Adaptive Fixed-Time Practically Tracking Control for n-Link Flexible-Joint Manipulator With Input Quantization and Input Delay via Command Filter-Based Approach

This paper investigates the fixed-time trajectory tracking control problem for n-link flexible joint manipulator arms subject to input quantization, input delay, and unmodeled dynamics. To address the "explosion of complexity" issue inherent in backstepping-based designs, the command-filtered backstepping technique is employed. However, conventional control scheme utilized in fixed-time control often suffer from the singularity problem. Tackling this critical challenge, a novel error compensation mechanism is proposed by introducing a novelly designed switching function into the compensation signal structure, thereby effectively circumventing the potential singularity. Furthermore, the effects of communication pressure and input delay are explicitly handled with a hysteresis uniform quantizer. Concurrently, the proposed method efficiently mitigates the adverse impacts of unmodelled dynamics by an auxiliary signal. Through the introduction of a compact set in the stability analysis, all signals within the closed-loop system are rigorously proven to exhibit semi-globally practically fixed-time stability (SGPFTS). Simulation results validate the effectiveness and superior performance of the proposed control scheme.