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Topic

The Development of a Portable Dynamometer for Upper Limb Strength and Power Assessment

Department of Mechanical Engineering

Date & location

• Monday, December 8, 2025

• 9:30 A.M.

• Clearihue Building, Room B021

• And Virtual Defence

Reviewers

Supervisory Committee

• Dr. Josh Giles, Department of Mechanical Engineering, ӣ��Ӱ�� (Supervisor)

• Dr. Zuomin Dong, Department of Mechanical Engineering, UVic (Member)

• Dr. Mike Berger, School of Medical Sciences, UVic (Non-Unit Member) 

External Examiner

• Dr. Ilamparithi Thirumarai Chelvan, Department of Electrical and Computer Engineering, UVic 

Chair of Oral Examination

• Dr. Erica Wooden, Department of Psychology, UVic

   

Abstract

Portable, practical assessment of upper-limb muscle function is limited by the inaccessibility of gold-standard isokinetic systems to most clinics, and the shortcomings of purely isometric devices. Clinically, isotonic (constant torque) testing enables assessment of power characteristics that isometric (static) measurements miss. Conventional isokinetic (constant velocity) systems are complex, expensive, and have a  large footprint. This thesis presents the design and technical validation of a table-top dynamometer that measures upper limb muscle isometric torque and isotonic power. Ituses a Brushless Direct Current (BLDC) motor and gearbox drivetrain with field-oriented control (FOC) to target a constant resisting torque. The device clamps on to a table.  It has a lever arm with a padded, adjustable cuff, and records torque and velocity while the user performs voluntary movement under a target resisting torque. The goals of this work are to (i) evaluate FOC as a strategy for producing precise, constant resisting torque, (ii) develop a prototype capable of both isotonic and isometric testing, and (iii) validate constant-torque behaviour across a clinically relevant range.

During validation, the drivetrain’s failure to maintain constant resisting torque was traced to gearbox inertia and velocity-dependent friction. These effects were quantified via passive deceleration tests across multiple added inertias and velocities, resulting in an empirical power-law friction fit implemented as real-time feed-forward compensation. A brake-chopper was added to stabilize the DC bus during backdriven operation. Validation with drop tests showed linear velocity-time profiles across resisting torques of 0.61-4.61 Nm and velocities of 0-22 rad/s, indicating constant resisting torque (R² ≥ 0.99; RMSE = 0.11 rad/s). The prototype (≈19.2 kg; 18.9 L) maintained a constant torque. These results show that FOC with empirical friction compensation is a viable approach to portable isotonic dynamometry. Future work will increase control loop frequency, unlock the hardware’s full torque capacity (≈23 Nm), and perform clinical validation toward standardized protocols and normative datasets.