Research On Structural Modal Analysis Method Of Single-axis Rotary Inertial Navigation System

To increase navigation performance with limited cost increase,the technique of rotation modulation is widely used in high accuracy inertial navigation systems based on optical gyros,forming a new-style rotary inertial navigation system.Compared to with SINS,extra rotary parts make rotary inertial navigation system weak dynamic stiffness,low environmental adaptiveness.Modal analysis is an important means to deal with vibration problem,and miscellaneous dynamical design theory centre on modal analysis is the significant basics of structure design.Single-axis rotary inertial navigation system is bearing-supported rotary machine with complicated connection,and belongs to MDOF complex nonlinear system.The nonlinear facts exist obvious coupling effect,resulting complicate modal and several special dynamic performance.Modal simulation is expected to acquire mechanical vibration characteristic and probable deformation type and evaluate structure defect.Based on modal analysis,we can conduct optimization design and explore the optimal design scheme.Based on modal analysis theory and rotor dynamics,this paper explores the high-precision and high-efficiency modal simulation method for rotary inertial navigation,thus laying solid foundations for follow-up optimization and dynamic design.Starting from modal tests,we set up modal test according to experimental modal analysis theory.Acquire modal test results and use it as the criterion.Secondly,discuss the difficulties of creating system finite element simulation model in view of system structure characteristics.Then,explore high-precision and high-efficiency modal simulation for system firet-order mode by comparing three simulation schemes,expanding the subjects from frame to rolling bearings and rotary parts in the study.And the rotor dynamic simulation scheme of elastic element representing bearing is proposed.Five research contents are discussed as followed: the equivalent modeling method of inertial navigation module,the equivalent modeling method of rolling bearings,the defining of rotation mechanical behavior,the boundary condition simulating the fact,and the impact of bearing stiffness nonlinear.The contrast between experiment results and simulation results verify that the modal simulation method authentic and valuable,especially first-order vibration frequency reaching the accuracy of 3Hz and goodness value of fit above 90%.At last,analyze the modal simulation results,and discuss the coupling between supporting mechanism and rotational mechanism.Simulate the sub-parts of supporting parts and rotational parts respectively,acquiring the inherent stiffness characteristics of each parts and discussing the coupling between the two.Confirm the optimization direction according to modal analysis and mechanism defect identification.