Black box white box method
In the face of the vibration and noise of electric vehicles, this predecessor created a new set of tricks. Although the theory is not the first, the application in electric vehicles is enough for my generation to look back. This method is called black box white box method.
The so-called "black box" is the black box of "black box test". The motor is regarded as an internal agnostic object. It does not consider how the internal part of the motor is constructed, and only pays attention to the external characteristics of the motor. The so-called "white box" and "black box" are opposite, the motor is completely open and transparent to us, we can clearly know the theoretical structure and characteristics of the motor. The black box white box method consists of three major steps:
The first step is to learn the white box model. Obtain two things: 1 the theoretical spectrum of the main electromagnetic force of the motor; 2 the constituent components behind these spectra, these components can be the first-order cogging harmonics or the third-order permanent harmonics;
The key to white box learning lies in the analysis of which electromagnetic force waves are formed by harmonics of each order, which electromagnetic force waves are the main ones, and which electromagnetic force waves are secondary, and the general space times are small, and the large amplitude force waves are the main contradiction. Then the frequency of these force waves is calculated along with the change characteristics of the rotational speed, drawn on the waterfall graph (the ordinate is the rotational speed, the abscissa is the frequency), it is a diagonal line, and the frequency increases linearly with the speed.
The second step is the black box physical test. The predecessor built a motor test platform that can test motor vibration and noise data during constant speed and acceleration. This test platform is a pair of tow test platforms, one running as a motor and one running as an engine to simulate various operating conditions in a car.
The black box test mainly obtains two things: 1 actual noise spectrum (including noise waterfall map); 2 overall sound pressure and sound power as a function of speed;
Through the analysis of the black box waterfall map and the white box waterfall map, it is found that in addition to the theoretical noise spectrum, there are more abundant noise spectrum features. These noise spectra are mostly generated by current harmonics other than the fundamental current. The predecessor broke down the complex noise spectrum into separate components.
The source of the decomposition noise needs to be based on the actual experience of the engineer to determine which are the fundamental noise, which are the harmonic noise and which are the mechanical noise. It was also found through testing that the most noisy state was at 400 rpm, and it was judged that 400 rpm no-load was the main analysis condition.
The third step is a four-step model analysis. It is to analyze the electromagnetic force and the vibration response and noise distribution under the no-load condition of 400 rpm. Use this to find out the source of abnormal noise.
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