Study of beam divergence and thrust vector eccentricity characteristics of the Hall thruster based on dual Faraday probe array planes and its applications

The accurate knowledge of the thrust vector eccentricity and beam divergence characteristics of Hall thrusters are of significant engineering value for the beneficial integration and successful application of Hall thrusters on spacecraft.For the characteristics of the plume bipolar diffusion due to the annular discharge channel of the Hall thruster,a Gaussian-fitted method for thrust vector deviation angle and beam divergence of Hall thrusters based on dual Faraday probe array planes was proposed in respect of the Hall thruster beam characteristics.The results show that the ratios of the deviation between the maximum and minimum values of the beam divergence angle and the thrust vector eccentricity angle using a Gaussian fit to the optimized Faraday probe dual plane to the mean value are 1.4%and 11.5%,respectively.The optimized thrust vector eccentricity angle obtained has been substantially improved,by approximately 20%.The beam divergence angle calculated using a Gaussian fitting to the optimized Faraday probe dual plane is approximately identical to the non-optimized one.The beam divergence and thrust vector eccentricity angles for different anode mass flow rates were obtained by averaging the beam divergence and thrust vector eccentricity angles calculated by the dual-plane,Gaussian-fitted ion current density method for different cross-sections.The study not only allows for an immediate and effective tool for determining the design of thrust vector adjustment mechanisms of spacecraft with different power Hall thrusters but also for characterizing the 3D spatial distribution of the Hall thruster plume.

INVESTIGATION OF FLIGHT DYNAMICS OF THRUST VECTORING AIRCRAFT USING EXTENDED CONTINUATION METHODS

This paper presents the flight dynamical behavior of the thrust vectoring aircraft with extended bifurcation and continuation methods. In contrast to the standard bifurcation and continuation methods, the extended methods are capable of calculating the continuation curves of the equilibrium points for the particular type of trimming flight. Therefore, these methods can not only give the performance measures of aircraft, but also determine the stability of trimming points. In this paper, the methods are used to verify the effectiveness of the thrust vectoring control law, to define the flight envelope boundary, to analyze the stability and controllability of trimming flight, and to predict the departures of the instable flight. The result shows that the extended methods provide more flight dynamic information and are useful in preliminary design of the thrust vectoring aircraft.

Numerical investigation of dynamic characteristics of dual throat nozzle and bypass dual throat nozzle in thrust vectoring starting process

The Bypass Dual Throat Nozzle(BDTN)is a novel fluidic Thrust Vectoring(TV)nozzle,it switches to TV state by opening the valve in the bypass.To greatly manipulate the BDTN,the dynamic characteristics in the TV starting process should be analyzed.This paper conducts numerical simulations to grasp the variation processes of performances and the flow field evolution of BDTN and Dual Throat Nozzle(DTN).The dynamic responses of TV starting in typical DTN models are investigated at first.Then,the TV starting processes of BDTN in different Nozzle Pressure Ratio(NPR)conditions are simulated,and the valve opening durations(T)are also considered.Before the expected TV direction is achieved in the DTN,the jet is deflected to the opposite direction at the beginning of the dynamic process,which is called the reverse TV phenomenon.However,this phenomenon disappears in the BDTN.The larger injection width of DTN intensifies unsteady oscillations,and the reverse TV phenomenon is strengthened.In the BDTN,T determines the delay degree of performance variations compared to the static results,which is called hysteresis effect.At NPR=10,the hysteresis affects the final stable performance of BDTN.This study analyses the dynamic characteristics in DTN and BDTN,laying a foundation for further design of nozzles and control strategies.

A Computational Study of Thrust Vectoring Control Using Dual Throat Nozzle

Dual throat nozzle (DTN) is fast becoming a popular technique for thrust vectoring. The DTN is designed with two throats, an upstream minimum and a downstream minimum at the nozzle exit, with a cavity in between the upstream throat and exit. In the present study, a computational work has been carried out to analyze the performance of a dual throat nozzle at various mass flow rates of secondary flow and nozzle pressure ratios (NPR). Two-dimensional, steady, compressible Navier-Stokes equations were solved using a fully implicit finite volume scheme. The present computational results were validated with available experimental data. Based on the present results, the control effectiveness of thrust-vectoring is discussed in terms of the thrust coefficient and the coefficient of discharge.

SIMULATION RESEARCH OF ACTIVE VIBRATION CONTROL FOR ELASTIC MISSILE WITH SWING NOZZLE THRUST VECTOR CONTROL

Aiming at the deficiencies of notch filters on the aspect of vibration suppression for elastic missile with swing nozzle thrust vector control(SNTVC),an active vibration controller(AVC)is proposed.It is composed of an optimal state feedback controller(OSFC)and an optimal minimal order state observer(OMOSO),which can be respectively designed based on the separation principle.The design rules of these two elements are successively given.Computer simulation results present that AVC can realize strong vibration suppression and good convergence property after disturbing.Moreover,it has simple design and then it is easily implemented in engineering.In addition,the AVC scheme can also resolve the poor system stability to a great extent,which is resulted from the bad static stability of missile body.

Review of the Debate and the Development of Thrust Vectoring Technology

In this paper, the interesting development of the very important innovation of thrust vectoring tech-nology in applied aerodynamics is described.

Thrust estimator design based on least squares support vector regression machine

In order to realize direct thrust control instead of traditional sensor-based control for aero-engines,it is indispensable to design a thrust estimator with high accuracy,so a scheme for thrust estimator design based on the least square support vector regression machine is proposed to solve this problem. Furthermore,numerical simulations confirm the effectiveness of our presented scheme. During the process of estimator design,a wrapper criterion that can not only reduce the computational complexity but also enhance the generalization performance is proposed to select variables as input variables for estimator.

基于推力矢量分配的ROV姿态控制技术研究

针对遥控水下机器人(ROV:Remote Operated Vehicle)在水下作业时,传统滑膜控制(SMC:Sliding Mode Control)方法存在抖振、稳定性差等问题,提出一种新型协同控制律,并设计出一种基于推力矢量分配的ROV姿态控制器。首先,建立ROV运动学和动力学模型,并解耦动力学模型;然后,提出了一种新型协同控制律,通过构造适当的宏变量使其呈指数收敛,从而为ROV姿态控制系统提供连续的控制律,达到消除ROV姿态控制系统抖振的目的;最后,采用新型协同控制律设计出基于推力矢量分配的ROV姿态控制器。通过Matlab/Simulink进行仿真,结果表明,所提出的新型协同控制律可提高ROV姿态控制系统的控制精度与稳定性。该控制策略为ROV姿态控制提供了一种新的可行方案。

新型矢量推力八旋翼飞行器的设计与控制

飞行器在物理交互场景中应用广泛,但现有的飞行器及装置在面对大矢量推力应用时,往往难以满足结构和控制简单的要求。为解决这一问题,设计了一种结构简单可行的矢量推力八旋翼飞行器,利用倾斜共轴转子和铰链—同步带的结构,只需一个额外的执行器,即可控制所有转子的倾转角度,从而实现矢量推力,可在物理交互场景中提供足够的横向推力。基于此,设计了对应的位姿控制器,采用SO(3)上的几何控制方法设计了全局稳定的位姿控制器,使用非线性扰动观测器对外部力和力矩进行估计并补偿,以提高整个控制系统的鲁棒性。在MATLAB/Simscape中,进行了飞行器的5D轨迹跟踪、倾转悬停和扰动估计的仿真实验,实验结果充分验证了该飞行器设计的可行性和相应控制算法的有效性。

S弯收扩喷管过膨胀状态下流动分离特性研究

为了研究S弯收扩喷管过膨胀状态下的流动分离特性,数值模拟了不同落压比(NPR)下S弯收扩喷管内的流动特征。结果表明:在落压比为2.0时,喷管内发生非对称分离,出现非对称的双“λ”激波结构,喷流整体向上偏转,上侧出现限制性流动分离RSS,下侧出现自由性流动分离FSS,并产生三维分离涡,喷流出现明显的三维效应。随着落压比从高度过膨胀状态下开始增加,喷管下侧保持FSS不变,喷管上侧RSS逐渐向后移动,直至与外界大气相连,转变为FSS,之后随着落压比增加,上下侧分离结构逐渐对称。推力矢量角随着落压比的增加先增加,后在极小的落压比变化范围内快速降低,直至变为0°,之后保持0°不变。

双喉道推力矢量喷管内外流特性

对二元双喉道推力矢量喷管内流特性进行了研究。针对一种简化的飞机后体模型,利用数值计算与风洞试验结合的方法研究了后机身一体化设计对矢量喷管内外流特性的影响,进一步分析了矢量喷流干扰效应对飞机后体的影响。研究结果表明,气流在喷管空腔内的分离导致了喷管上下壁面的压力差,而该压力差是双喉道喷管推力矢量产生的主要原因;随着二次流流量的增加,喷管上下壁面压差逐渐变大,喷管推力矢量角增加。无来流时,在主喷管落压比NPR=4.0,二次流落压比NPR s=4.8时,双喉道喷管具有的最大矢量角为16.6°;在来流Mach数Ma=0.4时,具有的最大矢量角为11.2°。喷管外罩表面声载荷频率主要集中在900 Hz以下,并且外罩型面变化剧烈处具有最高的噪声幅值。喷流矢量角的变化对噪声峰值频率没有影响,仅对下壁面1000 Hz以下幅值有影响,噪声最大频谱幅值影响量为2 dB。

双轴承旋转喷管型面设计及数值模拟研究

针对短距/垂直起降战斗机高机动飞行的迫切需求及其矢量喷管机械结构复杂笨重的问题,提出了基于轴对称双喉道气动矢量喷管设计的双轴承旋转喷管,通过采用双轴承结构和双喉道气动矢量喷管相结合的方式,减少驱动结构,使喷管能更高效、轻便地实现短距/垂直起降,并且赋予了飞行器平飞模态高机动飞行的潜力。基于典型轴对称双喉道气动矢量喷管构型,开展了双轴承旋转喷管的型面设计和运动规律研究,利用数值模拟开展关键设计参数对喷管流场的影响研究,获得喷管的性能变化规律。结果表明,短距/垂直起降模态下,典型构型的双轴承旋转喷管推力矢量角最大可达108°,满足短距/垂直起降飞行器对喷管的要求。凹腔段的长短轴比值对喷管短距/垂直起降模态的性能影响较大,相同落压比条件下,长短轴比值越大,喷管的总推力系数越低,推力矢量角越大,并且推力矢量角最大差值达到41°。本文所提出的双轴承旋转喷管可为未来具备短距/垂直起降、高机动性能的飞行器动力系统提供一种新的解决方案。

基于改进LADRC的矢量推力双旋翼飞行器姿态控制

针对矢量推力双旋翼无人机姿态控制过程中存在强耦合、模型不精确的问题,提出了一种改进型的线性自抗扰姿态控制(linear active disturbance rejection controller,LADRC)方法。该方法利用改进线性扩张状态观测器(linear extended state observer,LESO)提高对总扰动的实时观测精度,根据姿态角的误差及其变化率引入模糊控制思想对线性状态误差反馈控制律进行在线参数整定,最后以矢量推力双旋翼飞行器为研究对象,对比PID和常规LADRC对外界扰动的抗扰效果,仿真试验验证了该方法能够较好估计补偿系统的总扰动,具有更好的抗扰性能和收敛速度。

关节间隙对矢量喷管调节机构动态特性影响的数值仿真与验证

为研究飞机在不同飞行工况下关节间隙对矢量喷管运动调节机构动态特性的影响,采用第1类拉格朗日方程与混合接触力模型和LuGre摩擦模型相结合的方法,构建了考虑关节间隙和摩擦系数等特征的矢量喷管运动调节机构单叶动力学理论模型,进而构建了整体调节机构的运动学分析模型。结果表明:由于关节间隙的存在,在矢量喷管运动调节机构运动状态突然改变时,初始碰撞阶段调节片的位移几乎不受间隙碰撞的影响,但速度与加速度会产生剧烈且短暂的振动,振动大小受关节间隙影响较大,而间隙对平稳运动时的调节片运动精度几乎不产生影响;整机矢量喷管运动调节机构做收扩运动时,各关节产生的碰撞力几乎相同,做上下偏转运动时,C关节处产生的碰撞力最大,A关节处的受力次之,B和D关节处的受力最小。

基于喷管二次流控制的推力矢量特性研究

通过控制二次流喷口相对位置和宽度来改变喷管出口燃气流动方向是实现推力矢量控制的方法之一。为掌握落压比(NPR)、二次流压比(SPR)以及二次流喷口相对位置(X_(j))和宽度(d)对推力矢量性能的影响,通过数值计算分析了发动机推力矢量角(δ)、推力系数(C_(f))变化规律。结果表明,随着落压比的减小,喷管可以获得更大的推力矢量角度,但推力损失更大;主流落压比不同时,喷管推力矢量效率的最小值所对应的二次流压比不同;随着二次流喷口宽度的增加,喷管的推力矢量角度逐渐增大且随着二次流压比的增大其增幅也随之变大;推力矢量效率在SPR≤0.6时,随着二次流喷口宽度的增大而减小;SPR=0.8后随着二次流喷口宽度的增大先下降后上升,SPR=1.2时随着二次流喷口宽度的增大而增大;随着二次流喷口位置向喷管出口的移动,推力矢量角仅在喷口后的气流分离由闭式变为开式时发生一次突增,而推力系数发生一次突减;随着二次流喷射角度的增大,喷管的推力矢量角度不断增大,喷管的推力系数呈现不断减小的趋势。

三摆臂式扰流片矢量气动力数值仿真研究

为适应智能可控弹药发动机喷口愈来愈小的发展趋势,针对三摆臂式扰流片矢量控制形式开展了气动力数值仿真。研究三摆臂式扰流片推力和侧向力调节能力。结果表明:推力随着主推角的增加而降低,最大推力损失仅与主推角有关;当主推角大于36°,扰流片间的气动干扰增强;侧向力随着侧向角和入口压力的增加而增大;当3个扰流片均位于发动机尾流中,前后方向和左右方向侧向力调节干扰小,且侧向力调节对推力影响小。

正交柔顺矢量测力系统的设计和性能分析

针对多分支正交柔顺矢量测力系统的设计难题,提出了梁连接单元模拟测力元件的方法;采用该方法建立了测力分支及矢量测力系统的有限元模型,并对6种分支形式和平面布局形式进行了结构特点分析。在此基础上,结合矢量测力系统案例,通过有限元模型进行参数详细设计,最终获得了结构紧凑且耦合较小的方案。对台架的3个载荷分量(轴向力、法向力、俯仰力矩)进行了校准试验,其中,校准的不确定度均在0.5%满量程(Full Scale,FS)左右。针对大载荷矢量测力系统加载精度对校准测量的影响较大的问题,提出了基于载荷与测量比值的性能评估方法,采用该方法,得到设计的矢量测力系统的3个分量的测量重复性在0.4%FS左右,大量程测量滞后性在0.7%FS以内。研究成果对于正交矢量测力系统的结构设计和性能分析具有一定的参考意义。

分离线扩张比对超音速分离线摆动喷管流场影响规律的数值与试验研究

为进一步优化超音速分离线摆动喷管性能,通过数值计算分析了分离线处扩张比(ε)对超音速分离线摆动喷管流场的影响规律,并进行了试验验证。结果表明:相同ε下,随着摆动角度(θ)的增加,轴向推力系数(C_(fx))逐渐减小;ε取不同值时,相同θ下C_(fx)区别较大,在ε=1.68时C_(fx)达到最大值。相同ε下,随着θ的增加,偏转放大系数(K)先增加后减小,θ为1°~2°时,K值达到最大(K=2.5);不同ε下K区别较大,当ε≥1.46、θ为1°~8°时,K>1,ε=1.21时偏转效益受θ影响较大,K最小值小于1。数值仿真喷管羽流状态与地面试验一致,验证了仿真方法的有效性;分离线处压强由于模型误差存在一定偏差,摆动力矩由于分离线处压强的非均匀分布存在计算偏差。

电动伺服机构扰动补偿与神经网络模糊控制

针对电动伺服机构的模糊控制与扰动补偿问题进行研究,首先依据动力学理论建立电动伺服机构系统模型并利用Simulink软件搭建仿真模型。然后充分分析了系统所受到的摩擦力矩、齿槽力矩、时滞等非线性扰动,设计前馈控制器进行补偿。其次为了进一步改善系统的控制性能,在位置环PID控制器基础上引入模糊控制来动态调整PID控制参数。最后利用BP神经网络实现对量化因子和比例因子的实时整定,改善由于模糊规则及模糊输出论域的不对称性导致在正负行程上效果不一致的问题。从动态响应能力、跟随性能、抗干扰能力、频域响应等方面分别对传统PID控制器、模糊PID控制器和模糊BP网络PID控制器的控制性能进行仿真对比分析,结果表明模糊BP神经网络PID控制器提高了系统响应速度,改善了系统控制品质,可以为航天电动伺服机构结构和控制器设计提供借鉴。

安装间距和堵塞比对扰流片推力矢量特性影响数值研究

为了获得扰流片参数对推力矢量特性的影响,研究了圆弧凸形扰流片对发动机喷管性能的影响,采用数值方法探讨了扰流片与喷管出口截面之间安装间距、面积堵塞比对推力矢量特性及发动机喷管流场的影响。结果表明:扰流片安装间距增大将导致泄漏流体增多,降低了发动机喷管的推力、总侧向力;在扰流片面积增加的过程中,初期面积堵塞比的增加将导致喷管推力下降,总侧向力得到提升,当继续增加面积堵塞比,喷管推力和总侧向力骤降。此外,增加安装间距对喷管扩张段的马赫数基本没有影响,而增加面积阻塞比使得马赫数的下降位置提前,甚至促使斜激波发展为弓形激波。