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Investigation and Design of a New Ankle Rehabilitation System Based on Soft Robotics to Assist Children with Physical Disabilities

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Thesis(89.54 MB)

Date

2024

Authors

Supervisor

Garcia, Lorenzo
Kilby, Jeff

Item type

Thesis

Degree name

Doctor of Philosophy

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Publisher

Auckland University of Technology

Abstract

Ongoing paediatric physical disabilities can result from various causes, including neurological conditions like Cerebral Palsy (CP), strokes, Acquired Brain Injuries (ABI), neuromuscular diseases such as Duchenne Muscular Dystrophy (DMD) and Spinal Muscular Atrophy (SMA), as well as traumatic injuries. Children with physical disabilities often face limitations in performing Activities of Daily Living (ADL) independently, which can impede their typical development. Mobility and exploration are crucial aspects of a child's development, contributing to cognitive, physical, social, and emotional growth. Rehabilitation plays a vital role in assisting these children in recovering or maintaining functionality, enabling them to interact with their environment, and ultimately improving their quality of life and autonomy. Rehabilitation exoskeletons have gained significant attention for their potential to address mobility challenges in individuals with physical disabilities. They offer advantages such as enabling extensive practice for children with substantial disabilities, reducing the effort required from therapists during exercises, and providing a quantitative assessment of the patient's motor function. However, most existing rehabilitation exoskeletons rely on electric motors and rigid components for their functionality. Unfortunately, these designs are often cumbersome, heavy, and unsuitable for use outside clinical facilities. To overcome these limitations, researchers in this field are now focusing on the development of Soft Wearable Rehabilitation Robots (SWRRs) that incorporate artificial muscles based on smart materials (AMSMs). AMSM, provide increased compliance, adaptability, comfort, safety, and reduced weight—critical characteristics for SWRRs. One noteworthy type of AMSM is the Twisted and Coiled Polymer actuator (TCP). TCPs are created by twisting precursor polymer fibres and applying heat treatment. To activate TCPs, an external heat source, such as metallic wires, is employed to induce joule heating, thereby enabling precise electrical control. TCPs offer several advantages, including high-power density, stress tolerance, strain capacity, and linear behaviour with minimal hysteresis. However, they do face certain limitations, such as low operating frequencies and high operating temperatures. The focus of this thesis is to investigate the feasibility of using TCPs as artificial muscles to power SWRRs designed for children with muscular dystrophy. The research consists of several key components: literature review on paediatric rehabilitation robots design needs and on the biomechanical requirements for SWRR using AMSM. A characterisation of TCPs with Nichrome wire. A novel approach to enhance the temperature control and working frequency of TCPs is implemented using a Proportional-Integral-Derivative controller applied to long actuators. Finally, a preliminary prototype of a paediatric ankle SWRR based on TCPs was designed and tested on a dummy resembling the leg of a 10-year-old child. The prototype demonstrates the capability to provide a maximum Range of Motion (ROM) of 26° in the plantarflexion direction within 5 seconds, generating a torque of 1 Nm. However, the final frequency of the system was affected by the low response on the cooling phase. In summary, this thesis research explores the potential of TCPs as artificial muscles to power SWRRs for children with muscular dystrophy. The findings highlight the importance of developing strategies to address cooling phase limitations and further advance the development of effective and efficient rehabilitation technology for paediatric populations.

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http://hdl.handle.net/10292/17911

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