Stiffness analysis of a metamorphic parallel mechanism with three configurations

•A novel metamorphic parallel mechanism for robotic legs is proposed based on an innovative rotatable-axis revolute joint.•The inverse kinematic model of the new mechanism is established and the cloud picture of its workspace is obtained. Then the possible applications of the mechanism for mechanical legs is discussed.•The stiffness model is formulated with the consideration of the deformation of the main components caused by the actuation and constraints.•The stiffness distributions in the sub-workspace around the desired trajectory are evaluated.