Metrics
21 File views/ downloads
84 Record Views
Thesis
Development Of A Brushless Cycloidal Robotic Actuator For Assistive Exoskeleton Research
University of West Florida Libraries
Master of Science (MS), University of West Florida
2024
Abstract
The performance of commercial robotic actuators are reported to be efficient and offer the advantage of having a universal application-based design. However these advantages can fall short when applied to assistive exoskeletons, where the efficiency is no longer repeatable, and the designs of the actuating systems become a limiting factor in the capabilities and required performances of the exoskeleton overall. Many robotic actuators have embedded planetary reductions, which can be easily machined and mass produced. These planetary reductions can also become a source for backlash to occur between meshed gear pairs, and with cyclic impact forces propagating throughout the exoskeleton during standard operation, the backlash becomes continually worse due to material deformation and the actuator no longer complies with the required standards. By contrast, cycloidal reductions offer higher reduction ratios within the same height profile, and the curvatures of the gears themselves offer greater distribution of stress concentrations under continuous and cyclic loading. With a minimal backlash, low-friction design, and the same backdrivability as planetary reductions, actuation solutions with an embedded cycloidal reduction are a viable avenue for assisted lower-limb exoskeleton research.
The purpose of this research was to develop a custom cycloidal actuator prototype, which maximized the allowable output torques generated by the transmission while remaining within the generalized lower-limb joint velocities during running gait, which is not guaranteed by outsourcing commercial actuator units. The specifications of the motor input and the reduction ratio were tailored for the actuators performance across all lower-limb joints during various performances tasks. The targeted actuator output speed to serve as a universal actuation solution across lower-limb gait is task dependent, with an inversely proportional relationship to the output torque and assistance potential. After characterization, low-level controls strategies were derived, which operate simultaneously with the commanded input signals to compensate for transmission losses that would affect feed-forward accuracy.
Multiple experiments were conducted to identify and verify performance specifications, where the results ultimately inform the usability of this prototype in future exoskeleton research. The platform used for controlling and tuning the actuator input and output performance allow for greater creative liberty with parameter optimization. By setting the stringent requirements for the performance of the actuator, greater opportunities are generated for exercising various control strategies across multiple human performance objectives. Such objectives extend past the standard self-selected walking and running gaits, including but not limited to stair ascent and descent, jumping, and lunging.
Details
- Title
- Development Of A Brushless Cycloidal Robotic Actuator For Assistive Exoskeleton Research
- Resource Type
- Thesis
- Contributors
- Hakki Sevil (Committee Co-Chair)Gwendolyn Bryan (Committee Co-Chair)Jeff McGuirk (Committee Member)Ronda Easley (Committee Member)Jared Li (Committee Member)
- Publisher
- University of West Florida Libraries
- Format
- pdf
- Number of pages
- 96
- Copyright
- Permission granted to the University of West Florida Libraries by the author to digitize and/or display this information for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires the permission of the copyright holder.
- Identifiers
- 99380551697006600
- Academic Unit
- Dr. Muhammad Harunur Rashid Department of Electrical and Computer Engineering
- Language
- English
- Awarding Institution
- University of West Florida; Master of Science (MS)
- Theses and Dissertations
- Master of Science (MS), University of West Florida