| This paper is mainly to study leveling system of high-precision-platform, analyze its required performance and supporting trait, design a high-precision-platform leveling system controlled by PLC. And the system realized a fast, stabilization and high precision leveling. It mostly includes several parts as follows.The first, the platform's static model is build and its load trait is analyzed in different states. Then based on analysis and compare of platform leveling scheme, a 'highest point fixed' leveling scheme called 'chase' is choose for the system because it have the virtue of high precision and fast leveling. Reasons and solutions of 'vain leg' are analyzed, and the way of fixing a pressure transducer to every leg together with an only-rise motion is selected.Secondly, through comprehensive analysis of the system's design requirements, design principles and technological index, four-support-rigid platform, PLC controller and fluid drive is used in this leveling system. And then the type of key device of the system is fixed further. The hardware of the PLC leveling control system is configured after the research on its Structure and function, and then the system's software including structure, work flow as well as each control module of PLC is designed.Finally, to cover the shortage of the PLC control system, a predictive control algorithm of rigid model is brought forward based on comprehensive analysis of leveling policy and static analyses of the rigid model. Take the platform's nonrigid deformation into account, the output of simulation in the MATLAB 7.0 proven that, the predictive control algorithm could not only lead the system reach the required precision faster but also reduce the system's overshot and oscillation. So it could be applied in practice leveling system. |
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