Governed Discrete Integral Sliding Mode Control for Twisted-Coiled Polymer Actuators

This paper presents a novel control framework for twisted-coiled polymer actuators (TCPAs) based on a reduced-order electro-thermal model for controller design. In contrast to conventional approaches that rely on high-dimensional hysteresis models or data-driven techniques, the proposed method eliminates the need for explicit thermo-mechanical modeling. The approach combines an extended Kalman filter (EKF) for state estimation with a discrete integral sliding mode controller (DISMC) and a reference governor (RG) for constraint handling. Unlike conventional implementations, theRGis embedded into the system dynamics, enabling a unified treatment of control and constraint handling instead of a supervisory add-on structure. This integration enables a stability analysis of the complete closed-loop system, including both control and input constraint handling, using a polytopic framework with guaranteed uniform exponential stability under parameter uncertainty. Experimental validation demonstrates accurate trajectory tracking across different reference signals, achieving a root-mean-square error (RMSE) below0.06mm(less than 1.6%of full stroke), a maximum absolute error (MAE) below 0.26mm, and a maximum overshoot of 6.48%, while maintaining low computational complexity suitable for real-time embedded implementation. The results show that accurate and robust TCPA control can be achieved without explicit mechanical modeling, establishing a new structure-driven control paradigm that significantly reduces modeling effort while preserving performance and stability guarantees.