[Design and analysis of a serial ankle rehabilitation robot]

To address the complex mechanism configurations, strong motion coupling, and control complexity associated with some existing ankle rehabilitation robots, a two-degree-of-freedom serial ankle rehabilitation robot with independent actuation is proposed. The robot is capable of providing single-degree-of-freedom training in plantarflexion/dorsiflexion and adduction/abduction, as well as compound motion training. A kinematic model of the spatial orthogonal 2R mechanism was established, and its kinematic performance was analyzed. Ankle posture coupling constraints were introduced to refine the workspace. A prototype of the rehabilitation robot was subsequently fabricated, and ankle angle-tracking experiments were conducted using a Vicon three-dimensional motion capture system. The results showed that the mechanism had no singular configurations within the physiological range of motion of the human ankle. The maximum condition number was 1.414. In the prototype experiments, the mean absolute error and root mean square error for plantarflexion/dorsiflexion were 1.443° and 1.650°, respectively. For adduction/abduction, the corresponding values were 0.789° and 1.005°. These results demonstrate the feasibility of the proposed robot configuration for ankle rehabilitation and its favorable performance in tracking human ankle joint angles during robot-assisted motion.