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The attitude dynamics and control for solar sail orbiting a celestial body (e.g., the Earth) are critical for the space missions. In the paper, the pitch dynamics is addressed by considering the torques by the center-of-mass and center-of-pressure offset, the gravity gradient, the internal damping and the control vane. The chaotic pitch motion is analytically detected for the sailcraft in the circular and elliptical orbits with small eccentricities using the Melnikov’s method. The validity of the Melnikov method is numerically verified by checking the Poincare surface of section and the power spectral density. The stability criterion method with some improvements is utilized to stabilize the chaotic pitch motion onto the reference unstable periodic motion embedded in the chaotic attractor. The reference unstable periodic motion is obtained based on the calculation of the close return pairs. The small control input torques and the stabilization effects are presented, and the advantages of the modified stabilization method are clarified based on the numerical simulations. 相似文献
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A meso material model for polycrystalline metals is proposed, in which the tiny slip systems distributing randomly between
crystal slices in micro-grains or on grain boundaries are replaced by macro equivalent slip systems determined by the work-conjugate
principle. The elastoplastic constitutive equation of this model is formulated for the active hardening, latent hardening
and Bauschinger effect to predict macro elastoplastic stress-strain responses of polycrystalline metals under complex loading
conditions. The influence of the material property parameters on size and shape of the subsequent yield surfaces is numerically
investigated to demonstrate the fundamental features of the proposed material model. The derived constitutive equation is
proved accurate and efficient in numerical analysis. Compared with the self-consistent theories with crystal grains as their
basic components, the present theory is much simpler in mathematical treatment.
Project supported by the National Natural Science Foundation of China (Grant No. 19732006). 相似文献
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3-D network model and its parameter calibration 总被引:2,自引:0,他引:2
A material model, whose framework is parallel spring-bundles oriented in 3-D space, is proposed. Based on a discussion of
the discrete schemes and optimum discretization of the solid angles, a 3-D network cell consisted of one-dimensional components
is developed with its geometrical and physical parameters calibrated. It is proved that the 3-D network model is able to exactly
simulate materials with arbitrary Poisson ratio from 0 to 1/2, breaking through the limit that the previous models in the
literature are only suitable for materials with Poisson ratio from 0 to 1/3. A simplified model is also proposed to realize
high computation accuracy within low computation cost. Examples demonstrate that the 3-D network model has particular superiority
in the simulation of short-fiber reinforced composites. 相似文献
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有限弹塑性变形的三维组集式本构模型 总被引:2,自引:1,他引:2
本文将文[1]中提出的三维组集式弹塑性本构模型推广应用于有限变形分析,导出了全量型和增量型本构关系在初始构形上的拉格朗日(Total Lagrange)形式和瞬时构形上的拉格朗日(Updated Lagrange)形式。文中对晶体单轴拉伸中的宏观剪切带进行了分析。预测结果与实验吻合。从而说明这种本构模型能够模拟有限变形中的几何非线性效应和晶体材料塑性变形中的宏观力学行为。 相似文献
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本文提出了用有限元进行结构静力与动力分析的一种新算法。使用这种算法可以避免大矩阵运算,直接求得预先指定的未知数,或把结构的刚度、质量、阻尼及载荷凝聚到为数很少的控制自由度上,得到结构的凝缩运动方程。 相似文献
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We have proposed an “exact” strain gradient(SG) continuum model to properly predict the dispersive characteristics of diatomic lattice metamaterials with local and nonlocal interactions. The key enhancement is proposing a wavelength-dependent Taylor expansion to obtain a satisfactory accuracy when the wavelength gets close to the lattice spacing. Such a wavelength-dependent Taylor expansion is applied to the displacement field of the diatomic lattice, resulting in a novel SG model. For various k... 相似文献
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带模型误差系统的自适应卡尔曼滤波在捷联惯导系统初始对准中的应用研究 总被引:4,自引:0,他引:4
对于有模型误差的惯导系统,采用常规卡尔曼滤波会导致较大的状态估计误差,甚至使滤波器发散。可采用自适应卡尔曼滤波算法,通过引入虚拟噪声,利用观测数据带来的信息,在线改进滤波器的设计,并将其运用到捷联惯导系统的初始对准中,由此得到的滤波估计比常规卡尔曼估计具有更高的精度和准确度。试验及计算机仿真结果验证了该方法的有效性。 相似文献
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