A Pediatric Knee Exoskeleton With Real-Time Adaptive Control for Overground Walking in Ambulatory Individuals With Cerebral Palsy
Open Access
- 18 June 2021
- journal article
- research article
- Published by Frontiers Media SA in Frontiers in Robotics and AI
Abstract
Gait training via a wearable device in children with cerebral palsy (CP) offers the potential to increase therapy dosage and intensity compared to current approaches. Here, we report the design and characterization of a pediatric knee exoskeleton (P.REX) with a microcontroller based multi-layered closed loop control system to provide individualized control capability. Exoskeleton performance was evaluated through benchtop and human subject testing. Step response tests show the averaged 90% rise was 26 ± 0.2 ms for 5 Nm, 22 ± 0.2 ms for 10 Nm, 32 ± 0.4 ms for 15 Nm. Torque bandwidth of P.REX was 12 Hz and output impedance was less than 1.8 Nm with control on (Zero mode). Three different control strategies can be deployed to apply assistance to knee extension: state-based assistance, impedance-based trajectory tracking, and real-time adaptive control. One participant with typical development (TD) and one participant with crouch gait from CP were recruited to evaluate P.REX in overground walking tests. Data from the participant with TD were used to validate control system performance. Kinematic and kinetic data were collected by motion capture and compared to exoskeleton on-board sensors to evaluate control system performance with results demonstrating that the control system functioned as intended. The data from the participant with CP are part of a larger ongoing study. Results for this participant compare walking with P.REX in two control modes: a state-based approach that provided constant knee extension assistance during early stance, mid-stance and late swing (Est+Mst+Lsw mode) and an Adaptive mode providing knee extension assistance proportional to estimated knee moment during stance. Both were well tolerated and significantly improved knee extension compared to walking without extension assistance (Zero mode). There was less reduction in gait speed during use of the adaptive controller, suggesting that it may be more intuitive than state-based constant assistance for this individual. Future work will investigate the effects of exoskeleton assistance during overground gait training in children with neurological disorders and will aim to identify the optimal individualized control strategy for exoskeleton prescription.Funding Information
- National Institutes of Health
This publication has 37 references indexed in Scilit:
- Estimating the Mechanical Behavior of the Knee Joint During Crouch Gait: Implications for Real-Time Motor Control of Robotic Knee OrthosesIEEE Transactions on Neural Systems and Rehabilitation Engineering, 2016
- The H2 robotic exoskeleton for gait rehabilitation after stroke: early findings from a clinical studyJournal of NeuroEngineering and Rehabilitation, 2015
- A Preliminary Assessment of Legged Mobility Provided by a Lower Limb Exoskeleton for Persons With ParaplegiaIEEE Transactions on Neural Systems and Rehabilitation Engineering, 2013
- Should Body Weight–Supported Treadmill Training and Robotic-Assistive Steppers for Locomotor Training Trot Back to the Starting Gate?Neurorehabilitation and Neural Repair, 2012
- Review of control strategies for robotic movement training after neurologic injuryJournal of NeuroEngineering and Rehabilitation, 2009
- A Systematic Review of the Effectiveness of Treadmill Training and Body Weight Support in Pediatric RehabilitationJournal of Neurologic Physical Therapy, 2009
- Long-Term Retention Explained by a Model of Short-Term Learning in the Adaptive Control of ReachingJournal of Neurophysiology, 2008
- Partial body‐weight‐supported treadmill training can improve walking in children with cerebral palsy: a clinical controlled trialDevelopmental Medicine and Child Neurology, 2007
- Relationship of spasticity to knee angular velocity and motion during gait in cerebral palsyGait & Posture, 2006
- Design and development of torque-controlled jointsPublished by Springer Science and Business Media LLC ,2006