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.     

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。      

TiC-Ni材料燃烧合成与致密化工艺参数的优化

通过燃烧合成与致密化方法制备了TiC -xNi系金属陶瓷材料 ,通过实验优化了Ti -C -xNi体系燃烧合成与致密化过程中的工艺参数 ,最终确定了各体系燃烧合成时的最佳预制块相对密度为 5 6 %左右 ,预压力P1为 10MPa ;确定了致密化时的高压力P2 为 16 0MPa ,高压保压时间t2 为 2 0s ,并确定了各体系的最佳加压时间t1     

深空天线组阵宽带信号频域合成技术研究

分析了深空天线组阵中宽带信号合成需求,提出一种宽带信号频域波束形成方法,设计相应的信道化滤波器组,达到了近似完全重建的目的;采用多相FIR(Finite Impulse Response,有限脉冲响应)和FFT(Fast Fourier Transform,快速傅里叶变换)结合的方式降低了DFT(Discrete Fourier Transform,离散傅里叶变换)滤波器组的计算量。在此基础上开展了原理样机的研制,并通过数传基带对样机进行闭环BER(Bit Error Rate,比特误码率)测试,根据测试BER数据计算样机本身SNR(Signal Noise Ratio,信噪比)恶化和合成效率。测试结果表明:合成信噪比损失小于0.4dB,验证了设计的正确性和合理性。     

金属基纳米复合材料的制备技术研究

综述了复合材料家族中的新成员——金属基纳米复合材料制备技术的国内外研究现状和本课题组近期取得的研究成果，对6大类工艺方法的机理、特点、适用范围和现阶段开发程度，以及由这些制备工艺所开发出的新材料的优异的机械、物理、化学性能进行了全面分析，并综合评价了各种工艺的优缺点。在展望金属基纳米复合材料广阔的应用前景基础上，指出了其制备技术未来的发展方向。