This study describes the design, instrumentation and control of an exoskeleton for lower limb children rehabilitation with nine degrees of freedom. Three degrees of freedom in each leg exert the movements of hip, knee and ankle in the sagittal plane, and three control the drive track system composed by a caterpillar-like robot. The control scheme presents a model free decentralized output feedback adaptive high-order sliding mode control to solve the trajectory tracking problem in each degree of freedom of the exoskeleton. A high order sliding mode differentiator estimates the unmeasured states and, by means of a dynamical state extension, it approximates the unknown dynamical model of the exoskeleton. A second-order adaptive sliding mode controller based on the super-twisting algorithm drives the exoskeleton articulations to track the proposed reference trajectories, inducing an ultimate boundedness for the tracking error. Numerical and experimental simulation results demonstrate the effect of the adaptive gain on the super-twisting control design. Such evaluations confirmed the superior tracking performance forced by the adaptive law for the controller with a smaller chattering amplitude and smaller mean tracking error.

本研究描述了具有九个自由度的下肢儿童康复外骨骼的设计、仪器和控制。每条腿的三个自由度在矢状面施加髋关节、膝关节和踝关节的运动，三个控制由类似毛毛虫的机器人组成的驱动轨道系统。该控制方案提出了一种无模型分散输出反馈自适应高阶滑模控制来解决外骨骼各自由度的轨迹跟踪问题。高阶滑模微分器估计未测量的状态，并通过动态状态扩展来近似外骨骼的未知动力学模型。基于超扭曲算法的二阶自适应滑模控制器驱动外骨骼关节跟踪建议的参考轨迹，从而导致跟踪误差的最终有界。数值和实验仿真结果证明了自适应增益对超扭曲控制设计的影响。这样的评估证实了自适应律强制控制器具有更小的颤振幅度和更小的平均跟踪误差的优越跟踪性能。