Performance analysis of a 3-PS v U reconfigurable parallel mechanism

In addition to the inherent advantages of parallel mechanisms, such as high precision and high load capacity, reconfigurable parallel mechanisms (RPMs) can reconfigure themselves to adapt to diverse, complex and changeable task requirements. This paper proposes a new 3-PS _v U RPM driven by prismatic joints. The RPM can achieve translation and rotation capacity in different operation modes, which can reduce manufacturing costs. Besides, the proposed RPM is actuated by three lead screw and nut assemblies, resulting in a high driving accuracy. In this paper, the kinematic and dynamic performance of the proposed RPM are evaluated. Firstly, mobility analysis is conducted based on the screw theory. Secondly, the inverse kinematic models of the RPM are established, based on which the reachable workspace is searched by considering some constraint conditions. Thirdly, inverse rigid body dynamic models of the RPM are built through the virtual work principle, which is verified by a simulation model. Finally, a unified kinematic index and a unified dynamic index are proposed, based on which the kinematic and dynamic performance of the RPM are evaluated. Results show that the reachable workspace of the RPM is regular and continuous. A smaller radius of the platform and a longer length of the limb are conductive to achieving better kinematic performance. Correspondingly, the dynamic performance is more sensitive to the length of a limb and minimizing the limb length is prioritized to achieve better dynamic performance.