Development of a new parallel mechanism with five degrees of freedom for ankle rehabilitation

With the aging population problem getting more and more aggravated, the number of hemiplegia patients increases rapidly, which results in the increasing requirement of rehabilitation training for regaining the body movement function. Taking advantages of rehabilitation robots makes the rehabilitation training more scientific and efficient compared to traditional rehabilitation measures such as manual training. By now, many types of rehabilitation robots have been proposed by researchers. However, from the view of the physiological structure, many of them can't well fit the motion characteristics. Ankle plays an important role in standing, walking and so on. As the motion of these robots is different from the motion characteristics of ankles, it would make an undesired influence on the training effect. Rehabilitation robots have many structures, and they are mainly serial mechanism and parallel mechanism. However, serial mechanism is inconvenient to package. In this paper, a new type of parallel mechanism with five degrees of freedom was proposed. Compared to serial mechanism, parallel mechanism is convenient to package and it has larger motion area. It enables ankles to rotate around the rotary center of the ankle. With the screw theory, the degree of freedom was calculated. To verify the working space of the mechanism, the working space simulation was carried out by Matlab. Finally, the quantity and position of motors are determined.