Adaptive interval type-2 FNN enhanced fixed-time SMC for robust motion of piezoelectric stack actuators

This paper introduces a novel control strategy for precise motion control of piezoelectric stack actuators (PSAs) under load variations, stochastic disturbances, and model uncertainties. The approach combines fixed-time, nonsingular terminal sliding mode control (FNTSMC) with an adaptive interval type-2 fuzzy neural network (IT2FNN). Specifically, the FNTSMC ensures robust tracking via a fast, fixed-time nonlinear sliding surface and reaching law, while the IT2FNN adaptively estimates and compensates for lumped disturbances, thereby enhancing robustness. Moreover, closed-loop system stability is rigorously proven via Lyapunov theory. Experiments on a PSA test platform under lumped disturbances demonstrate superior tracking performance and robustness compared to existing sliding mode control methods.