Research on an Electro-pneumatic Vibration Isolation Stage

• Main Authors: Jia-Syong Li, 李佳雄
• Other Authors: Shang-Teh Wu
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/45163958873921857835

碩士 === 國立雲林科技大學 === 機械工程系碩士班 === 97 === In this thesis a linear variable differential transformer (LVDT) and a proportional pneumatic valve are used to replace the mechanical leveling valve in a vibration isolation table. Besides alleviating the problem of abrasion in a mechanical leveling valve, the electro-pneumatic isolation stage may also yield higher positioning precision. An 8-bit microcontroller is employed to implement the control algorithm. We first test a PI controller on the system. Significant stiction effect is found in the electro-pneumatic isolation system. While the PI controller is able to minimize the steady-state error, it takes a relatively long time for the system to settle down. We therefore improve the performance using a PID controller. It is found, however, that adding a negative derivative (D) feedback makes stiction worse. The situation is improved if positive D feedback is used instead. Finally we combine positive and negative D feedback in the PID controller and switch the sign of the derivative gain according to the magnitude of velocity. It turns out that much faster transient response can be achieved while the steady-state errors are maintained within mm.