Ergonomics and kinematic compatibility of PKankle, a fully-parallel spherical robot for ankle-foot rehabilitation

PKankle is a robotic device based on a fully-parallel kinematic architecture and specifically designed for the neuro-rehabilitation of the ankle-foot complex. The peculiar kinematics allows the foot support to rotate, with good approximation, about the instantaneous center of rotation of the foot. An adjusting mechanical system allows the device to be employed in different patient positionings. Moreover, it features an integrated load cell for measuring subject interaction forces/torques, both to close impedance-based control loops and to obtain valuable clinical data, and a synchronized electromyographic acquisition system to analyze patient's muscular activity. The present work describes kinematic and control aspects specifically addressed to enhance its ergonomics and physiological compatibility to the actual mobility of the ankle-foot complex. Preliminary experimental activities, performed by healthy subjects, have been carried out to assess the effectiveness of the adopted solutions.