The Crab pulsar is an isolated rotation-powered pulsar which emits large X-ray fluxes, making it a candidate source for carrying out the X-ray pulsar navigation (XNAV). The long-term stable profiles are considered as the foundation of XNAV. However, systematic studies of the long-term stability of the X-ray pulsar profile and its effect on range accuracy in XNAV are lacking. In this paper, we use the X-ray band (2-16 keV) data monitored by Rossi X-ray timing explorer (RXTE) spacecraft over the latest 11 years, to first investigate the stability of the Crab pulsar including the profiles after the glitches. Furthermore, some measurements of the long-term profile shape, including Pearson correlation coefficient, standard deviation and spectral entropy, are presented both in the time domain and in the frequency domain. In the data processing, the Fourier analysis and cross-correlation are used to deal with the 191 RXTE data sets. With the help of the Cramer-Rao theory, the effect of the profile variation on the error of the range determination in XNAV is studied. Furthermore, after analyzing those errors, the effect of the stability of the Crab pulsar on range determination is confined to more narrow limits. The results demonstrate that the 2-16 keV profiles are almost constant during the period 2001-2012. The profiles after the glitches show no significant discrepancy. The variation of Crab profile inevitably has an influence on the navigation precision to a certain extent. The calculated range error along the pulsar line-of-sight due to the stability of the pulsar profile is 34 m ±25 m.
Hai Feng Sun;为民 包;Hai Yan Fang;小平 李
Wuli Xuebao/Acta Physica Sinica
Taking six degrees of freedom model of a generic hypersonic vehicle as the research object, this paper proposes a terminal sliding mode attitude control method which can converge to the equilibrium point within finite time globally. In the design of the controller, dynamic inversion is applied to deal with strong couplings among pitch angle, yaw angle and roll angle. In the case of considering the model uncertainties and external disturbances, the terminal sliding mode variable structure control method is used to guarantee the robustness of the system. In addition, by improving the traditional exponential approach law, the control command can be tracked within finite time globally. Based on the Lyapunov stability theory, it is proved that the finite time convergence in both reaching and sliding phases can be achieved. Finally, simulation results demonstrate that the proposed attitude control method is efficient.
Haidong Liu;为民 包;Huifeng Li;Chunye Gong;Yuxin Liao
Beijing Hangkong Hangtian Daxue Xuebao/Journal of Beijing University of Aeronautics and Astronautics
An optimal guidance law with multi -targets which can satisfy impact point, impact angle and terminal velocity constraints is proposed to solve precise guidance and maneuver penetration problems for hypersonic vehicle in dive phase. Firstly, it analyses the control characters for this kind of vehicle, and establishes relative motion equations in diving-plane and turning-plane. Furthermore, reference motions for the LOS (line-of sight) angle rate with the form of sinusoid are designed, which can be tracked by optimal control with the integrated optimal index consists of maximum terminal velocity, minimum miss distance and impact angle error. Therefore, an optimal guidance law with terminal multiple constraints and can realize maneuvering flight is obtained. In addition, it takes advantage of predictor-corrector to ascertain the maneuver range to consume residual energy in order to satisfy terminal velocity constraint. Finally, the results of CAV-H vehicle simulation test show that the algorithm can realize maneuvering flight, and can satisfy multiple constraints with high precision. Therefore, it can offer references for high precision guidance and maneuver penetration for hypersonic vehicle in dive phase.
Jianwen Zhu;Luhua Liu;Guojian Tang;为民 包
The fractional reaction-diffusion equations play an important role in dynamical systems. Indeed, it is time consuming to numerically solve differential fractional diffusion equations. In this paper, we present a parallel algorithm for the Riesz space fractional diffusion equation. The parallel algorithm, which is implemented with MPI parallel programming model, consists of three procedures: preprocessing, parallel solver and postprocessing. The parallel solver involves the parallel matrix vector multiplication and vector vector addition. As to the authors' knowledge, this is the first parallel algorithm for the Riesz space fractional reaction-diffusion equation. The experimental results show that the parallel algorithm is as accurate as the serial algorithm. The parallel algorithm on single Intel Xeon X5540 CPU runs 3.3-3.4 times faster than the serial algorithm on single CPU core. The parallel efficiency of 64 processes is up to 79.39% compared with 8 processes on a distributed memory cluster system.
Chunye Gong;为民 包;Guojian Tang
Fractional Calculus and Applied Analysis
The computational complexity of the numerical simulation of fractional chaotic system and its synchronization control is O(N2) compared with O(N) for integer chaotic system, where N is step number and O is the computational complexity. In this paper, we propose optimizing methods to solve fractional chaotic systems, including equal-weight memory principle, improved equal-weight memory principle, chaotic combination and fractional chaotic precomputing operator. Numerical examples show that the combination of these algorithms can simulate fractional chaotic system and synchronize the fractional master and slave systems accurately. The presented algorithms for simulation and synchronization of fractional chaotic system are up to 1.82 and 1.75 times faster than the original implementation respectively.
Daliang Su;为民 包;Jie Liu;Chunye Gong
Journal of the Franklin Institute
An entry trajectory planning algorithm that generates flyable trajectories satisfying multiple no-fly zones and other path and terminal constraints is presented. The algorithm divides the entry trajectory into initial and glide phases. In the initial phase, the maximum value of heating rate is controlled accurately as the altitude of the quasi-equilibrium glide condition (QEGC) transition point is adjusted with a nominal angle of attack and a parameterized bank angle. In the glide phase, a geometry based planning algorithm that relies on the center positions and radius of the multiple no-fly zones, is proposed to calculate the waypoints of the virtual flight path. The magnitude and reversal point of the bank angle in each sub-phase are searched based on a reduced-order lateral system with the predictor-corrector method. The altitude is designed as an analytical function of energy, and the QEGC is employed to analytically solve the remaining state variables. Finally, a linear quadratic regulator is used to test the realization of the 3D trajectory. The algorithm is tested using the common aero vehicle-H model. The results demonstrate that the algorithm can rapidly generate the entry trajectory with multiple no-fly zone constraints and achieve complex flight missions satisfying all flight constraints.
Rui zhi He;Lu hua Liu;Guo jian Tang;为民 包
Advances in Space Research
The slide mode tracking guidance strategy for hypersonic vehicle that can realize both precise guidance and maneuver flight was investigated. First, the diving trajectory which can satisfy terminal constraints in longitudinal direction and the maneuvering trajectory were designed. Second, with the aid of feedback linearization, the nonlinear motion equations were converted into the linear ones, which can be used to track the designed trajectories. Besides, in order to improve the guidance performance, slide mode tracking guidance law was proposed and the law was converted into nonlinear system to get nonlinear slide mode tracking guidance law. The guidance law is formed from the current motion states completely, therefore, the relative motion information can be decreased enormously. Finally, the results of a CAV-H vehicle guidance test show that the algorithm can realize maneuver flight and high precision guidance under the path constraints even if the outside disturbances exist. Therefore, it can offer references for precision guidance and maneuver penetration for hypersonic vehicle in dive phase.
Jianwen Zhu;Luhua Liu;Guojian Tang;为民 包
Guofang Keji Daxue Xuebao/Journal of National University of Defense Technology
Landing footprint is critical in generating feasible entry trajectories for hypersonic glide vehicles. In this paper, a new landing footprint generation algorithm that considers multiple uncertainty effects is proposed, based on the improved 3D acceleration profile planning method. First, a new entry corridor with uncertainty effects is derived, in which the angle of attack profile is adjustable at any time during the entire flight. Second, the longitudinal drag profile is designed as the interpolation results of the upper and lower fitting safe boundaries. The corresponding lateral lift-to-drag corridor is obtained using the quasi-equilibrium glide condition. A combined Proportion Integration Differentiation (PID) tracker is used to follow the planned profiles in the longitudinal and lateral corridors, and the feasible entry trajectories are completed. Finally, feasible footprint is generated by repeatedly computing the reachable boundaries for all the profiles in the new safe corridor, as well as the analytical calculation of the maximum range point. The approach is tested using the Common Aero Vehicle-H model. Simulation results demonstrate that the proposed algorithm can rapidly generate a feasible footprint of entry for vehicles while satisfying all the path and terminal constraints.
Rui Zhi He;Yuan Long Zhang;Lu Lua Liu;Guo Jian Tang;为民 包
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
In order to improve the penetration performance of hypersonic glide vehicles, a lateral pendulum maneuvering strategy is proposed. A single radar trajectory tracking model is established and EKF is used to estimate the entire trajectory parameters. Based on the analysis of the composition of the defense system and the intercepting mechanism, the pendulum maneuvering trajectory is designed, and the influencing factors of the gliding penetration performance are analyzed. Then, an integrated index of penetration performance consists of the hit point prediction error, intercepting velocity, overload and the energy consumption caused by maneuver is constructed. Furthermore, a maneuvering strategy is proposed that the first maneuver is performed to enlarge prediction error of hitting point when the vehicle entrances the radar coverage, and the second one is carried out in the intercept zone to increase the maneuvering overload. The two maneuvers are the combat of the glider to the early warning system and the intercept system respectively, which can effectively enhance the penetration performance with less energy consumption.
Jianwen Zhu;Ruizhi He;Guojian Tang;为民 包
Aerospace Science and Technology
Chinese manned deep space exploration (CMDSE) will make outstanding contributions to the progress of human civilization, and make human beings understand the origin, evolution and status of the universe in a wider and deeper level. Intelligent autonomous technology, which has the ability of automatic acquisition and application of knowledge, thinking and reasoning, problem solving and automatic learning, will provide broader prospects for the development of CMDSE activities. This paper will introduce briefly the development of CMDSE and analyze the problems and challenges encountered in this missions, and summarize the requirements for intelligent autonomous technology from rocket launching, flighting into orbit, flight on orbit, celestial landing to successful return to earth. Secondly, intelligent autonomous technology will be discussed in some important fields including high reliability, low cost, adapting of different uncertainties and unknown environment disturbances, emergency handling and obtaining maximum scientific return. In addition, the prospects for the future development of CMDSE mission and the progress of intelligent autonomous technology will be discussed. Finally, in view of CMDSE mission, a system architecture which is based on intelligent sensing, intelligent computing, intelligent control, intelligent material, intelligent communication and other intelligent techniques will be presented, and the future development of those technologies will be also proposed.
Kunfeng Lu;Zhenqiang Qi;Jiarun Liu;为民 包