【作者】 游斌弟；

【导师】 庞宝君； 赵阳；

【作者基本信息】 哈尔滨工业大学 ， 航空宇航科学与技术， 2011， 博士

【摘要】 随着空间侦察技术的发展,对星载天线的跟踪和搜索能力提出了越来越高的要求。针对空间作业的无根树系统,卫星本体是空间漂浮基,其运动过程有很强的非线性、时变性及耦合性,且天线在指向过程中不可避免受到柔性关节动态误差、关节铰间隙、反射面挠性及空间热环境等因素影响,对星载天线动态指向精度造成了很大的影响,使得星载天线动态指向精度研究成为空间侦察领域中的难题之一。本文主要针对星载天线动态指向精度动力学分析和控制问题开展研究。星载天线是典型的空间多体系统,在轨工作时,其非线性特性使得动力学分析与计算较为复杂。为了提高动力学计算效率,本文针对链式拓扑结构的星载天线多体系统,描述其运动学关系,建立了系统动力学模型;在此基础上,进一步考虑反射面为柔性体,通过天线转轴末端与反射面交界面的协调关系,采用固定界面模态综合法和Lagrange方程,推导了大范围运动星载天线刚柔耦合动力学模型,实现了星载天线系统动力学计算程序,并与商业软件对比,验证了所建立模型的正确性。为了研究柔性关节动态误差的非线性因素对星载天线指向精度的影响,深入了分析柔性关节动态误差引起的动力学响应行为,并提出应用多尺度法求解不同频率谐波的强迫激励下动态误差的近似方法;仿真分析了柔性关节动态误差引起的振动响应,即可能产生强烈的力矩和速度波动。进一步设计了星载天线定位指向与轨迹跟踪非线性控制器,并利用Lyapunov理论证明所设计的控制算法是渐近稳定的。通过合理选取控制器参数可抑制其扰动,较好地补偿柔性关节动态误差,为星载天线指向控制提供有效的参考依据。关节铰间隙的存在不可避免破坏了星载天线多体系统的理想约束模型,为了研究关节铰间隙对星载天线扰动的影响,本文建立了铰间隙矢量矩模型,采用非线性弹簧阻尼及修正库仑摩擦描述了铰间隙碰撞力和摩擦力模型;进一步建立了含间隙铰变拓扑结构的星载天线多体系统动力学模型,通过接触碰撞判别准则,并采用Newmark法进行数值递推计算,由计算结果可知铰间隙极大增加关节的碰撞力,加剧了反射面振动,恶化了天线动态指向精度。最后引入挤压油膜润滑被动控制技术,消除了铰间隙运动副碰撞的可能,有效地提高天线的指向精度。针对柔性反射面的弹性振动与星载天线耦合,其动力学分析与计算较为复杂的情况,本文采用惯性完备性准则选取模态降低模型阶数,保证所建立动力学模型具有较高的计算效率和足够的精度。分析了反射面不同安装布局约束工况时柔性反射面弹性变形对星载天线的扰动。进一步利用PD+振动力反馈控制算法抑制系统振动,并基于Lyapunov方法证明了控制系统的渐近稳定性,通过仿真算例表明该控制策略能快速抑制系统振动。由于经受太阳辐射、深冷空间周期性作用,会引起温度剧烈变化,产生较大的热变形或热振动,为了研究空间热载荷对星载天线刚柔耦合多体系统的扰动,根据抛物反射面几何特征,利用壳体单元进行有限元离散化,并考虑了壳体厚度方向上的温度变化,建立了有限元列式热传导方程;引入与应变能有关的耦合项,推导了含空间热效应的星载天线系统刚柔耦合动力学模型,通过分析结果表明空间热效应因素加剧了柔性反射面的弹性振动,严重降低了天线指向精度。为此,本文根据热载荷对星载天线系统的不确定扰动,建立惯性空间下不确定扰动力的动力学模型,推导了自适应控制器模型,设计了参数自适应更新律,并利用Lyapunov证明其稳定性,为进一步提高卫星天线的指向精度和实现振动抑制提供了理论基础。更多还原

【Abstract】 With the development of space reconnaissance, the requirement of antenna pointing accuracy becomes more important. Satellite antenna system is the free-floating, and its movement has strong non-linearity. Further, satellite antenna system possess nonlinear attribute (such as dynamic errors, joint clearance, reflector flexibility and space environmental effects) that is responsible for performance degradation and present special challenges to modeling and control. Thus, this thesis focuses on research of the analysis of dynamic pointing accuracy of the satellite antenna and its control.Satellite antenna system is typical multibody flexible system. The dynamic coupling characteristics make the dynamic analysis complicated. In order to improve the computational efficiency, Lagrange and Newton-Euler method are used for establishing the forward and inverse dynamic model with characterization of its chain topology. Further, the fixed-interface component-mode synthesis is used to achieve a lower order dynamic model, and the rigid-flexible coupling dynamics model of satellite antenna is realized through compatibility relations at the interface between antenna shaft and flexible reflector under the large motions. Both the dynamic models are compared to the commercial dynamic software for validation.The flexible joint introduces dynamic error that is harmful for antenna pointing accuracy and satellite attitude. Under forcing excitations of different frequencies, the equation of approximate solution and frequency response are deduced by multi-scale method. Then, disturbance effects of satellite antenna are analyzed considering the dynamic error. Finally, the nonlinear control algorithm for compensation of antenna pointing accuracy is proposed for trajectory tracking. The asymptotic stability is established using Lyapunov stability theory. The nonlinear controller algorithm can completely compensate for the dynamic error and suppress its disturbance with reasonable controller parameters.The presence of clearances degrades the performance of the satellite antenna system. A methodology for modeling and analysis is presented considering the effects of the joint clearance and reflector flexibility in the system. The joint clearance model is established based on a thorough geometric description of eccentricity vector. The contact-impact forces are evaluated based on a Hertz contact theory and a modified Coulomb’s friction law. Further, through the contact-impact criterion, the multi-body dynamics of satellite antenna is analyzed based on Newmark method. Finally, the porous squeeze film-lubricated is introduced into joints which can control the clearance effects. The joint impact effects can be greatly reduced and steady-state performance is improved.The dynamic analysis is quite complicated due to flexible vibration of reflector for satellite antenna system. Thus, dimensions of dynamic model are reduced by means of modal reduction based on the criterion of inertia completeness. The disturbance of flexible antenna reflector elastic deformation to satellite antenna system is analyzed under the layout constraints. Further, the PD vibration force feedback control law is used to eliminate the system vibration, and the asymptotic stability of the system is proved based on Lyapunov method. The results show that the proposed control strategy can quickly suppress system vibration.According to the geometric characteristics of parabolic antenna reflector, the temperature function in one element along its thickness direction is built for shell structures, and the finite element equations for heat conduction equations are derived. The coupling terms of strain energy relations are introduced. And the rigid-flexible dynamics of satellite antenna system considering thermal load is studied under space environment. The result shows that, the temperature gradient induced vibration of flexible reflector to produce elastic deformation. Furthermore it excites to aggravation its own elastic vibration which can make the system vibrated and deviations of satellite base attitude and antenna pointing become larger. The proposed adaptive controller is proposed to improve the antenna pointing considering time varying parameters and external disturbances, and the asymptotic stability of the controller algorithm is proved based on Lyapunov method.更多还原