Study Of Dynamic Characteristics Of Misaligned Horizontal Rotors Of Opto-electronic Turntable

Opto-electronic tracking device is used widely in military area and aerospace area.The turntable has strong effect on the dynamic performance of this device.In this paper,modal analysis,modal measurement and swept-frequency analysis are conducted for the turntable.Adopt subspace iteration method for modal analysis,acquiring first six modes of turntable.Hammer modal measurement experiment validates the modal analysis results.Adopt implicit time integration for swept-frequency analysis.Resonance frequencies of opto-electronic turntable are obtained through acceleration and displacement spectrum.While due to the manufacturing error of the components,assembly error,thermal deformation in work place,deformation caused by loads and non-uniform settling of support,there will be parallel,angular or integrated misalignment between axes of rotor system in the turntable.Harmonic excitation response analysis is conducted on the turntable with angular misalignment.Result shows that the frequency response of the turntable contains one-time and two-time frequency vibration.In order to further study the dynamic characteristics of rotor system,the model of multi-rotor-rolling bearing-hinge joint system is established based on the horizontal system of turntable.The dynamic model of rotor system is established based on spring-damping,adopting centralized mass method,including the forces of misalignment,rubbing,unbalance and bearing forces.In the misalignment model,the misalignment force is acquired according to forces analysis,moment disintegration and geometric features.The coupled misalignment forces caused by motor driving axis and driven axis acting on the main rotor are introduced into the dynamic model.Because rolling bearing is important part of rotor system and has great effect on the system's dynamic features,in the dynamic model established in this paper,the rolling bearing model is built based on nonlinear Hertz contact theory and elastic deformation of rolling elements resulted from waviness error and varying compliance vibration.The rubbing force is modeled according to Coulomb rubbing rule.The dynamic response of rotor system is acquired using fourth-order Runge-Kutta method with varying steps.Adopting time displacement plot,orbit diagrams of axis center,spectrum,Poincaré plot and waterfall plot as parameters,the effect of kind and amount of misalignment,bearing forces,waviness amplitude,number of rolling elements and rotation speed on the dynamic characteristics of rotor system is analyzed.Numerical analysis results illustrate: under the effect of misalignment forces,the rotor vibration includes one-time and two-time frequency components.The displacement is in the formation of superposition of harmonic functions.There is period-doubling movement.The orbit of axis center is turned to ‘8' shape or crescent shape.Under the effect of bearing forces,the rotor vibration includes one-time frequency and two-time frequency components and low-frequency component whose frequency is same as the one of rotation of bearing cage.The motion of rotor is quasi-periodic motion.The simulation rotor model is designed according to the horizontal system.The finite element model is established.The relative rotation between rotor and support is defined by revolute joints.Contact between components is defined by augmented Lagrange method.The modal analysis and harmonic stimulation response analysis are conducted based on modal superposition method.The dynamic characteristics of rotor system under the coupled effect of misalignment and unbalance is investigated.The results are in accordance with the numerical analysis results.Because there are stimulations with unknown frequencies in real work places,swept-frequency analysis of rotor system is conducted and resonance frequencies are obtained.Rotor experiment platform is developed according to simulation rotor model.Measurement system is established based on accelerometers and signal acquisition device.The rotor misalignment experiment and swept-frequency experiment are conducted.Orbit diagrams of axis center and frequency response are obtained,validating the results of numerical analysis and finite element simulation.