Design and Evaluation of Torque Compensation Controllers for a Lower Extremity Exoskeleton

In this paper, we present an integrated human-in-the-loop simulation paradigm for design and evaluation of a lower extremity exoskeleton that is elastically strapped onto human lower limbs. The exoskeleton has 3 rotational DOF on each side and weights 23kg. Two torque compensation controllers of the exoskeleton are introduced, aiming to reduce interference and provide assistance to human motions, respectively. Their effects on the wearer's biomechanical loadings are studied with a running motion and ground reaction forces are predicted. By examining the interaction forces between the exoskeleton and the wearer, the wearer's joint torques, reaction forces, and muscle activations and then by comparing them with those of the passive exoskeleton, we show sound evidence of the efficacy of these two controllers on reducing the wearer's loadings. The presented simulation paradigm can be utilized for virtual design of exoskeletons and pave the way to build optimized exoskeleton prototypes for experimental evaluation.