| With the development of semiconductor related industry, TFT-LCD products are now showing the trends of becoming larger and thinner, and therefore non-contact mode is required during the conveying process in order to prevent scratch on the surface. Current non-contact conveying technologies typically employ magnetic, electrostatic, ultrasonic and pneumatic levitation. The pneumatic levitation based conveying system has several advantages such as clean, magnetic free and generating little heat, and therefore comes to dominate in the non-contact conveying field. Traditional conveyors supply pressurized air beneath the floating glass by means of small orifices, balancing the weight of the glass panel by the lifting force to achieve non-contact status. However, there exists a considerable pressure peak at the center of the orifice, where stress concentration is likely to be caused. Besides, the high speed airflow from the orifice will undoubtedly puff up a large amount of dust and deteriorate the cleanliness. In order to avoid these problems, porous media are usually used to replace orifices to relieve the stress concentration and also restrain the airflow speed. As the continuous construction of the advanced production line for large LCD panel, to build non-contact conveying system using porous media is sure to become future tendency, but, the absence of basic theory model undoubtedly restricts the improvement of productivity greatly.In order to give instructions for optimal design of the porous media based non-contact conveying system, the present thesis adopts methods including theory analysis, mathematical modeling, numerical simulation and experimental study, to carry out a systematically and deeply research on the basic knowledge involved in the process of system construction. First of all, a flow rate characteristics model is established on the basis of principle when flowing through porous media, and a simple, convenient charge method for determining the flow rate characteristics of porous media is also proposed, with great reduction in the testing time and air consumption. Secondary, mathematical models that are able to describe the static and dynamic pressure characteristics of the air film are established respectively. Influence of the system parameters on the air film characteristics is analyzed, and the validity of the models is verified experimentally. Finally, a partial porous conveyor is designed, and corresponding instructions for system construction are proposed considering the dimensions of the glass panel. The main content of each chapter is summarized as follows:In chapter1, developmental course and main features of the conveying technologies for glass panel are briefly introduced. A review on the non-contact conveying technology is presented into categories, and the principles, constructional features, advantages as well as disadvantages of each approaches, are summarized, pointing out the superiority of employing porous media to build the non-contact conveying system. Developmental course of some pneumatic technologies concerning the flow measurement and gas lubrication are also presented. Finally, significance and main contents of this research are illustrated briefly.In chapter2, in view of the existing problems of ISO6358standard as well as its expanded expression in representing the flow rate characteristics of porous media, a Darcy-Forchheimer model is established to describe the flow rate characteristics considering the flow pattern in the porous media.6sintered metal porous resistances with different dimensions and porosities are prepared to perform test for examining the flow rate characteristics. A charge method employing an isothermal chamber and a pressure differentiator to determine the permeability coefficient and inertia coefficient is proposed. The charge method has advantages over the conventional steady state method for it takes only seconds to finish the test and consumes less air. At last, it is confirmed that the model based calculated flow rate show good agreement with the experimental data, and the experimental testing system can afford sufficient accuracy for practical use.In chapter3, a theoretical model, considering the radial flow between two parallel disks, and a3D finite element model are established within a representative region, respectively. Comparison of the simulation results between the two models is presented, and pressure distribution experiment is performed to verify the validity of the models. Experiments are also carried out to measure the load capacity of the air film, revealing that some factors such as supply flow rate, gap height and region radius have impacts on the load capacity and stiffness of the air film, and the reliability of the models are further confirmed.In chapter4, considering the velocity-slip phenomenon on the porous surface, a theoretical model concerning the air flow through the porous media into the gap was established within a representative region unit, and solved by using finite volume method (FVM). An apparatus, which vibrates a work piece back and forth to squeeze the air film, is designed to investigate the pressure response, and the relationship among air film pressure, stiffness, damping, and gap height are studied experimentally and theoretically. The experiment of free vibration for work piece under pulse disturbance is conducted, and the decay characteristic is analyzed in comparison with the model based calculated results. Finally, a principle, for determining the damping ratio by amplitude of the second and the third wave crest in the vibrating decay curve. is provided to represent the decay speed, and its influencing factors are also investigated.In chapter5, based on the1D deformation theory, virtual deformation of the panel under distributed load is calculated. Influences from the space between conveyors, supply flow rate, and flange width are detailed, and basic principles for parameter determination are provided. A kind of assembling unit for partial porous conveyor is developed, and an experimental system is set up using a double line distributed conveyor which is assembled by3units. A fast-solving method, based on the combined model of the radial flow and the Hele-Shaw flow between two parallel disks, is proposed to calculate the pressure distribution, improving the efficiency greatly. Flow rate characteristics, energy consumptions, together with the vibrating problems encountered in the conveying process are investigated experimentally and theoretically. The flow rate characteristics are described subjected to the Darcy-Forchheimer equation, and the fundamental conception of air power is introduced for energy evaluation. The approach of loading with negative pressure is able to decrease the floating height, increase the air film stiffness, and improve the Anti-Disturbance ability. Comparisons between the partial and total porous conveyors are conducted from the aspect of the stability of the movement, and the effective power as well. Features and advantages for each type of the conveyor are also summarized. In the end,4series of the air conveyor are designed for the production line, and corresponding constructional instructions according to different glass panel are provided.In chapter6, main research work, conclusions and innovation points of the thesis are summarized and future work is suggested.
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