Abstract
Timely and reliable identification of control phases is functional to the control of a powered robotic lower-limb prosthesis. This study presents a commercial energy-store-and-release foot prosthesis instrumented with a multimodal sensory system comprising optoelectronic pressure sensors (PS) and IMU. The performance was verified with eight healthy participants, comparing signals processed by two different algorithms, based on PS and IMU, respectively, for real-time detection of heel strike (HS) and toe-off (TO) events and an estimate of relevant biomechanical variables such as vertical ground reaction force () and center of pressure along the sagittal axis (). The performance of both algorithms was benchmarked against a force platform and a marker-based stereophotogrammetric motion capture system. HS and TO were estimated with a time error lower than 0.100 s for both the algorithms, sufficient for the control of a lower-limb robotic prosthesis. Finally, the computed from the PS showed a Pearson correlation coefficient of 0.97 (0.02) with the same variable computed through the force platform.
Highlights
Lower-limb amputation affects millions of people worldwide
Regarding the estimate of stance duration (St), both algorithms of the sensory apparatus resulted in underestimating the actual value
The system consisted of an ESAR foot that integrated pressure sensor matrices and a single inertial measurement units (IMUs) on the rear part of the prosthetic foot
Summary
Lower-limb amputation affects millions of people worldwide. The daily living activities can be affected by limitations in locomotion tasks in terms of performance and asymmetry of the gait pattern [2]. Lower-limb prostheses have remarkably advanced, as companies and academic institutions are increasingly investing resources in their development to improve the living standards of amputees. Lower-limb prostheses can be divided into three main categories: passive, semi-active, and fully-active prostheses [4]. Passive energystorage-and-return (ESAR) prostheses have become very popular as they can restore a more natural ambulatory pattern than non-ESAR counterparts [5]. Semi-active prostheses can vary their inner mechanical properties (e.g., resistance, mainly by using dampers) or elastic properties (through smart clutches) to adapt to different terrains or locomotion phases and tasks [6]
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