Kinematics and dynamics comparison between three parallel robots for lower extremity rehabilitation

Ulceration of the foot is one of the most common complications of diabetes mellitus and diabetes-related cause of hospitalization and lower extremity amputations. There have been proposed several treatments and utilized different devices to prevent or at least improve this. It has been shown physical therapy interventions are the most effective in the treatment of diabetic foot wounds among of all the proposed treatments, where a fully controlled motion in patients' foot is desired on a pure rotational trajectory. Therefore, parallel robots represent a good candidate for this rehabilitation purpose because of their high accuracy. This paper is devoted to designing optimal structures of three six-degree-of-freedom parallel robots (i.e. Stewart, HEXA, and INRIA Active Wrist) for the lower extremity rehabilitation by the use of the genetic algorithm and Monte Carlo method. For this purpose, several key designing parameters such as the size of the platform, the length of manipulators, actuators' parameters, and reachable workspace are considered. These designing parameters are optimized such that results in the best systems' kinematics and dynamics performance. Consequently, the advantages and disadvantages of each platform are discussed.