MIMO Model-Free Adaptive Practical Prescribed Performance Control for Mechatronic Systems With Mismatched Disturbance and Quantized Input

This paper proposes a novel model-free adaptive control method with practical prescribed performance for coupled mechatronic systems subject to uncertain friction, unknown delays, mismatched disturbance, and input quantization. Different from the existing ultra-local model-based controllers, a multi-input multi-output (MIMO) ultra-local model with an alpha gain matrix is used to approximate the plant within a short time interval. This allows that the method in this paper can be directly applied to MIMO systems without the decoupling process. A recursive least square technique is utilized to identify the alpha gain matrix. Additionally, a practical prescribed performance function applicable to any initial condition is designed to transform the tracking error, achieving predefined convergence time and pre-assignable tracking precision. Then, a global sliding mode control with adaptive switch gain is constructed to stabilize the transformed error. Afterward, the stability and convergence of the closed-loop system with the designed controller are analyzed by using Lyapunov theorem. The co-simulations on PUMA 560 robotic manipulator and iReHave exoskeleton, and experiment on 2-DOF upper-limb exoskeleton are completed. The obtained results demonstrate the effectiveness and superiority of the proposed control method.