A Compact Mirror-Symmetrical XY Compliant Parallel Manipulator for Minimizing Parasitic Rotations

The design of XY compliant parallel manipulators (CPMs) remains challenging considering the tradeoff between mirror-symmetry for better constrained undesired rotations and a small footprint, although a significant number of XY CPMs have been reported in extensive applications. This paper presents a new XY CPM using mirror-symmetry without increasing its footprint, mainly aiming to reduce the undesired parasitic rotations of input and output motion stages. The concept of mirror-symmetry is deployed to tackle the parasitic rotations, with the help of using a multilayer compact XY CPM design method. A nonlinear and analytical model of the proposed XY CPM is derived using free body diagrams and the beam constraint model (BCM) to accurately analyze its performance characteristics over a large range of motion. The designed XY CPM is then verified by the nonlinear finite element analysis (FEA) method. Finally, the proposed multilayer design is fabricated using two pieces of aluminum plate and it is mounted in a measurement system to experimentally validate several performance characteristics. The analytical, FEA, and/or experimental results show that the proposed design can sufficiently constrain undesired motions including parasitic rotation of input and output stages, cross-axis coupling error, and actuator isolation index. Compared with exiting designs, the proposed design also shows its merits in large motion range and out-of-plane stiffness.