This brief presents a novel control strategy for a powered knee-ankle prosthesis that unifies the entire gait cycle, eliminating the need to switch between controllers during different periods of gait. A reduced-order discrete Fourier transformation (DFT) is used to define virtual constraints that continuously parameterize periodic joint patterns as functions of a mechanical phasing variable. In order to leverage the provable stability properties of hybrid zero dynamics (HZD), hybrid-invariant Bézier polynomials are converted into unified DFT virtual constraints for various walking speeds. Simulations of an amputee biped model show that the unified prosthesis controller approximates the behavior of the original HZD design under ideal scenarios and has advantages over the HZD design when hybrid invariance is violated by mismatches with the human controller. Two implementations of the unified virtual constraints, a feedback linearizing controller, and a more practical joint impedance controller produce similar results in simulation.

中文翻译：

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迈向动力假肢统一控制的仿真研究

本简介介绍了一种用于动力型膝踝假体的新颖控制策略，该策略统一了整个步态周期，从而消除了在不同步态周期之间切换控制器的需求。降阶离散傅里叶变换（DFT）用于定义虚拟约束，这些约束连续地将周期关节模式参数化为机械定相变量的函数。为了利用混合零动态（HZD）的可证明的稳定性，将混合不变Bézier多项式转换为针对各种步行速度的统一DFT虚拟约束。对截肢者两足动物模型的仿真表明，在理想情况下，统一的假体控制器可以逼近原始HZD设计的行为，并且在与人类控制器不匹配而违反混合不变性时，其优势优于HZD设计。统一虚拟约束的两种实现方式，反馈线性化控制器和更实用的联合阻抗控制器在仿真中产生相似的结果。