Design of Human–Machine Compatible Ankle Rehabilitation Robot Based on Equivalent Human Ankle Model

In this letter, a human–machine compatible ankle rehabilitation robot (HMCARR) is proposed to help stroke patients with motion dysfunction recover their motor function. The HMCARR can make the human ankle center-of-rotation (H-CoR) and the ankle rehabilitation robot center-of-rotation (R-CoR) coincide in real-time. The overall idea is to analyze from the “human” perspective to the “human–machine” perspective, and then to the “machine” perspective. Firstly, from the “human” perspective: a
spherical-pair-with-clearance equivalent human ankle model
and a
H-CoR estimation model
are proposed, and the motion range of the H-CoR is analyzed. Secondly, from the “ human–machine” perspective: to obtain the mechanical design principles of the HMCARR, degree-of-freedom (DOF) and kinematic analyses of the
human–machine closed chain model
are conducted. Finally, from the “machine” perspective: DOF, kinematics, singularity, sensitivity, and workspace analysis are performed for the HMCARR based on a 3-RRCRR parallel mechanism, where R and C represent a revolute pair and a cylindrical pair, respectively. This study indicates that the mechanical design principles of the HMCARR include three requirements for the
DOFs, kinematic independence, and position workspace.
The results suggest that the HMCARR based on the 3-RRCRR parallel mechanism can achieve coincidence between H-CoR and R-CoR in real-time.