Research On Algorithm Of Attitude Estimate Of Towed Linear Array Sonar Based On MIMU

Towed linear array sonar is a kind of mosaic line hydrophone arrays formed on the cable can be used to detect submarines radiation noise,to achieve the submarine remote monitoring.However,in order to accurately detect the location of the submarine,we must forecast the attitude of sonar array,so the attitude estimation algorithm of towed linear array sonar has great military value and significance.Micro inertial measurement unit(MIMU)based on MEMS technology integrated micro-accelerometer and micro-gyroscope,with miniaturization and integration and low cost,therefore attitude estimation system based MIMU has become a hot research field.However,MIMU have inherent shortcomings,which the system error over time to accumulate faster.Therefore,MIMU not able to for a long time,independent survey work completed,this study based of MIMU in magnetometer for assistance,through information fusion technology constitute attitude estimation system.The main contents of this paper are as follows:Firstly,the basic principles of several nonlinear filtering algorithms and their advantages and disadvantages were analyzed;several attitude description methods are analyzed and compared,and select quaternion description attitude for engineering applications;the Cubature Kalman Filter(CKF)was researched deeply,and deduced the steps of it.Gyro random drift is an important index that can affect the precision of MEMS gyro.In order to decrease the random drift error of MEMS gyro,applying wavelet thresholding denoising method to improve the precision of MEMS gyro.Therefore,the mathematical model of MEMS gyro output signal was established,the basic principle of wavelet thresholding method was analyzed deeply.An improved wavelet threshold denoising method is proposed by the analysis of conventional threshold wavelet denoising.Test is made by using improved wavelet threshold denoising method based on the actual output data of MEMS gyro,the results show that this method can improve the denoising effect.The error equation of large azimuth misalignment angle in MINS is nonlinear.To improve the accuracy of the initial alignment in nonlinear model,the quaternion Square-Root Cubature Kalman Filter(SR-CKF)was applied to the initial alignment.Therefore,a multiplicative quaternion attitude error equation is established,choose the speed information as an external observations.A lagrangian cost function method is presented to compute quaternion weighted mean,the mean quaternion can be calculated by seeking the minimal solution to the cost function.And then the specific implementation process of initial alignment algorithm was deduced,the simulation results show that heading alignment accuracy was improved significantly compared to the EKF.An attitude estimation algorithm based on MEMS gyroscope and magnetometer was proposed,when the tug can provide position information.Therefore,the geomagnetic field model and the method of gain magnetic field strength under the geographic coordinate by position information were analyzed deeply.The major sources of magnetic disturb and its characteristics were analyzed,on the basis of it,the linearization state space model was established,estimate the optimal state by Kalman Filter(KF).Test results show that this algorithm can provide a stable attitude information for towed linear array sonar.An attitude estimation algorithm based on MEMS gyroscope/accelerometer/ magnetometer was proposed,when Doppler Velocity Log(DVL)was loaded on towed linear array sonar.In order to improve performance of MEMS accelerometers,using FIR digital low-pass filter to remove the frequency noise of MEMS accelerometer's measurement signal.The advantages and disadvantages of using gravity component or angular rate information of carrier to estimation horizontal attitude were analyzed,for this reason,combinated those by quaternion SR-CKF,in order to get accurated horizontal attitude.Therefor,using speed information by DVL to calculate the gravity component was proposed,and then the non-linearization state space model was established.Test results show that the accuracy this algorithm can meet the requirements of towed linear array sonar.