents a new outer rotor type LSPMM which can be incorporated with FSD and can start up without sensors encoders or inverters To summarize the second improvement four axial winding coils are added to improve the actuator design which ensures that the axial magnetic field is controllable; thus the switching process becomes smoother and the performance more stable With these two improvements the actuator developed in this dissertation is applicable to various conditions

Date of Award	2014 Aug 15
Original language	English
Supervisor	Mi-Ching Tsai (Supervisor)