Lower-Limb Exoskeleton With Variable-Structure Series Elastic Actuators: Phase-Synchronized Force Control for Gait Asymmetry Correction
Lower-Limb Exoskeleton With Variable-Structure Series Elastic Actuators: Phase-Synchronized Force Control for Gait Asymmetry Correction
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DOI：
10.1109/tro.2020.3034017
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发表时间：
2021-06-01
影响因子：
7.8
通讯作者：
Yu, Haoyong
中科院分区：
文献类型：
--
作者：
Aguirre-Ollinger, Gabriel;Yu, Haoyong
串联弹性驱动器（SEA）可以提供精确的力控制和反向驱动能力的物理人机交互。SEA产生的力或扭矩的控制允许用户自己的意志控制，并允许实施各种各样的辅助策略。提出了一种基于SEA驱动的下肢辅助外骨骼力控制方法。该设备具有可变结构的SEA通过鲍登电缆耦合。致动器根据所命令的力的幅度在两个离散的刚度水平之间交替。该算法的特点是基于前向传播Riccati方程的切换力跟踪控制。抗干扰组件增加了零辅助模式下器件的透明度。力控制用于实施辅助策略，旨在纠正中风幸存者典型的不对称步态。辅助关节扭矩通过自适应频率振荡器与用户的步态同步，该振荡器使用来自麻痹侧和健康侧的数据提取患者步态的连续相位和频率。对照测试与健康受试者穿着外骨骼，同时受到模拟的膝关节屈曲损伤。对照证明有效地恢复空间和时间膝关节屈曲对称性的水平可比通畅的步态。
Series elastic actuators (SEAs) can provide accurate force control and backdrivability in physical human-robot interaction. Control of SEA-generated forces or torques makes allowance for the user's own volitional control and allows implementing a wide variety of assistive strategies. A novel force control method for a SEA-driven lower-limb assistive exoskeleton is presented. The device features variable-structure SEAs coupled via Bowden cables. The actuator alternates between two discrete levels of stiffness depending on the amplitude of the commanded force. The algorithm features a switching force-tracking control based on the forward-propagating Riccati equation. A disturbance-rejection component increases the device's transparency in zero assistance mode. The force control was used to implement an assistive strategy that aims to correct the asymmetric gait typical of stroke survivors. Assistive joint torques synchronize with the user's gait by means of an adaptive frequency oscillator, which extracts the continuous phase and frequency of the patient's gait using data from both the paretic and the healthy sides. The control was tested with healthy subjects wearing the exoskeleton while subject to a simulated knee flexion impairment. The control proved effective in restoring spatial and temporal knee flexion symmetry to levels comparable to unobstructed gait.