Research On SINS Dynamic Errors And Compensation Algorithms Based On Signal Frequency Domain Characteristics Of Dither RLG

With the improvement of ring laser gyro (RLG) in China, the dither RLG strapdown inertial navigation system (SINS) is playing a more and more important role in domestic inertial area. The gyros'unique mechanic dither property which is used to alleviate the gyro lock-in brings a lot of new and complicated dynamic error characteristics to the SINS, so system optimization and error compensation have important theoretic and practical meaning. Focusing on dither RLG-based SINS, the dissertation proposes that SINS algorithms must be designed to match the system signals and application environments, and researches on the dynamic error and compensation algorithms of dither RLG SINS based on the frequency domain characteristics of the RLG signals in various conditions. The main contents of this dissertation are:1. New digital control methods of RLG are designed through studying the gyro digital control characteristics, which sets a sound foundation for the ensuing research on the gyro signal frequency domain characteristics. According to the dither biasing mechanism, error characteristics of gyro static and dynamic lock-in are investigated. The relation between the dither parameters and the gyro precision is argued to obtain the design principles of dither parameters. Different from the analog methods, the new control methods of nonlinear dither magnitude and random dither are designed, and DC frequency-stabilization algorithm is implemented digitally. We then set up the whole digital control system of dither RLG. The new algorithms simplify the hardware and increase the reliability, expandability and precision of the control system.2. The dynamic errors of the dither RLG SINS are investigated and its optimization process principles are constituted. Firstly, it is underlined through peer comparison that the digital filter method, which gives more flexible ways and possibilities to increase the SINS accuracy, has been used widely instead of the whole period-synchronization method. Then, the SINS dynamic characteristics are investigated. The coning and sculling motions which might exist in SINS are assorted according to the source and property of motions. Optimization principles of system dynamic errors that the shock absorbers alleviate the disturbed motions and the filters eliminate the noise signals are set up. Finally, these conclusions are applied to the dither RLG SINS. The SINS dynamic errors introduced by the gyro dither bias, dither coupling in the static environment and the high frequency resonance in the vibration environment are studied, along with their process methods. It is pointed out that the high frequency harmonic vibrations are the major dynamic error source of SINS in the vibration environment.3. Based on the gyro signals process way of digital filter, it is proposed that the magnitude-frequency and phase-frequency distortion of gyro filtered signals should be studied as the important error factors of attitude computation for the SINS. The passband standard of the normal filters can not generally meet the requirement of signals stabilization for the attitude calculation, which may seriously decay the attitude precision. New optimal coning algorithms are thus designed to match the signals' frequency domain characteristics. Algorithm formulas are derived for the classical coning motions and its error characteristics are studied. It is proved that the optimal algorithms can also be used in general environments. Additionally, the optimization algorithms are extended to eliminate the pseudo coning errors and compensate the gyro frequency characteristics itself. The new algorithms do not complicate the algorithm realization and computation burden. The optimization effect depends on the filter performance. Simulations and experiments show that the optimized coning algorithms can compensate significantly coning errors introduced by signal filter and increase the attitude algorithm accuracy from times to orders depending on various filtering conditions.4. Sculling algorithms are influenced by both gyro and accelerometer signals, in contrast to coning algorithms that is affected only by gyro signals. Regarding the distortion of gyro and accelerometer filtered signals as the important error factors of navigation computation, new optimization sculling algorithms are designed to match the signals'frequency domain characteristics. Algorithm formulas are derived in the classical sculling motions. It is revealed that the optimal coning and sculling algorithms still keep the duality in common filtering conditions and can be also used in the general environments. Simulations and experiments show that the optimal sculling algorithms have similar error characteristics with the optimal coning algorithms and can improve remarkably SINS navigation accuracy by compensating the filter-dependence sculling errors.5. For angle vibration environments, a new coning algorithm is designed which is optimized to the fixed frequency motion. Different from the monotonic error characteristics of the standard algorithm with the coning frequency, the optimal coning algorithm has a minimization point at the specified frequency and can improve the attitude accuracy remarkably for those motions with the specified frequency band. The optimal algorithm has good effect for the motions with the known narrow frequency band.Finally, the optimal coning and sculling algorithms are integrated to form the whole navigation algorithms. SINS Matlab models and experiments (turn-table swinging, land runs in circles and in a long way) are carried out to investigate the effect of signals frequency domain characteristics on the SINS navigation accuracy. The performance of the optimization algorithms are verified favorably for various environments and signal filters.