检索结果-南通市图书馆

Adaptive Prescribed Performance Control for Flexible Spacecraft with Input Saturation and Actuator Misalignment

在线全文

学校读者我要写书评

暂无评论

Tsinghua Science and Technology 2019年第6期24卷 694-705页

作者： Jiawei tao tao Zhang Yongfang Nie Department of Automation Tsinghua UniversityBeijing 100084China Department of Strategic Missile and Underwater Weapon Naval Submarine AcademyQingdao 266071China

In this paper, a flexible spacecraft attitude control scheme that guarantees vibration suppression and prescribed performance on transient-state behavior is proposed. Here, parametric uncertainty, external disturbance, unmeasured elastic vibration, actuator saturation, and even configuration misalignment are considered. To guarantee prescribed performance bounds on the transient-and steady-state control errors, a performance constrained control law is formulated with an error transformed function. An elastic modal observer is employed to estimate the unmeasured flexible modal variables, and a command filter is adopted to avoid the tedious analytical computations of time derivatives of virtual control inherent in the control design. Subsequently, a novel auxiliary system is developed to compensate the adverse effects of the actuator saturation constraints, and a compensation term is integrated into the control law to tackle the configuration misalignment. A comparative simulation study is carried out to illustrate the effectiveness and advantages of the proposed approach.

关键词： flexible spacecraft modal observer vibration suppression prescribed performance input saturation actuator misalignment

Numerical Solution to Optimal Feedback Control by Dynamic Programming Approach:A Local Approximation Algorithm

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science & Complexity 2017年第4期30卷 782-802页

作者： GUO Bao-Zhu WU tao-tao Academy of Mathematics and Systems Science Chinese Academy of Sciences School of Mathematical Sciences University of Chinese Academy of Sciences

This paper considers optimal feedback control for a general continuous time finite-dimensional deterministic system with finite horizon cost functional. A practically feasible algorithm to calculate the numerical solution of the optimal feedback control by dynamic programming approach is developed. The highlights of this algorithm are: a) It is based on a convergent constructive algorithm for optimal feedback control law which was proposed by the authors before through an approximation for the viscosity solution of the time-space discretization scheme developed by dynamic programming method; b) The computation complexity is significantly reduced since only values of viscosity solution on some local cones around the optimal trajectory are calculated. Two numerical experiments are presented to illustrate the effectiveness and fastness of the algorithm.

关键词： Curse of dimensionality Hamilton-Jacobi-Bellman equation optimal feedback control upwind finite difference viscosity solutions

Estimation of component activities in some oxide solid solutions by the molecular interaction vacancy model

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2011年第6期24卷 432-442页

作者： Dongping tao Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology Kunming 650093 China

The molecular interaction vacancy model （MIVM） is used to estimate simultaneously activities of all components in a range of entire composition of six binary oxide solid solutions and the MnO-FeO-CaO ternary solid solution by their binary infinite dilute activity coefficients. The average errors are the 0.03%-5.0% for the binaries and the 4.11%-25.2% for the ternary which is less than that （4.84%-41.2%） of the sub-regular solution model （SRSM）. This shows that MIVM is more effective and reliable than SRSM for the ternary and does not depend on a polynomial approximation with some ternary adjustable parameters.

关键词： Estimation Activity Oxide Solid solution Thermodynamic model

A novel molecular interaction chemical model for silicate melts

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2010年第5期23卷 381-395页

作者： Dongping tao Faculty of Metallurgical and Energy Engineering Kunming University of Science and Technology Kunming 650093 China

A novel molecular interaction chemical model （MICM） for silicate melts has been suggested based on statistical thermodynamics. It can simultaneously predict activities of all components in the CaO-FeO-SiO2 and CaO-Al2O3-SiO2 melts using only four binary parameters for each binary melt which can be determined by fitting activities of its two components. The results indicate that the predicted values of activity of FeO and SiO2 are in good agreement with the experimental data at 1823 K and 1873 K, and those of CaO, SiO2 and Al2O3 are in reasonable agreement with the graphical integration data of the Gibbs-Duhem equation. This shows that the model is effective in which the physical interaction plays a main role and the chemical one does the auxiliary function.

关键词： Activity Prediction Oxide melts Silicates Thermodynamic model

Comparison of two approximal proximal point algorithms for monotone variational inequalities

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第6期8卷 969-977页

作者： tao Min School of Applied Mathematics and Physics Nanjing University of Posts and Telecommunications Nanjing 210003 China

Proximal point algorithms （PPA） are attractive methods for solving monotone variational inequalities （MVI）. Since solving the sub-problem exactly in each iteration is costly or sometimes impossible, various approximate versions ofPPA （APPA） are developed for practical applications. In this paper, we compare two APPA methods, both of which can be viewed as prediction-correction methods. The only difference is that they use different search directions in the correction-step. By extending the general forward-backward splitting methods, we obtain Algorithm Ⅰ; in the same way, Algorithm Ⅱ is proposed by spreading the general extra-gradient methods. Our analysis explains theoretically why Algorithm Ⅱ usually outperforms Algorithm Ⅰ. For computation practice, we consider a class of MVI with a special structure, and choose the extending Algorithm Ⅱ to implement, which is inspired by the idea of Gauss-Seidel iteration method making full use of information about the latest iteration. And in particular, self-adaptive techniques are adopted to adjust relevant parameters for faster convergence. Finally, some numerical experiments are reported on the separated MVI. Numerical results showed that the extending Algorithm II is feasible and easy to implement with relatively low computation load.

关键词： Projection and contraction methods Proximal point algorithm (PPA) Approximate PPA (APPA) Monotone variational inequality (MVI) Prediction and correction

Direct numerical simulation of Open Von Kármán Swirling Flow

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2014年第2期26卷 165-177页

作者： XING tao Department of Mechanical Engineering College of EngineeringUniversity of Idaho

Direct numerical simulations are used to investigate the Open Von Kfirmfin Swirling Flow, a new type of unsteady three-dimensional flow that is formed between two counter-rotating coaxial disks with an axial extraction enclosed by a cylinder chamber. Solution verification shows that monotonic convergence is achieved on three systematically refined grids for average pressure at the disk periphery with a small grid uncertainty at 3.5%. Effects of the rotational speeds and flow rates on the flow field are examined. When the disks are rotating at the lowest speed, ＋100 RPM, only circular vortices are formed regardless of the flow rates. When the disks are rotating at ＋300 RPM and ＋500 RPM, negative spiral vortex network is formed. The radial counterflow concept for such spiral vortex network is verified by examining various horizontal cuts and radial velocity component, which show radial outflows in two bands near the two disks and radial inflow in one band between them. Overall, the flow is similar to the Stewartson type flow but with significant differences for all three velocity components due to the axial suction at the upper disk center and gap between the disk periphery and chamber wall.

关键词： direct numerical simulation Open Von Kfirmfin flow swirling radial counterflow

A general framework for verification and validation of large eddy simulations

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2015年第2期27卷 163-175页

作者： XING tao Department of Mechanical Engineering College of EngineeringUniversity of Idaho

A general framework（methodology and procedures） for verification and validation（V＆V） of large eddy simulations in computational fluid dynamics（CFD） is derived based on two hypotheses. The framework allows for quantitative estimations of numerical error, modeling error, their coupling, and the associated uncertainties. To meet different needs of users based on their affordable computational cost, various large eddy simulation（LES） V＆V methods are proposed. These methods range from the most sophisticated seven equation estimator to the simplest one-grid estimator, which will be calibrated using factors of safety to achieve the objective reliability and confidence level. Evaluation, calibration and validation of various LES V＆V methods in this study will be performed using rigorous statistical analysis based on an extensive database. Identification of the error sources and magnitudes has the potential to improve existing or derive new LES models. Based on extensive parametric studies in the database, it is expected that guidelines for performing large eddy simulations that meet pre-specified quality and credibility criteria can be obtained. Extension of this framework to bubbly flow is also discussed.

关键词： framework verification and validation large eddy simulation(LES)

Predication of Component Activities in the Molten Aluminosilicate Slag CaO-Al_2O_3-SiO_2 by Molecular Interaction Volume Model

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2008年第5期24卷 797-802页

作者： Dongping tao Faculty of Materials and Metallurgical Engineering Kunming University of Science and Technology Kunming 650093China

A novel thermodynamic model-the molecular interaction volume model （MIVM） which can be reduced to the Flory-Huggins equation of polymer solution was employed for the prediction of component activities in the ternary molten aluminosilicate slag CaO-Al2O3-SiO2 at different temperatures. The results show that the predicted values of activity of CaO, Al2O3 and SiO2 are in reasonably agreement with experimental data in some ranges of their concentrations which are about x1 〈0.25 for CaO, x2=0.05-0.55 for Al2O3 and x3=0.03-0.85 for SiO2. This further shows that MIVM requires only two binary parameters for each sub-binary system to predict activities of all components in a multicomponent solution and is the superior alternative in a molten slag.

关键词： Activity Prediction Molten aluminosilicate slag Molecular interaction volumemodel

Robust Adaptive Attitude Maneuvering and Vibration Reducing Control of Flexible Spacecraft Under Input Saturation

在线全文

学校读者我要写书评

暂无评论

Transactions of Nanjing University of Aeronautics and Astronautics 2019年第2期36卷 98-108页

作者： tao Jiawei ZHANG tao Department of Automation Tsinghua University

A robust adaptive control scheme is proposed for attitude maneuver and vibration suppression of flexible spacecraft in situations where parametric uncertainties,external disturbances,unmeasured elastic vibration and input saturation constraints exist. The controller does not need the knowledge of modal variables but the estimates of modal variables provided by appropriate dynamics of the controller. The requirements to know the system parameters and the bound of the external disturbance in advance are also eliminated by adaptive updating technique. Moreover,an auxiliary design system is constructed to analyze and compensate the effect of input saturation,and the state of the auxiliary design system is applied to the procedure of control design and stability analysis. Within the framework of the Lyapunov theory,stabilization and disturbance rejection of the overall system are ensured. Finally,simulations are conducted to study the effectiveness of the proposed control scheme,and simulation results demonstrate that the precise attitude control and vibration suppression are successfully achieved.

关键词： flexible spacecraft attitude maneuver modal observer vibration suppression input constraints

同方期刊数据库