Research On Long-duration High-accuracy Error Inhibiting Technology Of Strapdown Inertial Navigation System

Nowadays, modern ships need to sail in large area and long duration, and accomplish theassigned missions. And the strapdown inertial navigation system (INS) on ship should providenavigation and manipulated information. Moreover, it also provides references for localequipments on ship. So the strapdown INS should be capable to give high-accuracy andlong-duration self-contained navigation information. Our thesis research is located on thesystem algorithm and scenario. We study on the rotation-modulation technology and dampingtechnology during the navigation phase. Our major works as follows:At first, we present the single-axis rotation strapdown INS concept. The normal framedefinitions are given here. With single-axis rotation table, we establish rotation strapdownINS and make analysis on the system. Specific force equation, velocity equation and positionequation are deduced. Considering gyro drift and accelerator bias as error sources, we get theerror propagation equation for the single-axis rotation strapdown INS. Furthermore, assumingthe carrier is on the static base, we could derive the error propagation model stimulated bymulti error sources.Secondly, through the error propagation model, the essence of error restrainingtechnology is explained, and the auto-compensation principle of constant error of inertialmeasurement unit (IMU) is analyzed. After showing the accumulating effect on the twosymmetry positions, we discuss the restraining results for constant error, scale factor,misalignment error and quadratic errors. Then the total error restrain condition, which isaffected by multi error sources in frequency domain, is presented. A four-position rotationscenario used in engineering practice is analyzed and simulated. By the simulation results, theabove analysis results are verified.Thirdly, damping algorithm is introduced to restrain the oscillation errors of thestrapdown INS and then network frameworks and parameters are designed for the leveldamping and azimuth damping respectively. Using information loop figure, we derive therelationship between the external velocity error and misalignments in external velocitydamping INS. We innovatively present the error of the external velocity damping INS by thesine oscillation with a long period. Also the simulation test is carried out to guarantee theanalysis results.Finally, a new method is presented to solve the problem that the system error oscillationbecomes greater as the ship undergoes maneuvers or the ocean current is changed. The damping net parameters could change in real time according to the external velocity error soas to reduce system errors by the ship maneuvers and ocean currents. The external velocitydamping matching method is compared with the traditional external velocity damping methodin the simulation circumstance. The simulation results show that the superiority and validityof our proposed method.