Load Identification Research On The Special-shaped Complicated Closed Cavity Of A Radar

Special-shaped complicated closed cavity is a typical part of the radar, the loadsacted on the cavity have a important influence on the radar’s performance, but theloads can not be measured directly, the loads identification of the special-shapedcomplicated closed cavity were researched in this thesis. The main work can besummarized as follows:（1）The structure of special-shaped complicated closed cavity is very complicated,if the dynamic simulation analysis is carried out according to the cavity’s actualstructure, there are many shortcomings, such as the difficulty of model building, thelarge of freedom degrees, the complex of calculation and so on. The method to build aequivalent model of the cavity that easy to operate, accurate and reliable was deeplystudied in the thesis. Simplify the cavity into shell by combining the finite elementmethod and optimization technique on the condition that unchanging the overalldimensions, and the first6stages natural frequencies stay the same. This paper tookthe orthotropic material’s9material parameters as design variables, and defined thesquare sum of differences between the simplified structure and former structure’ first6stages natural frequencies as objective function, the mathematical model was built,the process was expounded, the method of MATLAB invoke ANSYS and the datatransmission between them were stated, the APDL and genetic algorithm programwere write, the requested material parameters were obtained, this lays the foundationfor the load identification.（2）The harmonic load identification of the simplified cavity was researched. Thesingle point harmonic load identification and multipoint harmonic loads identificationthat exist phase difference or not were researched. Firstly, the cavity’s modal analysiswas carried out in ANSYS and the modal parameters were obtained, then thefrequency response functions were calculated; Secondly, the harmonic responseanalysis was carried out in ANSYS and the measuring-points’ displacement responseswere obtained; Finally, the harmonic loads were identified by using inverse matrix offrequency response function. The effect of the test point position, the number ofresponse test point, the number of modal order and the damping ratio to the precisionof harmonic load identification were analyzed.（3）The stationary random load identification of the simplified cavity was researched. The single point stationary random load identification and multipointstationary random loads identification were researched. The random vibration analysiswas carried out in ANSYS and the measuring-points’ displacement power spectrumwere obtained, the frequency response functions were calculated by the modalparameters, then the random load loads were identified by using inverse matrix offrequency response function. The effect of the damping ratio, the number of modalorder, the test point position and the number of response test point to the precision ofstationary random load identification were analyzed.（4）The measures to improve the precision of load identification of thespecial-shaped complicated closed cavity were presented based on the analysis resultin the end.