Cui Nai-gang

Attitude dynamics modeling and control of large flexible solar sail spacecraft

The problems of rigid-flexible coupling dynamics modeling and control are proved to be hard to resolve owing to the large size and super-flexible structure of the solar sail spacecraft. This paper utilizes moment of momentum theorem to deduce rigid-flexible coupling dynamics equations including the attitude dynamics and vibration equations for super-flexible solar sail spacecraft with control vanes, and then the dynamics equations solutions of solar sail on super-synchronous transfer orbit are presented combining with the unconstrained modes conception. Based on the proposed dynamics models, the PD control law incorporating the Bang-Bang control technique is designed to study the yaw axis earth-pointing problems of solar sail. Simulation results demonstrate that the solutions of the rigid-flexible coupling dynamics equations can truly describe the dynamical characteristics of the solar sail spacecraft and the attitude controller can perform the yaw axis earth-pointing mission exactly and quickly.

The determination of relative orbit for formation flying subject to J2

Purpose – The purpose of this paper is to consider relative navigation – a vital technology to satellites formation flying, and to propose a new concept for relative navigation determination along with a technical approach for its practical implementation.Design/methodology/approach – The determination of relative orbit is considered with the relative distance elevation and azimuth measurements about formation flying while the primary satellite is in a circle or ellipse orbit. This measurement is obtained by laser range finder and the estimations of the intersatellite relative position and velocity are obtained by utilizing the unscented Kalman filter instead of extended Kalman filter.Findings – The simulation results show that the error of the relative position and velocity can be estimated with the order of cm and mm/s, respectively, under the effect of J2, converge faster than EKF, and then demonstrate that the approach is feasible.Originality/value – The paper proposes a new concept for relative navig...

Vibration attenuation of spacecraft in the presence of parametric and unmodeled dynamics uncertainties using collocated and noncollocated control: A comparative study

µ-control synthesis offers the advantage of maintaining robust performance and stability in the presence of plant uncertainties. Expressions relating the 2-norm of the vector of regulated outputs and closed-loop modal damping to the weights used for µ-control synthesis are derived in this paper. By using these expressions, the amount of damping added to each mode can be controlled individually while maintaining equal importance for each controlled mode. Hence, the selection of weights for synthesizing a suitable µ-controller is greatly simplified. Furthermore, a comparative study of µ-controllers designed by the proposed procedure and positive position feedback (PPF) controllers designed by analytically derived optimal parameters is also presented. The techniques are compared for their vibration attenuation, energy utilization, and stability characteristics, in the presence of parametric and unmodeled dynamics uncertainties. Results for both time domain and frequency domain simulations are presented. As in some cases (sandwich plate structures etc.) the noncollocation of actuator/sensor becomes crucial for achieving good performance, the above-mentioned characteristics are evaluated for both collocated and noncollocated sensor locations.

Optimal Control of Initiative Anti-interception Penetration Using Multistage Hp-Adaptive Radau Pseudospectral Method

Considering the penetration guidance for initiative anti-interception penetration(IAIP), this paper presents an improved multistage hp-adaptive Radau pseudospectral Method (RPM) to solve non-smooth optimal control problem combined with mission decomposition. Firstly, the author builds a three-body motion model as dynamic constraint, which is composed of the attacker, interceptor and target, and establishes the optimal control model of each phase corresponded to keep flight, maneuver penetration, and attack target. Then this article takes segment points as optimization variables and proposed an adaptive curvature in order to improve the precision. The simulation results illustrate the effectiveness and superiority.

A criterion for optimal sensor placement for minimizing spillover effects on optimal controllers

Optimal control techniques (LQG, H∞, etc.) offer several advantages for active vibration control, such as possibility of trade-off between achievable vibration attenuation and required control inputs, simultaneous suppression of multiple modes, unified and systematic controller design procedure for MIMO systems. However, a major limitation in their application has been the phenomena of spillover. For optimal controllers robustness to spillover is achieved by rolling-off controller response. In this paper, a novel criterion of sensors placement to minimize roll-off requirement, for given actuator locations, is proposed. As an illustration H∞ control is applied for suppressing first two modes of a slewing spacecraft. Comparison of results obtained for sensor location based on proposed criterion with those of collocated sensor location showed: (a) for a given controller order, performance characteristics similar to collocated control with improved robustness to spillover can be obtained by using the proposed criterion of sensor placement; (b) with proposed placement criterion robustness to spillover can be maintained with lower order controller as compared with the minimum controller order required for collocated control.

Graph-based modeling and non-decoupling solution for distributed cooperative mission planning

This paper addresses the problems of autonomous task assignment and path planning for a fleet of heterogeneous unmanned aerial vehicles in cooperative mission. In previous work many algorithms almost run on centralized architecture and handle the task assignment decoupling with the path planning. This may result in poor solutions. Therefore, this paper investigates a novel integrated solution for UAV to perform multiple consecutive tasks cooperatively on multiple ground targets based on distributed planning architecture. In a given scenario, the heterogeneous vehicles have different capabilities, kinematic constraints, and fuel constraints. Furthermore, the task has other constraints, such as task execution orders, UAV conflict free constraints, etc. This paper presents details of the non-decoupling solution which produces optimal assignment and trajectories for several given scenarios. The performance of the algorithm is compared to that of some previous methods in real-time simulation environment. The simulations results show the viability of the non-decoupling approach, and the non-decoupling solution has an advantage over hierarchical algorithms, and the distributed architecture improves the operation efficiency of the algorithm and the robustness of the UAV.

Multi-scale information fusion method for integrated navigation of aerospace vehicle

A multi-scale information fusion estimation method based on wavelet filtering is presented in this paper. The method of signal multi-scale analysis and of multi-sensor information fusion technology have been combined, and used for the process of integrated navigation. The performance of system is also established, based on different ‘scale’ which could break the restriction of single scale one. The deficiency of regular filter estimating methods in dealing with high-frequency slowly time-varying noise is improved to some extent. Simulation results verified that multi-scale method used in integrated navigation could improve the precision and provide theory foundation for possible application of practical system.

A Knowledge Engineering Method for Track Initiation in Complex Conditions

In a complex environment radar plot is often changing dramatically, non-uniform, discontinuous, uncertain and containing lots of false alarms. It is difficult for tracking system to form tracks in such complex environment. Traditional track formation methods can not accurately determine the size of track initiation gate and select specific initiation criteria. In this paper, an intelligent information processing method is proposed to solve track initiation in complex environments. The track initiation is considered as a progress of plot identification, classification and fuzzy information processing. According to the integration and fusion of neural network (NN), fuzzy reasoning (FR) and expert system (ES) technology, an intellectualized track initiation knowledge reasoning system is constructed which can realize structural, functional, algorithmic and hierarchical complementation. Further more the adaptive robust learning algorithm and the weighted synthesis reasoning algorithm are used in this system. Real data experiment shows that the proposed knowledge engineering method can effectively solve track initiation problem in complex conditions.

Bi-station OTH radar locating and tracking using only range and Doppler measurements

Azimuthal measurements of the high frequency ground wave over-the-horizon (OTH) radar are either coarse or unavailable in an actual environment. It is very hard for a single station OTH radar to performance effective tracking under that condition. A bi-station OTH radar system is proposed to triangulate target tracks using range and Doppler measurements only. Multi-sensor data association and combining positioning are key issues of this system. This paper focuses on positioning and tracking filter algorithm. The locating and tracking model is established and the extended Kalman filter (EKF) is used to solve the bi-station nonlinear tracking problem. Simulation result shows that EKF can handle this well, and the bi-station OTH radar system can meet or slightly better than the accuracy of the conventional single station OTH radar tracking system with poor bearing resolution.

Collision-avoiding research based on barrier theory for satellites formation flying

It is mission critical to avoid collisions between satellites as they moving in space. We present a method based on the barrier theory of differential game that may consider one satellite as a pursuer, the other as evader. According to optimal control theory, Hamiltonian function with the state inequality constraints of the min distance between adjacent satellites is investigated, and then obtaining optimal control. Finally the barrier trace is achieved according to barrier theory.