| High speed processing technology, an advanced and practical manufacturingtechnology, is becoming the mainstream in manufacturing industry. With uniqueadvantages, it acquires the wordwide attention and gets stronger vitality and broaderapplication prospect. Because of the very high speed of the spindle, even tiny dynamicunbalance will cause huge centrifugal force and induce vibration of the spindle, whichwill subsequently influence the reliability, the service life, the working accuracy, etc.of the machine tool. Therefore, dynamic balance is an essential problem that must besolved in the manufacturing process of high speed, high accuracy CNC (computernumerical control) machine tool. The quality of dynamic balance will directlydetermine the work performance and service life of the high speed machine tool, andgreatly influence its quality.Avoiding frequently turning on and off the machine to adjust weights, thetechnology of online dynamic balance on machine tool spindle also has advantages inimproving balance efficiency and accuracy as well as producing automatic balance onimbalance according to the change of working condition. Therefore, the technology isincomparable and has become the first choice in high speed and high accuracy CNCmachine tool manufacturing center.This thesis is based on the spindle system dynamics and the related theory andaimed to realize the precisely online dynamic balance of high speed machine toolspindle system. The author carried out the research on the following key problems:the dynamics modeling and simulation of the spindle system, the extracting ofunbalance vibration signal, the development of built-in online dynamic balance deviceand its control system, the analysis of experimental effect and error, the application ofdouble-face online dynamic balance on flexible spindle, etc. The main contents of thethesis as follows:(1) The dynamics modeling and simulation of machine tool spindle. Based onrotor dynamics theory, the dynamic mathematical model of the spindle system wasestablished and the system simulation programs were designed by Labview. Spindledynamic characteristics were analyzed preliminarily by the application of simulationprograms, and the axial distribution curve of the double-face influence coefficient anddynamic unbalance adjustment value were proposed. The selection of the idealadjustment face and unbalance adjustment value were discussed. The selectingmethod of the ideal adjustment face based on the phase difference of system influencecoefficient was put forward in the thesis.(2) The extraction of unbalance vibration signal of the machine tool spindle. To measure and correctly extract the radial unbalance vibration signal of spindle is theprecondition of dynamic balance. In order to improve the extracting precision ofunbalance vibration signal, a new method was put forward in the project. Theprocessing of the method was to extract the form error of monitoring points on spindlefirst, and then to combine EMD (Empirical Mode Decomposition) and least squaremethod to extract fundamental frequency signal. The correlative study issues includedthe application of mathematical statistics in the spindle form error extraction, thetheory of fitting fundamental frequency with least square method and the practicaleffect analysis, the principle of EMD and its filtering, etc. The theory analysiscombining with simulation was adopted in the project. To improve the filtering effectof EMD method, the correlation function was employed to eliminate abnormal eventsin the original signal. The analysis showed that the signal extracting accuracy ofunbalance vibration was effectively improved by adopting these methodssynthetically.(3) The design of double-face online dynamic balance device and its controlsystem. According to the structure characteristics of high-speed spindle, a kind ofpneumatic online dynamic balance device was designed. The realization of the devicefunction, the overall structure, the hardware control system, the design or selection ofthe key parts, etc. were studied in the paper. Based on the requirement of the systemfunction, the mixed programming technology combining Matlab with Labview wasadopted to develop software control system. The software function included signalacquisition, signal analysis and processing, weight test, automatic monitoring andcontrolling, the control signal output, etc.(4) The analysis of experimental data and balance error. To examine thepracticality of double-face online dynamic balance system designed in the project,experimental researches were executed on location accuracy of balance disc, themeasure and calculation of influence coefficient and dynamic balance effect. The keyerrors and their influence on system balance accuracy were analyzed, such as themeasurement error, balance disc position adjustment error and inherent unbalancevalue error, the fit clearance between balance disc and spindle, the balance discquality distribution error, sensor installation error, etc. Some measures forimprovement were also put forward.(5) The rotor should be taken as flexible when work speed is close to or beyondthe first critical speed of rotation. Considering the generality of the double-face onlinedynamic balance system designed in the project, an adaptive gain dispatcher's controlmethod applied in online dynamic balance was put forward based on the analysis ofdynamic model and balance method of flexible rotor. The dynamic balance effect of the method was proved by simulation and experiment analysis on the basis oftheoretical analysis.The paper was based on practical application, and the research was carried outon double-face online dynamic balance for high-speed spindle and its keytechnologies. The correlative research has achieved its tentative goals respectively inthe extraction of unbalance vibration signal, the development of dynamic balancedevice and its controlling system, etc. However, because of the complexity of thesystem, further research or improvement of some aspects are still necessary.
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