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Identification Of The Key Characteristic Parameters In Dynamics For A Sliding Bearing-Rotor System Of High Speed Spindle

Posted on:2016-08-28Degree:DoctorType:Dissertation
Country:ChinaCandidate:W G MaoFull Text:PDF
GTID:1221330473967156Subject:Mechanical engineering
Abstract/Summary:PDF Full Text Request
With the development of advanced manufacturing technology, the high speed motorized spindle and sliding bearing are widely used in high-grade CNC grinding machine. The dynamic characteristics of a sliding bearing-rotor system of high speed spindle and the key characteristic parameters in dynamics such as bearing dynamic parameters and unbalance parameters are of complex relationship which plays an important role in the machining accuracy of the numerically controlled machine tools. However, it’s often difficult to obtain bearing dynamic parameters of sliding bearing and unbalance parameters of a motorized spindle system by measuring directly because of the influence of complex factors such as the processing conditions and test environment.This dissertaion is centering on the topic of parameter identification of bearing dynamic parameters and unbalance parameters for a sliding bearing-rotor system of high speed spindle.Firstly, the forward dynamics models of high precision and high efficiency are established to gain the mapping relation among bearing dynamic parameters, unbalance parameters and the dynamic characteristics of a motorized spindle system.Then the dissertaion conducts a systematical research to the problem that the inverse problem is ill-posed and bearing dynamic parameters is of uncertainty arising from the key characteristic parameters dentification in dynamics for a sliding bearing-rotor system of high speed spindle.Based on massive literature review,the major contents of this dissertation are listed as follows:1) In order to consider the weight and electromagnetic torque of the motor in building the fluid-solid coupling dynamics model of the motorized spindle system, the Riccati transfer matrix is improved. The status vector of typical unit is modified to ten for the introduction of the weight and torque of the motor. The displacement Riccati transfer matrix models are builded to calculate the complex frequency and the unbalance response of the motorized spindle system.Additionally, in order to eliminate the numerical instability of the transfer matrix method, this dissertaion extends the Riccati transfer matrix method to the transient analysis of the motorized spindle system, the acceleration Riccati transfer matrix is obtained with the aid of the Newmark acceleration formulation.2) Considering the time consuming and instability of the traditional method to analysis dynamic characterstcs of a bearing-rotor system.This dissertaion presents a high efficient and high precision method for calculating the unbalance response and the transient response of the motorized spindle system.Firstly, dynamic characterstcs of a hydrodynamic journal bearing in laminar flow and turbulent regime are achieved by the variational method instead of using the finite difference method in order to solve prescription generated by the iteration.Calculating efficiency is greatly improved.Secondly, considering the phenomenon that the critical speed was only focused on in the resonance region of the system in actual engineering, the complex frequency can be estimated and stability predicted by argument principle with greater efficiency and without missing any modes. Bi-group evolution strategy is used to search for the critical speed of the high speed spindle with the characteristic polynomial avoiding the traditional Muller theoretical method which is sensitive to initial value selection. Thirdly, the unbalance response of each section in the motorized spindle system is gained by the improved Riccati transfer matrix method. Additionally, In order to builde the transfer matrix of bearing elements, the deflections and velocities of the stations containing bearing element are predicted by Taylor series coupling with the dynamic analysis method of bearing dynamic parameters,the transient response is solved by the improved acceleration Riccati transfer matri method according to the boundary conditions.3) Considering the bearing dynamic parameters can not be gained by calculating directly when the oil cavity of sliding bearing is complex under the condition of high speed and heavy loads. A high efficient parameter identification method is presented to identify the bearing dynamic parameters of a sliding bearing-rotor system of high speed spindle. In this method, the parameter identification problem is formulated as an optimization problem.The bearing dynamic parameters have been characterized through minimizing the error squared of the motorized spindle system unbalance response between the experiment results and the computational ones.The Intergeneration Projection Genetic Algorithm is used to minimize the error squared.Results indicated that this method could identify the bearing dynamic parameters. It is also robust to the noise effects.Finally, this approach has been applied to identify the sixteen bearing dynamic parameters of a test rig supported by two anisotropic bearings according to the unbalance response experimental data.4) The traditional balancing method is often a time-consuming and expensive task because of requiring many machinery startups and in the rotor balancing field, there is a coupling relationship between the bearing dynamic parameters and unbalance parameters. A parameter identification method is presented to identify the unbalance parameters of a sliding bearing-rotor system of high speed spindle. In this method, the unbalance parameters identification problem is formulated as the unbalance forces reconstruction. In which the unbalance forces are expressed as the functions of time and the forward model for the unbalance forces identification is established through the discretized convolution integral of unbalance forces and the corresponding transient response functions of the motorized spindle system. A regularization method is adopted to deal with the ill-posedness arising from the deconvolution and noisy responses.Then, considering the uncertain parameters in the boundary conditions, based on the interval analysis method, an unbalance parameters identification method containing uncertain parameters is presented.Through interval mathematics and the interval analysis method, the unbalance parameters identification for uncertain parameters(bearing dynamic parameters) can be transformed into two deterministic inverse problems,and the upper and lower bounds of the unbalance parameters can be easily obtained through interval expanding operation. Finally, the efficiency and robustness of the proposed method are verified and this approach has been applied to balance a test rig by the identified unbalance parameters.
Keywords/Search Tags:Sliding bearing-rotor system, High Motorized spindle, Parameter identification, Improved transfer matrix method, Bearing dynamic parameters, unbalance parameters
PDF Full Text Request
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