Design and control of two planar cable-driven robots for upper-limb neurorehabilitation

Post-stroke robot-aided neurorehabilitation is an emerging research field, aiming to improve the intensity and the effectiveness of post-stroke rehabilitation protocols by using robotic technology and virtual reality. One classification that has been proposed for therapy robots is between exoskeletons and end-effector based machines. The latter are those devices whose interaction with the patient's arm takes place at the end-effector level. This paper presents the design of two novel end-effector based robots for upper-limb rehabilitation, named Sophia-4 and Sophia-3. Although the devices are based on a common concept (the cable-drive actuation over a planar workspace), the latter differs from the former by the number of employed cables (4 and 3, respectively), and, by several design solutions, such as the introduction of a moving pulley-block to enhance workspace and a tilting table to better target the patient's shoulder. Both mechanical and control system design are addressed and a comparison of performances is presented.