半模机翼振动的风洞实验技术研究

飞行器机模型振动是影响其风洞实验数据可靠性的主要因素之一。为此,通过专门研制的半模振动模型,采用对称翼型NACA0012和层流翼型NACA64-210两种半模机翼进行了低速风洞振动实验。选取五种激振方式,用直接测力法得到模型在静态和不同激振方式下升力特性变化曲线,研究了振动频率、自然转捩和固定转捩、数据采集方式等参数对机翼气动特性测量结果的影响。结果表明：振动对半模机翼气动特性的影响程度因不同翼型构型、不同采集方式和翼面不同流动模式等而产生不同效果。结论对提高飞机模型风洞实验大迎角振动情况下的测量精准度有参考价值。     

Properties of Ground Level Enhancement Events and the Associated Solar Eruptions During Solar Cycle 23

Solar cycle 23 witnessed the most complete set of observations of coronal mass ejections (CMEs) associated with the Ground Level Enhancement (GLE) events. We present an overview of the observed properties of the GLEs and those of the two associated phenomena, viz., flares and CMEs, both being potential sources of particle acceleration. Although we do not find a striking correlation between the GLE intensity and the parameters of flares and CMEs, the solar eruptions are very intense involving X-class flares and extreme CME speeds (average ～2000?km/s). An M7.1 flare and a 1200?km/s CME are the weakest events in the list of 16 GLE events. Most (80?%) of the CMEs are full halos with the three non-halos having widths in the range 167 to 212?degrees. The active regions in which the GLE events originate are generally large: 1290?msh (median 1010?msh) compared to 934?msh (median: 790?msh) for SEP-producing active regions. For accurate estimation of the CME height at the time of metric type?II onset and GLE particle release, we estimated the initial acceleration of the CMEs using flare and CME observations. The initial acceleration of GLE-associated CMEs is much larger (by a factor of 2) than that of ordinary CMEs (2.3?km/s² vs. 1?km/s²). We confirmed the initial acceleration for two events for which CME measurements are available in the inner corona. The GLE particle release is delayed with respect to the onset of all electromagnetic signatures of the eruptions: type?II bursts, low frequency type?III bursts, soft X-ray flares and CMEs. The presence of metric type?II radio bursts some 17?min (median: 16?min; range: 3 to 48?min) before the GLE onset indicates shock formation well before the particle release. The release of GLE particles occurs when the CMEs reach an average height of ～3.09?R _s (median: 3.18?R _s ; range: 1.71 to 4.01?R _s ) for well-connected events (source longitude in the range W20–W90). For poorly connected events, the average CME height at GLE particle release is ～66?% larger (mean: 5.18?R _s ; median: 4.61?R _s ; range: 2.75–8.49?R _s ). The longitudinal dependence is consistent with shock accelerations because the shocks from poorly connected events need to expand more to cross the field lines connecting to an Earth observer. On the other hand, the CME height at metric type?II burst onset has no longitudinal dependence because electromagnetic signals do not require magnetic connectivity to the observer. For several events, the GLE particle release is very close to the time of first appearance of the CME in the coronagraphic field of view, so we independently confirmed the CME height at particle release. The CME height at metric type?II burst onset is in the narrow range 1.29 to 1.8?R _s , with mean and median values of 1.53 and 1.47?R _s . The CME heights at metric type?II burst onset and GLE particle release correspond to the minimum and maximum in the Alfvén speed profile. The increase in CME speed between these two heights suggests an increase in Alfvénic Mach number from?2 to?3. The CME heights at GLE particle release are in good agreement with those obtained from the velocity dispersion analysis (Reames in Astrophys. J. 693:812, 2009a; Astrophys. J. 706:844, 2009b) including the source longitude dependence. We also discuss the implications of the delay of GLE particle release with respect to complex type?III bursts by ～18?min (median: 16?in; range: 2 to 44?min) for the flare acceleration mechanism. A?similar analysis is also performed on the delay of particle release relative to the hard X-ray emission.     

Static aeroelastic analysis of very flexible wings based on non-planar vortex lattice method

A rapid and efficient method for static aeroelastic analysis of a flexible slender wing when considering the structural geometric nonlinearity has been developed in this paper. A non-planar vortex lattice method herein is used to compute the non-planar aerodynamics of flexible wings with large deformation. The finite element method is introduced for structural nonlinear statics analysis. The surface spline method is used for structure/aerodynamics coupling. The static aeroelastic characteristics of the wind tunnel model of a flexible wing are studied by the nonlinear method presented, and the nonlinear method is also evaluated by comparing the results with those obtained from two other methods and the wind tunnel test. The results indicate that the traditional linear method of static aeroelastic analysis is not applicable for cases with large deformation because it produces results that are not realistic. However, the nonlinear methodology, which involves combining the structure finite element method with the non-planar vortex lattice method, could be used to solve the aeroelastic deformation with considerable accuracy, which is in fair agreement with the test results. Moreover, the nonlinear finite element method could consider complex structures. The non-planar vortex lattice method has advantages in both the computational accuracy and efficiency. Consequently, the nonlinear method presented is suitable for the rapid and efficient analysis requirements of engineering practice. It could be used in the preliminary stage and also in the detailed stage of aircraft design.     

某型直升机尾上舱结构失稳故障研究

针对某型直升机尾上舱结构失稳故障,从直升机结构组成、故障现象入手,深入分析故障产生的原因,将结构修理中单一的割修、贴补和加强等方法,综合运用在结构失稳故障的排除中,从根本上杜绝类似的故障再发生,为直升机用户提供了一个更加安全可靠的机体结构平台。     

用FPGA实现abc坐标系的三维空间矢量调制算法

研究了一种应用于三相四桥臂逆变器的基于abc坐标系的新的空间矢量调制算法,避免了传统的αβ0坐标变换,使开关矢量的选取和占空比的计算更简单,显著降低了调制算法的复杂性。同时详细说明了基于abc坐标系的空间矢量脉宽调制算法的原理,并研究了用FPGA来实现该空间矢量调制算法的方法。由于FPGA不需要顺序执行指令,可以多个进程并发执行,响应速度快,可明显提高系统性能。仿真和实验结果证明了该空间矢量调制算法的正确性和利用FPGA实现该算法的可行性。     

面向小行星微重力环境探测的自恢复直立弹跳机器人设计

针对小行星微重力环境,提出了一种具有蛋形外壳,利用弹簧蓄力的并联腿弹跳机器人.该机器人无论以何种姿态落地,均可在重力矩作用下恢复直立姿态.这一设计相对于需要额外主动装置恢复直立的先前方案,节省了恢复直立所需的能耗,在结构上更为简单可靠.文中阐述了完整的机构设计方案,及相应的结构参数优化计算方法.通过的样机实验,设计方法...     

适用于多星并行测试的应答机设计方法与验证*

为了提高星座的测试效率、降低测试成本,提出一种适合多星并行测试的应答机设计方法,通过地面测试设备和星上测控应答机复用星上的遥控RS422接口、遥测RS422接口的方式,突破了多星并行测试的瓶颈。新方法已经成功应用于某卫星星座的并行测试,降低了测试成本、提高了测试效率、缩短了星座的测试周期。     

高超音速热流数值计算中的误差匹配原则

通过对粘性边界层的数值模拟和误差分析,提出了差分格式的误差匹配原则.在边界层内的计算网格一般都具有很大的长宽比,而计算误差与网格长宽比密切相关.为了使不同坐标方向上的误差保持在同一量级上,需根据误差匹配原则确定计算网格的尺寸.对绕钝锥的高超音速流动进行了数值模拟,进而计算了钝锥表面的热流分布.数值计算表明,参照误差匹配原则进行网格划分是有益的,可在保持流场数值计算精度和提高热流计算准确性的同时,使网格的数量和分布更为合理.     

捷联惯性导航系统的姿态算法

非互易向量的确定与补偿是影响高动态、恶劣振动环境下捷联惯性导航系统姿态矩阵计算的重要问题.为了补偿由此引起的圆锥误差,对一些传统算法进行了分析和研究.由于以往各种算法过多过杂,不便于工程中选用,所以通过对传统的各种姿态算法的原理及数学形式进行归纳分析和研究,提出了通用的算法公式.另外,还提出将剩余误差表示为采样时间与角振动频率乘积的幂次,并根据此幂次来评定圆锥补偿算法的精度的方法.在此基础上,对所提出的通用姿态算法公式进行了误差分析,得到了关于算法精度和参数之间关系的一些结论,为其参数选择提供了选择标准,有工程实用价值.     

一种GPS双频多天线姿态测量方法

北京遥测技术研究所自主研制的双频GPS-OEM板可以提供精度很高的双频载波相位原始观测数据,利用其对载体进行姿态测量,将是一种即经济又方便的工作方式,而且还能获得很高的精度和稳定性。基于此展开对双频GPS载波相位测姿的研究工作,结合双频GPS载波相位可以组合出86 cm波长宽巷载波相位观测值的特性,基于伪距和载波相位组合获取模糊度搜索空间,再使用最小二乘降相关平差法(LAMBDA方法)搜索整周模糊度。大量的试验数据证明,利用双频GPS载波相位进行测姿切实可行,姿态初始化速度快,测姿结果精度高。