Mimetic Motion Control for a Lower-Extremity Active Orthosis for Hemiplegic People

In the past ten decades, assistive technologies have been proposed for mobility of individuals with spinal cord injury. One alternative consists of active orthotic devices; however, the control of these devices combines techniques that increase the complexity of adjustments in the joints and require customization of parameters depending on the individual and his/her disability. The aim of this study was to develop a control system for the electric actuators of an active lower limb orthosis that provides functional knee and hip movements in a single limb. DC motors were used as bracing actuators in the knee and hip joints, having one degree of freedom in each joint. The developed system operates in closed loop mode determining the differential error at each joint, and sync control with state machine. As a result, the control of each joint meets the biomechanical limits: a maximum knee flexion of 60 degrees, a maximum flexion of 26 degrees and a maximum length of 13 degrees limited by mechanical bracing. It also has a safety system that ceases the movement in case the maximum amplitude of movement is reached. The results were normalized and compared to the movements of a healthy individual. The system has shown consistent and reliable results since it works within the biomechanical limits and had similar results regarding other projects in the area and the healthy gait.