Bioinspired Design and Control of BATEX, An Exosuit With Biarticular Compliant Actuators

A more human-compatible design of exosuits provides new aspects in assisting people. This study presents a novel bioinspired method to design and control an exosuit to support human locomotion. We introduce a methodological design and development of the BATEX as an exosuit with compliant biarticular thigh actuators. By using series elastic actuator (SEA) resembling artificial muscles (AM) instead of direct drive motors in the BATEX, we propose an efficient switching control for the stance and swing phases of walking. Locking the motors in the swing phase converts the SEAs to passive biarticular springs to produce human-like leg swinging. This design is complemented by the force modulated compliance (FMC) controller that uses the ground reaction force to adjust the AM's stiffness in the stance phase. We utilized unassisted walking experiment data to validate the proposed design and control methodology in a simulation study. Optimizing BATEX control parameters with a training set of subjects predicts the energy consumption reduction in the upper leg (knee and hip joints) for more than 27% at five different walking speeds. Finding this measure of assistance level to be more than 21% for the test set of subjects supports the generalization of our approach. Further, individualization of the parameters for each subject shows significant improvement in slow and moderate walking speeds. Pilot assisted-walking experiments with four subjects support the applicability of the introduced method concerning individualization and generalization.