Active vibration suppression for flexible satellites using a novel component synthesis method

This paper is devoted to developing a closed-loop vibration suppression controller for a satellite with large flexible appendages based on component synthesis vibration suppression (CSVS) method. The dynamics model of a flexible satellite is firstly established by using the Newton–Euler methodology, and the dynamics model of the flywheel is also developed. A novel CSVS method is presented based on zero-vibration differentiator (ZVD), which can guarantee multi-order vibration suppression. Combined with the proposed CSVS method, traditional closed-loop controllers such as PD or sliding mode controllers can be applied to active vibration suppression. The stability of the proposed closed-loop CSVS controller is proved by the Lyapunov theory. Subsequently, the dynamic optimal control allocation algorithm is proposed for six flywheels, and a novel nonsingular fast terminal sliding mode controller is developed to obtain practical voltage control input for the flywheel drive control system. Finally, numerical simulations are carried out to validate the effectiveness of the proposed method.     

Type synthesis of deployable mechanisms for ring truss antenna based on constraint-synthesis method

Space deployable antenna is the key equipment in realizing the communication and data transmission between the spacecraft and the earth. In order to enrich the configurations of deployable antennas, the type synthesis of deployable mechanisms for ring truss antenna is conducted in this study. First, the principle of the constraint-synthesis method based on screw theory is briefly described, the structure of the ring truss deployable antenna and its folding principle are analyzed, and the ring truss mechanism is divided into upper edges, lower edges and linkages. Then, based on the constraint-synthesis method, the type synthesis of the basic unit edges is carried out, a series of basic unit mechanisms are obtained from combining the basic unit edge mechanisms, and five mechanism units with fewer joints and simple structures are selected. Furthermore, simulation models of the five ring truss deployable mechanisms are built in Solidworks and Matlab software, and the deploying process is verified by the movement simulation. Finally, mechanism characteristics of the five mechanisms are analyzed and discussed, and a prototype is manufactured, verifying the analysis in this paper. This research provides a new way for the type synthesis of spatial deployable mechanisms, and the ring truss deployable mechanisms obtained in this study can be well applied in the field of aerospace.     

Type synthesis of 2-DoF rotational parallel mechanisms actuating the inter-satellite link antenna

This paper focuses on the type synthesis of two degree-of-freedom (2-DoF) rotational parallel mechanisms (RPMs) that would be applied as mechanisms actuating the inter-satellite link antenna. Based upon Lie group theory, two steps are necessary to synthesize 2-DoF RPMs except describing the continuous desired motions of the moving platform. They are respectively generation of required open-loop limbs between the fixed base and the moving platform and definition of assembly principles for these limbs. Firstly, all available displacement subgroups or submanifolds are obtained readily according to that the continuous motion of the moving platform is the inter-section of those of all open-loop limbs. These subgroups or submanifolds are used to generate all the topology structures of limbs. By describing the characteristics of the displacement subgroups and submanifolds intuitively through employing simple geometrical symbols, their intersection and union operations can be carried out easily. Based on this, the assembly principles of two types are defined to synthesize all 2-DoF RPMs using obtained limbs. Finally, two novel categories of 2-DoF RPMs are provided by introducing a circular track and an articulated rotating platform, respectively. This work can lay the foundations for analysis and optimal design of 2-DoF RPMs that actuate the inter-satellite link antenna.     

一类有理递归序列的简单性态

在Alaa E.Hamza和A.Morsy Alaa等有关有理递归序列xn+1=α+xn-1xkn,n=0,1,2,…的稳定性研究的基础上,对时滞为k的情形做了进一步讨论,研究了有理递归序列xn+1=α+xn-kxmn的全局性和有界性,得到了关于该递归序列稳定性的几个判定定理。     

波导功分器温漂问题研究

波导功分器是电路合成技术中的关键器件。文章在叙述波导功分器制作原理的基础上,设计出了1分3波导功分器,并对其温漂问题进行了研究,得器由于温漂的存在会使功分器的功率分配不均匀现象进一步恶化的结论,并提出了改进措施。     

微波双通带滤波器多项式综合技术

文章提出了一种新的微波双通带滤波器多项式综合技术,这种方法将频率转换与优化方法结合,与频率转换方法相比较,文章中提出的新方法不仅能够有效地综合出具有等波纹响应特性的对称双通带滤波器的s参数多项式,而且对于两个不对称度很高的双通带也同样有效。文章最后给出了相应的设计实例,验证了该方法对所有双通带多项式综合的有效性。     

Configuration synthesis of planar folded and common overconstrained spatial rectangular pyramid deployable truss units

Compared with non-overconstrained deployable units, overconstrained deployable units are widely used in space missions for their higher stiffness characteristics. Besides the performance of a three-step topological structural analysis and design of the rectangular pyramid deployable truss unit(PDTU), conducting a structural synthesis of an overconstrained deployable unit requires the determination of the relative position and direction of each kinematic axis. The structural synthesis of an overconstrained deployable unit is investigated based on screw theory and its topological structure. The possible overconstrained cases of the rectangular PDTUs are analyzed, and corresponding screw expressions are obtained. Thus, the rectangular PDTUs, which can be folded into a plane, are synthesized systemically, and a series of overconstrained rectangular PDTUs is obtained. Furthermore, the feasibility of the folded and deployed motions under one degree of freedom for those deployable units is verified in dynamical simulation by using ADAMS 2010.     

航空发动机系统的动力分析

以包含复杂转子系统及支承结构系统的发动机总体模型为研究对象, 进行动态特性及动响应分析。为合理解决计算的准确性与经济性之间的矛盾, 提出了模态阻抗综合分析法, 将整体系统动力学问题化为低阶运动方程求解。应用按本文方法编制的程序对某型航发进行了整体动应力计算, 结果与实际相符。      

有理B样条曲线的形状修改方法

本文修正了均匀B样条曲线的定义,引入了左极限的概念来处理B样条函数在重节点处左连续阶降低的情况,通过补充适当的附加方程解决了重节点引起的插值方程的降秩问题。     

一类有理保形插值

给出了一个适用于一般数据集的有理保形插值函数。它不仅具有插值函数的形式简单、参数易于选取等特点,而且其C~2保形插值的参数可以很方便地求得,而不必求解非线性方程组。在给出C~k类函数(k=1,…,4)的Hermite插值的最佳误差估计的基础上,本文得到了一般数据集的保形插值的误差估计;作为其推论,又得到了对严格凸函数的保凸插值的误差估计。本文中C~1和C~2保形插值的参数仍可在一定范围内自由选取。故可利用其适当调整曲线的形状,使之更符合设计要求;或利用参数的适当选取以获得较好的逼近阶。提出的有理保形插值已用于正在开发的微机CAD并行系统。