Discrete-time variable structure control based on improved approach law
ZHU Qi-dan，LvKai-dong，LI Xin-fei，LIU Zhi-lin，ZHANG Zhi
Journal of Systems Engineering and Electronics . 2012, (6): 1211 -1214 .  DOI: 10.3969/j.issn.1001-506X.2012.06.23