Precision XY Positioning Stage With Coupled Flexures and Piezo Actuators for Avoiding Parasitic Tilt Error

In the field of scanning probe microscopes (SPMs), a precision positioning stage has become an important component as the requirement of the SPMs has been extended from high resolution to high accuracy. The stages used in SPMs plays a role of transferring a specimen or a probe in multiple directions. The stage should satisfy the requirements for small parasitic motion and compactness. Therefore a coupled flexure leaf spring is used as a guide mechanism at recently developed multi-directional nano positioning stage with piezo actuator. Using the coupled flexure leaf spring mechanism, a compact and symmetric stage can be embodied. However, in this case, there are some problems caused by assembly process of piezo actuators. The first is that piezo actuator can be broken because of bending force when another axis is working. Commercially stack type piezo actuators are composed some ceramic materials, so they are brittle. This problem causes the durability weakening of ultra precision positioning stage. The second is unnecessary parasitic tilt error. When an actuator of one axis is acting, the other non-acting actuator works as constraint force. As a consequence, the accuracy of each axis gets lower and the control to compensate parasitic motion becomes difficult. In this research, we will propose a precision positioning stage with coupled flexures and piezo actuator to withstand bending force and avoid a parasitic tilt error. This research includes performance analysis and parametric design of the stage. The stage is designed for motion of two degree of freedom using a flexure leaf spring. Design optimization based on a finite element method (FEM) is also covered in this study. Simulation results show that the optimally designed stage decreases a tilt error less than 25% compared to the stage without concerning the bending and constraint.© 2009 ASME