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燃料消耗下充液航天器等效动力学建模与分析

EQUIVALENT DYNAMICS MODELING AND ANALYSIS OF LIQUID-FILLED SPACECRAFT WITH FUEL CONSUMPTION

  • 摘要: 在轨航天器贮腔内的液体可能表现出多种不同的运动模式, 主要包括液体相对于贮腔的整体性刚体运动、自由液面横向晃动、液体起旋后逐步发生明显的旋转晃动及液体自旋运动; 复合三自由度刚体摆晃动模型能够较为全面地描述这些液体运动模式, 同时为研究起旋阶段的液体晃动动力学问题提供了有效手段. 本文对非线性液体晃动刚体摆复合模型作进一步发展, 考虑模型等效参数随贮腔充液比的变化, 提出了变参数的刚体摆复合模型, 该模型适用于研究燃料消耗下非线性晃动类充液航天器大范围运动耦合动力学问题. 采用刚体摆复合模型对球形贮腔内的液体晃动进行等效后, 基于混合坐标意义下的拉格朗日方程推导了一类充液航天器轨道-姿态-晃动全耦合的动力学方程组, 并展开了充液航天器大角度三轴稳定姿态机动和零冲量轨道机动仿真以及航天器耦合动力学响应特性分析. 研究表明: 液体相对于贮腔的运动会造成航天器主刚体位置发生偏移, 当航天器在执行零冲量机动时, 燃料消耗会造成航天器的轨道平动速度无法收敛到零; 贮腔偏心布放时, 航天器在执行轨道机动过程中贮腔内液体易发生剧烈而且形式复杂的晃动行为, 进而可能造成航天器刚体运动的不稳定.

     

    Abstract: The liquid in the tank of in-orbit spacecraft may experiences different types of motion, mainly including the overall rigid motion of liquid respect to the tank, the lateral sloshing of the liquid free surface, and the liquid rotation starting which will maybe eventually graduate into the rotary sloshing of the liquid free surface and/or the spinning motion of liquid, etc. The composite 3DOF-rigid-pendulum sloshing model is able to describe all of these main motion types of liquid, and it has been validated to be effective for the analysis of the liquid sloshing dynamics during the rotation-starting period. In this paper, the composite rigid-pendulum model is developed to investigate the large motion coupling dynamics of a variable-mass liquid-filled spacecraft with nonlinear liquid slosh and fuel consumption, by taking account of the variation of equivalent model parameters over liquid-fill ratio. Based on the Lagrangian equations, the orbital-attitude-slosh coupling dynamics model of a liquid-filled spacecraft is equivalently established by using the composite rigid-pendulum model to replace the liquid in a spherical tank. Then, simulations of a three-axis stabilized large angle attitude maneuver and a zero-impulse orbital maneuver of spacecraft are given for the coupling dynamics response analysis of the liquid-filled spacecraft system. Simulation results show that the liquid motion with respect to the tank will cause the position offset of spacecraft, and the orbital velocity of spacecraft will not converge to zero when the spacecraft executes zero-impulse maneuvers with fuel consumption; and that the liquid is likely to experience violent and complicated sloshing motion, which may cause the instability in the rigid-body motion of spacecraft, during the orbital maneuvering when the tank is eccentrically installed in the rigid hub.

     

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