Nonlinear Back-Calculation Anti-Windup Based on Operator Theory

Real-world plants have various nonlinear characteristics such as friction and hysteresis, so nonlinear control is essential for precise control. In addition, actuators of plants have input constraints, which cause the integrator of the controller to windup. So far, anti-windup methods have mainly been for linear controllers, and research on nonlinear controllers has not been sufficient. This paper proposes a back-calculation anti-windup method for nonlinear controllers. By analyzing and extending the back-calculation anti-windup for a Proportional–Integral controller using operator theory, it can be applied to nonlinear controllers. The proposed method is applied to integral sliding mode control and right coprime factorization. In the simulation, we compared the proposed method with and without its application, as well as with conditional integration, and confirmed the effectiveness of the proposed method. In the future, it is necessary to extend the method to be applicable to more complex systems. This study has the potential to contribute to the practical application of nonlinear control.