Ultra precision positioning system for servo motor-piezo actuator using the dual servo loop and digital filter implementation

The ultra precision positioning technique has become one of the important parts in the development of precision machines. For positioning systems having a long stroke with ultra precision, a combined system including a global stage (coarse stage) and a micro stage (fine stage) is designed in this paper. A ball screw based servo motor is used as the global stage and a piezo actuator as the micro stage, in which some design parameters are analysed. To improve positional accuracy and remove the noise components of motion, the digital Chebyshev filter has been designed and implemented. The implemented digital filter has been found to improve accuracy by as much as three times. Positional accuracy has been readily achieved within 10 nm over the typical 200 mm stroke, and therefore this technique can be applied to develop high precision semiconductor equipment such as lithography steppers and probers. (C) 2000 Elsevier Science Ltd. All rights reserved.