Stiffness modeling and analysis of a novel 4-DOF PKM for manufacturing large components

Faster response to orientation varying is one of the outstanding abilities of a parallel kinematic machine (PKM). It enables such a system to act as a reconfigurable module employed to machine large components efficiently. The stiffness formulation and analysis are the beforehand key tasks for its parameters design. A novel PKM with four degrees of freedom (DOFs) is proposed in this paper. The topology behind it is 2PUS–2PRS parallel mechanism. Its semi-analytical stiffness model is firstly obtained, where the generalized Jacobian matrix of 2PUS–2PRS is formulated with the help of the screw theory and the stiffness coefficients of complicated components are estimated by integrating finite element analysis and numerical fitting. Under the help of the model, it is predicted that the property of system stiffness distributes within the given workspace, which features symmetry about a certain plane and is also verified by performing finite element analysis of the virtual prototype. Furthermore, key parameters affecting the system stiffness are identified through sensitivity analysis. These provide insights for further optimization design of this PKM.