Dynamic Analysis And Optimization Of Astronomical Survey Camera

Astronomical Survey Camera as the rear imaging part of the multi-function optical facility,is very sensitive to vibrations and deformation,little disturbance will affect the image quality.In order to launch the camera successfully,it is necessary to consider whether the structure of the camera satisfies the launching kinetic environment.Therefore,it is necessary to analyze and optimize the structure of the camera.In this paper,the structure of Astronomical Survey Camera was taken as the analysis object.The finite element method was used to analyze the structure of the camera.The influence of micro-vibration such as rotary actuators and cryocooler on the main focal plane was studied and the cryocooler vibration isolation scheme was proposed;Optimized the flexible Bipod support of the main focal plane,put forward the optimization program;And analyzed if the camera structure withstood the launch dynamic environment,identified the weakness of the structure,gave recommendations for optimization.The main research contents were as follows:First of all,in order to study the impact of two vibration sources,such as the rotary actuator and refrigerator,on the main focal plane of the camera,micro-vibration analysis was carried out.For the rotary actuator,in order to ensure the clear imaging of the focal plane of the survey camera,the relative motion between the cold box and the CCD focal plane needs to be strictly controlled,and the control precision is required to be 1 μm.The finite element analysis shows that the CCD focal plane and the cold box are moving synchronously.They all make a 23″rotation around the center point of the main array.The offset of the focal point of the CCD focal plane is 1.6 μm,which is slightly lower than the control accuracy.For cryocooler components,in order to reduce the influence of cryocooler vibration on the imaging of the primary focal plane,Based on the basic theory of vibration isolation,the dynamic characteristics of the survey cameras are analyzed,and the dynamic characteristics of the survey cameras are combined with the vibration characteristics of cryocooler compressors to design the vibration isolation of the cryocooler.Before and after the vibration isolation design,the amplitude of the vibration of the focal plane was reduced from 1 μm to 0.06 μm after vibration isolation,and the effect of vibration isolation was obvious.Based on this,the launch conditions were verified and the simulation results showed that the displacement of the refrigerator does not exceed 10 mm,and the vibration isolation design meets the launch requirements.Then,optimized the flexible Bipod support of the main focal plane.Taking gravity release of deformation,modal frequency and thermal stress as the evaluation index,the number of flexible Bipod support,the Bipod support form and the thickness of the B ipod flexible sheet were explored.The analysis results showed that the four-point support performance was obviously superior to the three-point support in terms of structural dynamic characteristics and gravity release of deformation.The A-type Bipod and V-type Bipod are close to the twentieth-order modal frequencies,but the latter do not have the gravity deformation performance as well as the former.The thickness of Bipod flexible sheet has little effect on the deformation and dynamic characteristics of the structure.However,the smaller the thickness of the flexible sheet,the better the temperature adaptabilityFinally,it was verified whether the structure of the sky-watching camera could withstand the launch dynamics environment.According to the mechanical conditions,the over-load analysis,the frequency response analysis,the random vibration analysis and the impact analysis were respectively carried out.The results showed that under the random vibration and impact,the strength of the inner frame of the survey camera was obviously insufficient,which needed to be further optimized.Among them.In order to study the influence of the scan rate in the sinusoidal vibration test on the analysis,a simple T-plate model was established.Using transient analysis,simulated at different scan rates,from low frequency to high frequency(over resonance point)and got the maximum response of the transient response to the structure,and compared with the frequency response results.The results showed that the larger the scan rate,the smaller the maximum response of the transient response,because the structure has not had resonance and the excitation frequency crossed the resonance point;The smaller the scan frequency,the greater the maximum response of the transient response,and approaching the frequency response of the resonance point.Sinusoidal vibration test in the mechanical conditions of the scanning rate was very small,and frequency response could simulate sinusoidal vibration test accurately.In the impact analysis.In order to provide an effective time-domain waveform synthesis method for the simulated shaking environment of the electric shaker.According to the general principle of time-domain synthesis of shock response spectrum,the wavelet transform method was used to transform the emission response spectrum into time-domain waveforms,and the time-domain waveforms were transformed into shock response spectra using improved recursive numerical filtering method.Optimized the amplitude parameters of each wavelet component,repeated iterations,so that the final shock response spectrum to meet the accuracy requirements.And the acceleration peak of the synthesized waveform was within the allowable range of the electric vibration table by optimizing the delay time of each wavelet component.Based on FEM,the response spectrum analysis and transient analysis of the surveying camera were carried out by using the shock response spectrum and the synthesized acceleration time domain waveform.Response spectrum analysis and transient analysis results showed that the two coincidence was very good,proved the effectiveness of the synthesis of the time domain waveform.