Ergonomic Bio-Design and Motion Simulation of a Mechatronic Orthosis System for Knee Rehabilitation

Abstract

According to the INEI, 10.30% of the population has a disability in Peru. Among the causes, knee arthrosis affects more than 50% of people over 50 years of age, who perform physical therapy to recover. This research proposes the ergonomic bio-design of a mechatronic orthosis for passive knee rehabilitation processes, which consists of 4 parts: the support exoskeletons for the thigh and leg, the joint system, the actuator, and the control interface. The exoskeleton and the joining structure were designed in SolidWorks using Aluminium 1060 as material from the anthropometric study. An actuator based on a servomotor with 0.4 N.m was designed, considering the mass of 7.32 kg for the leg-foot set, and an arrangement of transmission gears to achieve the 40 N.m needed to move the lower extremity. The Spyder environment and Python were used to create the graphical interface that allows setting the speed of movement and the number of repetitions. The Von Mises stress analysis of the articulated zone was performed by applying a par motor of 200 N.m on the coupling section of the power mechanism. Likewise, a realist process with a rotation from 0° to 20° was simulated in CoppeliaSim, which included real conditions such as gravity and the properties associated with the leg and foot, thus verifying that the design torque and motion speeds were within the range of commercial products. For further work, the orthosis will be manufactured by the end of 2022, including the development of feedback control.