脉冲爆震火箭发动机高频实验研究

为了研究脉冲爆震发动机的高频工作特性,以航空煤油和压缩氧气为推进剂,采用爆震增强装置,增大推进剂供给压力以及增大电磁阀控制气压力等措施,在脉冲爆震火箭发动机模型上进行了实验,成功获得45Hz时的爆震压力波形。实验结果表明,频率增高,爆震波峰值压力下降,有利于加速缓燃向爆震的转变(Defla-gration to Detonation Transition,DDT)。当爆震充分发展时,爆震波波速基本不变,峰值压力上升时间趋于定值。工作频率为45 Hz时,爆震波峰值的压力为3.2 MPa,爆震波的波速为1 715.5m/s。     

Multiple model particle flter track-before-detect for range ambiguous radar

The middle pulse repetition frequency（MPRF）and high pulse repetition frequency（HPRF）modes are widely adopted in airborne pulse Doppler（PD）radar systems,which results in the problem that the range measurement of targets is ambiguous.The existing data processing based range ambiguity resolving methods work well on the condition that the signal-to-noise ratio（SNR）is high enough.In this paper,a multiple model particle flter（MMPF）based track-beforedetect（TBD）method is proposed to address the problem of target detection and tracking with range ambiguous radar in low-SNR environment.By introducing a discrete variable that denotes whether a target is present or not and the discrete pulse interval number（PIN）as components of the target state vector,and modeling the incremental variable of the PIN as a three-state Markov chain,the proposed algorithm converts the problem of range ambiguity resolving into a hybrid state fltering problem.At last,the hybrid fltering problem is implemented by a MMPF-based TBD method in the Bayesian framework.Simulation results demonstrate that the proposed Bayesian approach can estimate target state as well as the PIN simultaneously,and succeeds in detecting and tracking weak targets with the range ambiguous radar.Simulation results also show that the performance of the proposed method is superior to that of the multiple hypothesis（MH）method in low-SNR environment.     

基于自适应谱峰搜索的脉冲重复间隔最大似然估计

高精度的脉冲重复间隔（PRI）估计对于提高现代电子情报（ELINT）系统的辐射源识别能力具有重要意义。将观测的脉冲到达时间（TOA）序列建模成点过程信号,其周期图谱谱峰就对应于PRI的最大似然估计（MLE）。本文提出了一个“两步数值搜索”策略,可以确保搜索到谱峰而达到MLE。仿真表明,在低信噪比以及高脉冲丢失率条件下,本文算法性能远超已有算法。     

基于TDOA的非同步照射辐射源定位算法

针对现有基于信号到达时差（TDOA）的定位算法难以适应辐射源信号非同步到达的定位问题,提出了一种新的非同步照射辐射源定位算法。该算法利用脉冲样本图外推各站辐射源脉冲的到达时间（TOA）序列,进而计算TDOA序列（TDOAs）,解决了非同步照射引起的TDOA计算困难问题,通过两条双曲线的渐近线交点求取初值,通过牛顿迭代法实现对辐射源位置的估计。最后给出的数值仿真结果验证了该方法的有效性。     

回流型脉冲爆震燃烧室工作特性分析

为了获得回流型脉冲爆震燃烧室在不同工作频率下的工作特性,通过试验和数值相结合的方法对该爆震室工作频率10~30Hz时的出口燃气总压、总温、流量变化规律以及该爆震室的增压能力进行了测试与计算分析。结果表明：出口燃气总压、总温具有极高的峰值和较高的平台区,其工作频率10~30Hz时,压力平台值为0.36~0.91MPa,时均温度为710~1270K。此外,该爆震室排气流量十分集中,以10Hz为例,在一个爆震循环的16%时间内,排出了整个循环60.5%的燃气。为此对出口燃气总压进行质量加权平均,发现该爆震室的增压比随工作频率的增加而降低,在2.05~2.37。     

Experimental characteristics of a two-electrode plasma synthetic jet actuator array in serial

Plasma Synthetic Jet (PSJ) actuators have shown wide and promising application prospects in high-speed flow control, due to their advantages including high exhaust speed, wide frequency band, rapid response, and non-moving components. Although previous studies on PSJ actuators are abundant, most of them have focused on the performance of a single actuator. However, in practice, an actuator array is very necessary for large-scale aerodynamic actuation on account of the small affected area of a single PSJ. In this paper, the characteristics of a two-electrode plasma synthetic jet actuator array in serial are investigated experimentally. Compared to a parallel actuator array, the serial actuator array requires simpler power supply design and is much easier to realize. High-speed photography of the discharge evolution, voltage-current measurement, and shadowgraphy visualization are used in the investigation. Experimental results show that, for the serial actuator array, weak discharges happen firstly between energized and suspending electrodes, and then a strong pulse arc discharge is triggered. The breakdown voltage in serial is irrelevant to such factors as the number of actuators, the maximum or minimum gap in serial, the connection sequence, etc. It is mainly determined by the sum of gaps. For serial actuators with the same anode-to-cathode spacing, the energy deposition is the same, and the jet is synchronous and similar. Because of the entrainment and merging of adjacent jet vortices, the jet front speed of an aligned synchronous jet array increases as the orifice distance decreases. To achieve the highest jet front velocity, the orifice of the actuator has an optimal diameter.     

基于PWM的挠性航天器分力合成主动振动抑制方法

分力合成主动振动抑制方法可以有效抑制挠性振动. 其利用几个相同或相似的随时间变化的分力, 按一定的规律沿时间轴排列合成为合力作为系统输入, 此合力可以在保证完成规定刚体运动的同时抑制掉指定的任意阶振动谐波. 对于使用常幅值力矩喷气执行机构的航天器, 应用脉宽调制(PWM)技术将符合分力合成方法的时间最优机动控制指令变化为常幅值力矩形式, 设计出常幅值的时间最优大角度机动策略. 数值仿真结果证实了方法的有效性.      

一种采用脉冲调制器的空空导弹直/ 气复合控制系统稳定性研究

研究了一种采用脉冲调制器的空空导弹直/气复合控制系统设计方法及其稳定性。首先假设直接力是连续量,按照比例与气动舵进行混合,采用三回路设计方法得到混合后的控制量,之后采用脉冲调制器对得到的连续量进行调制,得到直接力装置的开关指令,最后采用非线性描述函数法分析控制系统的稳定性,在此基础上选取了合适的脉冲调制器参数,仿真结果表明了该方法的合理性。     

再入飞行器的RCS控制系统设计

针对再入飞行器初始再入段的发动机反作用控制系统(RCS)控制精度问题,提出了一种新型发动机控制方法。首先,将飞行器模型分为慢回路和快回路分别进行控制器设计,采用非线性干扰观测器(DOB)来获取不确定项的估计值,并使用反演法及滑模控制方法设计了飞行器的慢回路和快回路控制律;其次,采用线性规划方法来获取最优RCS指令分配方案;在此基础上,对传统PWPF调制器进行改进,提出了积分补偿型PWPF调制器(IPWPF),采用描述函数法证明了该IPWPF的调制稳定性;最后,通过仿真验证了该方法相比于传统的控制方法具有较高的控制精度。     

雷达测量误差模型的容错检验算法

空间飞行器导航定位的精度及可靠性很大程度上取决于雷达误差修正模型准确与否。以脉冲雷达为研究对象,采用统计假设检验理论,对雷达测量数据有无野值等不同情形,分别建立了误差模型拟合优度F 检验与容错F-检验、模型分量显著性T-检验和容错T-检验算法,并且利用雷达跟踪飞行器的实测数据对算法进行了验证。结果显示,模型拟合优度检验与模型分量显著性检验等系列算法具有良好的容错性和适应性,可用于诊断雷达误差模型是否正确有效。