Finite Element Analysis Of Airborne Opto-electronic Platform And Improved Design Of Its Key Parts

With the development of economy, science and technology, aviation reconnaissance measurement techniques has been widely used in both civil areas and military field because of its wide observation range, high precision measurement, well pertinence, good flexibility and high timeliness. Airborne opto-electronic stabilized platform is one of the important aviation reconnaissance equipments, and it is the bearing platform for the opto-electronic imaging and measuring system.The quality of the mechanical structure of the opto-electronic platform will directly affect the overall work performance of the system.Because the customer requires that the load of the platform is light, the mass and volume of the platform is small, and the cost of the platform is low, the two axis and two frame structure which is mature is adopted after comparing the advantages and disadvantages of several platform frame structures, and it is determined that the diameter of the airborne opto-electronic platform is 158mm. Because the requirements for the volume and quality of the opto-electronic platform are strict as well as the requirement for the tracking stable accuracy, the frame structure should have not only sufficient strength and rigidity but also high natural frequency. As the main forced part of the opto-electronic platform, the main frame should have enough strength and rigidity due to its large stress. In order to achieve this objective, suitable materials should be used, and the structure should be designed and analyzed carefully.The casted aluminum alloy ZL101A is adopted in the design of opto-electronic stabilized platform after comparing and analyzing the mechanical properties and maneuverability of common materials used on opto-electronic platforms. Establish entity model of the main frame using CATIA, and analyze the structure using ANSYS Workbench. The severest working condition is discussed, laying the groundwork for further improvement.According to the analyzing results that the main frame has excessive deformation and cannot satisfy the stiffness and strength requirement, the main frame structure needs to be improved. There are two ways to improve the weak part of the main frame, and it was found that the second plan of laying stiffeners is more effective after finite element analyzing of each plan. However, the deformation is 4.0309×10-5m which still cannot meet the deformation accuracy 0.025mm. After increasing the dimension of the azimuth shaft and the number of stiffeners, the deformation of the main frame decreases to 2.6338×10-5m which still cannot meet the maximum deformation requirement.In order to ensure the improvement of the main frame structure is reasonable that it can withstand the tremendous stress while the mass is light, several main frame structures with different positions and lengths of the stiffeners and side wall thicknesses are compared and analyzed by finite element analyzing. It was determined that the distance l between the stiffeners and the center is 8mm; the length L of the stiffeners is 30mm; the thickness h of the stiffeners is 2mm; the stiffeners are distributed circularly and their included angles are 45°; meanwhile, in order to decrease the mass of the platform, the side wall thickness h of the main frame decrease from 5mm to 3mm. Through the above structure improvement the main frame structure's strength and rigidity are greatly improved. The maximum deformation decreases to 2.3796×10-5m, and the first-order natural frequency value is 399.96Hz, meeting the design requirement.The working environment of the opto-electronic stabilized platform is harsh, the changing of the surrounding noise, airflow, and plane flight attitude and the vibration of the plane will possibly lead to the resonance of the platform, affecting its normal working, even destroy it. In order to avoid resonance, the modal analysis is conducted. Because the opto-electronic stabilized platform can turn freely both in the pitching direction and the orientation direction, the first and second order natural frequencies are tiny, close to zero. But the third order natural frequency is 112.23Hz which can meet the design requirements of 75Hz, with good dynamic performance. The research of opto-electronic stabilized platform in this thesis achieves good results, and can be used for reference during the design and manufacture of the like products.