Research On In-Flight Alignment Method Of INS/GNSS Integrated Navigation System With Application To Guided Projectile

The artillery which is the most popular way to fire strike always plays an important role in modern war.However,massive projectile need to be fired for achieving the objectives due to its poor accuracy.Obviously,it is unable to meet the requirements of modern warfare for the intelligence and informatization of weapons.So it is very necessary to transform the traditional projectile to guided ones.The combination of INS and GNSS is the mainstream guidance scheme due to their own advantages.The initial alignment must be carried out to obtain accurate initial attitude of projectile before the integrated navigation system starts working.To solve this problem,an in-flight alignment method of INS/GNSS integrated navigation system with application to guided projectile has been proposed in this paper.Firstly,the effect of the inertial sensors bias on the accuracy of the construction of multivectors is analyzed and an improved multi-vector construction algorithm has been designed according to this.Using this method,the error caused by the accumulation of accelerometer bias can be suppressed by reducing the integration interval of multi-vector construction.The gyro bias can be identified by Kalman filter to feedback to the procedure of construction for improving the accuracy of multi-vector.Secondly,the deficiencies of the traditional optimal attitude estimation method based on multi-vector are elaborated.To solve this problem,a new in-flight alignment method based on gradient descent is proposed and its cost function and gradient function are derived.The attitude can converge to the objective value along the fastest direction of gradient descent.Compared with the traditional methods,this method can obtain the initial attitude faster without complex operations.Finally,the simulation is carried out to compare the performance of the traditional method and the proposed algorithm.Using traditional multi-vector construction method,the gradient descent and QUEST are used for initial alignment respectively.And then these two algorithms are simulated again with the improved multi-vector construction method.The simulation results show that,the accuracy of the two attitude optimal estimation algorithms is significantly improved when using the improved multi-vector construction method,whose error is reduced by an order of magnitude from 0.50°,6.55°and 0.58°to 0.09°,0.70°and 0.07°.Moreover the time using proposed gradient descent method taken for alignment is reduced from 20.4 seconds to 9.6 seconds,which is reduced by 50%.The performance of the gradient descent method under different batch conditions is also discussed.The simulation results show that the algorithm will more efficiency as the batch size decreases,and more accurate and robust as the batch size increases.So,the algorithm has greater flexibility and can be adapted to different usage environments.Through simulation analysis,it can be seen that the proposed in-flight alignment method of INS/GNSS integrated navigation system with application to guided projectile plays a large role in obtaining the initial attitude parameters of the projectile,and has certain engineering application value.