Optimal Task-Invariant Energetic Control for a Knee-Ankle Exoskeleton
Optimal Task-Invariant Energetic Control for a Knee-Ankle Exoskeleton
复制标题
DOI：
10.1109/lcsys.2020.3043838
复制
发表时间：
2021-11-01
影响因子：
3
通讯作者：
Gregg, Robert D.
中科院分区：
文献类型：
--
作者：
Lin, Jianping;Divekar, Nikhil, V;Gregg, Robert D.
用于动力外骨骼的任务不变控制方法为跨越多种活动和环境的人类提供了灵活性。能量整形控制通过在闭环中改变人体的动态特性来达到这一目的。我们以前在势能塑造方面的工作改变了引力矢量来减少用户感知的重力，但这种方法不能提供与速度相关的辅助。基于互联和阻尼性配置的无源控制(IDA-PBC)方法通过端口受控哈密顿系统模型的互联结构提供了更大的自由度来塑造动态系统的能量。提出了一种基于IDA-PBC的新型后驱式膝关节外骨骼能量控制策略。控制律提供的力矩取决于与引力和陀螺相关的各种基函数。我们为这些基函数优化了一组恒定的权重参数，以获得在多个地面斜坡上行走时产生健全关节力矩的控制律。我们对一个穿着膝盖-脚踝外骨骼的健全的人体受试者进行了实验，以证明某些下肢肌肉的激活减少。
Task-invariant control methods for powered exoskeletons provide flexibility in assisting humans across multiple activities and environments. Energy shaping control serves this purpose by altering the human body's dynamic characteristics in closed loop. Our previous work on potential energy shaping alters the gravitational vector to reduce the user's perceived gravity, but this method cannot provide velocity-dependent assistance. The interconnection and damping assignment passivity-based control (IDA-PBC) method provides more freedom to shape a dynamical system's energy through the interconnection structure of a port-controlled Hamiltonian system model. This letter derives a novel energetic control strategy based on IDA-PBC for a backdrivable knee-ankle exoskeleton. The control law provides torques that depend on various basis functions related to gravitational and gyroscopic terms. We optimize a set of constant weighting parameters for these basis functions to obtain a control law that produces able-bodied joint torques during walking on multiple ground slopes. We perform experiments with an able-bodied human subject wearing a knee-ankle exoskeleton to demonstrate reduced activation in certain lower-limb muscles.