Integral variable-structure control with variable-structure sliding dynamics for antireset windup

This paper proposes a scheme of integral variable-structure control with variable-structure sliding dynamics, referred to as VSSD-IVSC, based on the framework of the so-called global sliding-mode control (GSMC) technique. Previous GSMC schemes encompass the robust eigenvalue-assignment GSMC (REA-GSMC) and the integral variable-structure control (IVSC). All GSMC schemes feature the insurance of existence of a sliding mode throughout an entire response for performance robustness. It is shown in this paper that both REA-GSMC and IVSC lead to the same robust tracking performance in theory. In practical implementations the IVSC has better steady-state error characteristics than the REA-GSMC. However, due to control saturation, the IVSC may suffer from the integrator windup problem common to control methods with integral compensation. The VSSD-IVSC scheme is proposed to combine the REA-GSMC and the IVSC using the GSMC framework, and it has variable-structure sliding dynamics for antireset windup. Experiments were conducted on a two-link direct-drive manipulator to demonstrate the effectiveness of the proposed scheme.