Xu Y.,Beihang University |
Chang Q.,Beihang University |
Yu Z.,Taiyuan Satellite Launch Center
Science China Technological Sciences | Year: 2012
This paper studies the key techniques of the measurement and communication system for inter-satellite links (ISLs) of global navigation satellite system. A fixed link topology is designed based on the analysis of inter-satellite geometric properties and spatial parameters of the standard Walker24/3/2 constellation. This design can achieve full network coverage with small number of hops, significantly reduce the number of ISLs, and enhance the feasibility and reliability of the system. A new time-division duplex mode, as well as an integrated measurement and communication scheme, is proposed based on the designed topology. Furthermore, mathematical formulas, error models, and modification methods regarding two-way ranging and time synchronization algorithms using spread spectrum non-coherent data frame for this new system are comprehensively discussed. Theoretical analysis and simulation studies demonstrate that our design, compared with current GPS systems, has higher ranging and time synchronization precision, improved measurement efficiency, and higher channel utilization ratio and data transmission rate. It has no restrictions of constellation configuration, making it suitable for both MEO and the future MEO/GEO hybrid constellations. The results in this paper can serve as strong technical support for the next generation of GNSS ISL. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.
Feng F.,Academy of Armored force Engineering |
Si A.,Academy of Armored force Engineering |
Zhang H.,Taiyuan Satellite Launch Center
Procedia Engineering | Year: 2011
Aimed at the problem of the feature of nonstationary vibration signal can not be extracted easily; the bispectrum analysis technique was researched in this paper. Bispectral characteristic frequency faces were searched along the parallel to the diagonal line at certain step in the bispectral modulus field, and the mean magnitude was calculated to get the feature parameters. The method was applied in fault feature extraction of piston-pin of diesel engine successfully. Finally, the piston-pin faults were diagnosed associated with genetic neural network. © 2011 Published by Elsevier Ltd.
Zhou Y.,Beijing Jiaotong University |
Yang X.,Beijing Jiaotong University |
Liu Q.,Beijing Jiaotong University |
Zhang Z.,Taiyuan Satellite Launch Center
IEEE ICIRT 2013 - Proceedings: IEEE International Conference on Intelligent Rail Transportation | Year: 2013
In the infrastructure of networked operation of high-speed trains, the justification of operation safety and the decision of scheduling strategies should be undertaken in a real-time way, which depends on the credible prediction model of train movements. This paper will incorporate the train movement high-level model into the real-time conflict detection and train scheduling based on the principle of model predictive control (MPC). The proposed model describes the restrictive, synergistic and autonomous train movements with continuous accelerations and decelerations in the discrete time and continuous space. The sufficient modeling accuracy can be achieved if the adjustable parameters are properly configured for the MPC-based control and management of train operations. Consequently, the detection of block-section occupation conflicts considering the virtual junctions and the decision of feasible scheduling strategies possess the considerable confidence level and safety guaranty. The conflict detection and the operation optimization are implemented over the rolling horizon according to the real-time feedback information. The numerical results demonstrate the utility and rationality of the proposed model for the real-time safety justification and the scheduling strategy evaluation. © 2013 IEEE.
Liu D.,Wuhan Naval University of Engineering |
Zhang X.,Wuhan Naval University of Engineering |
Chen C.,Taiyuan Satellite Launch Center
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2015
We have proposed a method for rectangular illumination in a (u, v) coordinate system with high collection efficiency and favorable uniformity. In our proposed approach, with the target plane rotating at a certain angle around the z axis, one of the diagonals on the rectangular target plane moves to the coordinate axis; then, we partition the light source and target plane into grids. The intersection points of the grids are in one-toone correspondence from the source to the target plane. This improved method will avoid the one-to-many correspondence topological relationship in the traditional (u, v) mapping method; uniformity of the illuminance pattern will be promoted. Based on this method, lenses are designed for rectangular target plane illumination; uniformity over 0.83 and efficiency of about 0.92 are obtained with a 1 mm × 1 mm LED Lambertian source. © 2015 Optical Society of America.
Zaixin Z.,Taiyuan Satellite Launch Center |
Zaixin Z.,National University of Defense Technology |
Lizhi C.,National University of Defense Technology |
Guangquan C.,National University of Defense Technology
IET Image Processing | Year: 2014
Fuzzy c-means (FCM) clustering algorithm has been widely used in image segmentation. In this study, a modified FCM algorithm is presented by utilising local contextual information and structure information. The authors first establish a novel similarity measure model based on image patches and local statistics, and then define the neighbourhood-weighted distance to replace the Euclidean distance in the objective function of FCM. Validation studies are performed on synthetic and real-world images with different noises, as well as magnetic resonance brain images. Experimental results show that the proposed method is very robust to noise and other image artefacts. © The Institution of Engineering and Technology 2014.
Zhao Z.,Taiyuan Satellite Launch Center |
Chang W.,Taiyuan Satellite Launch Center |
Jiang Y.,Taiyuan Satellite Launch Center
Proceedings - 2015 8th International Congress on Image and Signal Processing, CISP 2015 | Year: 2015
Segmentation for images with intensity inhomogeneity is very difficult. In this paper, a fuzzy clustering-based method to segment intensity inhomogeneity images is presented. Firstly, a new expression of the fuzzy C-means(FCM) object function is derived through altering the prototype of every clustering to a point-wise function. Then, a weight function defined on the local window is introduced into the objective function. The local weight makes the prototype for every pixel depends only on the information of its local region, which is more reasonable for the considered problem. The proposed method has been applied to artificial and real-world images, e.g. X-ray vessel images and MRI brain images. The comparison segmentation results have shown the proposed model is very applicable for image segmentation with intensity inhomogeneity. © 2015 IEEE.
Fan J.,Taiyuan Satellite Launch Center
Chinese Control Conference, CCC | Year: 2015
A matrix inequality approach is proposed for local stabilization of a class of uncertain linear systems subject to time-varying input delays, actuator saturation, and norm-bounded disturbances. Delay-dependent stability and stabilization conditions by using the linear state-feedback control law are obtained to guarantee the uniform boundedness of solutions of the closed-loop systems. Besides, an admissible maximum bound of disturbances can be ascertained to ensure the existence of a non-empty set of initial conditions. An optimization framework is formulated further for the maximization purpose of the admissible upper bound of disturbances and the size of the set of initial conditions. A numerical example is provided to demonstrate the effectiveness of proposed design techniques. © 2015 Technical Committee on Control Theory, Chinese Association of Automation.
Long Z.,Taiyuan Satellite Launch Center
Proceedings of the 28th Chinese Control and Decision Conference, CCDC 2016 | Year: 2016
In this paper, the three-axis rotational maneuver of flexible spacecraft is investigated and a robust composite controller is presented. The composite controller consists of a proportional-plus-derivative (PD) sub-controller which accomplishes the spacecraft attitude maneuver and a positive position feedback (PPF) sub-controller which suppresses the elastic vibration of flexible appendages. Utilizing angular velocities and quaternion of the spacecraft, the PD controller generates the control torques which act on the rigid body of flexible spacecraft. Utilizing the vibration modal information of the spacecraft flexible appendage, the PPF controller generates the piezoelectric inputs which act on the flexible appendage. Moreover, the composite controller is robust with respect to structure parameter uncertainties of flexible spacecraft. By properly choosing an elaborate Lyapunov function, the robust asymptotical stability of the whole closed-loop system is proved theoretically. Finally, simulations are included to illustrate the effectiveness of the proposed controller. © 2016 IEEE.
Hao Y.,Taiyuan Satellite Launch Center |
Shang L.,Taiyuan Satellite Launch Center
Lecture Notes in Electrical Engineering | Year: 2013
To support more and more satellite and launch vehicle missions, tracking, telemetry and command (TT&C) system is challenged by requirements of more equipments operation, more complex system management and more intelligent decision-making. With the development of information technology (IT), promoting IT usage in TT&C system is the only way to meet the challenge. Based on the views of IT evolution stages, information integration issues, combined with TT&C system, this paper proposed a TT&C information integration management model and a corresponding application system, which both have three levels, a base-level with automation as subject, a middle-level with process management as subject and a high-level with intelligence as subject. Comprehensive discussion shows that the information integration stage in IT evolution is the key development stage for TT&C system. To improve information integration efficiency and ability, the three-layer model is an instructive model for practical application. © 2013 Tsinghua University Press, and Springer-Verlag.
Fan J.,Taiyuan Satellite Launch Center |
Song J.,Taiyuan Satellite Launch Center |
Peng J.,Taiyuan Satellite Launch Center
Proceedings of the 28th Chinese Control and Decision Conference, CCDC 2016 | Year: 2016
The calculation issue of angle of attack at the warhead reentry point is discussed in this paper based on the missile flight test data, to indirectly verify the warhead penetration performance. By analyzing the warhead flight environment and the relationship among several coordinate systems, two equivalent approaches are provided to calculate the warhead angle of attack at the reentry point. The available flight test information is sufficiently utilized in the calculation process, including the telemetry data, the exterior trajectory measurement data, the ballistic design data, etc. The validity of the proposed approaches is demonstrated by the missile flight test data, and the calculation results indicate that the two approaches are absolutely equivalent and the calculated angle of attack is close to theoretically designed one. © 2016 IEEE.