Study Of Transfer Alignment Techniques In SDINS

This paper deals with several transfer alignment(TA) techniques of SDINS (Strap-Down Inertial Navigation System),including velocity matching, attitude matching, angular rate matching and velocity-plus-attitude matching approaches.The velocity matching method can achieve its alignment goal by oberserving the velocity difference between MINS and SINS. After deducing the mechanical equation of velocity matching method carefully, We draw a conclusion that not only the misalignment between the two systems but also the acceleration caused by bending, by true position error, by gravity and by carrier's accelerate introduce the velocity error to SINS. This paper models the velocity matching method and show the simulation results when the carrier in different movement.Attitude error can be expressed by the direct subtracting or Euler angle. So this paper researches two kinds of attitude matching methods based on two expressions for attitude and deduces the linear dynamic equations respectively.Referring to angular rate matching method, this paper assumes the SINS and MINS to be joined in rigid, and deduces the model of angular rate matching method under the assumption. In general, considering the true condition with bending between two systems, we model the second order Markov process and achieve the general model of angular rate matching method.Single matching method has its disadvantages, so this paper researches a rapid and efficient method of transfer alignment, namely the velocity plus attitude matching method. Beginning with analyzing the equations of the inertial navigation system, we express the angle error between two systems with true physical misalignment and error parameters of gyros, and formulate the dynamic equations of attitude and velocity error.To validate the model, Kalman filter is applied to estimate the misalignment between two systems, and simulation is given respectively to each method.