Determination of Forces Acting in the Joints of the Lower Extremities During Rehabilitation

Abstract

Currently, robotic stands are becoming widespread, and are used for the rehabilitation of the lower extremities based on the continuous passive development of one or more joints. In this case, additional excessive forces arise, which have a significant impact on the joints and the rehabilitation process. Direct measurement of these forces is not possible, as they are internal. The article considers the joint movement of the patient's leg and the rehabilitation exoskeleton as a human-machine system (HMS), with the help of which movement is provided in the joints of the lower extremities at a given law of change in the angle of rotation of the thigh. The method of estimating internal forces is based on the Dalembert principle, which allows us to consider and describe HMS under dynamic equilibrium conditions. The system of equations recorded for individual parts of the system allows real-time calculation of the forces acting in the joints based on data, including that obtained using a system of sensors installed on the exoskeleton. Thus, by calculation, it is possible to obtain the values of the forces acting in the thigh, knee and ankle joints. The results of numerical modeling, taking into account experimental studies, showed a significant effect of the coefficient of friction on horizontal forces arising in the femoral, knee and ankle joints, and a change in the angle of rotation of the thigh leads to an increase in the moments of resistance on the femoral and knee joints. This will help the rehabilitation doctor control the movement of the exoskeleton links and generate loads in passive and active modes of operation.