Pneumatically-Powered Robotic Exercise Device to Induce a Specific Activation Pattern in Target Lower Extremity Muscles
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The goal of this research is to establish a methodology to actively control a pneumatically driven robotic device that can induce specific muscle force patterns in target muscles during a subject’s voluntary movement. In this paper, the generation of constant forces in the rectus femoris muscle throughout the knee extension, i.e., isotonic contractions, was studied. Due to a highly nonlinear nature of mapping the joint torque to muscle force, a simple application of constant torques to the knee joint would not realize isotonic contractions. The proposed robotic exercise accounted for nonlinear moment arms of muscles as functions of joint angles and nonlinear coordination of multiple muscles in the neuromuscular system to accomplish individual muscle control. A pneumatically powered one degree of freedom (DOF) device that can impose active force feedback control has been designed and built. An exercise-planning algorithm has been developed that involved a musculoskeletal model of the lower-body, and the dynamics of a pneumatic actuator. Five constant force profiles were tested for twenty healthy volunteers and electromyographic (EMG) signals were collected while the device was applying calculated force profiles.