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572.
573.
The flexible attachments of spacecraft may undergo Thermally Induced Vibration (TIV) on orbit due to the suddenly changed solar heating. The unstable TIV, called thermal-flutter, can cause serious damage to the spacecraft. In this paper, the coupled bending-torsion thermal vibration equations for an open thin-walled circular cantilever beam are established. By analyzing the stability of these equations based on the first Lyapunov method, the thermal-flutter criterion can be obtained. The criterion is very different form that of closed thin-walled beams because the torsion has great impact on the stability of the TIV for open thin-walled beams. Several numerical simulations are conducted to demonstrate that the theoretical predictions agree very well with the finite element results, which mean that the criterion are reliable. 相似文献
574.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(5):2437-2448
This paper presents a coordinated control scheme for two capture tasks via a dual-arm space robot with its base on a flexible space structure. The robot system consists of a base, a mission arm for capture, and a balance arm for removing disturbance forces to the base. To counteract the impact of structural vibration, a two-stage strategy containing a vibration control stage and a target capture stage is proposed. In the first stage, the robot and structure are treated as a mass-spring system in which the coupling effect between the robot and the flexible structure is exploited to suppress structural vibration. Notably, the collision avoidance between two arms is achieved by a velocity inequality constraint, wherein the reactionless motion is utilized. In the second stage, a reactionless trajectory is planned for the mission arm to reach the target location and attitude, as the balance arm remove the coupling disturbance to the base. Afterwards, the balance arm becomes the new mission arm for capture and the other arm is defined as the new balance arm. Finally, numerical simulations are given to validate the efficiency of the proposed coordinated control strategy. 相似文献
575.
阐明了PZT压电材料的正、逆压电效应以及相应的压电作动器的机电耦合原理。针对航天自适应桁架结构的特点,运用PZT压电作动器进行了振动抑制实验并取得了良好的效果。 相似文献
576.
577.
《中国航空学报》2023,36(2):100-110
Within the linear framework, the Modal Electromechanical Coupling Factor (MEMCF) is an important indicator to quantify the dynamic conversion of mechanical energy and electrical energy of piezoelectric structures. It is also an important tool to guide the piezoelectric damping design of linear structures. Advanced aircraft often fly in maneuvers, and the variable working conditions induce drastic changes in the load level on structures. Geometric and contact nonlinearities of thin-walled structures and joint structures are often activated. To achieve a good vibration reduction effect covering all working conditions, one cannot directly use linear electromechanical coupling theory to instruct the piezoelectric damping design for nonlinear structures. Therefore, this paper defines the Nonlinear Modal Electromechanical Coupling Factor (NMEMCF) and proposes the corresponding numerical method for the first time to quantitatively evaluate the electromechanical coupling capability of nonlinear piezoelectric structures. Three candidate definitions of the NMEMCF are given, including two frequency definitions and one energy definition. The energy definition is the most promising one. It is not only applicable to both conservative and dissipative nonlinear structures but also compatible with the linear MEMCF. In addition, based on the energy formula, the NMEMCF can be obtained by only performing one nonlinear modal analysis in the open-circuit state. The analytical findings and the numerical tool are validated against two piezoelectric structures with different types of nonlinearities. A strong correlation among the NMEMCF, geometric parameters, and energy dissipation is observed. The results confirm that the proposed NMEMCF captures the physics of the electromechanical coupling phenomenon associated with nonlinear piezoelectric structures and can be used as an essential design indicator of piezoelectric damping, especially for variable working conditions. 相似文献
578.
The violent vibration of hydraulic pipelines in aircraft may cause faults or even an accident, especially for the large aircraft with the multi-pump system because of different vibration sources and complex pipelines system. Aiming to the vibration analysis and control of the multipump system, this paper proposed the clamps’ locations optimization to minimize the system impedance at vibration frequencies. Firstly, the models of the flexible clamp and other components in multi-pump system were es... 相似文献
579.
复杂的电磁环境是电磁辐射源集合与电波传播环境相互作用的总和.针对目前GNSS易受复杂电磁环境影响的问题,研究了GNSS复杂电磁环境综合监测测向与分析评估技术,提出了专用信道化监测方法、比幅与比相联合测向方法、卫星导航信号和电磁干扰信号综合分析方法以及GNSS复杂电磁环境影响效应分析评估方法,解决了现有通用设备在弱信号监测测向、电磁干扰信号与导航信号联合监测以及在复杂电磁环境影响效应分析评估方面存在的不足.该技术能够指导GNSS复杂电磁环境综合监测测向与分析评估设备的研制,为GNSS复杂电磁环境监测保障的工程化提供了技术支持. 相似文献
580.
The vibration of thermodynamic machinery will affect its cooling system. In this research, a high-resolution simulation of jet impingement was performed to quantify the unsteady turbulent convection under vibration conditions. A newly developed Self-Adaptive Turbulence Eddy Simulation(SATES) method was used. The Reynolds number was Re = 23000, the jet-towall distance was fixed at H/D = 2, and the vibrating frequency of the impinging wall f varied from 0 to 200 Hz. Compared with the static wall c... 相似文献