Lightweight Design Of Carbon Fiber Integral Main Frame For Micro Space Camera

Space cameras are the main effective optical loads for earth observation and remote sensing information,and are used in many fields such as agriculture,military,and meteorology.Micro Earth observation satellites have the advantages of low cost,short research and development period,and low risk.They can realize formation networking,constellation operation,obtain higher temporal resolution and spatial resolution,and complete complex observation tasks at a lower cost.This method has become an important development trend of earth observation.The miniature space camera is the payload of the tiny satellite.During the transportation and launch phases,the space camera will experience complex environments such as vibration,shock,and overload,which will have a huge impact on the camera.This requires the main support structure of the micro space camera to have good strength,stiffness and structural stability,so as to ensure that the spatial position between the optical elements is within the tolerance range and ensure that the camera can image clearly.In this paper,the optical system of small and medium-sized space camera adopts off-axis three mirror structure,which has compact structure and envelope size of810 mm × 285 mm × 490 mm.The structural materials commonly used in space cameras are compared and analyzed,and carbon fiber composite material(CFRP)is selected,which has the characteristics of low density,high specific stiffness and good thermal stability,and is a good structural material for space cameras.According to the optical system and design requirements of the camera,comparing the advantages and disadvantages of various typical main support structures of space cameras,an integral thin-walled cylinder main frame structure is designed as the initial configuration of the main support structure of the miniature space camera.In order to ensure the accuracy and stability of the connection,a connection method using titanium alloy embedded parts is designed.In order to enhance the overall stability and reduce the risk of structural instability,the topology optimization method of the variable density method was used to determine the force transmission path of the initial structure,and compared with the types of composite stiffeners,a T-shaped reinforcement with better manufacturability was selected.The ribs are arranged in a crisscross pattern inside the frame structure to improve the overall performance of the main frame.The final design is a monolithic carbon fiber main frame structure that can support various optical components,has high stability and high connection precision.The carbon fiber integrated main frame is optimized for lamination to achieve the purpose of optimizing performance and reducing weight.First,an optimization model is established based on Hyperstudy for parameterized optimization.Through DOE analysis,the influence of different variables on the overall structural quality and firstorder mode was explored,and the response surface model was established by the method of response surface fitting to reduce the required calculation amount.The thickness and angle information of the carbon fiber layup in the main frame structure is obtained.Then,according to the parameter optimization results,the thickness of each angle is discretized and the laying of carbon fiber T-shaped area and grid reinforced wall panels in actual processing is considered.The sequence is optimized for the best layup sequence.Finally,through the above optimization of the carbon fiber main frame,on the premise of ensuring the stiffness,it meets the requirements of high lightweight,with a mass of 4.5kg,which can achieve the expected goal within 5kg,and solves the optimization problem of complex carbon fiber parts manufactured as a whole.In order to verify whether the design meets the requirements,the simulation research and dynamic test of micro space camera are carried out.The performance of the carbon fiber main frame was comprehensively evaluated by means of finite element analysis.Static analysis shows that deformations are all within tolerances.Under the Ydirection gravity condition,the structural deformation is 28 ?m,the RMS value of the secondary mirror is 1.177 nm,and the PV value is 4.939 nm.Under the Z-direction gravity condition,the structural deformation is 3 ?m.Under the temperature rise condition of 4?,the structural deformation is 15?m,the RMS of the secondary mirror is 2.08 nm,and the PV value is 10.32 nm.The modal analysis shows that the first-order fundamental frequency of the whole structure is 81.59 Hz,which is greater than the design requirement of 60 Hz.The sinusoidal vibration analysis shows that the acceleration magnification is less than 6 times within 5?100Hz.The dynamic test of the carbon fiber main frame and the structural parts of the whole machine is carried out.In the frequency sweep test,the first-order fundamental frequency of the whole machine structure is 78.08 Hz.Compared with the simulation result of 81.59 Hz,the error between the two is 4.3%.For sinusoidal vibration test and random vibration test,the acceleration magnification is within 10 times.During the test,the overall structure is stable without abnormal conditions and damage,and the frequency sweep before and after vibration is basically the same,which proves that the main frame structure can resist the complex dynamic environment,verifies the rationality of the early main frame structure design and the optimization design of carbon fiber paving,and the performance of carbon fiber dimension main frame can meet the design needs.To sum up,an integral main frame structure is developed using carbon fiber composites for a micro off-axis three mirror space camera.The performance of the main frame is verified by means of finite element simulation analysis and test.The results show that the carbon fiber main frame can meet the practical application of miniature space cameras under the premise of being highly lightweight.