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research-article

Synergy-based Gaussian Process Estimation of Ankle Angle and Torque: Conceptualization for High level Controlling of Active Robotic Foot Prostheses/Orthoses

[+] Author and Article Information
Mahdy Eslamy

Advanced Service Robots (ASR) Laboratory, Department of Mechatronics Eng., Faculty of New Sciences and Technologies, University of Tehran, PO-Box 1439957131, Iran
eslamymahdy@ut.ac.ir

Khalil Alipour

Advanced Service Robots (ASR) Laboratory, Department of Mechatronics Eng., Faculty of New Sciences and Technologies, University of Tehran, PO-Box 1439957131, Iran
k.alipour@ut.ac.ir

1Corresponding author.

ASME doi:10.1115/1.4041767 History: Received March 26, 2018; Revised September 27, 2018

Abstract

Human gait is the result of a complex and fascinating cooperation between different joints and segments in the lower extremity. This study aims at investigating the existence of this cooperation or the so-called synergy between the shank motion and the ankle motion. One potential use of this synergy is to develop the high level controllers for active foot prostheses/orthoses. The central point in this paper is to develop a high level controller that is able to continuously map shank kinematics (inputs) to ankle angles and torques (outputs). At the same time, it does not require speed determination, gait percent identification, switching rules and look-up tables. Furthermore, having those targets in mind, an important part of this study is to determine which input type is required to achieve such targets. This should be fulfilled through using minimum number of inputs. To do this, the Gaussian Process (GP) regression has been used to estimate the ankle angles and torques for 11 subjects at three walking speeds (0.5, 1, 1.5 m/s) based on the shank angular velocity and angle. The results show that it is possible to estimate ankle motion based on the shank motion. It was found that the estimation achieved less quality with only shank angular velocity or angle, whereas, the aggregated angular velocity and angle resulted in much higher output estimation quality. The pros and cons of the proposed method are investigated at different scenarios.

Copyright (c) 2018 by ASME
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