A Perturbation Platform and Exoskeleton Simulator for Studying Balance Control of Hip Exoskeleton: Design and Preliminary Validation

In order to deal with the problem of imbalance of the elderly in the process of walking on level ground, this paper proposes a hip exoskeleton with series elastic actuator (SEA) to assist the wearer to adjust the step width, step length and step frequency in real time during walking to maintain balance walking. Through the built multi-sensor fusion gait perturbation and perception integrated platform, the experimenter's autonomous recovery of balance experiment and exoskeleton-assisted human body's recovery of balance experiment under external wrench state were carried out respectively. The perturbations were applied in four directions to the experimenter while walking, which verified the validity of the balance evaluation model and the assisting effect of the exoskeleton in restoring the balance of human walking. Firstly, according to the established kinematics model, the displacement and velocity of the experimenter's center of mass during walking are calculated, and the system is simplified to a linear inverted pendulum model (LIPM) to evaluate the motion state. Secondly, a balance state evaluation model is established based on the instantaneous capture point (ICP) theory, and the balance state evaluation of the human body is realized by judging the positional relationship between the instantaneous capture point and the support range of the feet. Finally, according to the step strategy in the human body balance strategy, the magnitude of the auxiliary torque when the experimenter is out of balance is calculated through the relative position of the center of mass and the instantaneous capture point. Therefore, it can be shown that the balance evaluation model and exoskeleton control strategy we established can provide the balance restoring torque for the experimenter to swing the leg when the system is about to become unbalanced, which can effectively slow down the unbalanced trend.