Design and Validation of a Partial-Assist Knee Orthosis with Compact, Backdrivable Actuation

This paper presents the mechatronic design and initial validation of a partial-assist knee orthosis for individuals with musculoskeletal disorders, e.g., knee osteoarthritis and lower back pain. This orthosis utilizes a quasi-direct drive actuator with a low-ratio transmission (7:1) to greatly reduc...

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Bibliographic Details
Main Authors: Zhu, Hanqi, Nesler, Christopher, Divekar, Nikhil, Ahmad, M. Taha, Gregg, Robert D.
Format: Conference Proceeding
Language:English
Subjects:
Actuators
Electromyography
Gears
Humans
Knee - physiology
Magnetic Fields
Male
Orthotic Devices
Permanent magnet motors
Prosthesis Design
Rotors
Stator cores
Temperature
Torque
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Summary:This paper presents the mechatronic design and initial validation of a partial-assist knee orthosis for individuals with musculoskeletal disorders, e.g., knee osteoarthritis and lower back pain. This orthosis utilizes a quasi-direct drive actuator with a low-ratio transmission (7:1) to greatly reduce the reflected inertia for high backdrivability. To provide meaningful assistance, a custom Brushless DC (BLDC) motor is designed with encapsulated windings to improve the motor's thermal environment and thus its continuous torque output. The 2.69 kg orthosis is constructed from all custom-made components with a high package factor for lighter weight and a more compact size. The combination of compactness, backdrivability, and torque output enables the orthosis to provide partial assistance without obstructing the natural movement of the user. Several benchtop tests verify the actuator's capabilities, and a human subject experiment demonstrates reduced quadriceps muscle activation when assisted during a repetitive lifting and lowering task.
ISSN:1945-7898
1945-7901
DOI:10.1109/ICORR.2019.8779479