标题：Global practical tracking for nonlinear systems with unknown relative degree
作者：Wang, Meiqiao; Liu, Yungang; Man, Yongchao
作者机构：[Wang, Meiqiao; Liu, Yungang; Man, Yongchao] Shandong Univ, Sch Control Sci & Engn, Jinan 250061, Shandong, Peoples R China.
会议名称：Chinese Automation Congress (CAC)
会议日期：OCT 20-22, 2017
来源：2017 CHINESE AUTOMATION CONGRESS (CAC)
关键词：Nonlinear systems; unknown relative degree; unknown control direction;; non-parametric uncertain nonlinearities; global practical tracking;; switching logic
摘要：This paper considers global practical tracking for a class of nonlinear systems with unknown relative degree, unknown control direction and non-parametric uncertain non-linearities. Different from the existing results, known upper bound is not required for the unknown relative degree, which makes it impossible to design a filter with fixed dimension. To compensate the multiple uncertainties, a novel strategy is proposed based on switching mechanism to construct a dynamic output-feedback controller with a varying-dimensional filter, whose gain and dimension are tuned online via a switching logic. It is rigorously shown that the switching type output-feedback controller can guarantee that the system error reaches prescribed small accuracy before a pre-specified time, with pre-specified maximum overshoot, and the system state is globally bounded.