Nonlinear Auto-Tuning PI Control With Desired Precision Within User-Specifiable Time

This article presents a novel nonlinear adaptive proportional-integral (PI)-like tracking control approach designed for a class of uncertain nonlinear systems. The proposed method offers several key advantages: 1) it maintains a simple PI structure while incorporating nonlinear elements; 2) unlike traditional PI control, which typically employs fixed PI gains and is susceptible to integration saturation, this approach utilizes self-tuning PI gains to effectively eliminate saturation issues, thereby addressing the long-standing windup problem; and 3)it skillfully manages both the transient behavior and steady-state accuracy of the tracking error through a new prescribed performance function that is independent of initial conditions. This ensures that, for any unknown bounded initial tracking errors, the proposed PI-like control can uniformly confine the tracking error to a specified boundary (accuracy) within a predetermined time rather than over an infinite duration. The effectiveness and advantages of this method are validated through simulation results.