Faculty Advisor or Committee Member

Edward A. Clancy, Advisor

Faculty Advisor or Committee Member

Xinming Huang, Committee Member

Faculty Advisor or Committee Member

Todd R. Farrell, Committee Member

Identifier

etd-3831

Abstract

Relating surface electromyogram (EMG) activity to force/torque models is used in many areas including: prosthesis control systems, to regulate direction and speed of movement in reaching and matching tasks; clinical biomechanics, to assess muscle deficiency and effort levels; and ergonomics analysis, to assess risk of work-related injury such as back pain, fatigue and skill tests. This thesis work concentrated on improving the performance of dynamic EMG-to-force models for the hand-wrist and multiple fingers. My contributions include: 1) rapid calibration of dynamic hand-wrist EMG-force models using a minimum number of electrodes, 2) efficiently training two degree of freedom (DoF) hand-wrist EMG-force models, and 3) estimating individual and combined fingertip forces from forearm EMG during constant-pose, force-varying tasks. My calibration approach for hand-wrist EMG-force models optimized three main factors for 1-DoF and 2-DoF tasks: training duration (14, 22, 30, 38, 44, 52, 60, 68, 76 s), number of electrodes (2 through 16), and model forms (subject-specific, DoF-specific, universal). The results show that training duration can be reduced from historical 76 s to 40–60 s without statistically affecting the average error for both 1-DoF and 2-DoF tasks. Reducing the number of electrodes depended on the number of DoFs. One-DoF models can be reduced to 2 electrodes with average test error range of 8.3–9.2% maximum voluntary contraction (MVC), depending on the DoF (e.g., flexion-extension, radial-ulnar deviation, pronation-supination, open-close). Additionally, 2-DoF models can be reduced to 6 electrodes with average error of 7.17–9.21 %MVC. Subject-specific models had the lowest error for 1-DoF tasks while DoF-specific and universal were the lowest for 2-DoF tasks. In the EMG-finger project, we studied independent contraction of one, two, three or four fingers (thumb excluded), as well as contraction of four fingers in unison. Using regression, we found that a pseudo-inverse tolerance (ratio of largest to smallest singular value) of 0.01 was optimal. Lower values produced erratic models and higher values produced models with higher errors. EMG-force errors using one finger ranged from 2.5–3.8 %MVC, using the optimal pseudoinverse tolerance. With additional fingers (two, three or four), the average error ranged from 5–8 %MVC. When four fingers contracted in unison, the average error was 4.3 %MVC. Additionally, I participated in two team projects—EMG-force dynamic models about the elbow and relating forearm muscle EMG to finger force during slowly force varying contractions. This work is also described herein.

Publisher

Worcester Polytechnic Institute

Degree Name

PhD

Department

Electrical & Computer Engineering

Project Type

Dissertation

Date Accepted

2020-05-14

Accessibility

Unrestricted

Subjects

electromyogram

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