Leading-edge flow separation control over an airfoil using a symmetrical dielectric barrier discharge plasma actuator

In order to promote an in-depth understanding of the mechanism of leading-edge flow separation control over an airfoil using a symmetrical Dielectric Barrier Discharge(DBD) plasma actuator excited by a steady-mode excitation, an experimental investigation of an SC(2)-0714 supercritical airfoil with a symmetrical DBD plasma actuator was performed in a closed chamber and a low-speed wind tunnel. The plasma actuator was mounted at the leading edge of the airfoil.Time-resolved Particle Image Velocimetry(PIV) results of the near-wall region in quiescent air suggested that the symmetrical DBD plasma actuator could induce some coherent structures in the separated shear layer, and these structures were linked to a dominant frequency of f0= 39 Hz when the peak-to-peak voltage of the plasma actuator was 9.8 kV. In addition, an analysis of flow structures without and with plasma actuation around the upper side of the airfoil at an angle of attack of18° for a wind speed of 3 m/s(Reynolds number Re = 20000) indicated that the dynamic process of leading-edge flow separation control over an airfoil could be divided into three stages. Initially, this plasma actuator could reinforce the shedding vortices in the separated shear layer. Then, these vortical structures could deflect the separated flow towards the wall by promoting the mixing between the outside flow with a high kinetic energy and the flow near the surface. After that, the plasma actuator induced a series of rolling vortices in the vicinity of the suction side of the airfoil, and these vortical structures could transfer momentum from the leading edge of the airfoil to the separated region, resulting in a reattachment of the separated flow around the airfoil.     

Modeling and control of a novel electro-hydrostatic actuator with adaptive pump displacement

The variable pump displacement and variable motor speed electro-hydrostatic actuator (EHA), one of the three types of EHAs, has advantages such as short response time, flexible speed regulation, and high efficiency. However, the nonlinearity of its double-input single-output system poses a great challenge for system control. This study proposes a novel EHA with adaptive pump displacement and variable motor speed (EHA-APVM). A closed-loop position is realized using a servomotor. Moreover, the displacement varies with the system pressure; thus, the EHA-APVM is a single-input and single-output system. Firstly, the working principles of the EHA-APVM and the pump used in the system are introduced. Secondly, a nonlinear mathematical model of the proposed EHA-APVM control system is established, and a feedback back-stepping (FBBS) control algorithm is introduced to transform the complex nonlinear system into a linear system on the basis of the back-stepping control theory. Finally, simulation results prove that the EHA-APVM has a quick response and high robustness to variations of the load and the pump displacement. In this work, the size and weight of the motor are significantly reduced because the maximum power requirement is reduced, which is very beneficial for using the actuator in airborne equipment.     

执行器饱和的多智能体一致性控制

针对执行器饱和约束下的一类离散多智能体系统，设计了一种基于线性矩阵不等式的一致性控制律，并对线性矩阵不等式解的存在性进行了分析。由于饱和环节的影响，导致多智能体系统的一致性与个体的初始状态有关，不同的控制律所能允许的个体之间的初始偏差的范围不同。为了定量分析控制律所对应的初始偏差范围，引入吸引域的概念对所设计的控制律进行评估，并对控制律参数进行优化以扩大吸引域的范围。最后，通过数值仿真说明了所设计控制律的有效性。     

基于改进HHT的一体化电液作动器故障诊断

介绍了机载变排量变转速一体化电动静液作动器(EHA-VPVM,Electro-Hydrostatic Actuator with Variable Pump displacement and Variable Motor speed)的系统结构,根据EHA-VPVM早期故障信号非平稳、时变等特点,采用一种新的时频分析方法希尔伯特黄变换(HHT,Hilbert-Huang Transform)进行信号分析.针对HHT方法的模态混叠和虚假本征模态函数问题,提出两点改进:通过集合经验模式分解算法抑制模态混叠的发生;采用相关系数法保留真实本征模态函数.对EHA-VPVM工程样机进行早期故障诊断实验,用Hilbert边际谱和HHT谱分析永磁无刷直流电机两种工作状态下的振动信号.实验结果表明:改进HHT方法较好解决了HHT的模态混叠和虚假本征模态函数问题,能准确提取研究对象的早期故障特征,对EHA-VPVM早期故障具有良好的诊断效果.     

Numerical investigation of aerodynamic flow actuation produced by surface plasma actuator on 2D oscillating airfoil

Numerical simulation of unsteady flow control over an oscillating NACA0012 airfoil is investigated. Flow actuation of a turbulent flow over the airfoil is provided by low current DC surface glow discharge plasma actuator which is analytically modeled as an ion pressure force produced in the cathode sheath region. The modeled plasma actuator has an induced pressure force of about 2 k Pa under a typical experiment condition and is placed on the airfoil surface at 0% chord length and/or at 10% chord length. The plasma actuator at deep-stall angles(from 5° to 25°) is able to slightly delay a dynamic stall and to weaken a pressure fluctuation in down-stroke motion. As a result, the wake region is reduced. The actuation effect varies with different plasma pulse frequencies, actuator locations and reduced frequencies. A lift coefficient can increase up to 70% by a selective operation of the plasma actuator with various plasma frequencies and locations as the angle of attack changes. Active flow control which is a key advantageous feature of the plasma actuator reveals that a dynamic stall phenomenon can be controlled by the surface plasma actuator with less power consumption if a careful control scheme of the plasma actuator is employed with the optimized plasma pulse frequency and actuator location corresponding to a dynamic change in reduced frequency.     

一种抑制电传系统PIO的非线性补偿方法

提出了一种不完全非线性补偿方法用来抑制电传系统飞行员诱发振荡，其补偿着眼点是电传系统内部的舵回路速率饱和。本文把新的补偿方法用于一个两回路的飞行控制系统中，其设计过程和仿真结果表明，该方法结构简单，可以有效抑制ＰＩＯ，而且不影响原有系统的正常工作，便于工程应用。     

基于Lab windows／CVI的电动舵机测试设备软件开发

基于Lab windows/CVI虚拟仪器开发平台,结合某飞控系统电动舵机自动测试设备的软件开发,介绍了数据库软件和功能模块软件应用的关键技术,并对软件的主要技术特点进行了分析.     

两种主动控制喘振现象作动机构的非线性分析

 对喘振主动控制中所采用的作动机构进行了介绍，导出了与作动机构有关的系统非线性方程组，并定性地解释了作动机构引起附加小扰动的机理，对实际作动机构的动态平衡点进行了标定，并分析了实际作动机构与压缩系统的非线性耦合特征     

基于螺旋机构的旋转作动器研究

 研究出一种翼面驱动用旋转作动器。利用逆滚动螺旋机构将油缸的直线运动直接转换为旋转运动。研究表明,这种新作动器与现有作动器比较,具有输出力矩大,直径小,重量轻,标准化通用化的优点。     

考虑扰动输入/性能输出分布时作动/传感器配置优化

 针对结构振动控制问题，提出了一种考虑扰动输入/性能输出分布信息时作动/传感器的优化配置准则。在降维的模态坐标下建立状态空间形式的结构动力学方程，通过Lyapunov方程求解扰动和作动器的能控性Gramian矩阵，并利用矩阵奇异值分解获得扰动的能控性方向和作动器的能控性方向，通过同时最大化作动器对结构的作动能力以及作动器的能控性方向与扰动的能控性方向的一致性来确定作动器的最优位置。类似思想用于确定传感器的最优位置。以采用压电片为作动器的悬臂梁为例阐述了新准则的应用。