Velocity distribution of elliptical galaxies in the framework of Non-local Gravity model

We investigate the velocity distribution of elliptical galaxies in the framework of Non-local Gravity. According to this approach, it is possible to recover the fundamental plane of elliptical galaxies without the dark matter hypothesis. Specifically, we compare theoretical predictions for circular velocity in Non-local Gravity context with the corresponding values coming from a large sample of observed elliptical galaxies. We adopt the surface brightness, effective radius and velocity dispersion as structural parameters for the fundamental plane. As final result, it is possible to show that non-local gravity effects can reproduce the stellar dynamics in elliptical galaxies and fit consistently observational data.     

Linear-quadratic and norm-bounded differential game combined guidance strategy against active defense aircraft in three-player engagement

A new type of guidance strategy, combining linear quadratic and norm-bounded game theory, is proposed for the scenario of an attacker against active defense aircraft in three-player engagement. The problem involves three players, an attacker, a defender and a target. The differential game theory and the solution of Hamiltonian equation are utilized to obtain the combined guidance strategy for each player with arbitrary-order dynamics. The game process is divided into 4 phases, C1-C4, according to the switching time. The linear quadratic differential game guidance scheme is employed to reduce the fuel cost in the game parts of C1 and C3. The norm-bounded game guidance strategy is adopted to satisfy the constraint of control input in the game stages C2 and C4. Furthermore, zero-effort miss distance is introduced to meet the constraints of game space and defender’s killing radius in the guidance strategy, which guarantees that the attacker is able to avoid the interception of the defender and hit the target with lower fuel cost and maximum acceleration. And it is proved that the proposed guidance strategy satisfies the Nash equilibrium condition. Finally, the feasibility and superiority of combined guidance strategy are respectively illustrated by nonlinear numerical simulation and verified by comparing with linear quadratic and norm-bounded differential game guidance strategies.     

Development and coupling test of active spacecraft potential control – Next generation (ASPOC-NG)

The active spacecraft potential control (ASPOC) system developed in the 1990s emits positive ions to neutralise the spacecraft potential, such as used in several missions like Geotail, Equator-S, Cluster, Doublestar and MMS. With the experience gained, the next generation of the active spacecraft potential control (ASPOC-NG) instrument has been developed over the last three years. Thereby, three emission technologies were tested including Liquid Metal Ion Source (LMIS), Liquid Metal Electron Source (LMES) and Solid Metal Electron Source (SMES). The development of the emitter module by FOTEC and the corresponding electronics control unit by IWF is presented. Optimisations were carried out with the focus on the reduction of mass and power consumption to comply with the requirements of future scientific missions. Coupling tests of the modules and the electronics control unit were performed including range, accuracy and lifetime tests. Both ASPOC-NG instruments for positive and negative charge compensation and their performance values show excellent results.     

Experimental study on transfer functions of an active rotor under different flight conditions

Vibrations impose negative impacts on the effectiveness and public acceptance of helicopters. Active rotors with trailing-edge flaps have been proved to be an effective way to actively eliminate helicopter vibrations. For the existing control algorithm based on offline system identification, the transfer functions of an active rotor under different flight conditions are pre-requisites to implement closed-loop vibration control. In this study, a three-bladed active rotor with improved trailing-edge flaps is designed, and wind-tunnel tests are conducted to identify the transfer functions of this active rotor using frequency sweep and phase sweep methods. The experimental results demonstrate that these transfer functions are insensitive to the variation of flight speeds: the amplitude of the transfer function varies slightly, while the phase delay almost remains unchanged. In addition, this finding is validated through closed-loop vibration control tests with the active rotor. The transfer function obtained from the hover test results is also applicable to closed-loop vibration control tests under the forward flight conditions. This will dramatically simplify the implementation and operation of an active rotor.     

Vector deflection stability control of aero-engine based on linear active disturbance rejection

Aimed at the problem of instability in engine control caused by vector deflection in experiment of turbofan engines with Axisymmetric Vectoring Exhaust Nozzle (AVEN), a vector deflection stability control method of aero-engine based on Linear Active Disturbance Rejection Control (LADRC) is proposed. Firstly, based on CFD numerical simulation, aerodynamic performance model of AVEN is established, and the aerodynamic load change rule of the nozzle throat area actuator during vector deflection is revealed. Subsequently, the integrated model of AVEN/turbofan engine is established by Simulink/AMESim co-simulation. Finally, the nozzle throat area control loop based on LADRC is designed. The simulation results show that the integrated model can reflect the influence of vector deflection on the stability of the control system. The accuracy comparison between the fan rotor speed and the test data during vector deflection is larger than 1%, indicating a high degree of confidence. Compared with the conventional PID control, the designed LADRC control loop reduces the speed of the low-pressure rotor during vector deflection by 70%, which effectively improves the control stability of the vector deflection. Meanwhile, the fuel flow ratechange during the vector deflection process is smaller and more economical, which provides an important reference for engineering applications.     

A high-safety active/passive hybrid control approach for compressor surge based on nonlinear model predictive control

Surge active control can expand the stable operating range of the compressor. However, the difficulty of flow measurement, dynamic uncertainty disturbance, actuator delay characteristics, hard constraints of control variable, and system security measures have not been fully considered in the existing active control system, which significantly hinders its engineering application. Therefore, a nonlinear model predictive surge active control method is first presented based on flow estimator designed by using a continuous-time Kalman filter for dealing with the hard constraint of control variable and the impact of actuator delay of compression system with dynamic uncertainty. Then, a high-safety active/surge passive hybrid control strategy is designed, dominated by the surge active control and supplemented by the surge passive control, to ensure the compression system’s safe and stable operation. Lastly, the simulation results suggest that the flow estimator accurately estimates the compressor flow. When considering the delay impact of the actuators and sensors and measurement noise on the system, the proposed method exhibits stronger robustness than the existing methods. The active/surge passive hybrid control strategy can successfully ensure the compression system's safe and stable operation. This paper is of high practical significance for the engineering application of future compressor surge active control technologies.     

Cooperative differential games guidance laws for multiple attackers against an active defense target

This paper is concerned with a scenario of multiple attackers trying to intercept a target with active defense. Three types of agents are considered in the guidance: The multiple attackers, the target and the defender, where the attackers aim to pursuit the target from different directions and evade from the defender simultaneously. The guidance engagement is formulated in the framework of a zero-sum two-person differential game between the two opposing teams, such that the measurements on the m...     

Virtual flight test of pitch and roll attitude control based on circulation control of tailless flying wing aircraft without rudders

Circulation Control(CC) realizes rudderless flight control by driving compressed air jet to generate a virtual rudder surface, which significantly improves low detectability. The layout plan of combined control rudder surface is proposed based on the tailless flying wing aircraft. The closed-loop jet actuator system and stepless rudder surface switching control strategy are used to quantitatively study the control characteristics of circulation actuator for pitch and roll attitude through 3-DOF ...     

大型低温液体火箭“零窗口”发射技术

我国大型低温液体运载火箭组成系统多、各系统耦合关联程度大、射前流程复杂，实现“零窗口”发射难度大。基于大型低温液体运载火箭的系统特点和射前约束条件，提出了实现“零窗口”发射的技术方案。通过能力挖潜主动拓展了任务故障适应性和窗口宽度，并辅以科学的测试发射策略，将技术和流程相结合，共同实现大型低温运载火箭“零窗口”发射目标。这对全面提升大型运载火箭和发射场“零窗口”发射能力、适应未来航天发展需求具有十分重要的意义。     

基于自抗扰的无人机俯仰姿态控制

针对无人机俯仰姿态控制回路在模型参数和复杂外界环境等不确定性干扰影响下鲁棒性差、系统响应速度慢的问题,采用工程上易实现的自抗扰控制(ADRC)方法设计了俯仰姿态控制器,通过构造线性扩张状态观测器(LESO)估计不确定性干扰,并在控制回路中对干扰进行实时补偿.性能分析与仿真结果表明,基于ADRC的无人机俯仰姿态控制器具有良好的性能和干扰抑制能力,并且能够实现对控制指令的精确跟踪.