Global Prescribed-Time Tracking Control of Nonlinear Systems With Unmodeled Dynamics and Its Application in Tower Crane

Many practical control systems contain unknown terms and parameters, and are required to complete a control task at prescribed time and operate for an infinite-time interval. This article considers a prescribed-time (PT) tracking control problem for strict feedback systems with unmodeled dynamics (UDs). A PT adjustment function is designed, which is sufficiently differentiable for an infinite-time interval. By applying the PT adjustment function, a modified PT dynamic signal is first introduced to dominate the impact of UDs. Utilizing a series of inequalities, the UDs are approximated. By using the backstepping design method and PT stability theory, a tracking controller is constructed. With the proposed control strategy, both PT and infinity-time tracking performance are guaranteed, and the output tracking error enters a neighborhood of the origin at PT, whose size can be made small enough. Finally, comparative simulation and experiment results are provided to illustrate the effectiveness of the proposed controller.