十字型柔性控制面气动控制力风洞试验验证

现代战争中,战场环境复杂多变,需要弹箭具备快速大角度机动转弯能力。然而,传统的气动舵无法满足弹箭类飞行器超90°的高机动转弯需求。本文创新性地提出了一种新型柔性控制机构--大尺度可展开可变构型的十字型柔性控制面,用于产生超量气动控制力,实现弹箭的迅捷机动转弯;同时对一个缩比1∶5的可变构型十字型柔性控制面所产生的气动控制力进行了风洞试验。试验结果显示,通过在不同挂载点位收缩控制绳的方式下,相比于没有构型改变的对称构型十字型柔性控制面,改变构型的十字型柔性控制面可以基本稳定在收缩控制绳的挂载点位一侧,不再出现旋转、摆动,这一结果说明改变构型的十字型柔性控制面可以产生较稳定的径向控制力;对变构型的十字型柔性控制面的气动控制力测量值进行定量分析,进一步确认了柔性面气动控制力的指向性;在来流Re≈2.3×10^(5),控制绳收缩比为0.9的情况下,产生了气动力系数为0.29~0.34的可用径向控制力。研究结果确认了变构型十字型柔性面控制力的可用性,为进一步研究柔性控制力的气动特性、变构型控制策略设计提供了基础。

ANALYSIS AND SIMULATION OF CONTROL MIXER CONCEPT FOR A CONTROL RECONFIGURABLE AIRCRAFT

In today's aircraft,the hardware redundancy is driven by the critical surfaces resulting in single point-failures.Reconfiguration technology remoVes the single surface criticality by employing control surfaces with aerodynamic redundancy.This paper studies a control reconfiguration scheme based on Control Mixer Concept.A technique for the design of a control mixer for an aircraft with damaged surfaces/actuators using the pseudo-inverse is developed and applied.This paper discusses its applications and limitations based on linear analysis and computer simulation.

Review on development progress of automatic manual transmissions control

In recent years, the sustainable development of automatic manual transmissions (AMTs) control in vehicles is conspicuous. The control applications have grown fast and steadily due to the tremendous progress in power electronics components and the control software that enhance the requirements for delivering higher vehicles performance. AMTs control strategies achieve a reduction in the driveline dynamic oscillations behavior during gear shifting and clutch starting up processes. AMTs future expectations are an increase of torque capacity, more speed ratios and the development of advanced and efficient electronic control systems. This paper concerns with the progressing view of AMTs in the past, today and future, gives an overview of the potential dynamic problems concerned with AMTs and some control strategies used to solve those problems.

An Improved Nonlinear Dynamic Inversion Method for Altitude and Attitude Control of Nano Quad-Rotors under Persistent Uncertainties

Nonlinear dynamic inversion(NDI)has been applied to the control law design of quad-rotors mainly thanks to its good robustness and simplicity of parameter tuning.However,the weakness of relying on accurate model greatly restrains its application on quad-rotors,especially nano quad-rotors(NQRs).NQRs are easy to be influenced by uncertainties such as model uncertainties(mainly from complicated aerodynamic interferences,strong coupling in roll-pitch-yaw channels and inaccurate aerodynamic prediction of rotors)and external uncertainties(mainly from winds or gusts),particularly persistent ones.Therefore,developing accurate model for altitude and attitude control of NQRs is difficult.To solve this problem,in this paper,an improved nonlinear dynamic inversion(INDI)method is developed,which can reject the above-mentioned uncertainties by estimating them and then counteracting in real time using linear extended state observer(LESO).Comparison with the traditional NDI(TNDI)method was carried out numerically,and the results show that,in coping with persistent uncertainties,the INDI-based method presents significant superiority.

Modeling and analysis of moving-mass actuated stratospheric airship

A moving-mass control method is introduced to stratospheric airship for its special working condition of low atmospheric density and low speed.The dynamic equation of airship is derived by using the Newton-Euler method and the mechanism of attitude control by moving masses is studied.Then the passive gliding of airship by the moving masses is given based on the theory of glider,and attitude control capability between moving mass and elevator is compared at different airspeed.Analysis results show that the motion of masses changes the gravity center of the airship system,which makes the inertia tensor and the gravity moment vary.Meanwhile,the aerodynamic angles are generated,which results in the change of aerodynamic moment.Control efficiency of moving masses is independent of airspeed.Thus the moving-mass control has the advantage over the aerodynamic surfaces at low airspeed.

CO2 emission driving forces and corresponding mitigation strategies under low-carbon economy mode:evidence from China's Beijing-Tianjin-Hebei region

On account of the background of China's "new normal" characterized by slower economic growth, this paper analyses the low-carbon economy status quo in the Beijing-Tianjin-Hebei region and empirically investigates the relationship between carbon dioxide(CO_2) emissions and its various factors for China's Beijing-Tianjin-Hebei region using panel data econometric technique. We find evidence of existence of Environmental Kuznets Curve. Results also show that economic scale, industrial structure, and urbanization rate are crucial factors to promote CO_2emissions. However, technological progress, especially the domestic independent research and development, plays a key role in C0_2 emissions abatement. Next, we further analyze the correlation between each subregion and various factors according to Grey Relation Analysis. Thereby,our findings provide important implications for policymakers in air pollution control and C0_2 emissions reduction for this region.

Modeling and control of MR damper considering trapped air effect

Due to the high viscosity of magnetorheological(MR)fluid,eliminating air pockets dissolved in the fluid is very difficult,which results in a force lag phenomenon.In order to evaluate the performance of a semi-active control system based on the MR damper considering the trapped air effect,a performance test on a MR damper is carried out under different loading cases,and the influence of the input current,excitation amplitude and frequency on the force lag phenomenon is analyzed.A concise and efficient parametric model,combining the simple Bouc-Wen model and a spring with small stiffness,is proposed to portray the experimental characteristics of the MR damper with force lag,and then the response analysis of the semi-active controlled single-degree-of-freedom(SDOF)structure is performed using the classic clipped-optimal control strategy based on acceleration feedback.Numerical results show that the trapped air in the MR fluid can weaken the control effect of the MR damper,and the performance of the semi-active control system will be reduced more obviously and become close to the passive-off control with the increasing content of air trapped in the MR fluid.

The State of Arts of Hall Thruster

Electric propulsion is broadly defined as the acceleration of a working fluid for propulsion by electrical heating and/or by electric and magnetic body forces. Compared with chemical propulsion, electric propulsion has the characteristic of higher specific impulse, lower thrust, lighter weight and longer lifetime. So electric propulsion is generally suitable for satellite attitude control, the orbit transfer and raising, orbit correction, resistance compensate, position keeping, reposi- tion, space exploration and interplanetary flight.

Dissolution-filling mechanism of atmospheric precipitation controlled by both thermodynamics and kinetics

Affected by structural uplift, the Ordovician carbonate rockbed in the Tarim Basin, China, was exposed to dissolution and reformation of atmospheric precipitation many times, and formed a large quantity of karst caves serving as hydrocarbon reser- voir. However, drilling in Tahe area showed that many large karst caves, small pores and fractures are filled by calcite, result- ing in decrease in their reservoir ability. Calcite filled in the karst caves has very light oxygen isotopic composition and STSr/S（＇Sr ratio. Its c^OpDB ranges from -21.2%o to 13.3%o with the average of -16.3%e and its 87Sr/86Nr ratio ranges from 0.709561 to 0.710070 with the average of 0.709843. The isotope composition showed that calcite is related to atmospheric precipitation. Theoretic analyses indicated that the dissolving and filling actions of the precipitation on carbonate rocks are controlled by both thermodynamic and kinetic mechanisms. Among them, the thermodynamic factor determines that the pre- cipitation during its flow from the earth surface downward plays important roles on carbonate rocks from dissolution to satura- tion, further sedimentation, and finally filling. In other words, the depth of the karstification development is not unrestricted, but limited by the precipitation beneath the earth surface. On the other hand, the kinetic factor controls the intensity, depth, and breadth of the karstification development, that is, the karstification is also affected by topographic, geomorphologic, climatic factors, the degree of fracture or fault, etc. Therefore, subject to their joint effects, the karstification of the precipitation on the Ordovician carbonate rocks occurs only within a certain depth （most about 200 m） under the unconformity surface, deeper than which carbonate minerals begin to sedimentate and fill the karst caves that were formed previously.

The Effect of Variable Stator on Performance of a Highly Loaded Tandem Axial Flow Compressor Stage

Increasing the aerodynamic load on compressor blades helps to obtain a higher pressure ratio in lower rotational speeds. Considering the high aerodynamic load effects and structural concerns in the design process, it is possible to obtain higher pressure ratios compared to conventional compressors. However, it must be noted that imposing higher aerodynamic loads results in higher loss coemcients and deteriorates the overall performance. To avoid the loss increase, the boundary layer quality must be studied carefully over the blade suction surface. Employment of advanced shaped airfoils （like CDAs）, slotted blades or other boundary layer control methods has helped the de- signers to use higher aerodynamic loads on compressor blades. Tandem cascade is a passive boundary layer control method, which is based on using the flow momentum to control the boundary layer on the suction surface and also to avoid the probable separation caused by higher aerodynamic loads. In fact, the front pressure side flow momentum helps to compensate the positive pressure gradient over the aft blade＇s suction side. Also, in compari- son to the single blade stators, tandem variable stators have more degrees of freedom, and this issue increases the possibility of finding enhanced conditions in the compressor off-design performance. In the current study, a 3D design procedure for an axial flow tandem compressor stage has been applied to design a highly loaded stage. Following, this design is numerically investigated using a CFD code and the stage characteristic map is reported. Also, the effect of various stator stagger angles on the compressor performance and especially on the compressor surge margin has been discussed. To validate the CFD method, another known compressor stage is presented and its performance is numerically investigated and the results are compared with available experimental results.

Studies on aeroservoelasticity semi-physical simulation test for missiles

Missiles may be damaged when aeroservoelastic problem occurs,which is caused by the interaction of structure flexibility and flight control system.Because of the limit of wind tunnel test condition,numerical methods are mostly used in previous aeroservoelastic studies.However,series of assumptions and simplification on structures,aerodynamics and flight control systems are unavoidably introduced,and various nonlinear factors are also ignored,therefore,they result in considerable errors.A novel method called aeroservoelasticity semi-physical simulation test is proposed in this paper,which takes the flexible missile with control system as the test object.Vibration signals at several locations of the missile are measured by accelerometers,then corresponding unsteady aerodynamics is computed based on the fact that airflow at high Mach is nearly quasi-steady,and finally unsteady aerodynamics is exerted simultaneously by shakers at certain locations of the missile.The aeroservoelasticity semi-physical simulation test system can be constructed after the control system is closed.Open loop transfer function test and closed loop stability test are carried out in sequence.The test principle and method proposed in this paper are verified by the concordance between the results of numerical simulation and experiment.

A Study of Maneuvering Control for an Air Cushion Vehicle Based on Back Propagation Neural Network

A back propagation （BP） neural network mathematical model was established to investigate the maneuvering control of an air cushion vehicle （ACV）. The calculation was based on four-freedom-degree model experiments of hydrodynamics and aerodynamics. It is necessary for the ACV to control the velocity and the yaw rate as well as the velocity angle at the same time. The yaw rate and the velocity angle must be controlled correspondingly because of the whipping, which is a special characteristic for the ACV. The calculation results show that it is an efficient way for the ACV＇s maneuvering control by using a BP neural network to adjust PID parameters online.

Lift enhancement method by synthetic jet circulation control

A novel circulation control technique is proposed to overcome the shortcomings of blowing jet circulation control, which uses the synthetic jet as the actuator and avoids the limitation about air supply requirement. The effectiveness of synthetic jet circulation control to enhance lift of NCCR1510-7067N airfoil is confirmed by solving the 2-D unsteady Reynolds-averaged Na- vier-Stokes equations. The aerodynamic characteristics and the flow structure （especially close to the trailing edge） of NCCR 1510-7067N airfoil at zero angle of attack are also presented to discuss the mechanism of lift enhancement of the airfoil with synthetic jet circulation control. The results indicate that the synthetic jet can effectively delay the separation point on the airfoil trailing edge and increase the circulation and lift of the airfoil by Coanda effect. The numerical simulation results demonstrate that the lift augmentation efficiency with synthetic jet circulation control reaches △C1/Cμ,=114 in the present study, which is much higher than the value 12.1 in the case with steady blowing jet circulation control.

Dielectric barrier plasma dynamics for active aerodynamic flow control

The paper investigates the dynamics of a new multiple bipolar multiple Dielectric Barrier Discharges(DBD)actuator using in large-scale flow control.Particle image velocimetry experiments are performed to characteristic the effectiveness of the multiple bipolar DBD plasma actuator.The results show that the mutual interaction between the electrodes,one major disadvantage of traditional DBD characterized by reverse discharge can be entirely avoided,and a constantly accelerating electric wind velocity can be obtained by using the new multiple bipolar DBD plasma actuator.

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.

Dynamic behaviors of cavitation bubble for the steady cavitating flow

In this paper, by introducing the flow velocity item into the classical Rayleigh-Plesset dynamic equation, a newequation, which does not involve the time term and can describe the motion of cavitation bubble in the steadycavitating flow, has been obtained. By solving the new motion equation using Runge-Kutta fourth order methodwith adaptive step size control, the dynamic behaviors of cavitation bubble driven by the varying pressure fielddownstream of a venturi cavitation reactor are numerically simulated. The effects of liquid temperature (correspondingto the saturated vapor pressure of liquid), cavitation number and inlet pressure of venturi on radial motionof bubble and pressure pulse due to the radial motion are analyzed and discussed in detail. Some dynamicbehaviors of bubble different from those in previous papers are displayed. In addition, the internal relationshipbetween bubble dynamics and process intensification is also discussed. The simulation results reported in thiswork reveal the variation laws of cavitation intensity with the flow conditions of liquid, and will lay a foundationfor the practical application of hydrodynamic cavitation technology.

Control of dynamic stall of helicopter rotor blades

An effective method for delaying the dynamic stall of helicopter retreating blade by using the trailing edge flap has been established in this paper.The aerodynamic loads of blade section are calculated by using the Leishman-Beddoes unsteady two-dimensional dynamic stall model and the aerodynamic loads of the trailing edge flap section are calculated by using the Hariharan-Leishman unsteady two-dimensional subsonic model.The analytical model for dynamic stall of elastic blade with the stiff trailing edge flap has been established.Adopting the aeroelastic analytical method and the Galerkin's method combined with numerical integration,the aeroelastic responses of rotor system in high-speed and high-load forward flight are solved.The mechanism for control of dynamic stall of retreating blade by using trailing edge flap has been presented.The numerical results indicate that the reasonably controlled swing of trailing edge flap can delay the dynamic stall of retreating blade under the same flight conditions.

Aerodynamic airfoil design using the Euler equations based on the dynamic evolution method and the control theory

Based on the idea of adjoint method and the dynamic evolution method,a new optimum aerodynamic design technique is presented in this paper.It can be applied to the optimum problems with a large number of design variables and is time saving.The key of the new method lies in that the optimization process is regarded as an unsteady evolution,i.e.,the optimization is executed,simultaneously with solving the unsteady flow governing equations and adjoint equations.Numerical examples for both the inverse problem and drag minimization using Euler equations have been presented,and the results show that the method presented in this paper is more efficient than the optimum methods based on the steady flow solution and the steady solution of adjoint equations.

Experimental and Analytical Analysis of Perforated Plate Aerodynamics

Perforated walls and transpiration flow play an important role in aerodynamics due to an increasing interest in application of flow control by means of blowing and/or suction. An experimental study was carried out which has led to the determination of a transpiration flow characteristics in the form of a simple formula that is very useful in modelling such flows. In connection to this relation a method of 'aerodynamic porosity' determination has been proposed which is much more reliable than geometric description of the porosity. A theoretical analysis of the flow through a perforation hole was also carried out. The flow was considered as compressible and viscous. The gasdynamic analysis led us to a very similar result to the relation obtained from the experiment. The adequacy of the theoretical result is discussed in respect to the experiment.

Counter Rotating Fans- An Aircraft Propulsion for the Future?

In the mid seventies a new propulsor for aircraft was designed and investigated - the so-called PROPFAN. With regard to the total pressure increase, it ranges between a conventional propeller and a turbofan with very high bypass ratio. This new propulsion system promised a reduction in fuel consumption of 15 to 25% compared to engines at that time.A lot of propfans (Hamilton Standard, USA) with different numbers of blades and blade shapes have been designed and tested in wind tunnels in order to find an optimum in efficiency, Fig.1. Parallel to this development GE, USA, made a design of a counter rotating unducted propfan, the so-called UDF, Fig.2. A prototype engine was manufactured and investigated on an in-flight test bed mounted at the MD82 and the B727. Since that time there has not been any further development of propfans (except AN 70 with NK 90-engine, Ukraine, which is more or less a propeller design) due to relatively low fuel prices and technical obstacles. Only technical programs in different countries are still going on in order to prepare a data base for designing counter rotating fans in terms of aeroacoustics, aerodynamics and aeroelasticities. In DLR, Germany, a lot of experimental and numerical work has been undertaken to understand the physical behaviour of the unsteady flow in a counter rotating fan.