1. Institute of Electrical Engineering;
2. National Engineering Research Center for Equipment and Technology of Cold Strip Rolling, Yanshan University, Qinhuangdao, Hebei 066004, China e-mail:
3. Institute of Electrical Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China
4. School of Information Science and Engineering, Yanshan University, Qinhuangdao, Hebei 066004, China