Observer-Based Fuzzy Adaptive Dynamic Surface Force Control for Pneumatic Polishing System End-Effector With Uncertain Contact Environment Model

This study presents an observer-based adaptive fuzzy dynamic surface force control strategy for pneumatic polishing system with uncertain contact environment model and full-state constraints. First, a fuzzy logic system is employed to approximate the uncertain nonlinear dynamics of the pneumatic polishing system end-effector, and a fuzzy state observer is designed to estimate the unmeasured states. Further, to enhance the controller’s response speed, a variable separation method employing fuzzy basis functions and the dynamic surface control technique are adopted to address algebraic loop issues and prevent computational complexity explosion. A logarithmic-type barrier Lyapunov function is embedded into each step of the controller design to ensure that all system states satisfy the predefined constraints. Finally, an adaptive fuzzy dynamic surface force controller with full-state constraints is developed to ensure fast and accurate control of the polishing force in an uncertain contact environment while maintaining all states within predefined constraints. The effectiveness and applicability of the proposed control algorithm are experimentally verified using a pneumatic polishing system. Note to Practitioners—The goal of this study was to investigate an adaptive fuzzy dynamic surface force control strategy for pneumatic polishing system with uncertain contact environment model and full-state constraints. Current pneumatic polishing force control schemes generally have low accuracy owing to dynamic time-varying contact characteristics that cannot be accurately modeled; therefore, this study proposes an adaptive fuzzy dynamic surface force control method that approximates model uncertainty and nonlinear functions using a fuzzy logic system. In addition, to improve the slow response speed of the polishing force, which easily leads to over- or under-polishing, the operational complexity of the controller is reduced by introducing a variable separation method based on a fuzzy basis function and dynamic surface control. This approach avoids problems such as component damage or poor machining consistency due to untimely adjustment of the polishing force. The stability and convergence of the proposed algorithm are theoretically analyzed, and its superiority and applicability are verified in polishing force control experiments.