[1] Shenzhen Univ, Shenzhen Key Lab Electromagnet Control, Shenzhen 518060, Peoples R China
[2] Southwest Jiaotong Univ, Coll Elect Engn, Chengdu 610031, Peoples R China
[3] Cent S Univ, State Key Lab High Performance Complex Manufactor, Changsha 410083, Peoples R China