ZD, ZG and IOL Controllers and Comparisons for Nonlinear System Output Tracking with DBZ Problem Conquered in Different Relative-Degree Cases.

This paper considers the output tracking control of general-form single-input single-output (SISO) nonlinear system, which may encounter the problem of division by zero (DBZ). First, via the Zhang dynamics (ZD) method, a ZD controller is proposed. Then, based on the ZD controller with the aid of gradient dynamics (GD) method, a Zhang-gradient (ZG) controller is proposed. For comparison, the conventional input-output linearization (IOL) controller is presented. The ZD, ZG and IOL controllers are compared in different relative-degree cases ( i.e., the standard relative-degree case, the loose relative-degree case and the DBZ relative-degree case). Note that the ZG controller is valid in three relative-degree cases, while the ZD and IOL controllers are valid only in the standard relative-degree case and the loose relative-degree case. In addition, performances of ZD and ZG controllers are guaranteed via theoretical analyses and computer simulations for the output tracking of general-form nonlinear system with the DBZ problem conquered. [ABSTRACT FROM AUTHOR]