This paper presents a method for robust flutter computation which uses flight altitude as the perturbation variable in order to obtain a match point solution. The air density and sound speed of standard atmosphere mod...This paper presents a method for robust flutter computation which uses flight altitude as the perturbation variable in order to obtain a match point solution. The air density and sound speed of standard atmosphere model are approximated as the polynomial function of altitude, such that the flight altitude becomes the single perturbation variable that describes the aeroelastic system. The uncertainties of generalized stiffness and damping are considered and the uncertain aeroelastic system can be formulated as linear fractional transformation （LFT） representation which is suitable for/.t analysis framework. Finally, the match point solutions of robust flutter margins can be computed with structured singular value （SSV） theory. The robust flutter analysis method provided in this paper is suitable for constant-Mach flight flutter test and provides valuable reference for flight envelope expansion.展开更多
Robust flutter analysis considering model uncertain parameters is very important in theory and engineering applications.Modern robust flutter solution based on structured singular value subject to real parametric unce...Robust flutter analysis considering model uncertain parameters is very important in theory and engineering applications.Modern robust flutter solution based on structured singular value subject to real parametric uncertainties may become difficult because the discontinuity and increasing complexity in real mu analysis.It is crucial to solve the worst-case flutter speed accurately and efficiently for real parametric uncertainties.In this paper,robust flutter analysis is formulated as a nonlinear programming problem.With proper nonlinear programming technique and classical flutter analysis method,the worst-case parametric perturbations and the robust flutter solution will be captured by optimization approach.In the derived nonlinear programming problem,the parametric uncertainties are taken as design variables bounded with perturbed intervals,while the flutter speed is selected as the objective function.This model is optimized by the genetic algorithm with promising global optimum performance.The present approach avoids calculating purely real mu and makes robust flutter analysis a plain job.It is illustrated by a special test case that the robust flutter results coincide well with the exhaustive method.It is also demonstrated that the present method can solve the match-point robust flutter solution under constant Mach number accurately and efficiently.This method is implemented in problem with more uncertain parameters and asymmetric perturbation interval.展开更多
Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An appr...Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An approach for aeroelastic robust stability analysis taking into account the perturbations of structural mass and stiffness is developed. Applying the perturbation method and harmonic unsteady aerodynamic forces, the frequency-domain linear fractal transformation （LFT） representation of perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by using the structured singular value ,u-method. The numerical results of a bi-spar wing show its effectiveness and low computational time in dealing with the robust problems with mass and stiffness perturbations. In engineering analysis for solving aeroelastic problems, the robust approach can be applied to flutter analysis for airplane with the fuel load variation and taking the damage conditions into consideration.展开更多
针对主动调谐质量阻尼器(active tuned mass damper,简称ATMD)控制系统用于结构振动控制工程中存在主动控制力偏大、控制系统鲁棒性较差的不足,基于线性二次型最优控制理论,设计了一种带有补偿器的滑模控制算法来计算ATMD系统的主动控...针对主动调谐质量阻尼器(active tuned mass damper,简称ATMD)控制系统用于结构振动控制工程中存在主动控制力偏大、控制系统鲁棒性较差的不足,基于线性二次型最优控制理论,设计了一种带有补偿器的滑模控制算法来计算ATMD系统的主动控制力。为了避免控制系统过大的颤振,提出一种含有饱和函数的指数趋近律,并且给出了相应准滑模控制器的设计方法。鉴于实际中会产生外部能量有限问题,引入了相应的饱和控制器。以一个单自由度结构模型为例进行了相应的数值分析,与相应的未含补偿器的指数趋近律方法设计的ATMD控制系统以及AMD和TMD控制系统的控制效果进行了对比。仿真结果表明,所提方法在保证控制系统较好鲁棒性和较小颤振的前提下,具有较好的控振效果。展开更多
Recently, frequency-based least-squares （LS） estimators have found wide application in identifying aircraft flutter parameters. However, the frequency methods are often known to suffer from numerical difficulties wh...Recently, frequency-based least-squares （LS） estimators have found wide application in identifying aircraft flutter parameters. However, the frequency methods are often known to suffer from numerical difficulties when identifying a continuous-time model, especially, of broader frequency or higher order. In this article, a numerically robust LS estimator based on vector orthogonal polynomial is proposed to solve the numerical problem of multivariable systems and applied to the flutter testing. The key idea of this method is to represent the frequency response function （FRF） matrix by a right matrix fraction description （RMFD） model, and expand the numerator and denominator polynomial matrices on a vector orthogonal basis. As a result, a perfect numerical condition （numerical condition equals 1） can be obtained for linear LS estimator. Finally, this method is verified by flutter test of a wing model in a wind tunnel and real flight flutter test of an aircraft. The results are compared to those with notably LMS PolyMAX, which is not troubled by the numerical problem as it is established in z domain （e.g. derived from a discrete-time model）. The verification has evidenced that this method, apart from overcoming the numerical problem, yields the results comparable to those acquired with LMS PolyMAX, or even considerably better at some frequency bands.展开更多
基金Ph.D. Programs Foundation of Ministy of Education of China (20040287019)
文摘This paper presents a method for robust flutter computation which uses flight altitude as the perturbation variable in order to obtain a match point solution. The air density and sound speed of standard atmosphere model are approximated as the polynomial function of altitude, such that the flight altitude becomes the single perturbation variable that describes the aeroelastic system. The uncertainties of generalized stiffness and damping are considered and the uncertain aeroelastic system can be formulated as linear fractional transformation （LFT） representation which is suitable for/.t analysis framework. Finally, the match point solutions of robust flutter margins can be computed with structured singular value （SSV） theory. The robust flutter analysis method provided in this paper is suitable for constant-Mach flight flutter test and provides valuable reference for flight envelope expansion.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11072198 and 11102162) "111" Project of China(Grant No. B07050)
文摘Robust flutter analysis considering model uncertain parameters is very important in theory and engineering applications.Modern robust flutter solution based on structured singular value subject to real parametric uncertainties may become difficult because the discontinuity and increasing complexity in real mu analysis.It is crucial to solve the worst-case flutter speed accurately and efficiently for real parametric uncertainties.In this paper,robust flutter analysis is formulated as a nonlinear programming problem.With proper nonlinear programming technique and classical flutter analysis method,the worst-case parametric perturbations and the robust flutter solution will be captured by optimization approach.In the derived nonlinear programming problem,the parametric uncertainties are taken as design variables bounded with perturbed intervals,while the flutter speed is selected as the objective function.This model is optimized by the genetic algorithm with promising global optimum performance.The present approach avoids calculating purely real mu and makes robust flutter analysis a plain job.It is illustrated by a special test case that the robust flutter results coincide well with the exhaustive method.It is also demonstrated that the present method can solve the match-point robust flutter solution under constant Mach number accurately and efficiently.This method is implemented in problem with more uncertain parameters and asymmetric perturbation interval.
基金National Natural Science Foundation of China (10432040, 90716006)
文摘Air vehicles undergo variations in structural mass and stiffness because of fuel consumption and the failure of structural components, which might lead to serious influences on the aeroelastic characteristics. An approach for aeroelastic robust stability analysis taking into account the perturbations of structural mass and stiffness is developed. Applying the perturbation method and harmonic unsteady aerodynamic forces, the frequency-domain linear fractal transformation （LFT） representation of perturbed aeroelastic system is modeled. Then, the robust stability is analyzed by using the structured singular value ,u-method. The numerical results of a bi-spar wing show its effectiveness and low computational time in dealing with the robust problems with mass and stiffness perturbations. In engineering analysis for solving aeroelastic problems, the robust approach can be applied to flutter analysis for airplane with the fuel load variation and taking the damage conditions into consideration.
文摘针对主动调谐质量阻尼器(active tuned mass damper,简称ATMD)控制系统用于结构振动控制工程中存在主动控制力偏大、控制系统鲁棒性较差的不足,基于线性二次型最优控制理论,设计了一种带有补偿器的滑模控制算法来计算ATMD系统的主动控制力。为了避免控制系统过大的颤振,提出一种含有饱和函数的指数趋近律,并且给出了相应准滑模控制器的设计方法。鉴于实际中会产生外部能量有限问题,引入了相应的饱和控制器。以一个单自由度结构模型为例进行了相应的数值分析,与相应的未含补偿器的指数趋近律方法设计的ATMD控制系统以及AMD和TMD控制系统的控制效果进行了对比。仿真结果表明,所提方法在保证控制系统较好鲁棒性和较小颤振的前提下,具有较好的控振效果。
基金Foundation items： Aeronautical Science Foundation of China （2007ZD53053） NPU Foundation for Fundamental Research （NPU-FFR-W018104）
文摘Recently, frequency-based least-squares （LS） estimators have found wide application in identifying aircraft flutter parameters. However, the frequency methods are often known to suffer from numerical difficulties when identifying a continuous-time model, especially, of broader frequency or higher order. In this article, a numerically robust LS estimator based on vector orthogonal polynomial is proposed to solve the numerical problem of multivariable systems and applied to the flutter testing. The key idea of this method is to represent the frequency response function （FRF） matrix by a right matrix fraction description （RMFD） model, and expand the numerator and denominator polynomial matrices on a vector orthogonal basis. As a result, a perfect numerical condition （numerical condition equals 1） can be obtained for linear LS estimator. Finally, this method is verified by flutter test of a wing model in a wind tunnel and real flight flutter test of an aircraft. The results are compared to those with notably LMS PolyMAX, which is not troubled by the numerical problem as it is established in z domain （e.g. derived from a discrete-time model）. The verification has evidenced that this method, apart from overcoming the numerical problem, yields the results comparable to those acquired with LMS PolyMAX, or even considerably better at some frequency bands.
