Radial rotation error prediction method for static air pressure main shaft

An aerostatic spindle and rotation error technology, applied in special data processing applications, instruments, electrical digital data processing, etc., can solve problems such as the influence of spindle vibration and the impact on bearing dynamic characteristics, and achieve the effect of optimal design and error control

Active Publication Date: 2018-07-17

BEIJING UNIV OF TECH

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AI-Extracted Technical Summary

Problems solved by technology

Due to the compressibility of the air film in the aerostatic bearing, the fluctuation of the air film will be directly reflected in the vibration of the spindle; at the same time, because the bearing gap of the aerostatic bearing is at the micron level, the gas flow inside it be...

Abstract

Provided is a radial rotation error prediction method for a static air pressure main shaft. The method conducts prediction in consideration of micro-scale effects of air film flow in a static air pressure bearing and nonlinear dynamic characteristics. According to the structure and a principle of the static air pressure bearing, flow factors embodying the micro-scale effects are introduced to establish a mathematical model of the air film flow of the static air pressure radial bearing under micro-scale; an air film is transformed into a spring damping system with two freedom degrees perpendicular to each other, the flow model is calculated, and nonlinear dynamic stiffness and damping coefficients are assigned to the spring damping system under the micro-scale; according to the structure and working principle of the static air pressure main shaft, a bearing-rotor system model composed of the air film and a rotor is established; based on the characteristics of main shaft vibration, a mathematical model of dynamic vibration of the bearing-rotor system is established; various vibration errors of the static air pressure main shaft are obtained, and total radial rotation errors of the main shaft are obtained by integrating the various errors.

Application Domain

Design optimisation/simulationSpecial data processing applications

Technology Topic

Damping factorNon linearity +13

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Examples

Experimental program(1)

Example Embodiment

The methods attached in the present invention are all realized by MATLAB software programming program.

The method of the present invention specifically comprises the following steps:

Step 1, by analyzing the structure of the aerostatic main shaft, considering the micro-scale effect, a micro-scale air film dynamic flow model of the aerostatic radial bearing is established.

Step 2: Calculate and obtain nonlinear dynamic parameters of the aerostatic radial bearing at the microscale.

It can be seen from Figures 2b)-2e) that the dynamic stiffness and dynamic damping coefficient of the aerostatic radial bearing change nonlinearly with the change of the gas film thickness; at the same time, it can be seen that when the micro-scale effect is considered, the dynamic Although the parameters have not changed the variation law, their values have decreased. Therefore, considering the nonlinear dynamic characteristics at the micro-scale, it is more accurate and in line with the actual situation to predict the radial rotation error of the aerostatic spindle.

Step 3, establish the bearing-rotor system model of the aerostatic main shaft and the corresponding dynamic vibration mathematical model.

In step 4, combined with the nonlinear dynamic parameters in the micro-scale, the mathematical model of dynamic vibration is calculated to obtain each vibration signal of the main shaft and the total vibration signal.

It can be seen from Fig. 4a)-4b) that the nonlinear analysis considering the micro-scale effect at the same time increases the vibration errors of various spindles to different degrees. It is closer to the experimental measurement data; compared with the predicted value of the gyroscopic error under the traditional situation, the error rate of the predicted value of the gyroscopic error of the nonlinear analysis in the micro-scale is increased by 5.4% to 6.6%.

Figure 4a) shows the predicted vibration signal of the spindle rotation error considering the microscale effect and the traditional situation, and Figure 4b) shows the comparison between the predicted value of the rotation error at different speeds and the experimental data.

PUM

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