主要参数对面齿轮传动噪声辐射的影响分析

为研究面齿轮传动力学特性及噪声辐射,通过建立面齿轮传动的弯扭耦合动力学模型,在分析轴承支承处动载荷的基础上,结合有限元法和边界元法,形成了面齿轮传动的噪声辐射计算流程.此外,利用该计算流程,开展了算例分析,讨论了单一几何参数和工况对面齿轮传动噪声辐射的影响规律.仿真结果表明:模数和传动比对改善面齿轮传动噪声辐射有益,压力角对其噪声辐射影响不明显.研究结果为低噪声面齿轮传动的设计奠定了必要的理论基础.      

一种极低载噪比高动态信号跟踪的线性预测器设计

针对深空通信高动态低载噪比微弱信号跟踪精度低、稳态均方性能差的问题,提出了一种高动态低载噪比信号跟踪的分级异构凸组合线性预测器算法,该算法将归一化最小均方算法(NLMS)和最小二乘算法(RLS)进行分级异构凸组合,给出了算法的结构、跟踪精度联合优化设计方案和最优参数选择的方法。在载噪比(CNR)为10~30dB-Hz、载波多普勒频移为-300~300kHz、多普勒频率变化率为-800~1200Hz/s、码速率为20bps条件下对分级异构凸组合线性预测器跟踪性能及跟踪精度指标(归一化均方根误差)进行了仿真。理论分析和仿真结果表明,该线性预测器与分级同构凸组合线性预测器相比,算法运算量减少、信号跟踪精度提高、收敛速度加快。因此,该新型结构线性预测有着良好的应用前景。     

自适应融合IMM的自主无线电载波跟踪算法

针对深空自主无线电接收技术中信噪比(SNR)未知的载波跟踪问题,提出了一种自适应融合的交互式多模型(IMM)算法,可以根据实际环境的信噪比自适应地调节IMM估计器的噪声方差,以实现对未知SNR信号的正常跟踪,并保证频率跟踪精度几乎不受初始噪声方差的影响。在分析系统收敛性的基础上,该算法采用模型概率自适应调整策略,根据系统收敛判断条件自适应地调整IMM模型集中各模型的概率,保证了系统的收敛性,提高了跟踪精度,与广泛使用的Sage-Husa自适应滤波算法相比,收敛时间缩短了一倍左右。     

A new component maps correction method using variable geometric parameters

Accurate engine performance models are important for model-based performance evaluation of aero engine. The accuracy of the model often depends on engine component maps, so there is a need for a method that can accurately correct the component maps of the model over a wide range. In this paper, a new method for modifying component maps is proposed, this method combines the correction of the scaling factors with the solution process of the off-design working point, and uses the adjustment of the variable geometric parameters of the engine to change the position of the working line, in order to obtain more correction results and guarantee high accuracy in a wider range. The method is validated by taking the main fan of the Adaptive Cycle Engine (ACE), an ideal power unit for a new generation of multi-purpose and ultra-wide working range aircraft, as an example. The results show that the maximum error between the corrected component maps and the target maps is less than 1%. New possibility for more precise component maps can be realized in this paper.     

Phase plane design based fast altitude tracking control for hypersonic flight vehicle with angle of attack constraint

In this paper, fast setpoint altitude tracking control for Hypersonic Flight Vehicle (HFV) satisfying Angle of Attack (AOA) constraint is studied with a two-loop structure controller, in the presence of parameter uncertainties and disturbances. For the outer loop, phase plane design is adopted for the simplified model under Bang-Bang controller to generate AOA command guaranteeing fast tracking performance. Modifications based on Feedback-Linearization (FL) technique are adopted to transform the phase trajectory into a sliding curve. Moreover, to resist mismatch between design model and actual model, Fast Exponential Reaching Law (FERL) is augmented with the baseline controller to maintain state on the sliding curve. The inner-loop controller is based on backstepping technique to track the AOA command generated by outer-loop controller. Barrier Lyapunov Function (BLF) design is employed to satisfy AOA requirement. Moreover, a novel auxiliary state is introduced to remove the restriction of BLF design on initial tracking errors. Dynamic Surface Control (DSC) is utilized to ease the computation burden. Rigorous stability proof is then given, and AOA is guaranteed to stay in predefined region theoretically. Simulations are conducted to verify the efficiency and superior performance of the proposed method.     

Adaptive-surrogate-based robust optimization of transonic natural laminar flow nacelle

Natural Laminar Flow (NLF) technology is very effective for reducing the skin friction drag of aircraft engine nacelle, but the aerodynamic performance of NLF nacelle is highly sensitive to uncertain working conditions. Therefore, it’s imperative to incorporate uncertainties into the design of NLF nacelle. In this study, for a robust optimization of NLF nacelle and for improving its efficiency, an adaptive-surrogate-based robust optimization strategy is established, which is an iterative optimization process where the surrogate model is updated to obtain the real Pareto front of multi-objective optimization problem. A case study is carried out to validate its feasibility and effectiveness. The results show that the optimization increases the favorable pressure gradient region and the volume ratio of the nacelle by increasing its lip radius and reducing its maximum diameter. And the aerodynamic robustness of the NLF nacelle is mainly determined by the lip radius, maximum diameter of nacelle and location of the maximum diameter. Compared to the initial nacelle, the optimized nacelle maintains a wide range of low drag and high laminar flow ratio in the disturbance space, which extends the average laminar flow region to 21.6% and facilitates a decrease of 1.98 counts in the average drag coefficient.     

虚拟层次化无线mesh网络信道分配策略

为了获得具备良好的用户分集效果和路由稳定性的无线mesh网络,提出了一种虚拟层次化网络架构.这种无线mesh网络将临近节点聚合为虚拟小区,该小区内部节点不仅能够直接通信,还具有路由转发功能.虚拟小区内部节点之间的连接构成虚拟的底层网络,虚拟小区之间的连接则构成虚拟的顶层网络.为解决虚拟层次化无线mesh网络的信道资源分配问题,提出了一种图着色模型——广义集合T-coloring模型.该模型以虚拟小区为无线信道的分配单位,并采用射频防卫度为无线信道的干扰约束指标,在保证网络连通性的前提下,既降低信道干扰又提高信道利用率.采用虚拟小区分裂方式进一步增加了网络容量也提升了信道分配公平性.仿真结果验证了该策略的有效性.     

三角网格曲面模型快速分层算法

提出一种三角网格曲面模型快速分层算法,该算法基于R*-tree建立三角网格动态空间索引结构,依据索引结构数据结点的分布状况计算各层截平面的位置;采用深度优先遍历方法获取与截平面相交的三角面片集合,并计算该集合中各面片与截平面的交线,将交线首尾相连,生成截面轮廓线,实现三角网格曲面模型的快速分层;实例证明该算法可对各种复杂三角网格曲面模型进行分层,算法准确、稳定,运行效率高.     

考虑特征模型的高超声速飞行器全通道自适应控制

针对高超声速飞行器具有强非线性、高不确定性及强耦合等特点,提出一种基于反馈线性化控制与特征模型自适应控制相结合的姿态控制律设计方法,解决姿态控制系统的非线性耦合与不确定性,保证飞行器控制系统稳定。首先,建立高超声速飞行器全通道非线性耦合的动力学模型。其次,利用反馈线性化控制方法将全通道非线性耦合系统解耦成近似线性系统,并对线性解耦系统设计输出反馈控制律;而对于反馈线性化控制依赖于系统的精确数学模型,并对建模误差和外部干扰敏感的问题,设计基于误差特征模型的自适应控制律,提高系统的适应性;针对原动力学模型,证明闭环控制系统是有界稳定的。最后,通过数学仿真校验了控制律设计的正确性与有效性,仿真结果表明设计的姿态控制系统可以很好地跟踪指令,具有较强的鲁棒稳定性。     

一种拦截机动目标的多导弹协同制导律

针对多导弹协同拦截一个机动目标问题,基于有限时间一致性理论提出了一种带有攻击角约束的多导弹协同制导律。首先建立了带有攻击角约束的多导弹协同制导模型。其次,把协同制导律的设计过程分离为两个部分：一是基于有限时间一致性,同时结合积分滑模和自适应控制设计沿着视线方向上的加速度指令,保证所有的导弹能够在有限时间内同时拦截机动目标;二是利用非齐次干扰观测器并运用滑模控制设计视线法向上的加速度指令来保证每枚导弹与目标间的视线角速率收敛到零和视线角收敛到期望的视线角。最后,对三枚导弹同时打击同一机动目标的情况进行仿真,仿真结果表明该设计的带有攻击角约束的协同制导律的有效性和正确性。