Research On Bearing Modeling And Structure Dynamics Of Photoelectric Tracking Equipment On Moving Platform

Photoelectric tracking equipment has a wide range of applications in astronomical observation,aviation and nautical target observation,laser communication and other fields.For photoelectric tracking devices on dynamic platforms(such as vehiclemounted,ship-borne,airborne,and satellite-based platforms),the frame structure will produce a complex dynamic response to the vibration excitation of the dynamic platform,and the optical components on the device will be optical disordered,then optical misalignment causes jitter of the device's line of sight(LOS)and reduces the performance of the photoelectric tracking device.The dynamic characteristics of the device structure determine the device's response to platform vibration excitation,which directly affects the device's jitter of LOS.Therefore,the structural dynamics study of the photoelectric tracking device can be used to evaluate the LOS jitter of the photoelectric device under the platform vibration excitation,which provides a solid theoretical foundation of prediction and evaluation for LOS jitter of the photoelectric tracking device.This paper focuses on a typical photoelectric tracking device: the photoelectric tracking pod,the structural dynamic analysis was carried out based on this device.This paper focuses on a typical photoelectric tracking device,photoelectric tracking pod,to carry out structural dynamic analysis and experimental research of the whole machine.The photoelectric tracking pod is a rotary motion machine composed of azimuth axis system,pitch axis system,focusing mechanism and other structures,and nonlinear joints such as bearings have a great influence on the dynamic characteristics of the whole structure.At present,most of the photoelectric tracking equipment dynamic analysis is based on the use of solid structures or spring units.Although these methods are simple,the accuracy of the dynamic simulation of the whole machine is insufficient.In this paper,a six-degree-of-freedom stiffness function matrix model is used to theoretically study the dynamic equivalent simplification of the photoelectric tracking pod bearings.The model is based on the Hertz theory and is obtained by solving the multivariate differential equation of bearing load with respect to displacement through the lumped parameter method.This paper establishes the stiffness function matrix model and solves the numerical solution of the stiffness matrix for each main bearing structure of the photoelectric pod,and applies it to the whole machine finite element dynamic model for dynamic analysis.In order to verify the theoretical model,the hammering modal test was carried out on the actual photoelectric pod,and the comparison between the test and the simulation showed that the simulation result and the test had a good fit.On this basis,the transient dynamics analysis for the photoelectric pod using the hammering excitation signal as input parameters was performed,and the surface shape changes of the primary and secondary mirrors were analyzed,and it was concluded that the primary and secondary mirrors can be regarded as rigid bodies under this condition.Using this conclusion,we conducted a preliminary study on the LOS jitter,and analyzed the LOS jitter of the primary and secondary mirrors during hammering.The main work of this paper is as follows.Introduce the research purpose and significance of the subject,summarize and analyze the research status at home and abroad.A brief description of the research object in this paper: the photoelectric pod,and points out that the dynamic equivalent treatment of the bearing and other joints is the focus of this research.Introduce the relevant theoretical basis of the dynamic modeling of the photoelectric tracking equipment.The equivalent methods of the main joints(screw,bolt and bearing)are described;the prerequisites and assumptions of the stiffness matrix model based on the Hertz theory are described;the minimum potential energy method is introduced.Deduced the stiffness function matrix of the bearing structure of the photoelectric tracking pod.Based on the force balance equations,the analytical formula of the stiffness function matrix of the bearing rotor is obtained,and the generalized displacement of each bearing rotor is solved using the minimum potential energy method to obtain the numerical solution of the bearing stiffness function matrix.Establish the complete machine finite element dynamic model of the photoelectric pod,apply the numerical solution of the stiffness matrix of each bearing to the complete machine finite element model,and carry out the modal analysis of structural dynamics;The dynamic modal test of hammering method is used to compare and verify the finite element model.Based on the theoretical and simulation results of the previous chapter,the device is subjected to transient dynamics simulation based on modal superposition.Using the time-series change data of the coordinates and displacement of the primary and secondary mirror nodes of the device,the RMS values and PV values of the primary and secondary mirror are obtained;based on the primary and secondary mirror boresight jitter models,the correlation analysis of the LOS jitter caused by the misalignment of the primary and secondary mirrors' optical paths was carried out,and the trajectory of light spot on the target was obtained.Summarize the research work and innovations of this article,and prospect the next step work.