Acceleration of DDT by non-thermal plasma in a single-trial detonation tube

This paper compares the flame acceleration in single-trial dual-detonation tubes triggered by a spark plug and non-thermal plasma igniter. The low-temperature plasma was generated by an in-house novel AC-driven dielectric barrier discharge igniter, which reduces the power supply requirements and was applied in the quiescent ignition of a single-trial detonation tube. Three different types of detonation mixtures were tested with flame propagation tracked by ion probes and pressure waves recorded by high-frequency pressure transducers. The flame propagation speeds were calculated and compared based on signals from the ion probes. The detonation combustion succeeded in the dual tubes, but the deflagration-to-detonation transition could be significantly accelerated by the plasma for all mixtures, as it was shortened by more than 50% compared to that of the spark plug. The present study provides a suitable technological approach for igniters of PDEs.     

鸭式飞机矢量喷流对大迎角气动特性的影响

针对单发鸭式布局飞机，通过低速风洞试验，研究了矢量喷流对飞机大迎角气动力的影响特性。研究结果表明：发动机喷口直径变大使得飞机大迎角升力和阻力系数增加，并产生低头力矩系数。喷流使得飞机大迎角升力和阻力系数明显增加，并产生低头力矩系数；大喷口状态喷流影响比小喷口状态高50%左右。发动机喷管上/下偏转时，矢量喷流对飞机上下表面气流诱导不对称，喷管上偏减小升力和阻力系数、产生抬头力矩系数，喷管下偏增加升力和阻力系数、产生低头力矩系数，且喷管下偏影响明显比上偏大。在此基础上，基于数值模拟结果对喷流与飞机主流的相互作用机理进行了分析。     

相控阵雷达长时跟踪波束调度与波形优化策略

针对相控阵雷达多目标跟踪波束调度和波形参数优化控制的问题，本文提出了一种基于马尔可夫决策过程（MDP）的相控阵雷达跟踪波束调度与波形参数优化策略，该方法以无迹卡尔曼滤波（UKF）算法为基础来估计目标的状态。首先将本文的序列决策问题建模为马尔可夫决策过程，定义了资源的效费比和长期回报率，然后与当前实际跟踪误差综合考虑作为MDP的回报函数，进而给出了调度的优化模型，最后将长时决策问题转化为动态规划算法结构进行求解，并且提出了一种并行混合遗传粒子群优化算法来求解各决策时刻的最优策略。仿真结果表明了长时策略的先进性以及寻优算法的优越性，与传统的短时策略相比，跟踪精度可提高11.17%。     

An improved real-time cycle slip correction algorithm based on Doppler-aided signals for BDS triple-frequency measurements

Doppler, which is an instantaneous GNSS observable signal, has been proven effective in determining velocity and acceleration due to its high availability and accuracy. We propose a real-time triple-frequency cycle slip correction (CSC) method based on Doppler-aided signals because Doppler shift is time-independent and immune to cycle slips. When the sampling interval is less than 1 s, cycle slips on triple-frequency can be detected and repaired using pure Doppler data with high reliability; however, this method cannot be used when the sampling interval exceeds 1 s because the integral cumulative error of Doppler increases significantly. For such cases, a modified triple-frequency CSC approach has been developed based on the raw phase and smoothed code data that was refined using the Doppler signal. To suppress the effect of the integral Doppler error, a balance factor is introduced to adjust the contributions of the raw code and Doppler observables. After the refinement of the GNSS data, three independent combinations need be selected to detect and repair cycle slips with triple-frequency observations. Four constrained criteria have been proposed to select optimal combinations that can reduce the residual ionospheric delay (RID) and measurement noise to a low level. Finally, experiments were carried out to test the performance of the new method using real triple-frequency BDS observations (GPST: 3:15:00–5:55:00, March 23, 2018). The results show that pure Doppler can detect and repair cycle slips effectively with small intervals, and modified Hatch-Melbourne-Wübbena (HMW) method based on Doppler-aided signals can achieve 99.7% success rate in cycle slip correction with large intervals (up to 30 s).     

Analysis of the cylinder block tilting inertia moment and its effect on the performance of high-speed electro-hydrostatic actuator pumps of aircraft

Electro-hydrostatic actuator (EHA) pumps are usually characterized as high speed and small displacement. The tilting inertia moment on the cylinder block produced by the inertia forces of piston/slipper assemblies cannot be ignored when analyzing the cylinder block balance. A large tilting inertia moment will make the cylinder block tilt away from the valve plate, resulting in severe wear and significantly increased leakage. This paper presents an analytical expression for the tilting inertia moment on the cylinder block by means of vector analysis. In addition, a high-speed test rig was built up, and experiments on an EHA pump prototype were carried out at high speeds of up to 10,000 r/min. The predicted nature of the cylinder block tilt at high speeds corresponds closely to the witness marks on the dismantled EHA pump prototype. It is suggested that more attention should be given to the tilting inertia moment acting on the cylinder block of an EHA pump since both wear and leakage flow between the cylinder block and the valve plate are very much dependent on this tilting moment.     

Effects of splined shaft bending rigidity on cylinder tilt behaviour for high-speed electro-hydrostatic actuator pumps

High-speed axial piston pumps are hydraulic power supplies for electro-hydrostatic actuators(EHAs). The efficiency of a pump directly affects the operating performance of an EHA, and an understanding of the physical phenomena occurring in the cylinder/valve plate interface is essential to investigate energy dissipation. The effects of the splined shaft bending rigidity on the cylinder tilt behaviour in an EHA pump need to be considered, because the deflection and radial expansion of a steel shaft rotating at a high speed cannot be ignored. This paper proposes a new mathematical model to predict the cylinder tilt behaviour by establishing a quantitative relationship between the splined shaft deflection, the cylinder tilt angle, and the tilt azimuth angle. The moments exerted by the splined shaft are included in the equilibrium equation of the cylinder. The effects of solid and hollow splined shafts equipped in an EHA pump prototype are compared at variable speeds of 5000–10,000 r/min. With a weight saving of 29.7%, the hollow shaft is experimentally found to have almost no influence on the volumetric efficiency, but to reduce the mechanical efficiency by 0.6–2.4%. The results agree with the trivial differences of the simulated central gap heights of the interface between the two shafts and the enlargement of the simulated tilt angles by the hollow shaft. The findings could guide designs of the cylinder/valve plate interface and the splined shaft to improve both the efficiency and power density of an EHA pump.     

一类有限时间观测器设计及其在飞控系统中的应用

文章针对强可观系统提出了一种有限时间全阶未知输入观测器(Unknown Input Observer,UIO)。首先,设计2个独立的全阶UIO,其特征值满足一定的要求;其次,合并这2个观测器得到新的有限时间观测器,并且能够在预先设定的时间内准确估计出系统状态和未知输入,并借助超螺旋微分器重构了未知输入;最后,用一个飞控系统例子诠释了算法的有效性。     

Adaptive Angular Velocity Tracking Control of Spacecraft with Dynamic Uncertainties

The tracking of orientation and angular velocity is a primary attitude control task for an on-orbit space- craft. The problem for a rigid spacecraft tracking a desired angular velocity profile is addressed using an adaptive feedback control. An angular velocity feedback tracking algorithm is firstly developed based on the precisely known attitude dynamics of the spacecraft, and the global tracking of the control algorithm is proved based on the Lya- punov analysis. An adaptation mechanism is then designed to deal with the dynamic uncertainties of the spacecraft. Such an adaptation mechanism enables the controller to track any desired angular velocity trajectories even in the presence of uncertain inertia parameters, although it does not guarantee the inertia tensor being precisely identified. To verify the effectiveness of the proposed adaptive control policy, computer simulations on dynamic equations of a spacecraft are conducted and their results are discussed.     

最佳平方逼近的异步时钟恢复插值滤波器设计

给出了一种异步时钟恢复的最佳平方逼近插值滤波器设计，该滤波器基于最小平方逼近理论，采用易于硬件实现的Farrow结构；克服了拉格朗日插值滤波器参数固定而窗函数截短插值滤波器结构复杂的问题。对我国航天测控设备的数字化和小型化具有较好的应用价值。     

《儒林外史》及其英译本人称照应衔接手段对比

人称照应衔接手段存在于英汉两种语言中。基于韩礼德的衔接理论,以《儒林外史》及其英译本为例,对比英汉语中人称照应衔接手段的异同,并从意合与形合,螺旋型与直线型及语法化程度对差异进行解释。