Time filter

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Yang Y.,Tianjin Navigation Instrument Research Institute | Li D.,Tianjin Navigation Instrument Research Institute | Gao W.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2016

In rotating accelerometer gravity gradiometer, due to the limitation of the accelerometer's process and performance level and the effects of various installation errors, there are lots of noises in the system output signal, and the SNRs are extremely low. In order to effectively extract the real gravity gradient signals in strong noises, the measurement errors caused by harmonic interference must be reduced in the process of signal demodulation. Combined with the error generation mechanism, the influences of different demo- dulation methods on the gravity gradient signal demodulation are analyzed and compared, and a reasonable method of signal demodulation is chosen. Meanwhile, a band-pass filter is added in the data processing process to further reduce the influence of the dynamic noise. Combined with dynamic swing test data, the simulations show that the above measures have obvious effect on the noise suppression of the original gravity data, and the noise amplitude of the demodulated signal is reduced to 20%, which improves the spatial resolution of the system, and has the engineering application value. © 2016, Editorial Department of Journal of Chinese Inertial Technology. All right reserved.


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.


Wang Z.-Q.,Beijing Institute of Technology | Fang J.-C.,Beihang University | Wang S.-T.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2012

Shuler oscillation in INS not only increases velocity, attitude and position errors, but also degrades the efficiency of realignment and position updates, which is a problem that must be solved for long-term INS. Using damping network of classical control theory to solve this problem in practice is the traditional design method which has been introduced in classical works of inertial navigation theory both in domestic and abroad. However, the damping network could cause calculating distortion of the INS. The technique using modern control theory to eliminate Shuler oscillation in the pure inertial calculating mode without disturbing the INS is presented. The simulation results were satisfactory which shows the method is feasible and practical.


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%.


Qi H.,Hebei University of Technology | Zhao Z.-Z.,Hebei University of Technology | Li Z.-H.,Tianjin Institute of Hydroelectric and Power Research | Zhao S.-W.,Tianjin Navigation Instrument Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2013

According to the characteristics of fault diagnosis for vacuum circuit breaker, a decision level information fusion diagnosis method is presented by using wavelet packet, RBF neural network and D-S evidence theory. Firstly, according to the method of wavelet packet-energy spectrum, vibration signals are decomposed and extracted feature vector as a basis for diagnosis; Then, neural network model is established, and the initial diagnosis results are obtained through the RBF neural network; Finally, the diagnosis results are used as the basic probability distribution value to each fault mode, and the D-S evidence theory is applied, and the final fusion diagnosis results are obtained. The experiment shows that the proposed method is effective to diagnose the faults of vacuum circuit breakers.


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.


Liu H.-G.,Tianjin Navigation Instrument Research Institute | Chen Z.-G.,Dalian Ship Factory | Chen G.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2012

The information computed by SINS do not synchronize with MINS information because of calculation and transfer time delay during transfer alignment, and sometimes time-delay is relatively large. In this paper, through establishing the velocity matching transfer alignment model of SINS on moving base, the time-delay's effect on the attitude accuracy, gyro constant drift and accelerometer constant bias were analysed by simulation under several typical ship movement states. The simulation results show that, in case with constant velocity and constant acceleration in alignment, the time-delay's effect on velocity matching transfer alignment can be ignored. In case with variable acceleration in alignment, the time-delay could affect the accuracy of Kalman filter, but the effect could become lower and lower after velocity is stabilized. In case with swerves and continuance maneuver, the time-delay's effect on velocity matching transfer alignment were severe, the azimuth error can attain 10', and the estimate accuracies of gyro constant drift and accelerometer constant bias can significantly decline.


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.


Weng H.-N.,Tianjin Navigation Instrument Research Institute | Yao Q.,Tianjin Navigation Instrument Research Institute | Hu X.-M.,Tianjin Navigation Instrument Research Institute
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2012

Speed and accuracy of initial alignment is the important indicators of INS on board ship. The algorithm of fast dynamic initial alignment is proposed in the condition that the vessel starts the laser gyro SINS in different working situations. Coarse alignment method for single rotary laser gyro SINS on moving base is studied. The single rotary SINS error models are established, and the rotary scheme during precise alignment is chosen. Precise alignment for single rotary SINS is designed using the Kalman filter. Different alignment schemes are designed to respectively fit the conditions that the vessel starts the INS in three different situations. The simulation results show that, after six hours' alignment, the estimated error for vertical gyro bias is less than 5.2%, and the estimated error for vertical accelerator bias is less than 1.8%.


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.

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