With the further development of infrared radiation research in sea-sky background and the requirement of spinning projectile's attitude measurement, the sea-sky infrared radiation field is used to carry out spinni...
详细信息
With the further development of infrared radiation research in sea-sky background and the requirement of spinning projectile's attitude measurement, the sea-sky infrared radiation field is used to carry out spinning projectile's attitude angle instead of inertial sensors. Firstly, the generation mechanism of sea-sky infrared radiation is analysed. The mathematical model of sea-sky infrared radiation is deduced in LW (long wave) infrared 8 similar to 14 mu m band by calculating the sea surface and sky infrared radiation. Secondly, according to the movement characteristics of spinning projectile, the attitude measurement model of infrared sensors on projectile's three axis is established. And the feasibility of the model is analysed by simulation. Finally, the projectile's attitude calculation algorithm is designed to improve the attitude angle estimation accuracy. The results of semi-physical experiments show that the segmented interactive algorithm estimation error of pitch and roll angle is within +/- 1.5 degrees. The attitude measurement method is effective and feasible, and provides accurate measurement basis for the guidance of spinning projectile. (C) 2018 Elsevier B.V. All rights reserved.
The constellation-to-ground coverage problem is a basic and important problem in satellite applications. The grid-point approach (GPA) is one of the most commonly used approaches to solving this problem. However, this...
详细信息
The constellation-to-ground coverage problem is a basic and important problem in satellite applications. The grid-point approach (GPA) is one of the most commonly used approaches to solving this problem. However, this approach also has some serious drawbacks. A group of strategies that can improve or overcome the drawbacks of this approach are proposed. The spatial and temporal characteristics of the GPA were analyzed, and a strategy that can compute the upper and lower bounds of the result was given. This strategy can not only acquire the result but can also yield the error range of the result. In addition, a strategy that uses low-precision results to compute a high-precision result is proposed. Simulation experiments of different types of coverage problems were conducted, and the results show that these strategies are effective.
Motivated by improving the performance of particle-based Monte-Carlo simulations in the transitional regime, Fokker-Planck kinetic models have been devised and studied as approximations of the Boltzmann collision oper...
详细信息
Motivated by improving the performance of particle-based Monte-Carlo simulations in the transitional regime, Fokker-Planck kinetic models have been devised and studied as approximations of the Boltzmann collision operator. By generalizing the linear drift model, the cubic Fokker-Planck (cubic-FP) and ellipsoidal Fokker-Planck (ES-FP) have been proposed, in order to obtain the correct Prandtl number of 2/3 for a dilute monatomic gas. This study provides a close comparison between both models in low Mach and supersonic settings. While direct simulation Monte-Carlo (DSMC) here serves as the benchmark, overall close performance between cubic-FP, ES-FP, and DSMC is observed. Furthermore, while the ES-FP outperforms the cubic-FP model in the shock region of the supersonic flow around a cylinder, the latter shows a better accuracy in the near continuum regime. It is argued that the reason behind these discrepancies lies in the entropy law besides the transport properties.
This paper presents several new methods for the solution of aeroelastic flutter problems with a partial polynomial structure: problems consisting of a mix of polynomial and more complex nonlinear components. The focus...
详细信息
This paper presents several new methods for the solution of aeroelastic flutter problems with a partial polynomial structure: problems consisting of a mix of polynomial and more complex nonlinear components. The focus is particularly on systems that use Theodorsen aerodynamics: for such systems, four new solution algorithms are devised. Two of these are direct but yield approximate results, and two are iterative. These algorithms are tested on an example system, and their computational characteristics are investigated and discussed. Three of them are suitable for practical implementation;the fourth is too computationally intensive to be of great practical use. Extensions and improvements to these algorithms, and the overall methods used, are also discussed.
In the present paper, a recent deterministic continuum-strategy two-player discrete-time dynamic leader-follower game with fixed finite time duration and closed-loop information structure is studied. The types of the ...
详细信息
In the present paper, a recent deterministic continuum-strategy two-player discrete-time dynamic leader-follower game with fixed finite time duration and closed-loop information structure is studied. The types of the considered payoff functions can be widely used in different applications (mainly in conflicts of consuming a limited resource, where one player, called the leader, is a superior authority choosing a strategy choice first, and another player, called the follower, chooses after). In case of certain payoff convexity, explicit conditions are given, when it can be known in advance that an equilibrium exists and consists of only two possible choices of both players at each step. The sub-game equilibrium from a given step may depend on the former selections of the players. Thus the continuum-strategy problem has been reduced to a general finite game of two possible choices corresponding to both players. Such type of games could be solved in a standard way with dynamic programming using a computer. Nevertheless, the game can be further simplified, and then an equilibrium can be directly determined, such decreasing the computational demand to a great extent. A solution algorithm and practical examples are also given to support the real-life application of the results.
In this article, we consider two classes of discrete bilevel optimization problems which have the peculiarity that the lower level variables do not affect the upper level constraints. In the first case, the objective ...
详细信息
In this article, we consider two classes of discrete bilevel optimization problems which have the peculiarity that the lower level variables do not affect the upper level constraints. In the first case, the objective functions are linear and the variables are discrete at both levels, and in the second case only the lower level variables are discrete and the objective function of the lower level is linear while the one of the upper level can be nonlinear. algorithms for computing global optimal solutions using Branch and Cut and approximation of the optimal value function of the lower level are suggested. Their convergence is shown and we illustrate each algorithm via an example.
The retrodictor–corrector filter (RCF) algorithm belongs to the first family of filters and consists of a single-stage recursive scheme, based upon a generalization of the iterated extended Kalman filter. The motivat...
详细信息
The retrodictor–corrector filter (RCF) algorithm belongs to the first family of filters and consists of a single-stage recursive scheme, based upon a generalization of the iterated extended Kalman filter. The motivating idea stems from recognizing an approximation shared by the nonlinear recursive methods, which is inherent to their predictor–corrector structure. Having obtained estimates for the state and error covariance matrix at a certain time instant, say k − 1, the estimate at the subsequent measurement instant k is computed through two steps. Despite its intuitive nature, the predictor step can be performed exactly only in the linear filtering problem, leading to the well-celebrated KF, whereas its extension to the nonlinear case gives rise to a certain degree of approximation, due to the fact that one needs to propagate through a nonlinear transformation the first and second moment of a random variable.
An algorithm is presented for solving bilevel optimization problems with fully convex lower level problems. Convergence to a local optimal solution is shown under certain weak assumptions. This algorithm uses the opti...
详细信息
An algorithm is presented for solving bilevel optimization problems with fully convex lower level problems. Convergence to a local optimal solution is shown under certain weak assumptions. This algorithm uses the optimal value transformation of the problem. Transformation of the bilevel optimization problem using the Fritz-John necessary optimality conditions applied to the lower level problem is shown to exhibit almost the same difficulties for solving the problem as the use of the Karush-Kuhn-Tucker conditions.
Convex optimization has found wide applications in recent years due to its unique theoretical advantages and the polynomial-time complexity of state-of-the-art solution algorithms for convex programming. This paper re...
详细信息
Convex optimization has found wide applications in recent years due to its unique theoretical advantages and the polynomial-time complexity of state-of-the-art solution algorithms for convex programming. This paper represents an attempt to apply second-order cone programming, a branch of convex optimization, to the class of highly nonlinear trajectory optimization problems in entry flight. The foremost challenge in applying convex optimization in most aerospace engineering problems lies in the nonlinearity and nonconvexity of the problem. Exclusive reliance on linearization does not always work well, as is the case in entry trajectory optimization. This paper focuses on how to formulate realistic, highly constrained entry trajectory optimization problems in a fashion suitable to be solved by second-order cone programming with a combination of successive linearization and relaxation techniques. Rigorous analysis is conducted to support the soundness of the approach. Numerical demonstrations are provided to show the efficacy and effectiveness of the proposed method.
暂无评论