Research On The Temperature Adaptability And Thermal Control Method For The Optical System Of Aviation Platform

As one of the important methods of information acquisition,aerial photoelectric imaging technology has the advantage of flexibility and real-time performance.It has been widely used in the fields of geographic surveying and mapping,emergency disaster reduction,national defense security,and aerial photography.During the mission of the airborne optoelectronic platform,the internal electronic components and the external environment will affect the temperature distribution of the platform,then temperature changes will reduce the imaging quality of the optical system.In order to obtain a clear and stable target image,the thermal control method must be used to control the temperature of the platform.Therefore,the use of thermal control technology to reduce the impact of environmental temperature changes on imaging quality has been one of the important contents in the optoelectronic platform research.With the continuous improvement of aerial remote sensing technology's requirements for imaging resolution,large-aperture and long-focus optical systems have been widely used in optoelectronic platforms.The influence of temperature on the imaging performance of high-resolution optical systems is more obvious.In order to meet the higher requirements of aviation remote sensing technology for thermal control,an airborne optoelectronic platform was taked as the research object,and the following studies were conducted for the thermal control problems of aviation optical systems.First of all,the model of the temperature change and optical system aberration of the aviation platform has been constructed,revealing the influence of temperature on the aberration of different optical elements,and providing theoretical guidance for the design of the thermal control system.Then based on the optical-mechanical thermal integration technology,considering the influence of processing,vibration and electronics on the system transfer function,distribution of the transfer function caused by temperature has been calculated.Secondly,the thermal environment of the aviation optoelectronic platform was analyzed,and the thermal boundary conditions of the platform were determined.The platform was installed on the belly of the carrier through a shock absorber.The entire platform was in direct contact with the outside atmosphere.The high-altitude and low-temperature environment will have a serious impact on the platform's temperature.According to the structural characteristics of the platform,the heat conduction between the platform and the carrier,the convection and radiation heat flow between the platform and the external environment have been analyzed and calculated,and the power consumption and distribution of the heat source in the platform has been analyzed.In the process of external heat flow calculation,the spherical forced convection heat transfer model was used to calculate the forced convection heat transfer coefficient,which improved the accuracy of the finite element analysis.Thirdly,according to the results of the temperature adaptability analysis of the optical system,a thermal control strategy based on the system temperature difference has been proposed.This method takes the temperature difference between the primary mirror and the secondary mirror as the thermal control target,which can achieve good optical performance in a wide temperature range.This control strategy reduces the design complexity and power consumption of the thermal control system.Then thermal control methods of the aviation photoelectric platform have been studied.Finally,in order to verify the effectiveness of the thermal control methods,the finite element analysis and thermal test were carried out on the thermal control effect of the photoelectric platform.According to the difference of the initial temperature of the platform,different thermal simulation calculations were carried out on the temperature changes of the optoelectronic platform under low temperature,normal temperature and high temperature conditions.The results showed that the temperature distribution of the optical system can meet the requirements of thermal control indicators under the three conditions.The air temperature and pressure box was used to simulate the high-altitude,low-temperature and low-pressure environment,the temperature changes of the optical system were measured in real time,and the resolution board was used to measure the imaging effect of the platform.The temperature of the primary and secondary mirrors can meet the thermal control requirements under low temperature,normal temperature and high temperature thermal tests,which verifying the effectiveness of the thermal control method.Combining optical,mechanical and thermal theory,the thesis has carried out research on the thermal control method of the airborne optoelectronic platform.The thermal control method has been verified by finite element analysis and thermal test,which provides a powerful design guide for the thermal control system of the aviation optoelectronic platform.The influence of temperature on the imaging performance of the airborne optoelectronic platform and the thermal control compensation method have been studied in this thesis.The results have important theoretical reference and application value for the development of the new generation of aerospace optoelectronic platform.