The lower limb exoskeleton provides assistance by following the lower limb joints’ desired motion trajectory. However, angle control is not enough to meet the requirements in some special circumstances such as encountering obstacles. In the swing phase of the attached leg with the exoskeleton, there is a different contact force between the sole and the road surface in different road conditions. Therefore, it is particularly important to control the joint angle and contact force simultaneously, that is, it is not only necessary to follow the desired angle but also to minimize the influence of external contact force. In this article, a novel scheme is proposed to adjust the trajectory dynamically in the swing phase. First of all, the physical model is streamlined and the Lagrangian principle is carried out to dynamic analysis and established a model of lower limb exoskeleton in the swing phase. Furthermore, the angle dynamics equation is transformed into a Cartesian coordinate system to calculate the end contact force for the impedance model. Finally, the impedance control strategy together with a disturbance observer is designed which is suitable for nonlinear and strong coupling characteristics. The simulation result shows that the control system can follow the angle accurately in the condition of minimizing external constraints. Hardware experiment shows that lower extremity exoskeleton can adjust motion trajectory actively when encountering obstacles and complete the movement trajectory tracking at the same time.

中文翻译：

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基于阻抗控制策略的摆动期下肢外骨骼动态轨迹调整

下肢外骨骼通过跟随下肢关节所需的运动轨迹来提供帮助。但是，在遇到障碍物等特殊情况下，角度控制还不足以满足要求。在附着腿与外骨骼的摆动阶段，在不同的路况下，鞋底与路面的接触力是不同的。因此，同时控制关节角度和接触力尤为重要，即不仅要遵循所需的角度，还要尽量减少外部接触力的影响。在本文中，提出了一种在摆动阶段动态调整轨迹的新方案。首先，精简物理模型，利用拉格朗日原理进行动力学分析，建立了摆动期下肢外骨骼模型。此外，角度动力学方程被转换为笛卡尔坐标系，以计算阻抗模型的端部接触力。最后，设计了阻抗控制策略和干扰观测器，适用于非线性和强耦合特性。仿真结果表明，控制系统能够在外部约束最小的情况下，准确地跟随角度。硬件实验表明，下肢外骨骼在遇到障碍物时可以主动调整运动轨迹，同时完成运动轨迹跟踪。此外，角度动力学方程被转换为笛卡尔坐标系，以计算阻抗模型的端部接触力。最后，设计了阻抗控制策略和干扰观测器，适用于非线性和强耦合特性。仿真结果表明，控制系统能够在外部约束最小的情况下，准确地跟随角度。硬件实验表明，下肢外骨骼在遇到障碍物时可以主动调整运动轨迹，同时完成运动轨迹跟踪。此外，角度动力学方程被转换为笛卡尔坐标系，以计算阻抗模型的端部接触力。最后，设计了阻抗控制策略和干扰观测器，适用于非线性和强耦合特性。仿真结果表明，控制系统能够在外部约束最小的情况下，准确地跟随角度。硬件实验表明，下肢外骨骼在遇到障碍物时可以主动调整运动轨迹，同时完成运动轨迹跟踪。设计了阻抗控制策略和干扰观测器，适用于非线性和强耦合特性。仿真结果表明，控制系统能够在外部约束最小的情况下，准确地跟随角度。硬件实验表明，下肢外骨骼在遇到障碍物时可以主动调整运动轨迹，同时完成运动轨迹跟踪。设计了阻抗控制策略和干扰观测器，适用于非线性和强耦合特性。仿真结果表明，控制系统能够在外部约束最小的情况下，准确地跟随角度。硬件实验表明，下肢外骨骼在遇到障碍物时可以主动调整运动轨迹，同时完成运动轨迹跟踪。