Affiliations:
1:
College of Mechanical and Electrical Engineering, Xinxiang University , Xinxiang , People's Republic of China ;
2:
XJ Electric Company Limited , Xuchang 461000 , People's Republic of China
This is an open access article published by the IET under the Creative Commons Attribution -NonCommercial License (http://creativecommons.org/licenses/by-nc/3.0/)
Received 23/08/2018,Accepted 19/09/2018,Published 26/10/2018