Control of a micro-forging system

• Main Author: Loh, Patrick Jin Kun.
• Other Authors: Ta Nguyen Binh Duong
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Mechanical engineering::Control engineering
• Online Access: http://hdl.handle.net/10356/53595
• Institution: Nanyang Technological University

Micro forging enable us to save cost and at the same time increases productivity, but as the forged material gets smaller it is inevitable to face problem such as size effect and also the struggle to keep surface roughness at a constant. Therefore in this project a piezoelectric actuator was selected as it provides features such as, high torque, precise positioning up to sub-nanometer, high stroke frequency, high resolution and repeatability. However due to inherent hysteresis and nonlinearity, if not properly studied and controlled a piezoelectric actuator can cause positioning error in open loop system and also instability in the closed loop system. This project is dedicated to characterize the hysteresis and nonlinearity in the piezoelectric actuator and compensating them with appropriate controllers. Experiment is conducted to collect data of the hysteresis of the system, to analysis the behavior of the system in a no load condition. Next an impact hammer test was done to simulate an excitation in the system, the acceleration data is collect via an accelerometer to get the stiffness, damping coefficient and mass of the system. Which allow us to form a closed loop transfer function of the system. In the attempt to control the piezoelectric actuator, a trial and error and root locus method was applied to identify the optimum gain of the system. It was observed that the optimum gain and displacement output can be varies even with the same system parameters, which was due to nonlinearity of the system and complexity of hysteresis. Therefore in the conclusion, suggestion of future control strategic to improve the current controller was highlighted.