Design and control of a cascaded piezoelectric actuated two-degrees-of-freedom positioning compliant stage

• We realized a 2-DOF piezoelectric driven stage.
• We performed PID, SMC, and input shaping controls.
• Stage bandwidth and resolution are 100 Hz and 0.1 μm.

A novel piezoelectric driven compliant stage and its associated PC-based X–Y axes control schemes have been developed as a potential carrier of automatic optical inspection (AOI) systems and other possible applications in precision positioning. The design is based on compliant structure with a mechanical amplifier mechanism. Two orthogonal stages are integrated into a final 2-DoF design. This approach offers the advantages of directly using a well-development design with minor modifications and the performance can be more precisely controlled. However, this also brings concerns in coupling between two motion axes due to manufacturing and alignment errors and this issue is examined experimentally. By integrating feedback control with the stage, it is possible to perform precision positioning and vibration suppression for improving the dynamic performance. This cascaded structure design can effectively reduce the system complexity and can be further extended for additional degrees of freedom. Based on the test results, the designed stage can achieve a closed loop bandwidth up to 100 Hz and a steady state resolution less than 50 nm using a model reference sliding mode controller. In addition, a shaping-control integration approach is also demonstrated for providing faster positioning while maintaining the robustness against possible external disturbances. Meanwhile, the experimental results indicate that the coupling due to manufacturing and assembly errors exists but this can be effectively reduced by proper trajectory planning with incorporating of dual-axis control. In summary, this study has realized a structurally-simple and low-cost positioning system and is able to achieve high-precise motion. It is hope that this study can be further expanded to longer stroke and higher precise positioning system, and integrates with cutting edge technologies for developing more superior precise instrument in the future.

A 10 Hz circular path control responses with a moving ratius of 5 μm.Figure optionsDownload as PowerPoint slide