The passive magnetic detection and localization technology of the magnetic field has the advantages of good concealment, continuous detection, high efficiency, reliable use, and rapid response. It has important application in the detection and localization of submarines and mines. The conventional location algorithm needs magnetic gradient tensor system moving to other points, we propose a kind of linear location algorithm with a unique solution based on a single measurement of the cuboid tri-axial magnetometer array. The magnetic gradient tensor of the magnetic target is first calculated at the center points of the six rectangles of the cuboid array, and then the distance between the magnetic target and the rectangle center of the cuboid array is calculated. Finally, according to the square difference of the distances of the three pairs of parallel rectangles, a linear equation set about the position coordinates of the magnetic dipole is formed and then these position coordinates are calculated fast. We derive an analytical formula of the location error for the linear location algorithm. The simulation shows that the position of the target can be calculated accurately and the relative error of the position is <1%, and the location errors are positively correlated with the noise standard deviation of the three-axis magnetometer, and more they are proportional to the non-orthogonality between every two axes, sensitivity deviation and bias of the three-axis magnetometer. The location errors of the linear location algorithm through numerical simulations are consistent with the location errors calculated by the analytical formula.
Based on trajectory information for the electric power system, this paper analyzes Transient Stability Prediction and new generation transient stability control of large power system.This method, which is independent of system parameter and model, can tell the transient stability of the electric power system faster and give the control strategy by the closed-loop control system.Firstly, System instability is detected by the characteristics concave or convex of the critical machine trajectory of the post-fault system.Secondly, to accelerate the speed of recognize the transient stability of the power system, the self-memory numerical predictive formula of multi-variables is derived.Thirdly, the control strategy by the closed-loop control system is given based on transient kinetic energy, when the power system is unstable.
Most multisensor association algorithms based on fuzzy set theory forms the opinion of fuzzy proposition using a simple triangular function. It does not take the randomness of measurements into account. Otherwise, the variance of sensors supposed to be known in the triangular function, but in fact the exact variance is difficult to acquire. This paper discuss about two situations with known and unknown variance of sensors. First, with known variance and known mean. This paper proposes a method, which use the probability ratio to calculate the fuzzy support degree. The interaction between the two objects is considered. Second, with unknown variance and known mean value, we replace the sample mean in the gray auto correlation function with the real sensor mean value to analysis the uncertainty which is the correlation coefficient between targets and measurements actually. In this way, it can deal with the case of small sample. Finally, form the opinion about the fuzzy proposition in terms of weighting the opinion of all the sensors based on the result of uncertainty analysis. Sufficient simulations on some typical scenarios are performed, and the results indicate that the method presented is efficient.
Generally, four three-axis magnetometers (TAMs) are used to measure magnetic gradient tensor. But the measurement precision of magnetic gradient tensor is tightly connected with the imperfect performance of sensors such as non-orthogonality, different scale factors and biases among sensitive axes, misalignment between different TAMs. It is necessary to calibrate and correct the measurement device to obtain precise magnetic gradient tensor. A mathematical model for calibration of the device measuring magnetic gradient tensor is established, and the calibration algorithm and its steps based on functional link artificial neural network (FLANN) and least-squares method (LSM) are proposed. The numerical simulations prove the effectiveness and good convergence of calibration algorithm, which can improve remarkably the measurement precision of magnetic gradient tensor.
To solve the problem of attitude determination using magnetometers independently and uniquely, which is important for underwater vehicles, a type of full attitude determination method based on geomagnetic gradient tensor is proposed in this paper. In this method, a group of non-linear equations concerning geomagnetic gradient tensors is established, where a quaternion is selected to calculate three attitude angles of an underwater vehicle. The optimal quaternion is estimated using Newton Down-hill to optimise the object function. The detailed steps of the full attitude determination based on geomagnetic gradient tensor are given, and the effects of the initial angle error and the sensor noise on the attitude determination are investigated. Simulations show that the algorithm can identify precisely and quickly the attitudes even in the presence of larger initial angle error and sensor noise, which proves the attitude determination algorithm.
The observer-based control for a class of uncertain linear systems is considered. Based on Lyapunov stability theory and Linear Matrix Inequality(LMI) approach,the observer-based controller is designed and a sufficient condition of exponential stabilizability for the systems is presented.
A modified particle filter is proposed and applied in real-time extracting of laser ranging information in this paper. We propose a particle of line type which can fit the character of laser echoes accurately and introduce it to the traditional particle filter algorithm. Further, the proposed line type particle filter is tested with simulation data and several real data from different earth-based laser ranging devices. The results demonstrate the good performance of the proposed line type particle filter in laser ranging information extracting.
Digital library is the existing form of future library. At the same time, it is the catalyst of economic and cultural de- velopment. Digital library can have the effect of updating urban culture and civilization, pushing forward urban economic de- velopment, promoting digital city development and filling up digital divide, etc. during urban development.
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