Optoelectronic Feedback Electrostatic Levitation Technology

With the development of modern industry and technology,some conveying and manipulating operations in non-contact mode need the suspension technology in the fields of guiding system,material processing,micro-electronics and semi-conductor industry and so on. Therefore,it is of great importance to develop the suspension technique. There have been some conventional suspension methods at present,among them,magnetic levitation,acoustic levitation,aerodynamic levitation,optical levitation,radio-frequency levitation,electric levitation and super-conducting levitation. Despite of their excellence,these methods should be further developed on several aspects. Magnetic levitation is unable to levitate non-magnetic material directly.Acoustic levitation,which needs the compelled vibration with high frequency,might destroy the levitated object. Aerodynamic levitation might produce some high noise,and it is difficult to realize accurate levitation. Radio-frequency levitation is only capable of levitating metallic conductors. Optical levitation is strictly limited to levitate micro-scale object such as a molecular. While electric levitation is not competent for high precision control because of low tuning precision and slow modulating speed. In viewpoint of the improvement of suspension technique,we developed a novel suspension technique,that is,the electrostatic suspension based on optoelectronic feedback control (ESOFC). The most significant advantages of the electrostatic suspension are as follows:(i) It keeps the characteristic elegance of the conventional electric suspension methods mentioned above;(ii) It is capable of realizing electrostatic levitation of conductors,semi-conductors and non-conductors,such as the liquid crystal display (LCD),the compact disk (CD),the silicon wafer and so on;and (iii) It provides the possibility of implementing non-contact conveying or manipulation of precision objects on the basis of suspension.The research content and achievements of this thesis are as follows.It provided a theoretical discussion about the mechanism of the electrostatic suspension,including the mechanism of electrostatic induction and polarization,as well as the behavior of electrostatic force acting on the suspended objects. We explained,for the first time,the detailed rules of electrostatic induction and polarization between electrostatic electrodes and different suspended objects (conductor,semi-conductor,and dielectric). On the other side,we have also built the theoretical model of the electrostatic force acting on suspended objects during suspension,and deduced the universal formula for calculating the forces. Based on the theoretical results mentioned above,we developed the new method of electrostatic suspension aided with an optoelectronic feedback control system.We have constructed the experimental setup and the equipment used to realize the non-contact operation of ESOFC. A few experiments were carried out to measure the electrostatic forces. The results show a satisfactory matching between the theoretical formula and the experimental data. To keep a stable suspension gap,we designed and built an optimized optoelectronicfeedback control system. The system has an accuracy of better than 10 umwhen controlling the gap within the range from 250 um to 400 um.Using our experimental setup,some experiments were further made to check the feasibility of ESOFC. An aluminum disk,a silicon wafer and a CD,which are of different electrical conductivity,were employed as the suspended objects respectively. Stable suspension states have been observed during all of the experiments,concluding that the majority of objects with different conductivity can be levitated by using the method of ESOFC.