Research On Modeling And Compensation Methods Of Interference Factors In Rapid Transfer Alignment

Transfer alignment process refers to the master and slave inertial navigation system(INS)sensitive to the same motion process,and estimates the attitude error by the difference of navigation information between the master and slave INS,and transmits the high-precision inertial navigation information to the low-precision inertial navigation,so that the low-precision inertial navigation has a higher precision initial attitude value.INS is one of the most common navigation systems.It mainly depends on the measurement information of accelerometer and gyroscope,and calculates the attitude,velocity and position information of the carrier at present time through the integration process.In this paper,a precise solution model of strapdown INS is established,and the position velocity and attitude of the carrier are described by combining the measurement information;The error model of strapdown INS is established to describe the update of the state error in the process of transfer alignment.In view of the transfer alignment process,the measurement parameters matching model,such as acceleration matching model and angular velocity matching model,are simulated,and the calculation parameter matching model,such as velocity matching model,attitude matching model and "velocity + attitude" matching model,are studied.The results show that the velocity + attitude matching transfer alignment model has fast convergence speed and high estimation accuracy,so it is also called rapid transfer alignment model.The "velocity + attitude" matching model only needs the wing swing motor excitation to achieve high-precision installation error angle estimation,and it is easy to realize the maneuvering requirements compared with other transfer alignment models.In the process of transfer alignment,the interference from itself will be caused.There is a certain distance between the sensitive centers of the master and slave INS,which will lead to the rotation movement of the master and slave INS around the same rotation center when the carrier is making turning maneuvers.It causes the master and sub INS to move around the axis,which causes the master and slave INS velocity to be inconsistent,thus causing interference to the observation of velocity error in the transfer alignment filter,that is,the lever arm effect;Because the master and slave INS are not rigid body connection,the wing will be affected by air during flight,which will cause dynamic deflection deformation,so the installation error angle between the master and slave INS change at all times,which will affect the estimation of the installation error angle,that is,the dynamic deflection deformation interference will be generated;Because of the deflection deformation,the length of the arms between the master and slave INS also changes at all times,which affects the measurement of velocity error,that is,the dynamic pole arm effect is produced.In this paper,the compensation method is designed to improve the accuracy of the transfer alignment process according to the above interference factors.In the process of transfer alignment,it is also subject to interference factors from flight process.Due to the deformation of connecting parts or installation process problems in the actual flight,the installation error angle between the master and slave INS is too large,which leads to the nonlinear enhancement of the system.When the system linearizes,the error of state equation is too large,and the system state can not be described accurately.At this time,the nonlinear filtering method will increase the calculation consumption and affect the velocity of transfer alignment;However,the linear filtering method will produce a large linearization error,which will affect the accuracy of the transfer alignment.In this paper,the method of establishing virtual slave INS is used to transform the problem of large installation angle into small angle problem,so as to reduce the linearization error of the system,and can continue to use the original linear filtering method,and avoid the increase of calculation.In the actual flight process,the flight mission requirements during long flight will make the navigation error accumulate with time,which leads to the decrease of accuracy.In this paper,the feedback mechanism is introduced into the slave INS state estimation and transfer alignment filter by using closed-loop Kalman filter algorithm.The navigation parameters after the measurement are used to modify the slave inertial navigation state and installation error angle,Thus,the system is approaching the real state and solving the problem of error accumulation.