The Development of Hybrid Volitional Control for Robotic Transtibial Prostheses

This dissertation contributes fundamental advances to the control of robotic transtibial prostheses by developing and assessing hybrid volitional control (HVC), a novel modular control framework. HVC is designed to enable reliable autonomous control for standard cyclic tasks, as well as direct user control to alter or augment the behavior of the prosthetic ankle and achieve non-standard tasks at the user’s discretion. In this dissertation, HVC is investigated through three primary pursuits. Firstly, a framework for HVC applied across the full gait cycle is presented for robotic ankle control, and its implementation is demonstrated by combining finite-state machine (FSM) impedance control with direct myoelectric control (DMC). The utility of HVC is shown, in that it allows users to walk on level ground with biomechanics similar to able-bodied individuals, as well as to volitionally stand on tip-toes, tap the foot, side step, walk backwards, and kick. Secondly, different volitional calibration postures and their relationships with volitional control performance are investigated to fill the need for calibration standardization within HVC and all myoelectric control approaches. Fundamental calibration differences due to lower-limb muscular physiology of individuals with and without amputation are uncovered, and myoelectric calibration recommendations are made. Thirdly, a novel continuous phase variable impedance control approach based on the global tibia kinematics is used to ultimately improve the performance of HVC. This HVC implementation enables seamless transition to other cyclic tasks, such as ramp ascent and descent, by volitionally adapting the controller without requiring task classification or additional controller tuning. User feedback throughout this work shows that HVC is more useful and produces higher overall satisfaction compared to various autonomous controllers. Effectively incorporating the volitional input of the user with reliable autonomous control via HVC offers a pathway to further improve the mobility, independence, and quality of life of individuals with amputation.

本论文通过对混合意愿控制（HVC）的开发与评估，为机器人截肢假肢的控制提供了根本性的进步，HVC是一种新型的模块化控制框架。HVC旨在实现标准循环任务中可靠的自主控制，以及直接的用户控制以改变或增强假肢踝关节的行为，并允许用户根据意愿执行非标准任务。在本论文中，HVC通过三个主要研究方向进行探究。首先，提出了一种适用于整个步态周期的HVC框架，用于机器人踝关节控制，并通过将有限状态机（FSM）阻抗控制与直接肌电图（DMC）控制相结合来展示其实施。HVC的应用价值得以体现，它使用户能够在水平地面上行走，其生物力学特征与健全人相似，并且能够通过意愿站立在脚尖上、轻触脚部、侧向行走、向后行走和踢腿。其次，研究了不同的意愿校准姿势及其与意愿控制性能之间的关系，以满足HVC以及所有肌电图控制方法中校准标准化的需求。揭示了由于截肢者与非截肢者下肢肌肉生理学的基本差异所导致的校准差异，并提出了肌电图校准建议。第三，采用了一种基于全局胫骨运动学的创新连续相位变量阻抗控制方法，以最终提高HVC的性能。这种HVC实现允许通过意愿调整控制器，无需任务分类或额外的控制器调整，实现无缝过渡到其他循环任务，如斜坡上升和下降。在整个研究过程中收集的用户反馈显示，与各种自主控制器相比，HVC更加有用，并能产生更高的整体满意度。通过HVC有效地结合用户的意愿输入和可靠的自主控制，为提高截肢者行动能力、独立性和生活质量提供了途径。