Vibration analysis and control technologies of hydraulic pipeline system in aircraft: A review

Vibrations in aircraft hydraulic pipeline system, due to multi-source excitation of high fluid pressure fluctuation and serious vibration environment of airframe, can cause the pipeline system vibration failures through overload in engineering field. Controlling the vibrations in hydraulic pipeline is a challenging work to ensure the flight safety of aircraft. The common vibration control technologies have been demonstrated to be effective in typical structures such as aerospace structures, shipbuilding structures, marine offshore structures, motor structures, etc. However, there are few research literatures on vibration control strategies of aircraft hydraulic pipeline. Combining with the development trend of aircraft hydraulic pipeline system and the requirement of vibration control technologies, this paper provides a detailed review on the current vibration control technologies in hydraulic pipeline system. A review of the general approaches following the passive and active control technologies are presented, which are including optimal layout technique of pipeline and clamps, constrained layer damping technique, vibration absorber technique, hydraulic hose technique, optimal pump structure technique, and active vibration control technique of pipeline system. Finally, some suggestions for the application of vibration control technologies in engineering field are given.     

Coordinated control of dual-arm robot on space structure for capturing space targets

This paper presents a coordinated control scheme for two capture tasks via a dual-arm space robot with its base on a flexible space structure. The robot system consists of a base, a mission arm for capture, and a balance arm for removing disturbance forces to the base. To counteract the impact of structural vibration, a two-stage strategy containing a vibration control stage and a target capture stage is proposed. In the first stage, the robot and structure are treated as a mass-spring system in which the coupling effect between the robot and the flexible structure is exploited to suppress structural vibration. Notably, the collision avoidance between two arms is achieved by a velocity inequality constraint, wherein the reactionless motion is utilized. In the second stage, a reactionless trajectory is planned for the mission arm to reach the target location and attitude, as the balance arm remove the coupling disturbance to the base. Afterwards, the balance arm becomes the new mission arm for capture and the other arm is defined as the new balance arm. Finally, numerical simulations are given to validate the efficiency of the proposed coordinated control strategy.     

锆钛酸铅压电陶瓷主动元件在航天自适应桁架结构中的应用

阐明了PZT压电材料的正、逆压电效应以及相应的压电作动器的机电耦合原理。针对航天自适应桁架结构的特点，运用PZT压电作动器进行了振动抑制实验并取得了良好的效果。     

基于DDS+PLL的光源调制与功率稳定控制方法CSCD

量子传感器是基于量子操控技术的研究成果,一般具有高精度、小体积等优势。激光器是量子传感器的核心部件,有抽运和检测功能,激光器的稳定性对量子传感器具有重要的意义。提出了一种直接数字合成法(DDS)与锁相回路(PLL)相结合的方法,对激光器进行调制并抑制调制噪声,实现了激光器的稳定输出。基于现有小型量子传感器装置,在DDS生成4kHz参考信号的情况下实现了激光器电流8kHz调制,抑制了调制时调制电流信号噪声约8dB,并提高了激光器输出光功率的稳定性。     

Control and utilization of range-dependent beampattern with waveform diverse array radars

The transmit antenna beampattern of the phased array radar is only a function of angle, limiting its ability to discriminate the targets from the same direction. Recently, the waveform diverse array radars expand the angle-dependent beampattern to an angle-time-range-dependent three-dimensional function by modulating the frequencies/time delays/phases across different transmit antenna elements. In this respect, extra Degrees-of-Freedom (DOFs) in the range domain are achieved, which opens up an innovative way to fulfil the tasks with enhanced system performance by jointly using the angle and range information. This paper summaries the developments of waveform diverse radars, including the Frequency Diverse Array (FDA), the Space-Time-Circulating-Array (STCA), and the Element-Pulse-Coding (EPC) frameworks, with emphasis on the analysis of the range-dependent beampattern from the basic properties upon how it is controlled. Moreover, the most recent advances of utilizing such a range-dependent beampattern in target detection, parameter estimation and identifiability, clutter suppression, jammer suppression and Synthetic Aperture Radar (SAR) imaging are discussed.     

Nonlinear modal electromechanical coupling factor for piezoelectric structures containing nonlinearities

Within the linear framework, the Modal Electromechanical Coupling Factor (MEMCF) is an important indicator to quantify the dynamic conversion of mechanical energy and electrical energy of piezoelectric structures. It is also an important tool to guide the piezoelectric damping design of linear structures. Advanced aircraft often fly in maneuvers, and the variable working conditions induce drastic changes in the load level on structures. Geometric and contact nonlinearities of thin-walled structures and joint structures are often activated. To achieve a good vibration reduction effect covering all working conditions, one cannot directly use linear electromechanical coupling theory to instruct the piezoelectric damping design for nonlinear structures. Therefore, this paper defines the Nonlinear Modal Electromechanical Coupling Factor (NMEMCF) and proposes the corresponding numerical method for the first time to quantitatively evaluate the electromechanical coupling capability of nonlinear piezoelectric structures. Three candidate definitions of the NMEMCF are given, including two frequency definitions and one energy definition. The energy definition is the most promising one. It is not only applicable to both conservative and dissipative nonlinear structures but also compatible with the linear MEMCF. In addition, based on the energy formula, the NMEMCF can be obtained by only performing one nonlinear modal analysis in the open-circuit state. The analytical findings and the numerical tool are validated against two piezoelectric structures with different types of nonlinearities. A strong correlation among the NMEMCF, geometric parameters, and energy dissipation is observed. The results confirm that the proposed NMEMCF captures the physics of the electromechanical coupling phenomenon associated with nonlinear piezoelectric structures and can be used as an essential design indicator of piezoelectric damping, especially for variable working conditions.     

变弯度后缘与常规舵面机翼的颤振主动抑制对比

后缘变弯度机翼的气动弹性建模与稳定性分析日益受到关注。为了探究变弯度后缘相比常规偏转舵面机翼颤振主动抑制的方法与特点，以一个小展弦比后缘变弯度机翼为对象，首先建立结构有限元模型，并引入变弯度后缘变形模态和常规舵面偏转模态，采用亚声速偶极子格网法计算非定常气动力；然后使用基于最小状态法的有理函数拟合进行频域到时域模型的转换，建立两种构型机翼的气动弹性模型，并在建模时考虑了变弯度后缘与常规舵面控制带宽的差异；最后利用线性高斯二次型方法设计控制律进行颤振主动抑制，分析对比两种控制方式的特性差异。结果表明：采用变弯度后缘的闭环系统能够将颤振临界速度提高22%，其提升效果优于常规舵面，所需舵面偏转峰值更小。     

柔性机械臂关节作动的振动抑制方法和原理性验证

空间机械臂具有柔性大、振动频率低等特点，受激后振动的持续时间长、自然衰减慢。针对空间机械臂运行完成后留存的残余振动，采用固定界面子结构方法推导出关节转动与航天器-机械臂组合体振动的动力学显式关系。从中发现了控制关节转动并使其角速度正比于组合体振动的模态坐标，便能消耗组合体的机械能，加速组合体振动衰减的力学机理。据此，设计了逻辑关系简洁的机械臂关节角速度控制律，分别通过数值仿真和试验件实测对航天器-机械臂组合体的原理性模型开展了振动抑制效果的验证。结果表明:机械臂关节作动可以显著缩短受激后组合体残余振动的持续时间。     

Star angle/ double-differenced pulse time of arrival integrated navigation method for Jupiter exploration

Pulsar navigation is a promising autonomous navigation system for spacecraft, which is applicable to the entire solar system. However, the pulsar’s directional error and the onboard clock error are two types of systematic errors that seriously reduce navigation accuracy. To solve this problem, a star angle/double-differenced pulse time of arrival(SA/DDTOA) integrated navigation method is proposed. Since measurements obtained by observing different pulsars contain the same clock errors, the measurements can be differed to eliminate the common clock error. Then, the pulsar-differenced measurements at neighbor filtering time can be differed to suppress the effect of the pulsar’s directional error on navigation precision. Star angle is used to obtain absolute navigation information, which denotes the angles between the light of sight of Jupiter and that of its background stars. Simulation results demonstrate that the proposed method can eliminate the influence of the onboard clock error and greatly weaken the effects of the pulsar’s directional error. The navigation accuracy is better than the traditional star angle/pulse time of arrival integrated navigation method and star angle/pulse time difference of arrival integrated navigation method. In addition, the navigation accuracy of the SA/DDTOA integrated navigation method is less affected by Jupiter’s ephemeris error. This work greatly reduces the influence of common systematic errors in pulsar navigation on navigation accuracy.     

一种导致压电式冲击传感器零漂原因分析及抑制措施

冲击加速度传感器输出零漂是影响传感器使用的重要特性，对零漂问题探索由来已久。根据冲击传感器输出信号特点，从传感器模型到传感器与变换电路角度进行了分析，结合传感器安装频响与冲击信号之间的关系，得出高频冲击信号在传感器安装谐振频率处被放大导致传感器零漂的结论。通过理论推导与实际传感器输出结果对比，验证了理论推导的正确性。最后，对零漂抑制措施以及实际作用结果进行了阐述。