Aiming at the problem that the navigation accuracy of strapdown inertial navigation system (SINS) is severely affected by oscillation errors

an external damping strapdown inertial navigation algorithm based on double filters is presented. Two serial filters are designed for the algorithm. First filter uses the external velocity as the reference input to estimate errors of strapdown inertial navigation system and the external velocity is smoothed at the same time. Employing the high-precision external velocity smoothed by first filter as the input

second filter conducts error state estimation process and eliminates the influence of velocity constant error on the system. At last

information fusion algorithm is designed to give consideration to advantages of both filters. Simulation results show that

in the presence of external velocity constant error

this algorithm has higher steady-state precision and reduces the convergence time of system errors

which effectively improves the navigation accuracy of strapdown inertial navigation system. Compared with the second filter

the convergence speed of Earth oscillation error is obviously faster after information fusion

and the short-term accuracy is significantly improved. Compared with the first filter

the steady-state navigation accuracy is significantly improved after information fusion.