在轨加注过程中组合体航天器动力学建模与分析

针对在轨加注过程中质量分布随时间变化的组合体航天器，研究动力学建模问题并对其动态特性进行分析。将航天器系统分为刚性组合体平台和贮箱内燃料两部分，贮箱内的燃料视为质量、外形和位置连续变化的质量块，将航天器系统抽象为一组有固定边界的变质量质点系；在推导出变质量质点系一般力学方程的基础上，通过对航天器结构进行一定限制消除方程中的反冲力和失调力矩，以组合体平台主轴作为参考坐标系，建立在轨加注过程中组合体动力学模型；该模型除了参数时变的特点外，与普通刚体动力学相比还含有阻尼项；基于李雅普诺夫稳定判据，对该时变动力学系统的动态特性进行分析。仿真计算展现了不同结构参数对姿态运动轨迹的影响，也证明了理论分析的正确性。
A research was presented to solve the problem of dynamics modeling and characteristics analysis in the case of the mass distribution of the spacecraft changes obviously during the on-orbit propellant refueling process. The variable-mass vehicle was considered to consist of two parts: a rigid platform and the liquid propellant confined in tanks. The liquid in tanks was regarded as a finite number of lumped masses with time-varying mass, configuration and position, so that, the actual physics could be abstracted as a set of variable mass particles with fixed border. Then, the dynamics model of refueling spacecraft was established by using the general equations of mass-varying particles set. Based on some reasonable assumptions about the structure of vehicle, the misalignment moment and the reactive force were eliminated from equations. It is remarkable that the established model include time-varying parameters and damping terms. Besides, the dynamics characteristics of the model were analyzed by using the Lyapunov′s stability criterion. Simulation results demonstrate that the difference structure of the vehicle effect the state trajectories dramatically, and prove that theoretic analysis is correct.