Hongwei Xia

Multiple satellite formation based on multi-agent

Formation flying of multiple satellites is an enabling technology for many future space science missions. This paper addresses the problem of formation control and coordination of multiple satellite formation flying systems. Several coordination strategies for satellite formation flying are discussed. A new coordination framework based on multi-agent with advantages of robustness, flexibility and realization is proposed which considers not only the control of relative motion but also the interactions among multiple satellites in the formation. An LQR controller is presented for relative position control of satellites formation and a two-satellite formation simulation analysis was performed to demonstrate and validate the efficacy of the scheme

A Novel Approach to Control Design for Linear Neutral Time-Delay Systems

This paper is concerned with the problem of control of linear neutral systems with time-varying delay. Firstly, by applying a novel Lyapunov-Krasovskii functional which is constructed with the idea of delay partitioning approach, appropriate free-weighting matrices, an improved delay-dependent bounded real lemma (BRL) for neutral systems is established. By using the obtained BRL, a delay-dependent sufficient condition for the existence of a state-feedback controller, which ensures asymptotic stability and a prescribed performance level of the corresponding closed-loop system, is formulated in terms of linear matrix inequalities. Some numerical examples are given to illustrate the effectiveness of the proposed design method.

Fault Detection Filter Design for Networked Control Systems with Networked-Induced Delay

The problem of fault detection for networked control systems with time-delay is investigated. Attention is focused on the design of fault detection filter based on states observer, which guarantees a pre-specified Hinfin performance for the closed-loop system with respect to all energy-bounded input signals. Using LMI and Lyapunov function technology, sufficient conditions for existence of such filter is established in terms of linear matrix inequalities, upon which the design of admissible filter is cast into a convex optimization problem. The proposed approach can be further extended to uncertain networked control systems. The simulation results demonstrate that the method is effective and robust.

Robust Fault Detection of Networked Control Systems: An Improved LMJ Approach

The problem of robust fault detection filter design for networked control systems with time-delay and parameter uncertainty residing in a polytope is investigated. The filtering strategies are based on a new robust performance criteria derived from a new result of parameter-dependent Lyapunov stability condition, which exhibit less conservativeness than previous results in the quadratic framework. The designed filter guaranteeing a prescribed Hinfin noise attenuation level can be obtained from the solution of convex optimization problems since it is presented in terms of linear matrix inequalities (LMI). An iterative algorithm is developed to further refine the sub-optimal controller. Numerical examples are provided to illustrate that the proposed method is effective and robust.

A ground semi-physical simulator for satellite autonomous rendezvous and space robot capture

The architecture of a ground semi-physical simulator is proposed, which can test the methodologies of the satellite formation flying, autonomous rendezvous and docking, and space robot capture. There are five subsystems in the ground simulator: the console system, the translation system, the rotation system, the target system, and the vision system. The console system is the most important part in the underlying system, which generates control commands based on the control algorithm. The translation system and the rotation system simulate 6 DOF motion of the follower, and the target system simulates 6 DOF motion of the target. The vision system is included in the feedback block. Through the Ethernet, the whole closed-loop system is developed and the provided real-time network communication for the system is introduced

New Results on Stability and Stabilization of Markovian Jump Systems with Time Delay

This technical paper deals with the problem of stochastic stability and stabilization for a class of linear Markovian jumping systems with discrete time-varying delay. A novel delay-dependent stochastic stability criterion for Markovian delay systems is established based on new augmented Lyapunov-Krasovskii functional and delay fractioning techniques. Then a state feedback controller is designed to guarantee the stochastic stability of the resulting closed-loop system. Numerical examples are provided to illustrate the effectiveness of the proposed design approach in this paper.

Mixed l 2 /l ∞ / H ∞ estimation for uncertain discrete-time systems

A new criterion of l₂ -l_infin / H_infin performance is established by introducing a slack matrix. The designed estimator possesses two outputs which are respectively used to estimate the different estimated signals with l₂-l_infin and H_infin performances. Conservatism inherent in the quadratic framework can be reduced in robust synthesis of systems with polytopic uncertainties, since the parameter dependent Lyapunov functions can be adopted. A numerical example is included to illustrate the feasibility and advantage of the proposed representations.

Improved Two-Dimensional Otsu Based on Firefly Optimization for Low Signal-to-Noise Ratio Images

To improve two-dimensional (2D) Otsu thresholding’s performance in both computation speed and segmentation quality, an improved 2D Otsu algorithm is proposed for low Signal-to-noise Ratio (SNR) images. A new 2D histogram is defined based on median gray-scale and Gaussian average gray-scale. By meeting better to the assumption of that the object’s probability and the background’s probability sum up to 1, the new 2D histogram enhances the thresholding algorithm’s robustness to severe noise. Then a scheme of calculating the fitness function based on firefly optimization algorithm is employed to search for optimal thresholds. The proposed algorithm is applied to typical low SNR images–microscopic images of ocean plankton, and to Lenna test image. Experiment results show that with better thresholding quality, the running time of the proposed algorithm is reduced to 2.5% of the conventional 2D Otsu.

Firefly Algorithm Optimized Particle Filter for Relative Navigation of Non-cooperative Target

Particle filter (PF) has been proved to be an effective tool in solving relative navigation problems. However, the sample impoverishment problem caused by resampling is the main disadvantage of PF, which strongly affect the accuracy of navigation. To solve this problem, an improved PF based on firefly algorithm (FA) is proposed. Combine with the operation mechanism of PF, the optimization mode of FA is revised, and a new update formula of attractiveness is designed. By means of firefly group’s mechanism of survival of the fittest and individual firefly’s attraction and movement behaviors, this algorithm enables the particles to move toward the high likelihood region. Thus, the number of meaningful particles can be increased, and the particles can approximate the true state of the target more accurately. Simulation results show that the improved algorithm improves the navigation accuracy and reduces the quantity of the particles required by the prediction of state value.

Improved Stability and Stabilization Criteria for T-S Fuzzy Systems with Distributed Time-Delay

This paper investigates the stability and stabilization analysis problem of nonlinear systems with distributed time-delay. The T-S fuzzy model is employed to describe the nonlinear plant. When designing fuzzy controller, the novel imperfect premise matching method is adopted, which allows the fuzzy model and the fuzzy controller to use different premise membership functions and different number of rules. As a result, greater design flexibility can be obtained. By applying a new tighter integral inequality which involves information about the double integral of the system states, and introducing the information of membership functions, less conservative stability and stabilization conditions are derived. Finally, a numerical example is provided to clarify the effectiveness of the proposed approach.