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A Comprehensive Strategy for Controlling the Hip and Knee with a Muscle-Driven Exoskeleton for Mobility after Paraplegia

Chang, Sarah Randall
http://rave.ohiolink.edu/etdc/view?acc_num=case1481151499958917

Abstract Details

2016, Doctor of Philosophy, Case Western Reserve University, Biomedical Engineering.
Stepping can be restored in individuals with paraplegia due to spinal cord injury (SCI) with a hybrid neuroprosthesis (HNP) that combines functional neuromuscular stimulation (FNS) and passive controllable lower-limb bracing. FNS applies small electrical pulses to peripheral motor nerves, thereby contracting the paralyzed muscles and generating joint torques capable of mobilizing the limb for stepping. Passive controllable lower-limb bracing can be designed to lock, unlock, or couple joints to provide support and stability. Prior work showed that the HNP enabled individuals with motor complete thoracic SCI to stand, walk, and negotiate stairs. However, knee flexion during pre-swing phase of gait can be inadequate and result in inconsistent foot-floor clearance, increasing the risk of tripping or falling. The stand-to-sit (STS) transition was also poorly controlled and resulted in high impact with the seating surface. Therefore, we hypothesized that a HNP with context-dependent hydraulic hip-knee coupling (HKC) would more effectively normalize STS maneuvers and restore pre-swing phase knee flexion during walking in individuals with paraplegia than stimulation alone. Novel kinematic HKC and kinetic knee damping hydraulic mechanisms were incorporated into the HNP to control the knee during STS transitions. By imposing simple coupling or damping constraints, individuals with SCI completed the STS with improved coordination between hip and knee joint angles, lowered knee angular velocities, decreased upper limb forces by 70%, and reduced impact forces by half when compared to sitting with stimulation alone. To achieve sufficient foot-floor clearance by assisting pre-swing knee flexion during gait, a kinematic HKC hydraulic mechanism and kinetic elastomer spring were evaluated. The hydraulic coupling mechanism had high passive resistances, making the system impractical during gait. Future work may evaluate alternative HKC methods. The elastomer spring successfully assisted pre-swing by reducing the time to reach 30 degrees of knee flexion, increasing peak knee angular velocities, and improving foot-clearance as compared to walking without the elastomer. Incorporating a kinetic assist has potential to increase foot-clearance by assisting pre-swing knee flexion during gait. Future work incorporating electromechanical actuators to assist on an "as-needed" basis or plantar flexor muscles activation via FNS may improve step-by-step consistency and increase walking speed and distance.
Dominique Durand, Ph.D. (Committee Chair)
Ronald Triolo, Ph.D. (Advisor)
Malcolm Cooke, Ph.D. (Committee Member)
Patrick Crago, Ph.D. (Committee Member)
Musa Audu, Ph.D. (Committee Member)
321 p.
Biomechanics; Biomedical Engineering; Robotics
Spinal Cord Injury; Hybrid Neuroprosthesis; Functional Neuromuscular Stimulation; Controllable Orthosis; Muscle-Driven Exoskeleton; Stand-to-Sit; Gait

Recommended Citations

Citations

  • Chang, S. R. (2016). A Comprehensive Strategy for Controlling the Hip and Knee with a Muscle-Driven Exoskeleton for Mobility after Paraplegia [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1481151499958917

    APA Style (7th edition)

  • Chang, Sarah. A Comprehensive Strategy for Controlling the Hip and Knee with a Muscle-Driven Exoskeleton for Mobility after Paraplegia . 2016. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1481151499958917.

    MLA Style (8th edition)

  • Chang, Sarah. "A Comprehensive Strategy for Controlling the Hip and Knee with a Muscle-Driven Exoskeleton for Mobility after Paraplegia ." Doctoral dissertation, Case Western Reserve University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1481151499958917

    Chicago Manual of Style (17th edition)

case1481151499958917
328
© 2016, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.