Design Of Ultra-Precision Hydrostatic B-Axis Rotary Table And Analysis Of Static And Dynamic Characteristics

With the development of advanced technology,ultra-precision machining technology and machine tools have been widely used in national defense and civilian industries.Hydrostatic rotary table has the advantages of large bearing capacity and high motion precision,which utilizes the hydrostatic support principle and the motor direct drive technology,and it is suitable for ultra-precision machining and testing equipment.As an important part of ultra-precision machine tools,the performance of hydrostatic rotary table has a significant influence on accuracy and stability of the machine.It is of great significance to analyze the static and dynamic characteristics of hydrostatic rotary table and design a hydrostatic rotary table with high stiffness and rotation accuracy.In this thesis,according to the indicator requirements of the hydrostatic rotary table,the structural configuration and the servo system scheme of hydrostatic table are designed.The structure dimensions of the thrust and radial bearings are designed by the engineering calculation software of hydrostatic bearings.The internal friction torque and average rising temperature of the hydrostatic bearings are calculated according to viscous fluid shear force formula.Finally,the thickness of thrust bearing plate is determined by simulation and the assembly structural model of hydrostatic rotary table is designed.The fluid-structure coupling analysis of thrust bearing and radial bearing in hydrostatic table is carried out by sequential coupling method and Workbench.The structural meshing and steady analysis of oil flow field in hydrostatic bearings are realized by ICEM and Fluent.The simulation results of flow field are imported into Mechanical static analysis module so as to simulate the deformation of the hydrostatic bearings under the pressure of flow field.And the variation of the bearing clearance and the stiffness of hydrostatic table is calculated after deformation.The dynamic characteristics of hydrostatic rotary table and its servo system are analyzed.The natural frequency and modal of hydrostatic table are obtained by modal analysis.The forced vibration under cyclic loading of hydrostatic table is analyzed by harmonic response analysis.A closed-loop servo system model of hydrostatic table is established.The parameters of the servo system are designed based on the PID control principle.And the steady-state error and tracking accuracy of servo system are simulated and analyzed.After the processing and assembly of hydrostatic table,the static and dynamic characteristics of the hydrostatic table are measured.And the axial stiffness of hydrostatic table are also measured by high-precision inductive gage.The natural frequency of the hydrostatic table is measured by a modal analysis instrument.Finally,the run-out errors are measured by inversion method,and the shape and eccentricity errors of the ultra-precision standard ball are separated.