Aerodynamic optimization and mechanism design of flexible variable camber trailing-edge flap

Trailing-edge flap is traditionally used to improve the takeoff and landing aerodynamic performance of aircraft.In order to improve flight efficiency during takeoff,cruise and landing states,the flexible variable camber trailing-edge flap is introduced,capable of changing its shape smoothly from 50% flap chord to the rear of the flap.Using a numerical simulation method for the case of the GA(W)-2 airfoil,the multi-objective optimization of the overlap,gap,deflection angle,and bending angle of the flap under takeoff and landing configurations is studied.The optimization results show that under takeoff configuration,the variable camber trailing-edge flap can increase lift coefficient by about 8% and lift-to-drag ratio by about 7% compared with the traditional flap at a takeoff angle of 8°.Under landing configuration,the flap can improve the lift coefficient at a stall angle of attack about 1.3%.Under cruise state,the flap helps to improve the lift-todrag ratio over a wide range of lift coefficients,and the maximum increment is about 30%.Finally,a corrugated structure–eccentric beam combination bending mechanism is introduced in this paper to bend the flap by rotating the eccentric beam.     

智能滑模变结构制导律

基于零化反导导弹的脱靶量,用变结构控制理论和非线性运动学方程推导了一种能适应目标作大机动的滑模变结构制导律。设计了一种新颖的模糊逻辑控制器,通过嵌入专家经验,实现了导引律系数的智能改变,建立了目标作螺旋机动的数学模型。末制导仿真结果表明：智能滑模变结构制导律在拦截三维螺旋机动目标时具有响应快速性,视线角速率和脱靶量较小,对高速大机动目标有较好的拦截效果。     

多星发射上面级姿态变结构控制方法研究

根据上面级飞行器存在强控制耦合和惯量耦合特性,基于上面级刚体姿态动力学简化模型,由变结构控制理论设计了上面级姿态控制律。采用趋近律减轻变结构控制引起的系统抖振。仿真结果表明：设计的控制律可自动适应强耦合对象特性,具强鲁棒性,使系统在有限时间收敛、精确跟踪。     

离心式压气机耦合松弛多学科设计优化方法

为提高多学科设计优化的寻优效率,以离心式压气机为对象,开展了耦合松弛多学科设计优化方法的研究.针对松散耦合方法建立的离心式压气机的流-热-固耦合分析模型,为了避免反复迭代导致的分析、优化时间过长,构建了分层次的离心式压气机耦合松弛优化设计系统.在气动优化中采用全局寻优算法探索系统最优气动设计方案;在耦合优化阶段,综合考虑学科间耦合及相互作用,在气动优化的基础上局部寻优校验气动优化结果并得到最终设计方案.这种不同复杂层次模型的优化设计有效缩减了系统优化设计周期.     

高超声速飞行器耦合系统变结构控制设计

为了解决高超声速飞行器耦合系统控制问题,将上述耦合系统表示成具有非匹配不确定性的关联大系统形式。利用关联大系统的Lyapunov稳定理论及其Riccati方程设计滑动模态及变结构控制。采用Lyapunov方法证明设计的变结构控制使得滑动模态满足可达条件,且关联大系统全局结构渐近稳定。根据Frobenius\|Perron定理得出控制器参数选择算法。最后对于所设计的控制系统在高超声速下的倾斜转弯运动进行了仿真验证。仿真结果表明该控制系统满足高超声速飞行器稳定飞行要求。
     

流体式高超声速可调进气道流动机理及工作特性分析

针对基于二次流控制的定几何高超声速可调进气道设计概念,给出了其具体的流道实现方案,而后通过全流道仿真分析,检验了该可调进气道在马赫数4~6范围内的可实现性,获得了其工作特性,并对弯曲激波后的总压损失特性、二次流的能量获取及消耗机制等流动机理进行了专门分析。结果表明：该流体式可调进气道能够依靠自身高压驱动二次流来实现对口部波系的调节,使进气道在低马赫数下的流量系数相对于常规定几何高超声速进气道提高24%以上,总压恢复提高7%左右,且最大二次流消耗量只占了进气道捕获流量的1.6%左右。另外,虽然弯曲激波的波后总压和马赫数分布表现出了一定的不均匀性,但是其平均总压恢复系数与相同倾角平面激波相比下降不大。二次流循环流动所消耗的机械能由外部外流剪切力做功补充,而二次流注入会使当地边界层的速度型变得瘦弱,形状因子增大。     

带变速控制力矩陀螺的航天器自适应姿态控制

航天器高精度姿态控制容易受到参数误差的影响,自适应控制能够合理地估计参数,使基于模型的控制器设计易于实现。自适应参数分为主星体惯量、变速控制力矩陀螺框架转子惯量及动摩擦系数3组,按参数分组对带变速控制力矩陀螺的航天器详细动力学模型进行变换,采用Lyapunov方法设计出姿态控制器、变速控制力矩陀螺群操纵律及参数自适应更新律,操纵律中引入加权矩阵以缓解陀螺奇异问题。理论分析和数值仿真表明闭环姿态控制系统全局一致最终有界稳定,参数自适应更新能有效减小角速度跟踪误差,使姿态四元数误差收敛更快。参数估计虽然不能准确收敛到其真值上,但均在可接受的范围内。     

基于拟欧拉角描述的上面级姿态控制律设计

上面级在多星部署过程中将涉及大角度姿态机动问题,卫星释放所引起的质心横移将给上面级姿态控制带来困难。根据系统质心的横移情况,在上面级体坐标系中确定矢量喷管的平衡位置,进而确定出矢量喷管指向指令方向时的上面级姿态。调制姿态四元数可以得到描述上面级姿态偏差的拟欧拉角及相应的拟欧拉角速度,在拟欧拉角描述的上面级姿态运动模型的基础上,选择合适的滑模面,构造变结构控制律。仿真结果表明,该控制律可对上面级姿态进行控制,进而实现对矢量喷管指向的间接控制,喷管摆角的限幅不会影响姿态控制的过程。     

Electrochemical machining on blisk channels with a variable feed rate mode

Electrochemical machining (ECM) is an economical and effective method for blisk manufacturing and includes two steps: channel machining and profile machining. The allowance distribution after the channel machining will directly affect the profile machining. Therefore, to improve the uniformity of allowance distribution in the machining of channels, a method that incorporates a variable feed rate mode is developed. During the machining process, the feed rates are dynamically changed according to the needs of the side gap at the different feed depths. As a result, the side gaps at the different feed depths vary, contributing to a decrease in the allowance difference. In this study, the dissolution processes of a blisk channel are simulated using different feed rates, and prediction profiles are obtained. Based on the prediction profiles, the relationship among the feed rate, feed depth, and side gap is established. Then, the feed rates at different feed depths are adjusted according to the relationship. In addition, contrast experiments are conducted. Compared with blisk channel ECM using a constant feed rate of 1 mm/min, using the variable feed rate decreases the allowance differences in the convex and concave parts by 62.2 % and 67.4 %, respectively. This indicates that using the variable feed rate in the ECM process for a blisk channel is feasible and efficient.     

Morphing wing flaps for large civil aircraft: Evolution of a smart technology across the Clean Sky program

Morphing wing structures are widely considered among the most promising technologies for the improvement of aerodynamic performances in large civil aircraft. The controlled adaptation of the wing shape to external operative conditions naturally enables the maximization of aircraft aerodynamic efficiency, with positive fallouts on the amount of fuel burned and pollutant emissions. The benefits brought by morphing wings at aircraft level are accompanied by the criticalities of the enabling technologies, mainly involving weight penalties, overconsumption of electrical power, and safety issues. The attempt to solve such criticalities passes through the development of novel design approaches, ensuring the consolidation of reliable structural solutions that are adequately mature for certification and in-flight operations. In this work, the development phases of a multimodal camber morphing wing flap, tailored for large civil aircraft applications, are outlined with specific reference to the activities addressed by the author in the framework of the Clean Sky program.The flap is morphed according to target shapes depending on aircraft flight conditions and defined to enhance high-lift performances during takeoff and landing, as well as wing aerodynamic efficiency during cruise. An innovative system based on finger-like robotic ribs driven by electromechanical actuators is proposed as morphing-enabling technology; the maturation process of the device is then traced from the proof of concept to the consolidation of a true-scale demonstrator for pre-flight ground validation tests. A step-by-step approach involving the design and testing of intermediate demonstrators is then carried out to show the compliance of the adaptive system with industrial standards and safety requirements. The technical issues encountered during the development of each intermediate demonstrator are critically analyzed, and justifications are provided for all the adopted engineering solutions. Finally, the layout of the true-scale demonstrator is presented, with emphasis on the architectural strengths, enabling the forthcoming validation in real operative conditions.