Research On Error Suppression Technology Of Duel-axis Rotational Modulation Strap-down Inertial Navigation System

It is important for us to develop submarine and underwater vehicle in order to protect our vast sea area and detect deep-sea resources.In particular,submarines must ensure their invisibility,autonomy and security when they complete missions autonomously.Therefore,the navigation system is the critical factor.Inertial navigation system(INS)with gyroscopes and accelerometers measures angular motion and linear motion of vehicles to get navigation information by the dead reckoning,which is the only applicable navigation system to the submarine.INS errors are subject to the precision of inertial sensors.When their accuracy meet certain level,they are difficult to be further improved in the short term due to the limitation of cost and manufacturing process.On the basis of existing sensors’ precision,rotation modulation is a low-cost and efficient way to restrain the error divergence of long-endurance INS.The dissertation is aiming at the problem of achieving high-accuracy and long-endurance navigation results,researching on error suppression mechanism of duel-axis rotation modulation,the optimal rotation scheme design,errors self-calibration,damping and rotation control etc.,putting forward the solutions of long-endurance navigation error suppression based on duel-axis rotation fiber-optic gyro SINS(DRINS),in order to improve the navigation precision.The main works and innovational contents are as follows:The error suppression characteristics of DRINS are studied firstly,and then the error suppression equation of DRINS,the non-orthogonal angle error model and the rotation angle error model are proposed.Meanwhile,the influence of long-endurance navigation precision impacted by the gyroscope drift,the accelerometer bias,scale factor error installation error,non-orthogonal angle error and rotation angle error are analyzed,respectively.The effect of error sources on navigation error is clarified.The rotation modulation strategy and the implementation of DRINS are studied,a duel-axis reciprocating alternating & intermittent rotation scheme and the optimal rotating rate are proposed,which are proved can mostly restrain the accumulation of system errors.A navigation solution strategy is proposed after the rotation modulation,which can help to improve the precision of attitude calculation,avoiding the impact of rotation angle errors.A thirty-two position rotation scheme is given,which can increase the rotation order and stop time through a single rotation of 90°,to reduce the effect of the second harmonic errors and improve the navigation precision.An isolation compensate method of vehicle’s heading motion based on the rotating attitude change is presented,solving the problem of the rotating angle of IMU hardly keep pace with the predetermine rotation scheme on moving base,which is significant for the engineering practice.A duel-axis continuous rotation error self-calibration method for the DRINS is proposed based on the relationship between rotation scheme and observability,and a 31 dimensional Kalman Filter system is established to estimate errors.In view of the non-orthogonality of duel-axis mechanism,non-orthogonal angles effect on navigation errors are given and a simple and efficient two-position rotation self-calibration method is established to calibrate non-orthogonal angles.Moreover,the periodic oscillation error caused by residual errors after modulation and compensation are studied,a full damping network is designed to effectively restrain the influence of periodic oscillation error caused by residual errors on navigation precision.In order to ensure the effective implementation of the rotation modulation scheme,a rotation control algorithm based on internal model control(IMC)is proposed to solve the influence of rotating rate error on the navigation precision.Based on the IMC algorithm,a full state feedback regulator is designed,and the steady state condition of the system is proved.The simulation results show that it can achieve the precision tracking input command control with little steady-state error,improving the ability of anti-interference.Finally,the experiment of DRINS is carried out.The feasibility and effectiveness of proposed the duel-axis rotation method,errors self-calibration and damping are verified.The experimental results show that using the gyroscope drift of 0.003°/h can obtain the positioning precision of 0.24 nmile in 38 h,which satisfies the long-endurance requirement of high precision navigation.