Random Dynamic Analysis And Parameter Optimization Of Ins Bracket

INS (Inertia Navigation System) is one of the most important precise apparatus in missiles and rockets, which is sensitive to random vibration in boost and reentry phase. For the demand of the flight safety, it is very important to analyze and optimize the bracket structure to minimize the INS equipment's random response. According to the positions and connecting relationship of bracket, plate and vibration absorber, the paper presents several analysis models of the vibration reduction system for INS under random base excitation. And the random dynamic response and parameter optimization are investigated using analytical and numerical methods. In the optimization model, the optimum object is the minimum of the acceleration mean square response, and the equivalent mass, rigidity and damper coefficients are regarded as the optimization control parameters. The main work is summarized as follows:The one- and two-degree-freedom equivalent dynamic models for the bracket absorber of INS are established respectively. And the analytical formulas of the power spectral density function and the acceleration mean square response are obtained by spectrum theory and James formula. The numeric optimization examples using simplex arithmetic and Powell arithmetic give the optimum parameter results for the bracket structure of INS.The multi-degree-freedom equivalent model of INS bracket is also given and analyzed to improve the analysis precision. The dynamic response spectrum of this model is achieved by modal analysis and spectrum theory. The numeric formulas of time-domain response are deduced by residue theorem. In all the discrete models mentioned above, the common source stationary random excitation is employed to calculate the force response spectrum in the vibration equation. The results of numeric examples show the validity of analytical and numerical formulas. Meanwhile, the optimization results give the optimal structural parameter characters for the equivalent model of INS bracket.The optimal design of the viscously damped beam-oscillator and plate-oscillator combined system are studied. The dynamic equations of beam, plate and lump-mass oscillators are presented according to the basic structural vibration theory. And the dynamic equations with non-proportional damping model are solved by the complex modal theory and Green function method. Mean square response of system under white noise excitation and band-limited white noise excitation is obtained by interval integral and infinitely dimensional integrals respectively. Powell arithmetic and simplex arithmetic are used in the numeric optimization process of thebracket absorber.In conclusion, the structural optimization models established for INS bracket in this paper are of much theoretical importance to the vibration reduction of precise apparatus.