Thesis Format

Monograph

Characterization and Control of a Woven Biomimetic Actuator for Wearable Neurorehabilitative Devices

Vaughan K. Murphy, The University of Western OntarioFollow

Degree

Master of Engineering Science

Program

Electrical and Computer Engineering

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Trejos, Ana Luisa

Abstract

Strokes are a major cause of death and disability, with nearly 300,000 Canadians suffering from stroke-related disability. Many survivors suffer from upper limb paresis, which makes ordinary tasks difficult. Availability of care is an issue, with only 43.3% of patients in Ontario receiving proper treatment. Robot-assisted neurorehabilitation has been used to address limited clinician availability, and has been shown to improve patient strength and range of motion faster than or comparable to traditional methods. However, the size and weight of current devices limit their use to within therapists’ offices. Incorporating actuators into clothing would make the devices more comfortable, natural to use, and allow for at-home care, which has been shown to improve therapy compliance, frequency, and efficacy. In this work, a woven fabric bi-pennate artificial muscle system is presented. Its contractive stroke, force, speed, and efficiency were characterized, and the transient stroke and force were modelled. The latter was used to create a composite feedforward-feedback controller, which was tested to determine its performance in controlling the actuator using solely force feedback. The maximum stroke, force, and controlled contraction period were found to be 12.23%, 11.28 N, and 2.60 s respectively, with the first two scaling linearly with the number of active actuators. Results indicate that the actuator is able to meet or exceed clinical performance requirements, albeit nonconcurrently, and that the designed controller was an effective force feedback control method, limiting overshoot to 2.6% and steady state error to 0.94%. Further work is suggested to refine the actuator’s design.

Summary for Lay Audience

Strokes are one of the leading causes of death and disability in developed countries, with nearly 300,000 Canadians being disabled because of them. Many stroke survivors suffer from nervous system damage affecting their arms, limiting their ability to perform acts of daily living. It has been shown that therapy that uses robots to move the patient’s wrists and arms for them can help improve their strength and range of motion. However, currently available devices are very big, heavy, and rigid, making them uncomfortable and limiting their use to inside therapist offices. Putting the moving components of the therapy devices into clothing would make them more natural to use, more comfortable, and let people use them from the comfort of their own homes, which would let more people get the help they need. In this work, a soft artificial muscle system woven into a fabric that could be used for such devices is presented. To determine its suitability, its maximum range of motion, strength, speed, and efficiency were found and compared to therapy requirements. These data were also used to find mathematical relationships to predict the force and distance during operation of the muscle system, based on how many muscles were being used at a time. Finally, two different methods of controlling the system were designed, tested, and compared, to see which was better if one were to be used for a therapy device. The results suggest that the designed artificial muscle system could be used to create soft, wearable robotic therapy devices that can easily be controlled, but work remains to be done to further improve the design.

Recommended Citation

Murphy, Vaughan K., "Characterization and Control of a Woven Biomimetic Actuator for Wearable Neurorehabilitative Devices" (2020). Electronic Thesis and Dissertation Repository. 7548.
https://ir.lib.uwo.ca/etd/7548