Research On The Integrated Multi-scale Methodology For Designof Ultra-precision Machine Tools

Ultra-precision machine tools relate strongly to the strategies of national interestsand security, and their relevant technology are listed as the national key technologies bythe United States, European Union, Japan and other countries, and received special aidfor development. The ultra-precision machine tools have their own distinguishingfeatures: structures span the spatial scales from nanometers to hundreds of millimeter;fluid medium between structures form fluid membrane bound surface with a certainamount of stiffness and carrying capacity. The performance of ultra-precision machinetools is a function of structures and bound surface parameters, and the tiny change ofworking position, posture and bound surface will bring a decisive affection to the wholemachine performance. Currently the design method of ultra-precision machine toolslacks the mechanism investigation of the affecting from the motion of multi-scalestructures and bound surface micro changing to the performance of ultra-precisionmachine tools. So this project proposes a ultra-precision machine tools multi-scaleintegration design method, and through the analysis of the characteristics of spatialscales and function scales of ultra-precision machine tools, interpret the micro-macrochanging of structure position and posture, the interpret the affecting mechanism frommicro feature of structures bound surface to the stiffness, accuracy, thermalcharacteristics, etc., thus provide a scientific guidance to the whole machine design ofultra-precision machine tools including stiffness, accuracy and thermal characteristics.This project takes research of ultra-precision machine tools into three levels:macro-scale, core-scale, and micro-scale. And three research goals are set tomacro-scale design, and they are the varying rules of accuracy and stillness, and thespatial analysis of the whole machine thermal characteristics. In core-scale, based on thekinematics, dynamics, heat transfer theory and spatial statistics method, relate thedesign parameters to the whole machine performance, and thus establish the mappingrelation between core-scale to macro-scale. In micro-scale, investigate the samplingmechanism and acuteness of the core-scale parameters, and build the tuning rules ofcore-scale-parameters. Through parameters seamless integration analysis of the threescales, obtain the relating rules between ultra-precision machine tools and multi-scaledesign parameters, thus determine the selecting rules of ultra-precision machine toolsdesign parameters, and finally guide the design process.Based on the antecedent thought, establish the whole machine stiffness model ofultra-precision machine tool systems, in order to investigate the integrated affectingrules from the multi-scale feature, such as surface micro structures, air bearing stiffness,structural stiffness, to the whole machine spatial stiffness. With the stiffness model based spatial statistics and Kriging method, parse out the design space to thecharacteristics of the state space mapping relationship, and analyze the modal-pose toget machine processing space modal information to guide the system stiffness design.Aiming at the fact that the whole machine thermal characteristics is a strongcoupling embedded multi-scale problems, adopt lumped parameter method to predictthe strong coupling distribution, and then establish the ultra-precision machine toolsthermal characteristics analyzing model based on local refining thermal resistancenetwork method, to investigate the spatial thermal distribution characteristics and thetemporal thermal transmission rules. The multi-scale method overcomes the weaknessof lagging in traditional thermal characteristics analysis, since it conduct thermalcharacteristics prediction in elementary design process, and propose coolingrequirement, and simulate the machine thermal distribution in detailed design process.In the research of the conjunction between various scale parts with their boundingsection, the positioning accuracy and the precision preserve, take the minimum spatialchanging of the difference value between the endpoint vectors of accuracy chain, as thedesign goal. Build error analyzing model based on multi-body kinematics theory, andadopt experimental design and effect analysis, solve the affecting rules from the varyingof3core-scale parameters, the verticality error, the tilt angular error and the straightnesserror. According the influence level from the former parameters to accuracy, determinekey design parameters, and provide theoretical support to ultra-precision machine toolsdesign. On this basis, build multi-parameter quadratic regression model for5-axis (160parameters), and compare the model with linear model (38parameters) and secondaryerror (741parameters), and obtain the optimized positioning accuracy and accuracypreserve, and validate the constraint settings of parameters during design process.Based on the above multi-scale analyzing method and principle of accuracy,stiffness and thermal characteristics, establish an integrated mathematical modelincluding stiffness, accuracy and thermal characteristics, and adopt the multi-scaleintegration design and simulation platform, achieve seamless data transmission amongmulti-scale parameters, to investigate the coupling effect of the performance relatedparameters, and explore the influence rules from the various factors and parameterschanging to the whole machine performance. Complete the integrated design andanalysis for a5-axis ultra-precision milling machine, and compared with the initialdesign, obtain more accurate performance parameters in design stage, and provideguidance principles to optimization design, and finally experimentally validate thedesign method proposed in this thesis.