Turmell-Bot.pdf

We present the design of the Turmell-Bot, an assistive robot for human ankle physical therapy. We studied ankle biomechanics from a multidisciplinary holistic approach and analyzed the two-rotational serial chain known as the talocrural and subtalar axes.

Moreover, we implemented a two-rotational cable-driven mechanism based on the ankle biomechanics. And, by using the screw theory framework, we study the tensegrity and mobility interaction between tendons and joints on the ankle joint. Then, we synthesized a four-tendon-driven robot that considers the human ankle approximation in the closed-loop mechanism. We represented the human ankle axis by Pl\"ucker line coordinates, integrating a draw-wire sensor system to capture the ankle movements and estimate the ankle axes' position and orientation. Then, we used the axis coordinates projected to the base and platform planes to reconfigure the cable anchor endpoints to equilibrate the antagonistic cable-driven actuators. Finally, we computed the workspace, the kinematics and validated the robot's stability with the software Mujoco and proposed a mechanical design.