Research On Transfer Alignment Method Of Airborne Photoelectric Pod

Airborne photoelectric pod is a kind of photoelectric equipment used for aerial reconnaissance.It is usually installed in the abdomen or under the wing of an aircraft for the aircraft’s observation,precise search,tracking and locking of targets.The fastness and accuracy of the dynamic alignment become important performance indicators for judging the internal navigation system of the pod.In the airborne system,the carrier itself is equipped with a high-precision main inertial navigation system,and self-alignment has been completed before work.How to use the navigation information of the high-precision primary inertial navigation system to assist the rapid transfer alignment of the sub-inertial navigation system inside the pod is the focus of this paper.Aiming at the problems of low accuracy of transfer alignment of airborne photoelectric pods and any initial misalignment angle,this paper focuses on the inertial navigation system error model,measurement information error characteristics,and transfer alignment matching methods of photoelectric pods in transfer alignment Carry out research and analysis in other aspects.The main research contents are as follows:First,the basic principles of transfer alignment technology are introduced.The error model of strapdown inertial navigation system is derived,and the information fusion algorithms commonly used in transfer alignment are introduced.Secondly,analyze and compensate the error sources appearing in the photoelectric pod transfer alignment.Based on the theoretical analysis of the flexural deformation error,rod arm error,and transmission delay error of the photoelectric pod during transmission alignment,a mathematical model is established,and the system state variables are added for real-time estimation,and then the navigation parameters are output corrected.,And verify the effectiveness of the method through simulation and experimental data;In view of the data packet loss phenomenon in the transmission alignment,a one-step prediction value at the time of data packet loss is proposed to replace the measured value,and then the adaptive kalman filter estimator is used The error of measured information,simulation and experimental data verify the effectiveness of the method.Finally,for the initial misalignment angle of the photoelectric pod that is prone to occurduring the transmission alignment,the pod is fixed and the optical axis is stable.In the fixed state,the angular rate integral and specific force integral matching method under the inertial system are used to establish a unified model of arbitrary misalignment angle,and the simulation is compared with the nonlinear filtering model.The results show that the model has uniform convergence accuracy under any misalignment angle.Better than nonlinear filtering model.In the steady state of the optical axis,the attitude information of the main inertial guide and the sub-inertial guide do not match.The speed matching method has a slow alignment speed and is easy to fail to align under a large misalignment angle.The optical axis steady-state photoelectric pod simulation model is established,and the attitude acceleration transfer alignment matching method combining the pod encoder value and the attitude information of the main inertial navigation system is designed.The simulation and measured data verify that the proposed method can not only improve The transfer alignment accuracy still has good convergence accuracy under the condition of initial large misalignment angle,which enhances the robustness of the algorithm.