| Ultra-precision equipment equipped with a vertical axis can process and measure complex surface optical surfaces,free-form surface molds and large ultra-precision optical parts.The ultra-precision vertical axis can expand the functions of machine tools and measuring instruments,and improve the processing capabilities of ultra-precision equipment.Measurement capability is an important part of ultra-precision machine tools and measuring instruments.The direction of motion of the ultra-precision vertical axis is the same as the direction of gravity.The main research contents of this article are as follows:(1)An ultra-precision air-floating vertical shaft system is designed,which mainly includes a gas static pressure guide,an unloading system and a drive control system.The porous air bearing is selected as the support method of the ultra-precision vertical shaft system,the advantages and disadvantages of different structural guide rails are studied and analyzed,and finally the internal slider type "U" type with high rigidity,machinability and good assemblability is adopted.Rail structure.The frictionless cylinder unloading system is used to compensate the gravity of the moving part;an ultra-precision air-floating vertical axis full closed-loop control system composed of hardware such as a controller,a linear motor and a grating ruler is constructed.(2)The mathematical model of the aerostatic bearing is established,and the aerostatic bearing is simulated and analyzed by FLUENT software,and the pressure distribution and velocity distribution of the gas passing through the porous material are obtained,and then the gas supply pressure,the average thickness of the gas film and the slip are obtained by calculation.The influence of the off-center position of the plate on the bearing capacity and stiffness of the system;the stiffness test experiment on the ultra-precision air bearing vertical shaft system verifies the correctness of the relationship between the thickness of the air film and the stiffness of the bearing in the finite element analysis.(3)Modal analysis and thermal analysis are carried out on the ultra-precision air-floating vertical axis system.The dynamic mathematical model of the ultra-precision air-floating vertical axis system is established.Through the modal analysis of the system,the first sixorder natural frequencies and mode shape diagrams of the system are obtained,verifying that the dynamic characteristics of the vertical axis system can meet the processing and measurement requirements;Through the thermal structure analysis of the system,the temperature distribution and thermal deformation cloud diagram of the system are obtained,the maximum thermal deformation is 0.11 mm,and the influence law of the temperature rise of the motor on the guide rail is obtained.(4)The influencing factors of the errors of the ultra-precision air-floating vertical axis system are analyzed,and the straightness of the ultra-precision air-floating vertical axis system is measured.When placed horizontally,the linearity errors in the x and y directions are 0.355μm and 0.691μm,respectively,and placed vertically.The linearity errors in the x and y directions are 0.568μm and 0.662μm.Experiments have been carried out on the smooth stepping trajectory and stepwise positioning of the controller,and the system’s position stability error is ±40nm and the minimum resolution is 100 nm,the measurement results show that the air-floating vertical axis system developed can meet the design requirements. |
PDF Full Text Request