Xiaokui Yue

A time domain collocation method for studying the aeroelasticity of a two dimensional airfoil with a structural nonlinearity

Article history: A time domain collocation method for the study of the motion of a two dimensional aeroelastic airfoil with a cubic structural nonlinearity is presented. This method first transforms the governing ordinary differential equations into a system of nonlinear algebraic equations (NAEs), which are then solved by a Jacobian-inverse-free NAE solver. Using the aeroelastic airfoil as a prototypical system, the time domain collocation method is shown here to be mathematically equivalent to the well known high dimensional harmonic balance method. Based on the fact that the high dimensional harmonic balance method is essentially a collocation method in disguise, we clearly explain the aliasing phenomenon of the high dimensional harmonic balance method. On the other hand, the conventional harmonic balance method is also applied. Previous studies show that the harmonic balance method does not produce aliasing in the framework of solving the Duffing equation. However, we demonstrate that a mathematical type of aliasing occurs in the harmonic balance method for the present self-excited nonlinear dynamical system. Besides, a parameter marching procedure is used to sufficiently eliminate the effects of aliasing pertaining to the time domain collocation method. Moreover, the accuracy of the time domain collocation method is compared with the harmonic balance method.

Feature extraction algorithm for space targets based on fractal theory

In order to offer a potential for extending the life of satellites and reducing the launch and operating costs, satellite servicing including conducting repairs, upgrading and refueling spacecraft on-orbit become much more frequently. Future space operations can be more economically and reliably executed using machine vision systems, which can meet real time and tracking reliability requirements for image tracking of space surveillance system. Machine vision was applied to the research of relative pose for spacecrafts, the feature extraction algorithm was the basis of relative pose. In this paper fractal geometry based edge extraction algorithm which can be used in determining and tracking the relative pose of an observed satellite during proximity operations in machine vision system was presented. The method gets the gray-level image distributed by fractal dimension used the Differential Box-Counting (DBC) approach of the fractal theory to restrain the noise. After this, we detect the consecutive edge using Mathematical Morphology. The validity of the proposed method is examined by processing and analyzing images of space targets. The edge extraction method not only extracts the outline of the target, but also keeps the inner details. Meanwhile, edge extraction is only processed in moving area to reduce computation greatly. Simulation results compared edge detection using the method which presented by us with other detection methods. The results indicate that the presented algorithm is a valid method to solve the problems of relative pose for spacecrafts.

Stochastic bifurcation in a model of love with colored noise

In this paper, we wish to examine the stochastic bifurcation induced by multiplicative Gaussian colored noise in a dynamical model of love where the random factor is used to describe the complexity and unpredictability of psychological systems. First, the dynamics in deterministic love-triangle model are considered briefly including equilibrium points and their stability, chaotic behaviors and chaotic attractors. Then, the influences of Gaussian colored noise with different parameters are explored such as the phase plots, top Lyapunov exponents, stationary probability density function (PDF) and stochastic bifurcation. The stochastic P-bifurcation through a qualitative change of the stationary PDF will be observed and bifurcation diagram on parameter plane of correlation time and noise intensity is presented to find the bifurcation behaviors in detail. Finally, the top Lyapunov exponent is computed to determine the D-bifurcation when the noise intensity achieves to a critical value. By comparison, we find there is no connection between two kinds of stochastic bifurcation.

Feedback-Accelerated Picard Iteration for Orbit Propagation and Lambert’s Problem

This paper presents a new feedback-accelerated Picard iteration method for solving long-term orbit-propagation problems and perturbed Lambert’s problems. This method is developed by combining the c...

A Simple Time Domain Collocation Method to Precisely Search for the Periodic Orbits of Satellite Relative Motion

A numerical approach for obtaining periodic orbits of satellite relative motion is proposed, based on using the time domain collocation (TDC) method to search for the periodic solutions of an exact nonlinear relative model. The initial conditions for periodic relative orbits of the Clohessy-Wiltshire (C-W) equations or Tschauner-Hempel (T-H) equations can be refined with this approach to generate nearly bounded orbits. With these orbits, a method based on the least-squares principle is then proposed to generate projected closed orbit (PCO), which is a reference for the relative motion control. Numerical simulations reveal that the presented TDC searching scheme is effective and simple, and the projected closed orbit is very fuel saving.

Pseudospectral control for 6-DOF electromagnetic formation flying

Electromagnetic formation is a novel method of propellantless formation, which enables synchronous control of both relative translation and rotation in the array. To fully utilize the inherent electromagnetic coupling effects, an integrated relative dynamic model is established. Considering the reconfiguration of electromagnetic formation as an optimal control problem with regard to relative translation and angular momentum management, it is transformed into a constrained non-linear programming problem through the Legendre pseudospectral method. Facing the system’s strong nonlinearity and coupling, a novel high-precision numerical computation method is developed. Feasible trajectories for a specific planar transformation and a more general case of reconfiguration are generated to verify the proposed dynamic model and optimization algorithm.

Evaluating operational effectiveness of electro-optical imaging reconnaissance satellite

As an important part of operational effectiveness analysis of space-based system, the research on operational effectiveness of electro-optical imaging reconnaissance satellite has great academic and realistic significance. In this paper, we consider a certain scenario, in which a missile aided with an electro-optical imaging reconnaissance satellite attacks a ground-based target. The operational effectiveness analysis and evaluating model of electro-optical imaging reconnaissance satellite is built. The results of simulation demonstrate that operational effectiveness analysis and evaluating model of electro-optical imaging reconnaissance satellite is feasible and reasonable. The models can be used to analysis design, evaluating and development of space-based.

Research on effectiveness evaluation of space-based electro-optical imaging system in attack-defense confrontation

In this paper, the architecture of the system effectiveness is put forward and methods for assessing the effectiveness of the space-based electro-optical imaging system are focused on. And then, we consider a certain scenario, in which a missile aided by an the space-based electro-optical imaging system attacks a ground-based target. The effectiveness evaluation model of the space-based electro-optical imaging system is built. It is important for us to study and analyze effectiveness system of the space-based electro-optical imaging system in attack-defense confrontation. The models can be used to analysis design, evaluating and development of space-based system.