Towards an ankle-foot orthosis powered by a dielectric elastomer actuator

Abstract Foot drop is the inability to dorsiflex the ankle (raise the toes) due to neuromuscular impairment, and this common condition can cause trips and falls. Current treatments for chronic foot drop provide dorsiflexion support, but they either impede ankle push off or are not suitable for all patients. Powered ankle-foot orthosis (AFO) can counteract foot drop without these drawbacks, but they are heavy and bulky and have short battery life. To counteract foot drop without the drawbacks of current treatments or powered AFO, we designed and built an AFO powered by dielectric elastomer actuators (DEAs), a type of artificial muscle technology. This paper presents our design and the results of benchtop testing. We found that the DEA AFO can provide 49 % of the dorsiflexion support necessary to raise the foot. Further, charging the DEAs reduced the effort that would be required for plantarflexion compared to that with passive DEA behavior, and this operation could be powered for 7000 steps or more in actual operation. DEAs are a promising approach for building an AFO that counteracts foot drop without impeding plantarflexion, and they may prove useful for other powered prosthesis and orthosis designs.

[1]  Iain A. Anderson,et al.  Transferring electrical energy between two dielectric elastomer actuators , 2014 .

[2]  Richard W. Bohannon,et al.  Number of Pedometer-Assessed Steps Taken Per Day by Adults: A Descriptive Meta-Analysis , 2007, Physical Therapy.

[3]  Elizabeth T. Hsiao-Wecksler,et al.  Modeling, control, and analysis of a robotic assist device , 2012 .

[4]  Alexandre Poulin,et al.  An open-loop control scheme to increase the speed and reduce the viscoelastic drift of dielectric elastomer actuators , 2019, Extreme Mechanics Letters.

[5]  Jung Kim,et al.  Design of a Portable Pneumatic Power Source With High Output Pressure for Wearable Robotic Applications , 2018, IEEE Robotics and Automation Letters.

[6]  Mazharul Islam,et al.  Fuel efficiency of a Portable Powered Ankle-Foot Orthosis , 2013, 2013 IEEE 13th International Conference on Rehabilitation Robotics (ICORR).

[7]  Ron Pelrine,et al.  Chapter 1 – ELECTROMECHANICAL TRANSDUCTION EFFECTS IN DIELECTRIC ELASTOMERS: ACTUATION, SENSING, STIFFNESS MODULATION AND ELECTRIC ENERGY GENERATION , 2008 .

[8]  Eric Loth,et al.  A portable powered ankle-foot orthosis for rehabilitation. , 2011, Journal of rehabilitation research and development.

[9]  Ho Cheong Lo.  Converters for Milliwatt Dielectric Elastomer Generators , 2015 .

[10]  Bo Li,et al.  Thermal, Mechanical, and Dielectric Properties of a Dielectric Elastomer for Actuator Applications , 2012 .

[11]  Robert D. Gregg,et al.  Continuous-Phase Control of a Powered Knee–Ankle Prosthesis: Amputee Experiments Across Speeds and Inclines , 2018, IEEE Transactions on Robotics.

[12]  J. Perry,et al.  Gait Analysis , 2024 .

[13]  A. Nakagawa,et al.  Development of Shear Type Compact MR Brake for the Intelligent Ankle-Foot Orthosis and Its Control; Research and Development in NEDO for Practical Application of Human Support Robot , 2007, 2007 IEEE 10th International Conference on Rehabilitation Robotics.

[14]  B. Shadbolt,et al.  Recovery of ankle dorsiflexion weakness following lumbar decompressive surgery , 2009, Journal of Clinical Neuroscience.

[15]  Gwang Min Gu,et al.  SMAFO: Stiffness modulated Ankle Foot Orthosis for a patient with foot drop , 2015, 2015 IEEE International Conference on Rehabilitation Robotics (ICORR).

[16]  Carmel Majidi,et al.  A lightweight, low-power electroadhesive clutch and spring for exoskeleton actuation , 2016, 2016 IEEE International Conference on Robotics and Automation (ICRA).

[17]  P. Steinmann,et al.  On thermo-viscoelastic experimental characterization and numerical modelling of VHB polymer , 2020, International Journal of Non-Linear Mechanics.

[18]  S. Smoukov,et al.  Pulsed actuation avoids failure in dielectric elastomer artificial muscles , 2014 .

[19]  Karl E. Zelik,et al.  Design of a Low Profile, Unpowered Ankle Exoskeleton That Fits Under Clothes: Overcoming Practical Barriers to Widespread Societal Adoption , 2019, IEEE Transactions on Neural Systems and Rehabilitation Engineering.

[20]  H. Herr,et al.  Adaptive control of a variable-impedance ankle-foot orthosis to assist drop-foot gait , 2004, IEEE Transactions on Neural Systems and Rehabilitation Engineering.

[21]  Hugh M. Herr,et al.  New horizons for orthotic and prosthetic technology: artificial muscle for ambulation , 2004, SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring.

[22]  Kai-Yu Tong,et al.  Design of an exoskeleton ankle robot for robot-assisted gait training of stroke patients , 2017, 2017 International Conference on Rehabilitation Robotics (ICORR).

[23]  Richard A. Brand,et al.  The biomechanics and motor control of human gait: Normal, elderly, and pathological , 1992 .

[24]  K. Tong,et al.  Randomized controlled trial of robot-assisted gait training with dorsiflexion assistance on chronic stroke patients wearing ankle-foot-orthosis , 2018, Journal of NeuroEngineering and Rehabilitation.

[25]  Thomas G. Sugar,et al.  A novel control algorithm for wearable robotics using phase plane invariants , 2009, 2009 IEEE International Conference on Robotics and Automation.

[26]  J. Maytorena,et al.  Thermal difference reflectivity of tilted 2D Dirac materials , 2023, 2306.03383.

[27]  Roy Kornbluh,et al.  Chapter 19 – A NEW FRONTIER FOR ORTHOTICS AND PROSTHETICS: APPLICATION OF DIELECTRIC ELASTOMER ACTUATORS TO BIONICS , 2007 .

[28]  Uriel Martinez-Hernandez,et al.  Towards an intelligent wearable ankle robot for assistance to foot drop , 2019, 2019 IEEE International Conference on Systems, Man and Cybernetics (SMC).

[29]  Ashok K. Singal.  The Paradox of Two Charged Capacitors -- A New Perspective , 2013 .

[30]  Ron Pelrine,et al.  Chapter 4 – HIGH-PERFORMANCE ACRYLIC AND SILICONE ELASTOMERS , 2008 .

[31]  Ulf Holmberg,et al.  Ankle-Foot-Orthosis Control in Inclinations and Stairs , 2008, 2008 IEEE Conference on Robotics, Automation and Mechatronics.

[32]  Gregory S. Sawicki,et al.  Reducing the energy cost of human walking using an unpowered exoskeleton , 2015, Nature.

[33]  R. Brand,et al.  The biomechanics and motor control of human gait: Normal, elderly, and pathological , 1992 .

[34]  F. B. Madsen,et al.  The Current State of Silicone-Based Dielectric Elastomer Transducers. , 2016, Macromolecular rapid communications.

[36]  Dake Wang.  The most energy efficient way to charge the capacitor in a RC circuit , 2017 .

[37]  J-S Plante,et al.  Experimental Study of Dielectric Elastomer Actuator Energy Conversion Efficiency , 2013, IEEE/ASME Transactions on Mechatronics.