基于动态表面的上肢外骨骼固定时间控制方法OA

Aiming at the problem of trajectory tracking of a 3-degree of freedom(DOF)wearable upper limb exoskeleton system with state constraints and model uncertainty,a fixed-time dynamic surface control strategy based on fuzzy adaptive was proposed.First,the fuzzy logic system(FLS)was employed to approximate unknown nonlinear dynamics,and the introduction of a nonlinear transfer function addressed the state constraint problem,which could avoid the"feasibility condition"restriction of virtual controller.Then,a modified dynamic surface control technique was proposed to reduce the computation complexity for the repetitive differential associated with virtual signals in the traditional backstepping algorithm.Additionally,a fixed-time filter was designed to provide an effective filtering solution for the fixed-time control of the exoskeleton system.Theoretical analysis shows that the proposed control scheme can guarantee the boundedness of the system tracking error without violating the state constraints.Meanwhile,the system output can accurately track the reference trajectory in a fixed time,and the convergence time is independent of the initial state of the system.Finally,the effectiveness of the proposed algorithm was verified by the simulation results.