Design and Performance Assessment of a Cable-Driven, 3-DoFs Exoskeleton for Orthopedic and Poststroke Rehabilitation of the Wrist

Abstract

This research presents the mechanical design and performance evaluation of a novel 3-Degrees-of-Freedom (DoFs) wrist exoskeleton (W-EXOS) for orthopedic and poststroke patients' upper limbs rehabilitation. The device covers the 93.3% of the human Range of Motion (RoM), simulating the pronosupination, radioulnar deviation, and flexion–extension motion. W-EXOS is actuated through electric motors via an efficient cable transmission, having high torque/weight and torque/volume ratios. Its kinematics is a serial chain of three rotational joints with nonperpendicular axes competing at the wrist rotation center. So, the device joints are coupled but the structure is compact and with good mass distribution. Theoretical modeling allowed the study of the human wrist and the device axes matching, evaluating the RoM and torques at each joint. With the W-EXOS integrated into a rehabilitation station, the performance assessment was done using: 1) a position control test, for the device RoM validation and 2) a virtual reality serious game test, to prove the device assistance strategy during wrist motion tasks performed by healthy subjects in a typical rehabilitation session. Further, the W-EXOS handle has been replaced by a hand exoskeleton and the whole system has been mounted on a 4-DoFs shoulder–elbow exoskeleton, proving the W-EXOS integrability in multiple, highly wearable, compact, and usable, bimanual, upper limb robotic setups.