Cheng Shihao, Laubscher Curt A, Best T Kevin, Gregg Robert D
Department of Robotics, University of Michigan, Ann Arbor, MI, 48109 USA.
IEEE Trans Robot. 2025;41:2251-2267. doi: 10.1109/tro.2025.3539206. Epub 2025 Feb 5.
For powered prosthetic legs to be viable in everyday situations, they require an activity classification system that is not only accurate but also straightforward to understand and use. However, incorporating the numerous activity modes in real-world ambulation often requires high-dimensional feature spaces and restrictions on the leg leading each transition. This article addresses these challenges by delegating sit/stand transitions and variable-incline walking to the mid-level controller, effectively reducing the classification space to four states with easily distinguishable features. We implement simple heuristic rules for both prosthetic-led and intact-led (i.e., ambilateral) transitions, using lower-limb kinematic features, ground contact and inclination, and environmental distance from an ultrasonic sensor. Two transfemoral amputee subjects using a powered knee-ankle prosthesis demonstrated an ambilateral transition accuracy of 99.2% under both self-paced and rapid-paced/fatiguing conditions, with a 100% recovery rate due to backup logic or user-cued resets. The incline estimator enabled the prosthesis to continuously adapt between level and inclined surfaces without explicit classification. These results and an outdoor multi-terrain demonstration indicate that simple and straightforward transition logic can enable powered prosthetic legs to be used reliably across a broad array of daily activities.
为了使电动假肢在日常情况下可行，它们需要一个活动分类系统，该系统不仅要准确，而且要易于理解和使用。然而，在现实世界的行走中纳入众多活动模式通常需要高维特征空间以及对每次转换时腿部动作的限制。本文通过将坐/站转换和可变坡度行走委托给中级控制器来应对这些挑战，有效地将分类空间减少到具有易于区分特征的四种状态。我们利用下肢运动学特征、地面接触和倾斜度以及超声波传感器与环境的距离，为假肢主导和健全肢体主导（即双侧）的转换实施了简单的启发式规则。两名使用电动膝踝假肢的经大腿截肢受试者在自定节奏和快速/疲劳条件下均表现出99.2%的双侧转换准确率，由于备用逻辑或用户提示重置，恢复率达到100%。坡度估计器使假肢能够在水平和倾斜表面之间连续自适应，而无需明确分类。这些结果以及户外多地形演示表明，简单直接的转换逻辑可以使电动假肢在广泛的日常活动中可靠使用。
