Control of Regular Walking for an Exoskeleton with the Electric Drive

Abstract

We consider dynamic model of the motion in the sagittal plane of the exoskeleton of lower limbs, integrated with the similar model of the human operator by means of straps with one or two controllable actuators in each leg. The exoskeleton is additionally loaded with heavy point weight. Considered models of visco-elastic and the rigid attachment of the exoskeleton to the person. The model also takes into account the dynamics of the electric actuators. We study the possibility of designing control systems for various options of the actuators in the joints of the exoskeleton (knee or both in the knee and hip), which also take into account the different degrees of force action of the human operator on the process of movement. The synthesis is based on the method of solving the inverse tasks of the dynamics. The analytical motion control for exoskeleton was designed, which provided locomotion to the hip and knee joints in accordance with the selected desired mode. Synthesis of the control system was carried out on the example of a flat, single support for comfortable walking. The algorithms provide a good quality performance of a given motion and an acceptable cost of energy from the human operator. With sufficient size nominal torque for actuators, the exoskeleton is able to provide substantial assistance to the person carrying the heavy weight, as is evident from the analysis of energy costs. The best energy results with good precision implementation can be obtained in the case of a perfectly rigid model, in which the design of the exoskeleton and the human body are one.