Cooperative Control of a Pediatric Exoskeleton System for Active-Assist Gait Rehabilitation

During active-assist rehabilitation mode, the patient started to interact with lower-limb exoskeleton by applying the recovered muscle strength which demands a cooperative control strategy based on the outer and inner loop control scheme. This work proposes a such cooperative framework based on admittance and position control scheme to regulate the compliance of subject-exoskeleton system for pediatric gait rehabilitation. At first, the mechanical design and dynamic modeling of the exoskeleton robot are briefly presented. Thereafter, admittance controller is designed in outer loop which modifies the desired human trajectory and generates the reference trajectory. Thereafter, as an inner loop control scheme, a computed torque position controller is exploited to track the reference trajectory. The effectiveness of the proposed cooperative control is investigated with low and high admittance parameters. From the results, it is observed that the proposed control with low admittance parameters allows the subject to participate in the training process more actively. However, the inner loop position control promisingly tracks the reference trajectory in case of high admittance parameters.