Fault tolerant control methods of dual type independent multi-phase BLDC motor under open-switch fault conditions

Open-switch faults of DI-BLDCM (Dual type Independent multi-phase BLDC Motor) drive system cause torque ripple of motor. This torque ripple makes unwanted noise and vibrations in the drive system. This paper proposes four control methods for fault tolerant system and analyzes characteristics of DI-BLDCM controlled by the methods. All proposed methods can reduce the torque ripple to similar level under healthy conditions, although the motor is operated in open-switch fault conditions. But, these methods have different characteristics in various conditions. Therefore, from results of the analysis, the suitable methods can be chosen according to the various operation conditions and the fault cases.

I. Introduction

In recent years, motor drive systems are used to serve main power in many applications such as manufacturing industries, transportation and military systems due to the environment and energy problems. The motor drive systems used in these applications require high reliability because the operation of the entire system is highly dependent on its motor drive system. In this aspect, many studies about fault tolerant drive system have been continued to improve the reliability of system about the different types of motors [1] [2] [3] [4] [5] [6]. Despite these efforts to improve the reliability of motor drive systems, DIBLDCM (Dual type Independent multi-phase BLDC Motor) can serve more useful solution. DI-BLDCM consists of electrically separated two stators. And all phase windings are separated from each other. These structural features make the DI-BLDCM be able to operate continuously without other efforts even under the faulty conditions [7], [8]. However, it doesn't mean that the DI-BLDCM does not require fault tolerant controls. If the DI-BLDCM is operated under the faulty condition, torque ripple can be generated by the phase currents of the fault phases. The torque ripple cause unwanted noise and vibration in the entire motor system. Therefore, fault-tolerant control for DI-BLDCM drive system is also necessary to make more reliable system without the sound noise and the mechanical vibration.