1. Department of Automatic Control Engineering, Feng Chia Univ., Taichung 407, TW (Corresponding author), e-mail: lincs@fcu.edu.tw
2. Department of Automatic Control Engineering, Feng Chia Univ., Taichung 407, TW.
3. Department of Electronic Engineering, National Chinyi Univ. of Technology, Taiping 411, TW.
4. Department of Electrical Engineering, Feng Chia Univ. Taichung 407, TW.