可穿戴五自由度上肢外骨骼机器人固定时间控制

Fixed-time control for wearable 5 degrees of freedom upper-limb exoskeleton

中文关键词  外骨骼机器人  固定时间控制  干扰观测器  滑模控制  轨迹跟踪

英文关键词  Exoskeleton  Fixed-time control  Disturbance observer  Sliding mode  Trajectory tracking

中文摘要

      针对可穿戴上肢外骨骼系统在外部干扰及参数不确定条件下的轨迹跟踪问题，提出了一种基于观测器的固定时间控制策略。首先，采用拉格朗日方法对五自由度上肢外骨骼系统的动力学模型进行面向控制处理。其次，考虑模型中存在参数不确定及外部干扰，基于改进超螺旋算法设计了固定时间干扰观测器，实现对系统干扰的实时估计，完成对控制器的在线补偿；在此基础上，设计了非奇异终端滑模固定时间控制律，保证外骨骼关节角度跟踪误差在固定时间内收敛至原点。再次，基于Lyapunov方法证明了闭环系统的稳定性。最后，通过对比和数值仿真结果证明所提出控制策略的有效性。

英文摘要

      Aiming at the trajectory tracking problems of wearable upper-limb exoskeleton under the condition of lumped perturbations, an observer-based fixed-time control strategy is proposed in this paper. Firstly, the dynamic model of 5 degrees of freedom (DOF) upper-limb exoskeleton is constructed by Lagrange method for control purpose. Secondly, considering the parameter uncertainties and external disturbances existing in the model, a fixed-time disturbance observer (FTDO) based on improved super-twisting algorithm is designed to estimate the lumped perturbations and compensate the controller online. Furthermore, a non-singular terminal sliding mode controller (NTSMC) is proposed to guarantee that the angle tracking errors can be forced to the origin in fixed-time and maintained zero in all subsequent time. Subsequently, the stability of closed-loop system is proved by Lyapunov theory. Finally, Comparison and numerical simulation results are given to demonstrate the effectiveness of the proposed integrated control strategy.