Design and Control of An Active Gravity Offloading System for Rehabilitation Training of Gait and Balance
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摘要: 针对患者神经损伤后发生的下肢运动障碍,减重步行训练是一种重要的康复训练方式.对于中度和轻度患者,为其提供部分身体重力支撑(Body weight support,BWS)并激励其自主行走,可以提高患者的主动参与,并有助于改善其步态和平衡控制能力,从而有望取得更好的康复效果.现有的减重技术多存在运动空间小、减重力变化大、会对患者产生前后和侧向拉力等问题.为此,本文面向步态和平衡康复训练应用,采用单绳悬吊方式,设计电机驱动的竖直拉力单元,从而构建了一种主动减重系统.在水平方向,采用桥式吊架结构,通过伺服控制消除吊绳偏摆使其保持竖直,从而避免对患者产生前后和侧向的拉力干扰.在竖直方向,只有一个控制自由度却需要完成位置随动和减重力控制两个目标,是典型的欠驱动系统.为此,采用绳牵引串联弹性驱动方法,将位置和吊绳拉力耦合起来.针对系统中存在的非线性、摩擦等不利因素,采用滑模控制方法,分别设计了吊绳偏角控制器和吊绳拉力控制器.为保证系统安全运行,进一步针对竖直拉力单元中的弹簧连接动板设计了位置控制器.最后,通过仿真实验检验了本文提出的主动减重系统和控制方案效果.由此,可为下肢运动障碍患者提供一种方便高效的康复训练手段.Abstract: Gait training with body weight support (BWS) is an effective rehabilitation therapy for patients with neural disorders and locomotion difficulties. For medium and mild patients, walking with BWS may encourage their active participations into locomotion training and balance control to improved functional recovery. However, current BWS technologies suffer from problems of limited movement space, force inaccuracy, undesired lateral force, etc. In this work, we propose an active gravity offloading system for gait and balance training. The BWS force is provided with a single rope suspension. In the horizontal X-Y plane, the servo unit moves the BWS unit to follow the motion of the patient and keeps the rope perpendicular to the ground so that no lateral force is produced to disturb the patient. In the vertical direction, since there is only one control degree of freedom for position following in Z-direction and suspension force control along the cable the BWS is designed with a cable-driven series elastic actuation structure, which couples the force and displacement along the rope. To deal with nonlinearities, friction and uncertainties in the system, the sliding mode control method is taken for the rope deflection angle controller and force controller. Further, to keep the system running inside a safety boundary, another position controller is designed for the moving plate that connects with the spring in the BWS unit. With extensive simulations experiments, feasibility and efficacy of the active gravity offloading system are validated. This system promises an effective rehabilitation platform for patients with locomotion difficulties.1) 本文责任编委 王卫群
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图 5 主动减重系统工作原理框图(${C_\theta }$控制吊绳竖直; ${C_f}$在跟随吊绳竖直方向运动的同时, 控制吊绳拉力; ${C_x}$在必要情况下开始工作, 控制动板位置在安全的范围内)
Fig. 5 The working diagram of the active gravity offloading system ($C_{\theta}$ controls the cable to be perpendicular to the ground; $C_{f}$ controls the cable force while following its motion; $C_x$ works in necessary conditions to control the moving plates stay within the safety range)
表 1 仿真实验参数列表
Table 1 List of simulation parameters
物理量 符号 数值和单位 目标减重力 Fd 600 N 压簧劲度系数 Ks1 10 000 N/m 拉簧劲度系数 Ks2 5 000 N/m 吊架质量 M 20 kg 动板1质量 ml 1 kg 动板2质量 mr 1 kg -
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