1. Department of Electrical Engineering, Zanjan BranchIslamic Azad UniversityZanjan45156‐58145Iran
2. Advanced Control Systems LabElectrical Engineering DepartmentSharif University of TechnologyTehran11155‐4363Iran
3. School of Automation, Huazhong University of Science and TechnologyLuoyu Road 1037Wuhan430074People's Republic of China