Fixed-time adaptive fuzzy command filtering control for a two-joint robotic manipulator with input dead zone saturation and time-varying delay

Abstract

This paper studies an adaptive fuzzy fixed-time tracking control problem for the two-joint robotic manipulator with input deadzone saturation and time-varying delay. By employing auxiliary signals to compensate for the effects of time-varying delay, the need for the Pade approximation method is avoided, and the requirement for the input time-varying delay to be relatively small is relaxed. Fuzzy logic systems are utilized as adaptive nonlinear approximators to identify and compensate for unknown packaged nonlinear functions within the backstepping framework. In the design of the controller, command filtering technology is introduced to address the “complexity explosion” phenomenon faced by traditional backstepping techniques. In addition, the non-smooth input saturation and dead zone nonlinearities are approximated using a non-affine smooth function, then transformed into an affine form using the mean-value theorem. The proposed method effectively combines the backstepping approach with practical fixed-time stability criteria. This guarantees the boundedness of all closed-loop signals and ensures tracking errors diminish to a small range near zero within a fixed time. More importantly, the convergence time depends solely on the design parameters. The effectiveness of the theoretical results is validated through one simulation example.