Research On Error Analysis And Structural Optimization Of Semi-Strapdown Inertial Stabilized Platform For Aerial Remote Sensing

Because of its advantages of small volume, light weight and low cost, Semi-Strapdown Inertial Stabilized Platform for Aerial Remote Sensing could be of great practical value. However, because of its low pointing accuracy and eliminating rotation accuracy, Semi-Strapdown Inertial Stabilized Platform had not been used in reality. In this paper, Semi-Strapdown Inertial Stabilized Platform for Aerial Remote Sensing was studied. In order to improve the pointing and eliminating rotation accuracy, the stabilization principle and error of stabilized platform were analyzed. The structural rigidity and drive space of the stabilized platform were optimized. Finally, the pointing accuracy and eliminating rotation accuracy was verified by the laboratory testing and the flight test.The structural form of semi-strapdown aerial remote sensing stabilized platform was analyzed. Using the theory of coordinate transformation, the paper mixed the sensor information of Semi-Strapdown Inertial Stabilized Platform for Aerial Remote Sensing, and obtained the coupling relationship of velocity among frameworks of stabilized platform. The isolation mechanism that overcame the disturbance of carrier was analyzed. Finally the stability equation of optical axis in inertial space was established.The error sources from Semi-Strapdown Inertial Stabilized Platform for Aerial Remote Sensing were analyzed. The paper established the pointing error and eliminating rotation error model of stabilized platform according to the kinematics error theory of multi-body system and definitions on pointing error and eliminating rotation error. Using software of MATLAB, the paper analyzed the effect of the vertical errors and transmission errors on the pointing error and eliminating rotation error. When the vertical errors of three-axis were 1 ’, the pointing error and the error of eliminating rotation were up to 110 〃and 80 〃. When the transmission errors of three-axis were 1’, the pointing error and the error of eliminating rotation were up to 111 〃and 90 〃. The analysis results showed that the vertical errors and the transmission errors of the shaft system lead to large pointing error and eliminating rotation error. In the structural design, it was necessary to take measures.In order to reduce the verticality error of the shafting, the vertical error of the shafting brought by the structural frame deformation was optimized. The mathematical model of topological optimization based on variable density method was established. Based on the finite element method, the topological optimization of the structural frame was analyzed, and the optimal topology was obtained. The deformation of the frame was analyzed by the static analysis. Finally, the error of the verticality of the shafting caused by the deformation of the frame and the errors of the pointing and eliminating rotation was analyzed. In the condition of ensuring structural rigidity and pointing accuracy, the total mass of frames was reduced by 33%. The results showed that the vertical errors of the frames were 0.25 mrad, 0.18 mrad, 0.18 mrad, 0.15 mrad, respectively, which brought 0.26 mrad of the pointing error and 0.18 mrad of the eliminating rotation error. The results showed that the topology optimization method based on variable density method could reduce the structure quality and ensure the accuracy and performance of the stabilized platform.In order to eliminate the transmission error between shafts, a structure of eliminating the gap of gear transmission was designed. According to this structure, the dynamic model was established. Using the software of NX, The influence of stiffness and damping on the response of the system in the vibration environment of the carrier was analyzed. At the same time, the reasonable stiffness of the spring and friction coefficient of the slide was given. The transmission errors of the dynamic backlash structure and the errors of the pointing and eliminating rotation were analyzed. After eliminating the transmission gap, the transmission error of the three-axis system was 0.04 mrad, which brouht 0.05 mrad of the pointing error and 0.04 mrad of the error eliminating rotation. The analysis results showed that the local optimal parameters could be obtained by dynamic response analysis, which was helpful to reduce the transmission gap and improve the pointing and eliminating rotation precision of stabilized platform.At last, the experiment platform of Semi-Strapdown Inertial Stabilized Platform for Aerial Remote Sensing was established. By using mirror method, the zero-position error of the platform was calibrated. After that, the angle precision and stability precision were tested in the laboratory and verified in the field. The stability precision of the platform was less than 0.9mrad, and the pointing error was less than 1.4mrad. The experimental results validated the correctness of the theoretical and simulation analysis.