Research On Signal Processing Method And Attitude Algorithm Of Strapdown Inertial Attitude And Heading Reference System Based On Fiber Optic Gyro

Strapdown Inertial Attitude and Heading Reference System (SIAHRS) is an important airborne equipment, SIAHRS consisting of FOG has been widely applied in the field of military and civil use.This paper studies key technologies of SIAHRS for engineering application. The objective is to improve attitude accuracy and engineering practicability of SIAHRS as much as possible, with the information only from inertial sensors.Firstly, error elimination methods for FOG based Inertial Measuring Unit (FIMU) are studied. On one hand, this paper deeply discusses calibration algorithm for error parameters of FIMU. Based on conventional rate calibration algorithm, a new one named Adaptive Recursive Least Square (ARLS) rate calibration algorithm is proposed. Adaptive forgetting factor is employed to enhance the ability to adapt to FOG's temperature characteristics and improve the calibration accuracy. On the basis of this algorithm, a set of FIMU error calibration platform is developed which is able to calibrate all the parameters in FIMU error model conveniently and effectively. On the other hand, self-adaptive filtering methods to reduce random drift of FIMU are explored. Considering the practical engineering requirement, we have done some positive work on the traditional least mean square (LMS) algorithm, and put forward a new variable step-size sign LMS self-adaptive filtering algorithm, which improves the filtering accuracy and stability significantly. Further more, recursive least square filter is also presented to reduce noise in FIMU. With this method, higher filtering precision and faster rapidity of convergence are achieved.Secondly, in order to improve attitude accuracy of FOG based SIAHRS in High dynamic environment, this paper researches on coning error compensation algorithm in-depth. For the actual application environment, the kinematics model of two-frequency coning motion is established, and the coning error characteristic is also derived and analyzed. Especially, by numerical calculation, the vibration condition is founded on which the coning error remains zero in any case. This discovery has engineering significance. Then, based on the analysis of Miller's method to optimize coefficients of rotation vector, a new one which is named as parameter analysis method is brought forward. The method is demonstrated on the condition of multiple motion models, and the results show that it is effective and supplies a new idea to optimize coefficients of rotation vector. After that, for the output of FOG is angular rate, the general expression of improved coning compensation algorithm with angular rate input is proposed. The simulation results validate the algorithm.Thirdly, in some special military situation, external sensors are unavailable in the system, how to obtain more accurate attitude with the information from IMU its own is meaningful. This paper studies a special integrated navigation algorithm called damping attitude algorithm based on self-test of vehicle's movement. The focal point is designing the proper methods to examine vehicle's movment only by the information from FIMU. Three different methods are put forward, and they are the test by output of accelerometers, the state chi-square test and the residual chi-square test. By theoretical derivation and simulating certification, some conclusions are obtained as follows: the first method applies to FIMU of high accuracy; both chi-square tests are not subject to accuracy restrictions. The chi-square test is integrated in the process of damping Kalman filter. It is able to control the use of damping attitude correctly and improve attitude accuracy of SIAHRS effectively. So, the damping attitude algorithm based on self-test of vehicle's movement has significant practical value.Finally, a set of SIAHRS based on FOG is built successfully. The important algorithms discussed above are applied in the actual system. The experiment results prove that the system hardware is reliable, the algorithms are effective. The research work in this paper is valuable for SIAHRS to improve attitude accuracy and has important military significance and engineering value.