Research On Thermal Control Technology Of Altitude Optical Ensor Mounted On Unmanned Aerial Vehicle

With the rapid development of science and technology and the promotion of manylocal wars in the world, altitude optical sensor mounted on unmanned aerial vehicle ismore widely applied in the airborne remote sensing, measurement and detection. It is anew and effective optoelectronic payload. The object of altitude optical sensor is toobtain the high resolution and quality images. Temperature is an important factor whichaffects the imaging quality of optical sensor in altitude complex environment. Thechanges of temperature will make the defocus and generate additional aberration, andhave an influence on the performance of CCD assembly. Therefore, it is one of the keytechnologies during the development of the altitude optical sensor mounted onunmanned aerial vehicle that how to utilize the thermal control technology to stabilizeits temperatures level and eliminate the temperature gradient.This research is in the context of the high resolution, long focus and refractivealtitude optical sensor which mounted on the unmanned aerial vehicle. It was mainlyabout the thermal design for the optical system, CCD assembly and optical window.This paper shows an overview of the status and development of unmannedreconnaissance aircraft and aerial optical sensor, the necessity of thermal control foraltitude optical sensor, the introduce of thermal control technology for aerial cameras at home and abroad, and the characteristic of thermal control technology for altitudeoptical sensor. Based on the working condition of altitude optical sensor, the inside andoutside thermal environments are analyzed, and the heat-transfer models areestablished. The thermal boundary condition for the altitude optical sensor isdetermined, which includes thermal conduction, convection and radiation. Theinfluence of the refractive index change on defocusing amount and focal lengthvariation of optical system caused by temperature change is analyzed, and the thermalcontrol index of altitude optical sensor is gained. Based on the result of thermal-opticalanalysis for optical window, the optimum thickness of window glass is determined. Inaccordance of the usual thermal design principles, the thermal control measures areresearched, which include thermal insulation material, phase change material andheating system. And the thermal design for altitude optical sensor is done. After that,the convective heat transfer coefficient between the camera and the outside atmosphereand the aerodynamic heat flux are calculated in detail, and the finite element thermalmodel is established for thermal analysis, the analysis result shows that the thermaldesign is correct. Based on the heat balance equations, the sensitivity of thermal designparameters is analyzed, the results show that heat transfer, internal heat source andthermal resistance are main factors which would influence the temperature differenceof optical lens component.Finally, the thermal control test in simulated low temperature and low pressureenvironment and the actual flight test are carried out to validate the thermal design. Theresults show that the thermal control design is feasible and correct, and the stable anddistinct image is obtained.