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Sun X.-C.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2011

To analyze the relationship between the deceleration-free servo system's tracking error and electrostatic gyroscope monitor's six-time calibration, the reason and the solution method of six-time calibration working abnormally are given. By analyzing the academic relationship among the deceleration-free servo system's tracking error, h angle transformation and azimuth angle, a new six-time calibration method is proposed. In this method, the equatorial gyroscope and polar gyroscope are calibrated at the different time according their azimuth angles. By several dynamic tests, the method is proved effectively with 100% success rate when the deceleration-free servo system's tracking error or the ship rocking is over the mark. By using the method, the electrostatic gyroscope monitor is more applicable in the ships. Source


Zhu J.-L.,Nanjing University of Science and Technology | Wang X.-Q.,Tianjin Navigation Instrument Research Institute | Wu P.-L.,Nanjing University of Science and Technology | Bo Y.-M.,Nanjing University of Science and Technology
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2012

The SNR(signal noise ratio) of weak GPS signal is relatively low, and the coherent integral and incoherent integral are need to take longer time in order to increase the SNR, so this paper puts forward a method to analyze the calculating process of coherent integral and incoherent integral from the aspect of probability statistics. First it gives the calculating expression of the integral of complex down-converter input signal. Then it deduces the mathematical expectation and variance of the correlation output of coherent integral, and calculates the probability density and expression of acquiring failure of a unit. Moreover it uses Matlab to simulate the signal's coherent integral and incoherent integral. The simulation results verify the probability expression of acquiring failure, that is, the incoherent integral's acquiring ability is weaker than that of coherent integral by 3.5 dB, due to the performance loss caused by Gaussian approximation and incoherent integral. Source


Fang J.-C.,Beihang University | Han X.-Y.,Beihang University | Yang F.-Y.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2013

In view of the bad precision caused by inertial sensor noise for airborne POS(Position and Orientation System), a preprocessing method based on wavelet filter and HMM(Hidden Markov Model) combined with AKF(Adaptive Kalman Filter) is proposed. Firstly, the spectrum characteristic of the inertial sensors is analyzed, and a wavelet filter is employed to eliminate the high-frequency noise. Then the HMM is build to decrease the influence of random walk error. The inertial information is processed, so the noise statistical distribution of the system is uncertain. An adaptive Kalman filter is used to improve alignment accuracy. Experiment results indicate that, after 600 s strapdown calculation with the proposed method, the horizontal velocity error decreases from 1.27 m/s to 0.6061 m/s, and the horizontal position error decreases from 274.6 m to 128.2 m, and horizontal velocity and position error are reduced by about 50%. Source


Han X.-J.,Beijing Institute of Technology | Deng N.-M.,Beijing Institute of Technology | Wang J.-Z.,Beijing Institute of Technology | Liu J.-Z.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2012

In studying the precise north-seeking based on gyrocompass, it is found that the precise north-seeking lasts too long to meet the requirement. In modern war, it's urgent to shorten the precise north-seeking time of gyrocompass under the premise of certain precision. Giving consideration to both above aspects, a math model of gyrocompass' precise north-seeking is analysed and it is concluded that the gyro rotor does simple harmonic oscillation around north. Then an algorithm based on sine curve fitting is put forward to calculate the azimuth angle of gyrocompass' principal axis. Experiments show that, when using 1/4 period's data for sine curve fitting, compared to the integral method, the precision is only a little worse while time of precise north-seeking is shortened from 150 s to 37.5 s. Therefore, sine curve fitting is an effective way to improve the gyrocompass' north-seeking efficiency. Source


Yue P.,Harbin Engineering University | Shi Z.,Harbin Engineering University | Wang J.,Tianjin Navigation Instrument Research Institute | Yang J.,Harbin Engineering University
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2011

Due to low precision and large drift of MEMS gyro, the navigation precision of micro inertial navigation system equipped with MEMS gyro and accelerometers is very low and its position error and attitude error could diverge quickly, so the vehicle's navigation requirement on position and attitude determination could not met. While the precision of MEMS accelerometer is higher than that of MEMS gyro, a gyro free inertial navigation system (GFINS) only with the MEMS accelerometer is proposed to replace the MINS system for some short time moving vehicle. The MEMS accelerometer with high accuracy will be placed at the non center of mass in this GFINS to measure angular motion information instead of MEMS gyro. Finally, two inertial navigation systems are simulated to track a trajectory of a short-term moving vehicle. The simulation results show that, after the error compensation, the navigation error in 100 s for the GFSINS constituted by MEMS accelerometers is equivalent to that of the traditional gyro-INS error when caused by gyro drift of 0.1 (°) / h. Source

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