超临界机翼多目标气动优化设计的策略与方法

超临界机翼的气动设计十分复杂,往往需要借助于有效的优化手段。然而,优化方法本身往往无法直接表达真实完整的设计意图,因此需要将工程需求和约束转换为优化方法所能处理的数学形式。本文首先探讨了梯度优化方法和进化类优化方法在气动优化中的表现。之后简要总结了前人在飞机气动设计中提出的准则和要求,并基于压力分布形态定义了超临界机翼气动设计的关键特征及定量要求,探究其在超临界机翼气动优化设计中的应用效果。研究结果表明,在多目标优化中引入面向压力分布形态特征的目标和约束,能有效引导优化体现工程设计思想,进而提高优化效率。     

Numerical simulation of compression corner flows at Mach number 9

A hypersonic vehicle encounters a wide range of conditions during its complete flight regime. These flight conditions may vary from low to high Mach numbers with varying angles of attack. The near-wall viscous dissipation associated with flows at combined high Mach and Reynolds numbers leads to significant wall heat transfer rates and shear stresses. The shock wave/boundary-layer interaction results in a flow separation region, which commonly augments total pressure losses in the flow and lowers the efficiency of aerodynamic control surfaces such as fins installed on a vehicle. The standard turbulence models, when used to resolve such flows, result in incorrect separation bubble size for large separated flows. Therefore, it results in an inaccurate aerodynamic load, such as the wall pressures, skin friction distribution, and heat transfer rate. In previous studies, the application of the shock-unsteadiness correction to the standard two-equation k-ω turbulence model improved the separation bubble size leading to an accurate pressure prediction and shock definition with the assumption of constant Prandtl number. In the present work, the new shock-unsteadiness modification to the k-ω turbulence model is applied to the hypersonic compression corner flows. This new model with variable Prandtl number is based on the model parameter, which depends upon the local density ratio. The computed wall pressures, heat flux and flow field are compared to the experimental data. A parametric study is carried out by varying compression deflection angles, free stream Reynolds number and wall temperatures to compute the flow field and wall data accurately, particularly in the shock boundary layer interaction region. The new shock-unsteadiness modified k-ω model with variable Prandtl number shows an accurate prediction of initial pressure rise location, pressure distribution in the plateau region and heat flux in comparison to the standard k-ω model.     

Effective control allocation using hierarchical multi-objective optimization for multi-phase flight

For different flight phases in an overall flight mission, different control and allocation preferences should be pursued considering lift, drag or maneuverability characteristics. The multi-objective flight control allocation problem for a multi-phase flight mission is studied. For an overall flight mission, different flight phases namely climbing, cruise, maneuver and gliding phases are defined. Firstly, a multi-objective control allocation problem considering drag, lift or control energy preference is constructed. Secondly, considering different control preferences at different flight phases, the analytic hierarchical process method is used to construct a comprehensive performance index from different objectives such as lift or drag preferences. The active set based dynamic programming optimization method is used to solve the real-time optimization problem. For the validation, the Innovative Control Effector (ICE) tailless aircraft nonlinear model and the angular acceleration measurements based adaptive Incremental Backstepping (IBKS) are used to construct the validation platform. Finally, an overall flight mission is simulated to demonstrate the efficiency of the proposed multi-phase and multi-objective flight control allocation method. The results show that the comprehensive performance index for different phases, which are determined from the Analytic Hierarchy Process (AHP) method, can suitably satisfy the preference requirements for different flight phases.     

全电推进卫星小推力变轨策略星上计算方法研究

全电推进卫星星上自主变轨,是全电推进卫星重要的发展方向。为了获得运算量小、计算简单、可以星上计算且变轨时间最短的小推力变轨策略,研究了Lyapunov反馈制导律和推力矢量分段固定法两种方法。基于Lyapunov反馈制导律的变轨策略,权重系数在地面进行优化,推力指向星上实时计算,在标称任务工况下变轨时间比理论最优解加长8.18%。推力矢量分段固定法变轨策略更为简单,每10天星上对两个关键控制参数Ψ1,Ψ2进行修正,推力指向变化规律恒定,变轨时间比理论最优解加长7.43%。两种方法都具有任务适应性好和计算简单的优点,Lyapunov反馈制导律对姿态控制能力要求较高,推力矢量分段固定法姿态控制要求容易满足,后者更适合于卫星应用。     

主惯导速度误差短周期波动对子惯导传递对准影响分析

随着激光陀螺技术的发展,旋转调制式激光陀螺惯性导航系统逐渐成为舰载主惯导系统,舰载机、舰载武器系统需要旋转调制式激光惯导系统提供的姿态、速度和位置信息进行对准,即主子惯导的传递对准。由于旋转调制式系统中的姿态、速度和位置具有随旋转的短周期波动问题,势必会影响对准时间较短的子惯导对准精度。为了保证传递对准的快速性,一般采用速度匹配方法。定量分析了主子惯导传递对准过程中主惯导速度误差短周期波动对子惯导系统对准精度的影响,首先进行了数字仿真,之后利用双轴激光陀螺惯导、纯捷联光纤陀螺惯导数据进行了半实物仿真,验证了主惯导速度误差的一次项系数与子惯导初始对准水平姿态误差呈线性关系,二次项系数与子惯导初始对准航向误差呈线性关系。     

连续下降运行中的飞行冲突预测与解脱算法

针对连续下降运行（Continuous descent operation,CDO）中的航空器冲突预测与解脱策略问题,构建了四维航迹（Four-dimensional trajectory,4DT）预测模型,实现飞行冲突的准确预测;以燃油消耗量、冲突时长为优化目标,以航空器在连续下降运行时的飞机速度、下降轨迹角（Descent path angle,DPA）为优化变量,基于多目标遗传算法NSGA-Ⅱ实现飞行冲突解脱。最后以某终端区内多机CDO飞行为例进行冲突预测和解脱,分析了优化目标权重系数对空域内平均耗油量和优化变量影响。结果表明,给出的解脱算法可以实现终端空域内的多机无冲突连续下降运行。与优化前相比,20架飞机的平均耗油节约了11 kg/架,空域内飞机之间的飞行冲突累积时间从984 s减少到0,即消除了飞行冲突。研究结果有助于实现空域内多机无冲突连续下降运行,提高CDO在繁忙机场的实施率和运行效果。     

一种喷口控制的多目标约束设计方法

为克服试凑法在控制回路参数优化中的局限性,针对涡扇发动机在加力状态易出现喷口摆动的不协调现象,考虑喷口双环控制结构工作特点,采用按需正向设计策略,按照控制系统时域、频域性能指标设计要求,制定兼顾频域、时域性能要求的内、外环协调控制的设计目标准则,提出一种喷口控制的多目标约束的差分进化内外环控制参数自整定优化设计方法,在双转子涡扇发动机非线性模型上进行闭环控制系统仿真验证。结果表明：在飞行高度从0增加到10 km、飞行马赫数从0加速到0.9的起飞和爬升状态进入加力过程以及平飞中保持飞行马赫数不变的关断加力过程中,发动机未出现喷口摆动等现象,涡轮落压比最大相对误差不大于1.5%,喷口闭环控制系统具有期望的伺服跟踪和抗飞行条件变化干扰能力。     

随机型多目标决策的新方法

设计了一种多目标随机型决策分析新方法——交互式参考目标满足度与可行度法(IRGSD-FD),讨论了随机型决策分析的希望水平原则、解及替代模型的定义和确定性等价等问题,并对IRGSD-FD的应用结果进行了讨论。     

具有环路复现特性的Luenberger观测器设计(二)

从一个一般的环路传递复现(Loop transfer recovery)条件出发,基于线性系统Luenberger函数观测器设计的一种参数化方法,给出了具有环路复现特性的Luenberger观测器设计的一种方法。该方法适用范围广,且具有较小的保守性。数值算例说明了共有效性。