Type synthesis and preliminary design of devices supporting lower limb’s rehabilitation

Purpose: Based on the analysis of existing solutions, biomechanics of human lower limbs and anticipated applications, results of considerations concerning the necessary number of degrees of freedom for the designed device supporting rehabilitation of lower extremities are presented. An analysis was carried out in order to determine the innovative kinematic structure of the device, ensuring sufficient mobility and functionality while minimizing the number of degrees of freedom. Methods: With the aid of appropriate formalised methods, for instance, type synthesis, a complete variety of solutions for leg joints were obtained in the form of basic and kinematic schemes, having the potential to find application in devices supporting lower limb rehabilitation. Results: A 3D model of ankle joint module was built in Autodesk Inventor System, then imported to Adams and assembled into a moving numerical model of a mechanism. Several conducted simulations resulted in finding the required maximum stroke of the cylinders. Conclusions: A comparison of the angular ranges of ankle joint and similar devices with the ones achieved by the designed device indicated a sufficient reserve allowing not only movements typical of gait, but approximately achieving the passive range of motion for the ankle joint.