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Title: Stable Cadence Tracking of Admitting Functional Electrical Stimulation Cycle
Rehabilitation robotics and functional electrical stimulation (FES) are two promising methods of rehabilitation for people with neurological disorders. In motorized FES cycling, both the rider and the motorized cycle must be controlled for cooperative human-machine interaction. While rehabilitation goals vary widely, FES cycling traditionally rejects rider disturbances to accomplish cadence and power tracking; however, this paper ensures that the cycle accommodates the rider without rejecting rider disturbances as a means to promote function and strength recovery while ensuring rider safety. A cadence and admittance controller are developed to activate the cycle’s electric motor and the rider’s leg muscles through FES when kinematically efficient. Using a single set of combined cycle-rider dynamics, a Lyapunov-like switched systems analysis is conducted to conclude global exponential cadence tracking. A subsequent passivity analysis is conducted to show the admittance controller is passive with respect to the rider. For a desired cadence of 50 RPM, preliminary experiments on one able-bodied participant and one participant with spina bifida demonstrate tracking errors of −0.07±2.59 RPM and −0.20±3.86 RPM, respectively. *Note this paper does not properly cite the specific NSF project number.  more » « less
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Proc. ASME Dynamic Systems and Control Conference
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Medium: X
Sponsoring Org:
National Science Foundation
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  1. Functional electrical stimulation (FES) can be combined with a motorized cycle to offer various rehabilitation options for individuals with neurological conditions. Typically, FES cycling controllers use cooperating muscles and an electric motor to track cadence. In this paper, in addition to cooperative cadence tracking, the motorized cycle tracks an admittance trajectory generated using torque feedback. This method allows the cycle to deviate from the desired cadence trajectory and admit to the rider-applied torque, ensuring safe human-machine interaction. Two sets of uncertain, nonlinear dynamics are presented, one for the human rider and one for the robot, linked by a common measurable interaction torque. After developing cadence and admittance controllers, a Lyapunov-like switched system stability analysis is provided to prove global exponential tracking of the cadence error system, and a passivity analysis is conducted to prove passivity of the cycle’s admittance controller with respect to the rider’s interaction torque. *Note this paper does not properly cite the specific project. 
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  5. null (Ed.)
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