Model-free based fixed-time control for the uncertain wearable exoskeleton with preset performance

In this paper, the issue of fixed-time tracking control for the uncertain wearable exoskeleton with prescribed performance is addressed. To heighten the transient and steady-state performance of the exoskeleton system, a variable exponent coefficient-based fixed-time control approach is formulated. Benefiting from model-free control, the dynamic model of the exoskeleton is replaced by an ultra-local model that relies solely on input–output (IO) data. The tracking control problem of the exoskeleton system boils down to the boundedness problem of auxiliary variables via designing a nonlinear conversion function. The tracking errors converge to the origin in a fixed time and never violate predefined constraints. The mechanical design of the wearable exoskeleton is carried out by Solidworks, and the actual control system is meticulously constructed. The simulation and experimental outcomes confirm the efficacy and superiority of the presented control methodology.