To whom correspondence should be addressed. E-mail : guorui@ ysu. edu. cn Guo Rui, born in 1980. He is currently an associate professor in mechatronic engineering at Yanshan University, China. He received his Ph. D degree from the Department of Mechanical Engineering of Yanshan University, Qinhuangdao, China, in 2010. His research interests include innovative design and reliability of complex electromechanical products.