Development of novel piezo-driven parallel-kinematics micropositioning stages.

摘要

Micro(nano)positioning capability is critical to many applications such as scanning probe microscopy, precision machining, microelectromechanical systems (MEMS) and high definition displays. They demand micropositioning stages with large work space, high bandwidth and accurate positioning. The major problem of the existing stages lies in their serial kinematic mechanisms (SKM), which are typically characterized by large moving mass, low bandwidth and high positioning error accumulation. They significantly hinder the stages' kinematic and dynamic performance. Meanwhile, other design issues have been found to cause overconstrained mechanisms, large machine volume, small travel range and etc.;To solve the above problems, we proposed novel designs for micropositioning stages. The key idea is to build the stages based on parallel kinematic mechanisms (PKM) that are more suitable for micropositioning than their serial counterparts. In order to further improve their kinematic and dynamic performance, the stages are built as monolithic systems by using flexure hinges as their motion joints, completely eliminating friction and backlash. These stages are driven by piezoelectric actuators which greatly enhance the bandwidth and positioning resolution. Our work addresses challenges in synthesizing, analyzing and manufacturing the novel piezo-driven parallel kinematic micropositioning stages. A meso-scale XY stage is firstly designed and fabricated by wire-EDM. The stage is tested in open-loop and closed-loop modes and its dynamic model was established based on the experiment data. It can move within a 87mum by 87 mum square with over 500Hz bandwidth along any in-plane directions. The work was extended to develop an XYZ stage, which features a similar but far more complex design. Numerical simulation is used for its kinematics and dynamics analysis. The design of the XY stage is further combined with microfabrication techniques to develop an XY stage made from single crystal silicon to achieve better performance and compatibility with MEMS devices. In addition to the development of the above stages, auto-calibration procedures and set-ups were proposed to allow these stages to be calibrated automatically and routinely using low-cost embedded calibration/sensing module. The mathematical validity of the procedures is proved by computer simulation. Ideas for future development of parallelkinematics micropositioning stages are also discussed.