| The vehicle’s the attitude and position informations can been confirmed by inertial navigation system(INS)of inertial measurement unit(IMU)independent measurement and navigation computer integral operation.Due to the advantages of lower cost,smaller size and higher reliability,the strapdown inertial navigation system(SINS)have get research focus recent years.Coarse alignment algorithm can quickly determine a rough initial attitude matrix,which is an important premise of fine alignment.The existing coarse alignment algorithm under the condition of static base is relatively mature,but there are still problems of low alignment accuracy,large random error and poor dynamic alignment performance under the swing base and the moving base.The precision of the algorithm will affect the performance of the inertial navigation system,so research of improved coarse alignment algorithm is crucial.Firstly,this paper introduces three kind of the commonly used coarse alignment algorithm.The analytic coarse alignment,second-order leveling coarse alignment and coarse alignment algorithm on inertial frame are theoretically derived and simulated.Then this paper analyzes several aspects of the alignment accuracy from alignment error sources on inertial frame,the gyro and accelerometer constant drifts,and analyzes the advantages and disadvantages of coarse alignment algorithm on inertial frame.On this basis,an improved coarse alignment algorithm is proposed from two aspects of mooring and motion state.Then,this paper proposes an improved coarse alignment algorithm on moored condition for existing problems of coarse alignment on inertial frame.IIR filter is designed to control interference acceleration by spectrum analysis according to moored test data.A method is designed by converting problem of attitude matrix to problem of Wahba for solving large random error,and the effectiveness of the proposed improved algorithm are verified from two aspects of simulation and experiment,respectively.Meanwhile,the rotating modulation mechanism is introduced to complete IMU error suppression according to the result of error analysis.The system alignment accuracy is improved,and the effectiveness of the proposed algorithm is verified by simulation.Finally,the working principle of coarse alignment algorithm on inertial frame under moving base is analyzed,and the theoretical analysis has been carried on by simulation for the alignment performance under complex sea condition,and he problems of the existing algorithm are pointed out under the moving base.On this basis,an improved coarse alignment algorithm on moving base is designed,which smooth the external measurement speed by horizontal alignment of compass.The iterative improved algorithm based on inertial frame is designed at the same time,and simulation and experiment results are given in the end. |
