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根据现代搜索理论的发展,对船载直升机在目标搜索中的具体运用进行了研究,建立了船载直升机目标搜索时搜索力的最优配置模型,解决了在已知目标分布的条件下船载直升机搜索中选择初始探测点、确定搜索路径、确定搜索次数以及搜索效率评估等问题. 相似文献
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The stability and control characteristics of two twin-lift helicopter configurations are analyzed in this paper. In order to address the issue of configuration selection from a handling qualities viewpoint, their open-and closed-loop characteristics are compared. The two twin-lift configurations considered are the twin-lift with spreader bar and twin-lift without spreader bar. The nonlinear models describing the dynamics of these two configurations in the lateral/vertical plane are derived. The open-loop characteristics of the two systems are compared by linearizing the nonlinear models about a symmetric hovering equilibrium condition. The closed-loop characteristics of the two systems are compared using nonlinear controllers based on feedback linearization schemes. The performance of the resulting closed-loop systems in carrying out a typical twin-lift mission is evaluated through nonlinear simulation. Also, the effects of helicopter performance degradation and measurement errors on the overall system performance are discussed.[B] Matrix multiplying the control vector in the nonlinear model[B1] Matrix multiplying the control vector in the linear model[C] Matrix defining vector of variables to be controlled[C1] Damping matrixCijElement of the damping matrix
e Parameter used in the linear model = M
1
h
1/I
1=M
2
h
2/I
2,/ft{f} Vector independent of controls in the nonlinear model
g Acceleration due to gravity, ft/sec2
h1, h2Distance of tether attachment point to the center of gravity for helicopters 1 and 2, ft
h Parameter used in the linear model, =h
1=h
2, ft
h Distance between rotor hub and the helicopter center of gravity, ft
h h/l
H Distance of the load from the spreader bar c.g., ftH1, H2Length of tethers 1 and 2, ftIRMass moment of inertia of spreader bar, slug-ft2
I1, I2Roll moments of inertia of helicopters 1 and 2, slug-ft2
k Non-dimensional hub control moment coefficientKDDerivative gainsKIIntegral gainsKPProportional gains[Ki] Stiffness matrixKijElement of the stiffness matrix
l Parameter used in the linear model, =H
1=H
2, ft
L Spreader bar length, ftNomenclature 相似文献
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In this paper, the switched safe tracking control scheme is investigated for the attitude and altitude system of a medium-scale unmanned autonomous helicopter with output constraints and unknown external disturbances. To keep the attitude angles and altitude within the desired constrained range, an output boundary protection approach is adopted to generate an output constrained trajectory which is piecewise differentiable. The disturbance observer-based control method is employed to handle the unknown external disturbances of the system. Because of the piecewise differentiability of the output constrained trajectory, the closed-loop error system with the safe tracking controller can be seen as a switched system with jump dynamics. The multiple Lyapunov function method is adopted to guarantee the tracking performance with designed average dwell time. Simulation results of an example are provided to illustrate the effectiveness of the proposed control scheme for the unmanned autonomous helicopter system. 相似文献
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亚音主旋翼的噪声预测和声隐身分析 总被引:2,自引:1,他引:1
本文介绍了基于FW-H方程的亚音主旋翼噪声预测方法,并在螺桨噪声预测程序基础上发展了主旋翼噪声预测程序。本文采用商用CFD软件FINE/TURBO模拟直升机旋翼流场,为噪声预测程序提供所需要的桨叶表面载荷,并用算例验证了载荷数据的准确性和噪声预测程序的有效性。本文计算和讨论了亚音悬停条件下的辐射噪声,并重点分析了不同形状桨叶对辐射噪声的影响,结果表明采用合理的薄翼型叶尖、尖削叶尖及线性扭转桨叶都可以降低辐射噪声,为通过改变桨叶形状降低旋翼辐射噪声提供了合理途径。 相似文献
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发展了一种基于鲁棒Riemann求解器和运动重叠网格技术计算直升机悬停旋翼流场的方法。基于惯性坐标系,悬停旋翼流场是非定常流场,控制方程为可压缩Reynolds平均Navier-Stoke方程,其对流项采用Roe近似Reimann求解器离散,使用改进的五阶加权基本无振荡格式进行高阶重构,非定常时间推进采用含牛顿型LUSGS子迭代的全隐式双时间步方法。为实施旋转运动和便于捕捉尾迹,计算采用运动重叠网格技术。计算得到的桨叶表面压力分布及桨尖涡涡核位置都与实验结果吻合较好。数值结果表明:所发展方法对桨尖涡具有较高的分辨率,对激波具有较好的捕捉能力,该方法可进一步推广到前飞旋翼粘性绕流的计算。 相似文献
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IntroductionTheproblemwasfirstencounteredduringflighttestofaCH_53EdevelopedbySikorsky[1].Astheaircraftwasincreasingitsairspeedfrom 2 77km·h- 1,aphenomenonofexcessiveoscillationswasobserved .Itwasrealizedthattherewasaself_excitedoscillationofcoupledfirstcolle… 相似文献
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Summary The aeroelastic response analysis of a coupled rotor/fuselage system is approached by iterative solution of the blade aeroelastic
response in the non-inertial reference frame fixed on the hub, and the periodic response of the fuselage in the inertial reference
frame. A model of the coupled system hinged with the flap and lag hinges, the pitching bearing which may not coincide with
the hinges, and the sweeping-blade configuration is established. The moderate-deflection beam theory and the two-dimensional
quasi-steady aerodynamic model are employed to model the aeroelastic blade, all the kinetic and inertial factors are taken
into account in a unified manner. A five-nodes, 15-DOFs pre-twisted nonuniform beam element is developed for the discretization
of the blade, three rigid-body-motion DOFs are introduced for the motion of the hinges and the bearing. The Hamilton's principle
is employed to evaluate the equation of motion of the blade. The derived nonlinear ordinary differential equations with time-dependent
periodic coefficients are solved by a modified quasi-linearization method, which is developed for the higher DOF periodic
system. The resulting periodic forces and moments exerted on the fuselage by all the blades are evaluated every time, when
the converged nonlinear periodic response of the blade is obtained under the consideration of the equilibrium of the blades.
The fuselage structure is simplified to be a beam structure, the governing equation is established in the inertial reference
frame and a two-nodes beam element is used to discretize the flexible fuselage. The periodic response of the fuselage is solved
by a simple shooting method. The iteration of the rotor/fuselage response is continued, until the aeroelastic responses of
the blade and the fuselage converge simultaneously. Both the hovering and the forward flight states can be considered. The
results of a computed numerical example by the developed program are presented to verify in practice the economy of the modeling
as well as the reliability and efficiency of the corresponding solving methods.
Received 4 May 1998; accepted 11 August 1998 相似文献
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A third‐order mesh generation and adaptation method is presented for solving the steady compressible Euler equations. For interior points, a third‐order scheme is used on Cartesian and curvilinear meshes. Concerning the mesh adaptation, the method of Meakin is also extended to third order. The accuracy of the new overset mesh adaptation method is demonstrated by a grid convergence study for 2‐D inviscid model problems and results are compared with a second‐order method. Finally, the method is applied to the computation of an inviscid 3‐D flow around a hovering blade of the ONERA 7A helicopter rotor exhibiting an improvement in the wake capture. With a 7 million point mesh, the tip vortex can be followed for more than three rotor revolutions with the third‐order method. The CPU time needed for this calculation is only 3% higher than with a conventional second‐order method. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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