Optimally Biomimetic Passivity-Based Control of a Lower-Limb Exoskeleton Over the Primary Activities of Daily Life
Optimally Biomimetic Passivity-Based Control of a Lower-Limb Exoskeleton Over the Primary Activities of Daily Life
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DOI：
10.1109/ojcsys.2022.3165733
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Jianping Lin;Nikhil V. Divekar;G. Thomas;R. Gregg
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文献类型：
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作者：
Jianping Lin;Nikhil V. Divekar;G. Thomas;R. Gregg
外骨骼中常用的特定任务、基于轨迹的控制方法可能适合截瘫个体，但它们过度限制了具有残余自愿能力的个体（代表更大的人群）的意志运动。人体外骨骼系统可以用欧拉-拉格朗日方程或等效的端口控制哈密顿方程的形式表示，以设计控制律，通过改变人体的能量特性，在连续的活动/环境中提供任务不变的帮助。我们之前介绍了一个端口控制的哈密顿框架，该框架通过与重力和陀螺仪项相关的基函数参数化控制律，这些基函数经过优化以适应不同地面坡度上多个步行步态的标准化健全关节扭矩。然而，由于与输入输出被动性相关的严格假设，这种方法不具备为更广泛的活动（包括爬楼梯和站立到坐）重现关节扭矩的灵活性，这确保了人类仍然能够控制闭环动态中的能量增长。为了在日常生活的所有主要活动中提供仿生帮助，本文通过将垂直地面反作用力和全局平面方向纳入基础集来概括这种能量塑造框架，同时保留人体关节扭矩和人体关节速度之间的被动性。我们在动力膝踝外骨骼上进行了一项实验性实施，由三名身体健全的受试者在不同的斜坡上行走、坡道上升/下降和站立到坐时使用，展示了这种控制方法的多功能性及其对肌肉力量的影响。
Task-specific, trajectory-based control methods commonly used in exoskeletons may be appropriate for individuals with paraplegia, but they overly constrain the volitional motion of individuals with remnant voluntary ability (representing a far larger population). Human-exoskeleton systems can be represented in the form of the Euler-Lagrange equations or, equivalently, the port-controlled Hamiltonian equations to design control laws that provide task-invariant assistance across a continuum of activities/environments by altering energetic properties of the human body. We previously introduced a port-controlled Hamiltonian framework that parameterizes the control law through basis functions related to gravitational and gyroscopic terms, which are optimized to fit normalized able-bodied joint torques across multiple walking gaits on different ground inclines. However, this approach did not have the flexibility to reproduce joint torques for a broader set of activities, including stair climbing and stand-to-sit, due to strict assumptions related to input-output passivity, which ensures the human remains in control of energy growth in the closed-loop dynamics. To provide biomimetic assistance across all primary activities of daily life, this paper generalizes this energy shaping framework by incorporating vertical ground reaction forces and global planar orientation into the basis set, while preserving passivity between the human joint torques and human joint velocities. We present an experimental implementation on a powered knee-ankle exoskeleton used by three able-bodied human subjects during walking on various inclines, ramp ascent/descent, and stand-to-sit, demonstrating the versatility of this control approach and its effect on muscular effort.