Optics and Precision Engineering,2018,Vol 26,No. 03
【Abstract】 Modern ships are usually redundantly equipped with one-axis indexing ring laser gyro (RLG) marine inertial navigation system (MINS) and several two-axis indexing RLG MINS. In order to online evaluate the relative performance of the redundant two-axis indexing RLG MINS, an online evaluation method based on joint rotation and modulation was proposed without using external benchmark information. Several joint error Kalman filters were constructed. The system states of each Kalman filter included the position differences, the velocity differences and the attitude error differences between the one-axis indexing RLG MINS and the corresponding two-axis indexing RLG MINS, as well as the gyro drifts and horizontal accelerometer biases. With the position and velocity difference between the systems being observations, the observability analysis showed that all states including azimuth gyro drift of the one-axis indexing MINS were observable if the relative attitude between the systems was changed by the joint rotation and modulation. The standard deviation of azimuth gyro drift estimation of the one-axis indexing MINS was defined as the assessment criteria to online evaluate the random errors of the two-axis indexing MINS. The semi-physical simulations and the experimental results show that the RLG random error difference of the two-axis indexing MINS can be distinguished at a level of 10% noise and the position accuracies of different two-axis indexing MINS are online evaluated according to the standard deviation of azimuth gyro drift of the one-axis indexing MINS during 144 h navigation time. The proposed method provides theoretical basis for optimum system choosing in the case of one-axis and two-axis indexing RLG MINS redundant configuration.
Chinese Journal of Lasers,2018,Vol 45,No. 06
【Abstract】 In view of the low frequency stabilization accuracy of prism laser gyros, the characteristics of frequency stabilization control system of prism laser gyros are systematically studied. The light intensity tuning curve and the frequency stabilizing actuator are analyzed theoretically. The mathematical model of the frequency stabilization control system of the prism laser gyros is established. The steady state performance and dynamic performance of the system are further analyzed. The analysis results show that the system has different steady-state errors and the adjustment time is too long under the influence of constant temperature and slow temperature change, which leads to the decline of the stability frequency accuracy. We optimize the controller parameters to provide optimal damping ratio and rapidity for second-order system. And the feedforward control system with temperature compensation is adopted to realize the full compensation of the frequency stability error caused by the temperature and improve the frequency stability accuracy of the system. The experimental results show that the optimized frequency stabilization control system can improve the frequency stability accuracy by one order of magnitude compared with the original frequency stabilization control system, and the gyro accuracy can be improved by more than 30%.
Optics and Precision Engineering,2018,Vol 26,No. 05
【Abstract】 The control method of the drive axis was investigated with the goal of rapid start-up of the MEMS gyroscope with a high Q-factor. The change rate of the vibration phase of the high Q-factor resonator with frequency was analyzed, and the reason for the long starting time of the phase-locked loop scheme in addition to its sensitivity to the initial frequency deviation was elucidated. The variation rule of the amplitude at the initial stage of the self-excited oscillation scheme with time was deduced by using the averaging method. A control scheme that combines the self-exited oscillation loop and the phase-locked loop (SEOL-PLL) of the drive axis was proposed. The self-excited oscillation mode was used to quickly start the gyroscope, and then the phase-locked loop was used to maintain the accuracy and stability of the vibration frequency. In the experiment, when the initial frequency deviation of the PLL is in the range of ± 10 Hz, the starting time of the gyroscope is 2 s. Whereas with the SEOL-PLL scheme, a frequency error of 0.01% is achieved in 0.3 s and an amplitude error of 0.1% is achieved in 0.4 s, as long as the initial frequency deviation is within ± 1 000 Hz. The “SEOL-PLL” solution considerably reduces the start-up time and is insensitive to the initial frequency deviation of the gyroscope. It is therefore suitable for the mass production of MEMS gyroscope and has a good adaptability to ambient temperature change.