Research On Determination Of Three-axis Six Degree Of Freedom Vibration Test Conditions

The three-axis six-degree-of-freedom(6-DOF)vibration test realizes the translation of three orthogonal axes and the rotation around three orthogonal axes,which can restore the actual working state of the equipment or structure to the greatest extent,and the premise of the test is to have Vibration test conditions.Based on induction method of the single excitation vibration environment test condition provided by the US military standard and the national military standard,the paper studies the three-axis six-degree-of-freedom vibration test conditions.The specific work of this paper is as follows:The basic theory of 6-DOF vibration test is explained.Based on the characterization method of single excitation vibration test conditions,the characterization method of 6-DOF vibration test conditions is derived.The measurement method of the 6-DOF measured signal is deduced in detail,and finally the conversion matrix from the three-axis signal to the 6-DOF signal is obtained.The data inspection method of random vibration signal is discussed to prepare for signal induction.The power spectral density(PSD)estimation method of 6-DOF signal is derived,and the characteristics of signal power spectral density are expounded.Next,combining the single excitation vibration test conditions and the power spectral density characteristics of the 6-DOF signal,two methods for determining the 6-DOF vibration test conditions based on the measured data are proposed.The mathematical analysis software MATLAB and the proposed determination method were used to summarize the measured signals,and the 6-DOF vibration test conditions obtained by the two methods were obtained.A comparative analysis of them shows that the test conditions of the two methods are consistent and can meet the requirements of the 6-DOF vibration test.After that,based on the previous paper,the induction method of non-Gaussian test conditions is proposed.The non-Gaussian signal is generated and generalized,and compared with the vibration test conditions of Gaussian signals.Finally,based on the GUI function in MATLAB and the test condition determination method proposed in this paper,a set of software is developed,which allows engineers to easily obtain the vibration test conditions.