Regardless of the method used, in any case it is not possible to reproduce the transport environment in the laboratory, they can only approximate the transport environment to some extent or from a certain point of view. With numerical control equipment, it not only simulates the test conditions described by the accelerated power spectral density, but also has a Gaussian distribution in the amplitude range, which is quite close to the actual situation in the amplitude range. Therefore, the transportation test simulation realized by the current numerical control equipment has made great progress compared with the past.
Under the control of the DP-550win vibration controller, the specified test conditions are generated at the control point. The main technical indicators of the equipment are as follows: maximum sinusoidal thrust: 100kN; maximum random thrust: 70kN; maximum amplitude: 50mm; maximum acceleration: 10g (1t load); operating frequency range: 0.5500Hz; allowable maximum eccentricity: 50mm (1t load) ).
The lower frequency limit of the simulation is determined by the maximum displacement that the vibrating table can provide. The vibration table displacement required for the test conditions is usually estimated by the following formula. XPP=1066.8(G(f)f) 1/2, mm. Usually, according to the calculation result, according to the actual capacity of the hydraulic platform, the lower limit frequency of the simulation condition is finally determined.
As mentioned earlier, large acceleration peaks are generated during transportation, resulting in a distribution of amplitude probability density that does not conform to the Gaussian distribution. As an example, the acceleration power spectral density, acceleration time history, and amplitude probability distribution of the acceleration of the trailer vibration given in the MIL-STD-810E standard are taken. There are two probability density maps: one is the middle region of the probability density and the other is the tail of the probability density. When the discrete large peaks are small, the probability density distribution of the acceleration amplitude is consistent with the normal distribution; when the large discrete peaks are large and the amplitude is large, the difference between the two is large, and there is a long tail, and the region is also normal. Distribution of sharp points.
However, today's CNC devices can only simulate random signals with a normal distribution of amplitude fields. For non-Gaussian distributions, the only thing that can be done is to cut off the tail of the distribution compared to the Gaussian distribution without changing the middle of the distribution. Therefore, in order to simulate a similar transportation environment, the existing numerical control equipment should be supplemented with appropriate amplitude probability density distribution control. This requires the development of a dual domain CNC system with frequency domain and time domain.
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