Delayed Output Feedback Control for Gait Assistance With a Robotic Hip Exoskeleton
Delayed Output Feedback Control for Gait Assistance With a Robotic Hip Exoskeleton
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DOI：
10.1109/tro.2019.2913318
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发表时间：
2019-08-01
影响因子：
7.8
通讯作者：
Shim, Youngbo
中科院分区：
文献类型：
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作者：
Lim, Bokman;Lee, Jusuk;Shim, Youngbo
在本文中，我们提出了一种新的、简单的髋外骨骼机器人步态辅助控制策略。该控制器基于延时自反馈，已知用于在某些条件下稳定振荡系统。在该控制器中，没有针对步态阶段和环境的单独估计器，但控制器可以泛化为在各种步行条件下运行（例如，楼梯和坡道步行）。我们首先定义一个状态变量，表示当前腿的运动与髋关节角度。简单的辅助控制可以用带有延迟状态反馈的闭环形式来描述。通过分配适当的延时和自反馈增益，我们可以在人与外骨骼的相互作用下稳定地产生辅助扭矩。控制器通过反映每个控制周期的腿部运动变化，为用户运动提供即时、平滑的帮助。所提出的基于关节角度的延迟反馈辅助控制器可以在各种步行速度和环境变化（例如楼梯和坡道）下运行，而不需要额外的传感器、计算处理和参数调整。使用简单的腿部摆动模型，我们在简化的条件下进行稳定性分析，以深入了解振荡系统中时滞反馈的影响。然后，我们通过测量水平跑步机行走的代谢能量消耗来实验验证所提出的辅助控制器的功效。我们还测试和分析了不同步行条件下生成的辅助扭矩和功率，以显示控制器的通用性。
In this paper, we propose a new and simple control strategy for gait assistance with a hip exoskeleton robot. This controller is based on the time delayed, self-feedback known for stabilizing oscillatory systems under certain conditions. In this controller, there are no separate estimators for the gait phase nor the environment, yet the controller can be generalized to operate under various walking conditions (e.g., stair and ramp walking). We first define a state variable representing the current leg's movement with hip joint angles. A simple assistance control can be described in closed-loop form with the delayed state feedback. By assigning the appropriate time-delay and self-feedback gain, we can generate assistive torques stably under the interaction between human and exoskeleton. The controller provides immediate and smooth assistance to user movement by reflecting the change of leg motion at every control period. The proposed joint-angle-based delayed-feedback assistance controller can operate under various walking speeds and environmental changes (e.g., stairs and ramps) without the need for additional sensors, computational processing, and parameter adjustment. Using a simple leg swing model, we perform a stability analysis under a simplified condition to provide insights into the effects of the time-delayed feedback in oscillatory systems. Then, we experimentally validate the efficacy of the proposed assistance controller by measuring the metabolic energy expenditure for level treadmill walking. We also test and analyze the generated assistive torques and power under the different walking conditions to show the generalizability of the controller.