Optimal Design Of High Precision Hydrostatic Guideway

With the progress of industrialization in our country,the machining precisionrequirements of processing and manufacturing industry have become higher,the ordinary guideway can not meet the requirements of modern machine tools for high precision and high speed.Hydrostatic guideway has the advantages of low friction coefficient,high precision,long service life and no creeping movement at low speed,which makes it the best choice for high precision machine tools.After the research on the mechanical structure and hydraulic system of the closed hydrostatic guideway,this article carries on the optimized design to it.The ordinary fixed throttle or membrane restrictor is replaced by servo valve to control actively,which improves the load and stiffness of the guideway obviously,and avoid the resonance phenomenon of the membrane restrictor.The research in this paper has the following main contents:(1)After comparing the pros and cons of open and closed rail structures,we chose to use a closed structure because it can carry two-way load.The upper and lower oil chamber and the left and right oil chamber work together,so that the guideway can bear the eccentric load and torsion torque,and the rail stiffness of the closed structure is significantly improved compared with the open type.(2)In view of the fact that the membrane restrictor adjust the pressure of the upper and lower oil chamber according to the change of load,it difficult to produce,and it is prone to resonance,we innovatively adopt the high frequency response servo valve as the throttle,and ues active control to adjust the oil film thickness.A closed loop hydraulic system is formed by the displacement feedback of the displacement sensor.(3)I set up mathematical model for each part of the guideway hydraulic system.According to the structure of the oil chamber of the guideway,the flow pressure equation of the oil chamber is listed,then the force balance equation of the guideway is established,finally the flow continuity equation is listed.After the Laplace transform of the three equations,the mathematical model of the oil chamber of the guideway can be obtained simultaneously;Then the mathematical models of displacement sensor,servo valve and servo amplifier are established;The system transfer function is obtained by combining the mathematical models of each link,and then the simulation analysis is carried out by using the simulation software Simulink.(4)The traditional PID and fuzzy PID control strategy are adopted to optimize the control of the closed-loop hydraulic system of the guideway,and the effects of various control methods are compared and analyzed.(5)Firstly,the three-dimensional model of the oil chamber of the guideway is established,and then the 3D simulation software Fluent is used to analyze the flow field pressure in the guidewayl oil chamber.The assumptions of oil pressure in the design stage were verified.Observe the influence of the size of the inlet pipe on the oil pressure field and optimize the oil chamber structure designed before.