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Investigation of a Unified Phase Variable in Human Locomotion for Applications in Powered Prostheses

机译：用于动力假肢的人体运动中统一相位变量的研究

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摘要

Estimates indicate that by 2050 the U.S. will incur a two-fold increase in the incidence of amputation and stroke, due largely to the prevalence of vascular disease. Amputees suffer from a slower, less stable, and less efficient gait than that of able-bodied persons. Developing methods to control powered prosthetic legs in a simple, efficient, and customizable manner could help current and future amputees ambulate more efficiently. The current methodology used to control powered prosthetic legs sees the gait cycle as a process consisting of discrete states (e.g., heel strike, load acceptance, toe off, pre-swing, mid-swing, etc). Thus, current powered prosthetic legs synchronize to their wearer by transitioning between a finite numbers of states based on switching rules. This approach is limited as state machine control strategies end up dictating the walking speed and response of the robotic leg rather than the amputee. Novel approaches from the biped robotic field have led to new ways of visualizing the gait cycle. The gait cycle is seen and controlled as a continuous periodic process synchronized by a phase variable rather than a sequence of discrete events. A phase variable is a mechanical signal that changes monotonically, i.e., it strictly increases or decreases, over time and therefore is able to parameterize a rhythmic process. This approach allows biped robots to synchronize all their joint actuators seamlessly in order to achieve a stable and steady gait. In this dissertation, this type of control architecture is translated to control a powered prosthetic leg by studying the human gait cycle from a phase variable perspective. Before designing a controller for a powered prosthetic leg that is capable of matching the timing of the amputee's gait cycle, the human sense of phase in locomotion must be understood. In this dissertation, the design of a perturbation mechanism and experimental protocol capable of producing multi-joint phase-shifting perturbations in able-bodied subjects is presented. These phase-shifting perturbations helped us statistically compare different parameterizations of nominal and perturbed joint trajectories in ten able-bodied subjects. We derived and analyzed unified phase variable candidates (i.e., able to parameterize the entire stride) in human locomotion from the results of these perturbation experiments. A statistical analysis found the correlations between nominal and perturbed joint trajectories to be significantly greater when parameterized by the derived unified phase variable (0.95+) than by time. Finally, we performed experiments on three above knee amputee subjects wearing a powered knee and ankle prosthetic leg with a unified phase variable that correctly parameterizes perturbed kinematics and is suitable for real-time controllers. Implementing our bioinspired phase variable in the robotic leg not only allowed amputee subjects to walk steadily at different speeds and inclines, but also gave them voluntary control over the leg during non-rhythmic tasks (e.g., walking backwards and stepping back and forth). In addition, no tuning of the controller was required between subjects due to the versatility of the phase variable algorithm. The results from the amputee experiments show that we have developed a control architecture that allows the powered prosthetic leg to behave as a plug-and-play device due to the simple, yet effective, derivation of a unified phase variable.
机译：估计表明，到2050年，由于血管疾病的盛行，美国的截肢和中风发病率将增加两倍。与健壮的人相比，截肢者的步态更慢，更不稳定，效率也更低。开发一种以简单，高效和可自定义方式控制动力假肢的方法，可以帮助当前和将来的截肢者更有效地行走。用于控制动力假肢的当前方法将步态周期视为由离散状态（例如脚跟撞击，负荷接受，脚趾脱开，预挥杆，中挥杆等）组成的过程。因此，当前的动力假肢通过基于切换规则在有限数量的状态之间进行转换而同步到其穿戴者。由于状态机控制策略最终决定了机器人腿而不是被截肢者的行走速度和响应，因此这种方法受到限制。来自两足动物机器人领域的新颖方法带来了可视化步态周期的新方法。步态周期被视为和控制为一个连续的周期性过程，由一个相位变量而不是一系列离散事件同步。相位变量是一种机械信号，它随时间单调变化，即严格随时间增加或减小，因此可以对节奏过程进行参数设置。这种方法允许Biped机器人无缝同步其所有关节执行器，以实现稳定的步态。本文通过从相位变量的角度研究人的步态周期，将这种类型的控制结构转化为控制动力假肢。在设计能够与截肢者步态周期的时间相匹配的动力假肢控制器之前，必须先了解人类对运动的相位感。本文提出了一种能在健全主体中产生多关节相移扰动的扰动机制和实验方案的设计。这些相移扰动帮助我们从统计学上比较了十个健全主体中名义和扰动关节轨迹的不同参数化。我们从这些摄动实验的结果中得出并分析了人类运动中统一的相位变量候选者（即能够对整个步幅进行参数化）。统计分析发现，在通过导出的统一相位变量（0.95+）进行参数化时，名义和受扰关节轨迹之间的相关性明显大于时间。最后，我们对三个以上膝盖截肢者受试者进行了实验，这些受试者穿着动力膝和踝假肢腿，并具有统一的相位变量，该相位变量正确设置了扰动的运动学参数，适合于实时控制器。在机器人腿中实施受生物启发的相位变量，不仅使截肢者能够以不同的速度和倾斜平稳地行走，而且在非有节奏的任务（例如，向后行走和来回走动）中让他们自愿控制腿。此外，由于相位变量算法的多功能性，因此无需在受试者之间调节控制器。截肢者实验的结果表明，我们开发了一种控制体系结构，由于简单但有效地推导出了统一的相位变量，该方法使得有动力的假肢可以充当即插即用设备。

著录项

  • 作者

    Villarreal Suarez, Dario J.;

  • 作者单位

    The University of Texas at Dallas.;

  • 授予单位 The University of Texas at Dallas.;
  • 学科 Biomedical engineering.;Robotics.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 149 p.
  • 总页数 149
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 康复医学;
  • 关键词

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