Adaptive Tracking Control for Nonlinear Time-Varying Input Delay System With Output Constraints

In this paper, the thickness control problem of adaptive output feedback for the hydraulic automatic gague control (HAGC) system is studied. Firstly, a mathematical model of HAGC system of the cold rolling mill with time-varying measurement delay, output constraints and unknown external disturbances is established. Then time-varying measurement delay is converted into time-varying input delay, and auxiliary systems are constructed to compensate for the impacts of input delay. In addition, an asymmetric barrier Lyapunov function (BLF) is constructed for output constraints to improve transient performance. By utilizing backstepping technique and Lyapunov Krasovskii functional (LKF) stability theorem, it can be obtained that stability of the original system with adaptive output feedback controller and the auxiliary system separately. The proposed controller can ensure that all signals are semi-global ultimately uniformly bounded. Simulation results verify the effectiveness of the proposed control strategy.