磁悬浮框架飞轮磁轴承技术研究与发展现状

对磁悬浮框架飞轮(MSGFW)和高精度磁轴承研究现状及其未来发展进行了详细阐述。根据转子悬浮力类型，将磁悬浮框架飞轮分为磁阻力构型、洛伦兹力构型和混合力构型，并结合三种构型论述了国内外框架飞轮的发展过程。在此基础上，对球面磁阻力磁轴承和洛伦兹力磁轴承进行了详细介绍，并结合磁路图分析其工作原理，比较了同类磁轴承的优劣。展望了磁悬浮框架飞轮与高精度磁轴承的未来发展方向，指出高动态响应检控共位平动球面磁阻力磁轴承，标准磁悬浮动量球和磁悬浮控制敏感球是磁悬浮框架飞轮的研究重点。     

Sliding mode control based guidance law with impact angle constraint

The terminal guidance problem for an unpowered lifting reentry vehicle against a sta- tionary target is considered. In addition to attacking the target with high accuracy, the vehicle is also expected to achieve a desired impact angle. In this paper, a sliding mode control （SMC）-based guidance law is developed to satisfy the terminal angle constraint. Firstly, a specific sliding mode function is designed, and the terminal requirements can be achieved by enforcing both the sliding mode function and its derivative to zero at the end of the flight. Then, a backstepping approach is used to ensure the finite-time reaching phase of the sliding mode and the analytic expression of the control effort can be obtained. The trajectories generated by this method only depend on the initial and terminal conditions of the terminal phase and the instantaneous states of the vehicle. In order to test the performance of the proposed guidance law in practical application, numerical simulations are carried out by taking all the aerodynamic parameters into consideration. The effec- tiveness of the proposed guidance law is verified by the simulation results in various scenarios.     

An extended chirp scaling algorithm for spaceborne sliding spotlight synthetic aperture radar imaging

A system impulse response with low sidelobes is critical in synthetic aperture radar（SAR） images because sidelobes contribute to noise and interfere with nearby scatterers. However,the conventional tricks of sidelobe suppression are unable to be exactly applied to the case of spaceborne sliding spotlight SAR due to great azimuth shifts in both time and frequency domains. In this paper, an extended chirp scaling algorithm is presented for spaceborne sliding spotlight SAR data imaging. The proposed algorithm firstly uses the spectral analysis（SPECAN） technique to avoid the azimuth spectrum folding effect and then employs the chirp scaling（CS） algorithm to achieve data focusing, i.e., the so-called two-step approach. To suppress the sidelobe level, an efficient strategy for the azimuth spectral weighting which only involves matrix multiplications and short fast Fourier transformations（FFTs） is proposed, which is a post-process executed on the focused SAR image and particularly simple to be implemented. The SAR image processed by the proposed extended CS algorithm is very precise and perfectly phase-preserving. In the end, computer simulation results verify the analysis and confirm the validity of the proposed algorithm.     

中心承力筒数控加工工艺

通过制定合理的数控加工工艺方案,实现了中心承力筒的数控加工,有效保证了孔的加工精度和

表面质量,提高了零件的加工效率。通过在5 轴联动数控加工中心上实际加工,证明该数控加工工艺切实可

行。

     

运动油滴/固体壁面斜碰撞的状态辨识及特征分析

 航空发动机轴承腔油气两相流动与换热研究是轴承腔润滑与换热设计的重要基础工作,而运动油滴与轴承腔壁面的碰撞状态辨识及特征分析是轴承腔油气两相流动与换热研究的组成部分。基于VOF方法建立了运动油滴与固体壁面斜碰撞数值仿真模型,实现了运动油滴与固体壁面斜碰撞状态的数值模拟,分析了碰撞油滴直径、入射角和碰撞速度对沉积油膜铺展长度、油膜堆积厚度和溅射油滴数目等碰撞状态特征参数的影响规律,提出了运动油滴与固体壁面斜碰撞条件下的状态判断准则,并得到了文献的物理试验工作的支持。研究结果表明:随着油滴入射角减小,沉积油膜铺展长度和油膜堆积厚度增大,溅射油滴数目减少;随着碰撞速度和油滴直径的增大,沉积油膜铺展长度和溅射油滴数目均增大,但油膜堆积厚度对应前者呈减小趋势、对应后者仍呈增大趋势。     

Backstepping sliding-mode control of stratospheric airships using disturbance-observer

In the presence of unknown disturbances and model parameter uncertainties, this paper develop a nonlinear backstepping sliding-mode controller (BSMC) for trajectory tracking control of a stratospheric airship using a disturbance-observer (DO). Compared with the conventional sliding mode surface (SMS) constructed by a linear combination of the errors, the new SMS manifold is selected as the last back-step error to improve independence of the adjustment of the controller gains. Furthermore, a nonlinear disturbance-observer is designed to process unknown disturbance inputs and improve the BSMC performances. The closed-loop system of trajectory tracking control plant is proved to be globally asymptotically stable by using Lyapunov theory. By comparing with traditional backstepping control and SMC design, the results obtained demonstrate the capacity of the airship to execute a realistic trajectory tracking mission, even in the presence of unknown disturbances, and aerodynamic coefficient uncertainties.     

Sliding mode control design for oblique wing aircraft in wing skewing process

When the wing of Oblique Wing Aircraft (OWA) is skewed, the center of gravity, inertia and aerodynamic characteristics of the aircraft all significantly change, causing an undesirable flight dynamic response, affecting the flying qualities, and even endangering the flight safety. In this study, the dynamic response of an OWA in the wing skewing process is simulated, showing that the three-axis movements of the OWA are highly coupled and present nonlinear characteristics during the wing skewing. As the roll control efficiency of the aileron decreases due to the shortened control arm in an oblique configuration, the all-moving horizontal tail is used for additional roll and the control allocation is performed based on minimum control energy. Given the properties of pitch-roll-yaw coupling and control input and state coupling, and the difficulty of establishing an accurate aerodynamic model in the wing skewing process due to unsteady aerodynamic force, a multi-loop sliding mode controller is formulated by the time-scale separation method. The closed-loop simulation results show that the asymmetric aerodynamics can be balanced and that the velocity and altitude of the aircraft maintain stable, which means that a smooth transition is obtained during the OWA’s wing skewing.     

多故障转子-滚动轴承系统的动力学特性

为深入研究多故障转子-滚动轴承系统的机理,充分考虑了旋转部件的扭矩、剪切力、转动惯量及陀螺力矩等效应,采用Timoshenko梁单元和转盘单元建立了转子的有限元模型,集成了滚动轴承动力学模型,及不平衡、不对中、碰摩、裂纹及松动等故障模型,得到了多故障转子-滚动轴承系统的动力学方程。采用变步长龙格库塔法,获得了转子-滚动轴承系统的位移响应,研究了系统位移响应随转速变化的分岔图、庞加莱截面,以及故障特征处的时域波形图、轴心轨迹图、相平面图和频谱图,探究了多故障转子-滚动轴承系统的故障特征及其动力学特性和规律。仿真分析结果表明：多故障转子-滚动轴承系统在运行过程中存在周期运动,拟周期运动和复杂的类混沌运动等丰富的非线性行为,且在各非线性行为转速区间内,会呈现不平衡、不对中、碰摩、裂纹和松动等单一故障或耦合故障的特征和现象。     

三轴承矢量喷管红外辐射特性

针对涡扇发动机用三轴承矢量喷管（3BSN）,通过数值模拟的方法研究了在巡航和垂直起降（VTOL）状态即非矢量和90°矢量状态下三轴承矢量喷管的红外辐射空间分布特征,并分析了其影响机理。结果表明,在非矢量状态下由于特殊的几何型面使得喷管下壁面出现了局部高温区,喷流形状也变成椭圆锥形,造成垂直探测面上正探测角壁面红外辐射较负探测角最大增加44.6%,水平探测面上的燃气红外辐射大于垂直探测面;90°矢量状态下,由于偏转的喷管结构对前端高温部件的遮挡,总辐射峰值仅为非矢量状态的43.3%;喷管90°矢量偏转使得远离曲率中心一侧的气流速度降低温度升高,喷管外侧出现了大范围的局部高温区,导致垂直探测面负探测角范围的壁面辐射大于正探测角范围,最大相对差值达到71.9%。喷管偏转也遮挡了部分喷管内部的高温燃气,垂直探测面负探测角的仅能覆盖喷管出口处的高温燃气区域,明显小于正探测角,造成燃气辐射出现了20%的最大相对差值。     

基于AFI混合聚类算法的轴承故障诊断方法

针对滚动轴承振动信号标记数据量小、故障模式多样的现状,提出了一种基于AFI混合聚类算法的半监督式轴承振动信号故障诊断方法。利用小波包分解方法提取了信号的能量特征谱,并通过主成分分析方法增强了信号的特征;参考迭代自组织数据分析的“分裂”和“合并”的思想,为人工鱼群算法中的个体鱼增加了“分裂进化”和“合并进化”行为;采用模糊C均值方法定义了隶属度矩阵和目标函数,并利用改进的人工鱼群算法,迭代搜寻了目标函数的全局最优解,得到了各故障模式的聚类中心;通过计算测试数据的最近邻聚类中心,实现了故障模式识别。结果表明,该方法无需指定聚类簇数,能在标记数据量小的情况下完成训练,较同类方法表现出了更优的故障模式识别性能。