Effect of Target Impedance Selection on the Lower Extremity Assistive Exoskeleton Performance

Exoskeletons are utilized extensively in robotic rehabilitation and power augmentation purposes. One of the most recognised control algorithms utilized in this field is the impedance controller. Impedance control approach provides the capability of realizing different rehabilitation exercises by tuning the target impedance gains. Trial and error experimental approach is one of the most common methods reported in the literature used to tune the target impedance. In this research, a general framework is proposed to study the effect of the target impedance selection on the exoskeleton performance and generation of the human gait profile. The dynamic model of the human-exoskeleton in the sagittal plane is derived for gait simulation study. In addition, a novel human-exoskeleton interaction model is introduced. The simulation study was carried out to illustrate that how the target impedance gains should be selected to minimize several criterias such as energy consumption, interaction forces and position tracking errors during walking. As a result, the proposed method provides better insight into the effective selection methods of the impedance control gains.