Kinematically identical manipulators for the Exechon parallel manipulator and their comparison study

• The principle for deriving kinematically identical manipulators (KIMs) is proposed.
• Some overconstrained and non-overconstrained KIMs of the Exechon PM are derived.
• The unified force/stiffness model for the Exechon PM and its KIMs is established.
• The global stiffness indices for the Exechon PM and its KIMs are compared.

This paper presents the kinematically identical manipulators (KIMs) for the Exechon parallel manipulator (PM) and studies the differences among them. First, based on the linear transformations and the velocity transmission equation, the original Exechon PM is converted into six novel KIMs. Second, to reveal the differences among the Exechon PM and its KIMs, the unified force and stiffness model which is suitable for these PMs including overconstrained and non-overconstrained PMs is established, and the stiffness performance indices of these PMs are studied. Finally, by expressing the rotation parameters using position parameters, the workspace is homogenized and the numerical solutions of the global stiffness indices for the Exechon PM and its KIMs are obtained and compared. This study provides insights into lower-mobility PMs with identical kinematics and increases the possibility to obtain mechanism with better performance.