摘要：AbstractThis paper studies the PID robust tracking control problem for second-order nonlinear systems with time-varying input delay. An input-output approach is adopted to show the existence of robust PID control, which can tolerant the time-varying delay and the uncertain nonlinearity. First, the uncertain nonlinearity can be scaled by unknown bounds and the time-varying input delay is approximated by using the three-term approximation method. Next, the uncertain nonlinear time-varying delay system under PID control can be transferred into two interconnected subsystems, which is prone to be analyzed by the input-output approach. Then, by using the scaled small-gain theorem and constructing the Lyapunov-Krasovskii functional, a sufficient condition on the existence of robust PID controller to stabilize the closed-loop system against time-varying delay and uncertain nonlinearity is proposed, which implies the tracking performance of the original PID control system. A numerical example is given to demonstrate the effectiveness of the proposed method.
