Time filter

Source Type

Chang G.,China Institute of Technology | Chang G.,Wuhan Naval University of Engineering
IET Radar, Sonar and Navigation | Year: 2014

The independence of the process and observation noises is the prerequisite of many Kalman-type filters. However, the fact is that these two noises may be correlated with each other in actual applications. The filtering of the non-linear systems with cross-correlated process and observation noises at the same epoch is studied. First, a decorrelated scheme is introduced and a pseudo non-linear process equation is reconstructed in which the corresponding pseudo process noise is no longer cross-correlated with the observation noise; so a celebrated non-linear filter, that is, the unscented Kalman filter (UKF) can be used to filter the non-linear problem. Second, the (conditionally) linear substructure in the above non-linear system is exploited and a refined filter called marginal UKF is employed so as to reduce computational load without deteriorating the accuracy. The performance of the standard UKF for the original system equations, the standard and marginal unscented UKFs for the reconstructed system equation are compared in the simulation. From the results of the simulation, the theoretical statements are validated, and some interesting but not surprising phenomena are also founded, that is, the performance of the conventional filter actually does not degenerate, whereas that of the proposed filters become better when cross-correlation exists and increases. This phenomenon can be due to the fact that the proposed filters exploited the extra information buried in the cross-correlation, whereas the conventional filter fails to do so. © The Institution of Engineering and Technology 2013.

Chang G.,Tianjin Institute of Hydrographic Surveying and Charting | Chang G.,Wuhan Naval University of Engineering
Journal of Geodesy | Year: 2014

A robust Kalman filter scheme is proposed to resist the influence of the outliers in the observations. Two kinds of observation error are studied, i.e., the outliers in the actual observations and the heavy-tailed distribution of the observation noise. Either of the two kinds of errors can seriously degrade the performance of the standard Kalman filter. In the proposed method, a judging index is defined as the square of the Mahalanobis distance from the observation to its prediction. By assuming that the observation is Gaussian distributed with the mean and covariance being the observation prediction and its associate covariance, the judging index should be Chi-square distributed with the dimension of the observation vector as the degree of freedom. Hypothesis test is performed to the actual observation by treating the above Gaussian distribution as the null hypothesis and the judging index as the test statistic. If the null hypothesis should be rejected, it is concluded that outliers exist in the observations. In the presence of outliers scaling factors can be introduced to rescale the covariance of the observation noise or of the innovation vector, both resulting in a decreased filter gain. And the scaling factors can be solved using the Newton's iterative method or in an analytical manner. The harmful influence of either of the two kinds of errors can be effectively resisted in the proposed method, so robustness can be achieved. Moreover, as the number of iterations needed in the iterative method may be rather large, the analytically calculated scaling factor should be preferred. © 2014 Springer-Verlag Berlin Heidelberg.

Yan B.H.,Wuhan Naval University of Engineering
Nuclear Engineering and Design | Year: 2011

The periodic large scale vortex structure is highly accounted for the local flow and heat transfer and turbulent mixing in rod bundles. In this paper, the mechanism of the periodic large scale structures is studied in terms of the vortex dynamics. The vortex structure in rectangular channels with different inlet velocities is also analyzed. It is found that the periodic large scale vortex structure exists in the rectangular channels with transverse vorticity gradient. The distribution of vorticity is strictly related with that of vortex structure. Copyright © 2011 Published by Elsevier B.V. All rights reserved.

Chen L.G.,Wuhan Naval University of Engineering
Science China Technological Sciences | Year: 2014

The mass entransy and its dissipation extremum principle have opened up a new direction for the mass transfer optimization. Firstly, the emergence and development process of both the mass entransy and its dissipation extremum principle are reviewed. Secondly, the combination of the mass entransy dissipation extremum principle and the finite-time thermodynamics for optimizing the mass transfer processes of one-way isothermal mass transfer, two-way isothermal equimolar mass transfer, and isothermal throttling and isothermal crystallization are summarized. Thirdly, the combination of the mass entransy dissipation extremum principle and the constructal theory for optimizing the mass transfer processes of disc-to-point and volume-to-point problems are summarized. The scientific features of the mass entransy dissipation extremum principle are emphasized. © 2014, Science China Press and Springer-Verlag Berlin Heidelberg.

Yan B.H.,Wuhan Naval University of Engineering
Annals of Nuclear Energy | Year: 2011

The laminar to turbulent transition process of pulsating flow in ocean environment is investigated with the theory of energy gradient. The effect of ocean environment on the flow breakdown position is weak. The effect of oscillating period on the laminar to turbulent transition increases with the increasing of oscillating period. The influence of ocean environment on the transition also increases with the increasing of oscillating amplitude. If the oscillating amplitude is very high, the traditional calculation method could not give a satisfactory prediction for the laminar to turbulent transition. © 2011 Elsevier Ltd. All rights reserved.

Ma W.,Wuhan Naval University of Engineering
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2011

Power electronic technology is developing rapidly in recent years, and it is widely used in shipboard power systems. Typical applications of power electronics in naval ship power systems such as static excitation regulation in high speed induction machines, static power conversion systems, DC zonal electric distribution systems, and electric propulsion systems are proposed. Some suggestions are given about how to accelerate the development of power electronic technology.

Weiming M.,Wuhan Naval University of Engineering
2011 International Conference on Electrical Machines and Systems, ICEMS 2011 | Year: 2011

The Integrated Power System (IPS) is not only an important basis of the shipbased high-energy weapons but also a revolutionary way of the developing naval vessel power because it is characterized by lower noise, higher survivability, fewer prime movers, less fuel consumption, and greater convenience for general arrangement. This paper has described both the constitution and the latest developments of IPS, proposed the concept of two-generation IPSs, and presented their remarkable technical characteristics and typical architectures. The quantitative analyses of volume, weight, efficiency, power supply continuity, load flow adjustment and control capability, stability, protection and reconfiguration abilities demonstrate that the second-generation IPS has the advantage over the first-generation IPS. Finally, several key technologies concerning the second-generation IPS that need a breakthrough have been proposed according to the current technical level. © 2011 IEEE.

Yan B.H.,Wuhan Naval University of Engineering
Nuclear Engineering and Design | Year: 2013

A new lattice with non-uniform wall roughness and excellent heat transfer enhancement is introduced. The similar lattice with non-uniform wall thickness is also given in this paper. This kind of lattice could not only enhance the heat transfer and fluid mixing effectively but also avoid the disadvantages of tight lattice. The flow pulsation, vortex structure, flow and heat transfer in lattice were investigated with unsteady Reynolds Averaged Navier-Stokes simulation. The maximum heat transfer coefficient in the non-uniform wall roughness is about two times of that in traditional rod bundles. With the same power, the heat transfer could be increased by 40% compared to the traditional rod bundles in heat exchangers and nuclear systems. © © 2013 Elsevier B.V. All rights reserved.

Chen L.,Wuhan Naval University of Engineering
Science China Technological Sciences | Year: 2012

The emergence and development of constructal theory, which has been a new discipline branch to research sorts of structures in nature and engineering, are reviewed. The core of the constructal theory is that various shapes and structures of the matters in nature are generated from the tendency to obtain optimal performance. Constructal theory and its application are summarized, from disciplines such as heat, mechanism, fluid flow, electricity, magnetism and chemistry, to life and non-life systems in nature. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.

Chang L.,Wuhan Naval University of Engineering | Hu B.,Wuhan Naval University of Engineering | Li A.,Wuhan Naval University of Engineering | Qin F.,Wuhan Naval University of Engineering
IEEE Transactions on Automatic Control | Year: 2013

This technical note concerns the deterministic sampling points construction strategy for unscented Kalman filter (UKF) and cubature Kalman filter (CKF). From the numerical-integration viewpoint, a new deterministic sampling points set is derived by orthogonal transformation on the cubature points. By embedding these points into the UKF framework, a modified nonlinear filter named transformed unscented Kalman filter (TUKF) is derived. The TUKF can address the nonlocal sampling problem inherent in CKF while maintaining the virtue of numerical stability for high dimensional problems. Moreover, the methodology proposed in this technical note can be used to construct nonlinear filters with improved accuracy for certain problems. The performance of the proposed algorithm is demonstrated through a nonlinear high dimensional problem. © 2012 IEEE.

Loading Wuhan Naval University of Engineering collaborators
Loading Wuhan Naval University of Engineering collaborators