基于平面线圈的高分辨力时栅角位移传感器

针对现有时栅角位移传感器采用漆包线绕制工艺加工线圈,导致线圈布线不均且容易随时间发生变化进而影响测量精度的问题,提出一种基于PCB技术的新型时栅角位移传感器。该传感器通过在PCB基板的不同层上布置特定形状的激励线圈和感应线圈,形成两个完全相同并沿圆周空间正交的传感单元;当在两传感单元的激励线圈中分别通入时间正交的两相激励电流后,通过导磁定子基体和具有特定齿、槽结构的导磁转子对传感单元内的磁场实施精确约束,使两传感单元的感应线圈串联输出初相角随转子转角变化的正弦感应信号;最后通过高频时钟脉冲插补初相角实现精密角位移测量。利用有限元分析软件对传感器进行了建模和仿真。根据仿真模型制作了传感器实物,开展了验证实验,并对实验中角位移测量误差的频次和来源进行了详细分析。经过标定和补偿,最终获得了整周范围内误差在-2.82″~2.02″的时栅角位移传感器。理论推导、仿真分析和实验验证均表明,该传感器不仅能实现精密角位移测量,还能在激励线圈和感应线圈空间极距和信号质量不变的情况下,将位移测量的分辨力从信号源头提高1倍,且结构简单稳定、极易实现,特别适用于环境恶劣的工业现场。     

双联角接触球轴承轴向预载荷试验

以角接触球轴承轴向载荷和轴向位移的非线性函数关系为基础,进行了双联轴承加载试验。通过对加载曲线的分析对比,得到了施加在双联轴承上的轴向预载荷。串联型双联轴承虽然不存在预载荷问题,但通过加载试验曲线的测试与分析,可以使两套轴承承受相同的轴向载荷。     

1000 L/min 2D伺服阀实验研究

2D伺服阀采用伺服螺旋机构实现阀芯的角位移转换为阀芯的轴向位移。采用2D阀的结构方案实现了1000 L/min大流量阀的设计。采用步进电机作为电 机械转换器,并采用位置和电流闭环来驱动阀芯转动。为了实现步进电机输出角位移连续可控采用了步进电机连续跟踪算法的控制方法并在步进控制中引入脉宽调制控制技术,并以此为基础搭建了试验平台,设计了以TMS320F2812作为CPU的2D伺服阀控制器。在分析该阀的结构和工作原理基础上,对该阀频率响应进行实验研究。实验表明：该阀具有良好的动态特性,在幅值为25%阀满开口的正弦信号输入下,相位滞后90°对应的频宽约为50 Hz 。     

大型精密转台高精度角度微驱动装置的研制

针对用于标定和检测的大型精密转台(要求其定位误差≤±0.5″),研制了高精度角度微驱动装置。介绍了转台的总体结构,给出了角度微驱动装置的驱动原理和构成。该角度微驱动装置主要通过一个角位移转换机构把精密直线位移转化为精密角位移来实现高的角度分辨率,其在驱动转台旋转的过程中几乎不给转台带来轴向力和径向力,因此不影响转台的轴系精度。为了满足定位要求,转台设计采用了粗精结合、二次定位的方法,即先采用力矩电机进行粗定位,然后使用角度微驱动装置来实现精定位。最后,从理论上计算了角度微驱动装置的分辨率并进行了测试和应用验证,证明此角度微驱动装置的分辨率优于0.08″,满足转台定位精度要求。     

井下组合动密封波纹管设计及有限元分析

井下导向工具的组合动密封由机械密封、波纹管等组成,其中波纹管起角位移补偿和静密封作用,要求有足够的强度、轴向刚度和角位移补偿能力。根据导向工具的工作环境和空间结构设计角位移补偿波纹管的结构及参数。采用控制变量法对U型波纹管进行刚度计算,得出刚度的变化规律,确定波纹管的最终结构参数,并用有限元方法研究在内压载荷与径向弯曲载荷共同作用下,波纹管的结构参数变化对波纹管性能的影响,验证波纹管最终结构参数的合理性。     

Development of a novel two-dimensional(2D) three-way(3W) fuel flow control servo valve with constant pressure difference

To solve the problems of large volume, and low integration of traditional electro-hydraulic servo valve with constant pressure differential fuel metering device, a new two-dimensional three-way constant pressure differential fuel flow control servo valve (2D3WFFCSV) is developed. It innovatively adopts the advantages of lightweight of “two-dimensional hydraulic technology”, The constant differential pressure function and flow regulation function are integrated into a two-dimensional (2D) main spool with two degrees of freedom (rotational and axial degrees of freedom). The flow control process of 2D3WFFCSV is as follows: firstly, the armature of the torque motor and the two-dimensional piston are coaxially installed at the end of the two-dimensional piston, so the torque motor can directly drive the two-dimensional piston to rotate; secondly the “hydraulic servo screw mechanism”, which can amplify the power, is used to drive the two-dimensional piston to move in line; Finally, a pair of conversion mechanisms (roller group and spiral track conversion mechanism) are converted into the angular displacement of 2D main spool to control the area of flow valve port. The axial degree of freedom of 2D main spool realizes the function of constant differential pressure. To improve the flow control accuracy of the servo valve, the axial position of the 2D piston is detected by the linear displacement sensor (LVDT), and the signal is transmitted to the controller to realize the closed-loop control. To explore its open-loop characteristics, the mathematical models of torque motor, two-dimensional piston and main spool are established to obtain its open-loop transfer function. Then the AMESIM simulation model is built. To optimize the design of the system, through the dynamic simulation of the system, the influence of key parameters on the dynamic response of the system can be studied. An experimental study is carried out to verify the design feasibility of the servo valve. The experimental results show that under the condition of no-load and full-scale input, the closed-loop delay of the servo valve is 1.84%, the linearity is 2.14%, the step response time is 43 ms, and the dynamic frequency response is 38 Hz. The newly developed 2D3WFFCSV has the advantages of high integration, small size, light weight (801.5 g) and high response and control accuracy. It can replace the constant differential pressure, metering valve and hydraulic servo valve in the aeroengine fuel regulator.     

考虑附加质量的中心刚体-柔性悬臂梁系统的动力特性研究

对考虑附加质量的中心刚体-柔性悬臂梁系统的动力特性进行研究.首先采用Hamilton原理和有限元离散化方法,在计入柔性梁由于横向变形而引起的轴向变形的二阶耦合量的条件下,给出该系统的刚柔耦合动力学方程(即一次近似耦合模型),以及相应的非惯性系下的动力学模型,然后通过数值仿真对系统的动力特性进行研究.仿真结果显示,即使是小的附加质量也会对系统动力特性产生重要影响,附加质量使得梁的响应幅值变大和响应频率降低,且会影响柔性梁和中心刚体的终点位置.附加质量的影响随系统大范围运动的角速度的增大而变大.当系统大范围运动为低速时,传统的混合坐标模型仍然会导致较大误差;当系统大范围运动为高速时,传统的混合坐标模型存在失效的可能.     

A method for accurate localisation of EBSD pattern centres

The moving screen technique for pattern centre localisation is revisited. A cross-correlation based iterative procedure is developed to find both the zoom factor and the zoom centre (which is also the pattern centre) between two EBSD diffraction patterns acquired at two camera positions. The procedure involves two steps: first, a rough estimate of the pattern centre position and zoom factor (the ratio of the two detector distances) is obtained by cross-correlating the entire images. Then, based on this first estimate, cross-correlation of smaller regions of interest (ROIs) gives the displacement field which is interpreted as a zoom factor misfit coupled with a zoom centre position misfit. These misfits are iteratively decreased until the displacement field is reduced to the noise level. The procedure is first applied to simulated patterns and it is shown that the iterative procedure converges very rapidly to the exact solution with an accuracy better than 1/100th of pixel. The potential of this technique for experimental patterns is discussed and recommendations for new EBSD detectors are proposed.     

数控机床进给系统刚度分析及前馈补偿控制研究

根据滚珠丝杠一端止推和两端止推两种方式,基于弹性力学原理建立了进给系统的轴向刚度模型和扭转刚度模型。分析了刚度对进给系统死区误差的影响,在对轴向变形引起的位移偏差和扭转变形引起的角位移偏差分析计算的基础上,给出了刚度引起的死区误差计算方法。建立了包含刚度环节的进给系统模型,通过仿真对系统动、静态性能和稳态误差进行了分析。为减小刚度因素对系统性能的影响,提出前馈控制方法进行刚度补偿,仿真结果表明该方法提高了系统的动、静态性能,使系统稳态误差减少了58%以上。     

变量型阀配流柱塞式液压电机泵的研制

研制了一种双斜盘阀配流轴向柱塞式液压电机泵的样机,并阐述了一种依靠改变左右斜盘相对位置角度关系来实现液压泵排量改变的变量方式。研究表明：样机技术指标达到了额定压力20 MPa,输出流量298 mL/min,容积效率达到96%,并验证了新变量方式的可行性和具有余弦规律的变量特性。实验也证明了适当增大吸入阀弹簧预压紧力以抵消配流阀旋转时所受的离心力,与在吸入阀的前腔设计简易的离心增压装置以利用液体离心力等方式是可行的,不仅使得泵在中速（750~1200 r/min）时可保持较好的排量,而且在高速(1200~1500 r/min)时排量降低不显著。     

基于 ABAQUS 的角接触球轴承动力学仿真分析

为研究角接触球轴承在不同转速下温度及位移变化,基于 Palmgren 摩擦生热理论,综合考虑轴向载荷、切向摩擦和法向摩擦等边界条件,在 ABAQUS 软件中建立了轴承完全热力耦合模型。对轴承外圈施加固定的轴向载荷,并对内圈加载不同的转速,使用显示求解器求解轴承在不同转速下各部件温度和轴承内圈位移变化。仿真分析表明,该模型能够准确地反映轴承的温升以及轴承内圈位移情况,为轴承选取合适工作转速区间提供理论支撑。     

关节联轴器轴向位移补偿能力的研究

提出新结构型式的叠片联轴器——关节轴承式叠片联轴器，简称关节联轴器。采用关节轴承，从结构设计上提高了两轴线之间的轴向和角向补偿能力；分析了此联轴器在运行过程中的受力状况，并就三种不同尺寸的关节联轴器分别用经典的材料力学法和ANSYS有限元软件法对其所能补偿轴向位移的能力进行了具体的分析，得出了应力最大值所在位置以及每一种尺寸的关节联轴器所能补偿的轴向位移的大小。该分析结果为此类新型联轴器的设计提供了理论依据。     

大角速率动调陀螺仪的运动分析与误差研究

研究的大角速率动调陀螺仪，挠性支承在所有方向上均具有有限刚度。因此，即使平衡环及转子不存在安装误差和其质点相对原点的位移，但是由于挠性轴在所有方向上均存在有限刚度，仍会引起陀螺仪轴向不平衡漂移及支承不等刚度漂移。利用广义坐标的理论，对动力调谐速率陀螺仪进行了运动分析：分析了挠性支承特性对动力调谐速度陀螺仪精度的影响；对大角速率动调陀螺仪挠性支承的刚度及柔性矩阵进行了具体计算，并在此基础上对陀螺仪轴向不平衡漂移及支承不等刚度漂移进行了仿真分析。     

油气两相动压密封自振稳定性流固热耦合分析

考虑热与变形对油气两相动压密封自振稳定性的影响,建立基于油气两相动压密封自振稳定性数学模型,采用流固热耦合有限元方法,研究油气比、转速、压差和O形圈阻尼等参数对油气两相动压密封受干扰后的轴向、角向自振稳定性能的影响。结果表明:转速较低时轴向自振稳定性较好而角向自振稳定性较差,转速高时两者相反,O形圈阻尼较低时轴向自振稳定性较差而角向自振稳定性较好,O形圈阻尼高时两者相反,因此在极端转速和取极端O形圈阻尼的情况下轴向或角向临界频率较小,不利于油气两相动压密封自振稳定;压差越大轴向临界频率越大,轴向自振稳定性越好,但角向临界频率越小,角向自振稳定性越差;随着两相介质油气比的增大,轴向临界频率减小而轴向临界质量增大,油气比在0.1～0.15时临界频率、质量以及转动惯量较大,密封综合自振稳定性能较好。     

螺旋槽干气密封稳态特性分析模型的对比研究

干气密封的稳态特性是密封设计中的重要依据和指标。干气密封稳态特性可通过基于轴向力平衡的静态模型和轴向-角向耦合的动态模型两种途径获得。基于上述两种模型间存在的差异点,就动环偏摆角、静环静态偏摆角和副密封阻尼展开参数研究,讨论两种模型计算所得的稳态特性（膜厚与泄漏率）之间存在的差异,进而给出它们在干气密封稳态特性研究中的适用性分析。计算中,动力学方程和流场方程分别采用有限差分法和有限元法进行离散求解,以膜厚与泄漏量为稳态特性的主要指标。结果表明,当副密封阻尼较小时,角向偏摆角对于静环稳态特性的影响极小,可用静态模型来近似动态模型,以简化计算过程和缩短计算时间。而当副密封阻尼较大时,密封动静环的角向相位差较大,显著地影响密封静环的稳态特性,使用静态模型获得的结果与动态模型的结果差别较大,而且此时前者无法反映由于静环角向追随性较差引起两环端面易发生接触的问题,因此大阻尼情况下宜采用动态模型。     

Model study and active control of a rotating flexible cantilever beam

For a dynamic system of a rotating flexible cantilever beam, the traditional model assumes the small deformation in structural dynamics where axial and transverse displacements at any point in the beam are uncoupled. This traditional hybrid coordinate model is referred as the zero-order approximation coupling model in this paper, which may result in divergence to the dynamic problem of a flexible cantilever beam with a high rotational speed. In this paper, a first-order approximation coupling model is presented to analyze the dynamics of rotating flexible beam system, which is based on the Hamilton theory and the finite element discretization method. The proposed model for the system considers the second-order coupling quantity of the axial displacement caused by the transverse displacement of the beam. The dynamic characteristics of the rotating beam system when using the zero-order approximation coupling model are compared with those when using the first-order approximation coupling models through numerical simulations. In addition, the applicability of the two dynamic models for control design are studied by using the classical optimal control method. Simulation and comparison studies show that, for the case without control for the system, there exists big difference between the result using the zero-order approximation coupling model and that using the first-order approximation coupling model even for the case of small angular velocity of the system. The larger is the angular velocity, the bigger is the difference. Vibration frequency of the beam by using the first-order approximation coupling model is higher than that by using the zero-order approximation coupling model. When the angular velocity of the system is close to or is larger than the fundamental frequency of the beam without rotation motion, the zero-order approximation coupling results in a wrong result, while the first-order approximation coupling model is valid. For the case with control for the system, the applicability of the zero-order approximation coupling model can be much broadened. The critical angular velocity of the system for validity of the zero-order approximation coupling model is much larger than that without control for the system. The first-order approximation coupling model is available not only for the case of small angular velocity but also for the case of large angular velocity of the system, and is applicable to the cases with or without control for the system.     

Influence analysis of secondary O-ring seals in dynamic behavior of spiral groove gas face seals

The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior (steady-state performance and transient performance) of face seals. A numerical finite element method (FEM) model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.     

多列组合角接触球轴承刚度和位移量

以滚动轴承动力学分析和滚道控制理论为基础,提出了应用Powell优化算法和Newton-Raphson算法相结合的方式计算非线性方程组,给出了预紧力和转速的多列组合角接触球轴承组合刚度相应程序。对7016A5轴承DBD组合的研究结果表明:预紧力和转速与单个轴承和轴承的组合刚度及位移量呈现非线性关系。轴承的组合轴向刚度小于单个轴承的轴向刚度,其径向刚度大于单个轴承的径向刚度。为实现预定的轴承动态性能,单双侧轴承内圈的间隙量须大于两侧轴承位移量之和。     

Electron microscopy of unstained,freeze-dried macromolecular assemblies

A rapid cooling/cryotransfer system was designed to achieve a high reproducibility in vitrifying thin water films containing biological specimens. In order to improve the contrast these unstained specimens were deliberately freeze-dried in situ in the electron microscope. The preservation of the structure obtained by freeze-drying at 180 K and subsequent microscopy at 90 K is very encouraging as has been shown with two types of test specimen. Tubular photosynthetic membranes were used to examine the effects of a variety of freeze-drying conditions on structural preservation, as judged by flattening of the tubes. A two-dimensional protein crystal was used to evaluate problems of low-dose microscopy of unstained, freeze-dried proteins, e.g. optical density of films, motif detection by cross-correlation and transferring the accurate molecular positions from medium-dose to corresponding low-dose micrographs. The radiation sensitivity of the unstained, freeze-dried protein crystal was investigated by a dose series covering a wide range.     

含间隙运动副的空间机构的实验研究

在研制的实验台上对含间隙转动副的空间机构进行了研究。使用ＴＤ８００测试系统，能够实时地测出转动副轴心的运动轨迹、振动波形以及轴在空间的运动姿态。通过大量的实验，得出了轴与套的分离主要发生在摇杆摆动的极限位置处，而其它位置大部分是接触的。同时也发现轴存在轴向窜动，大部分时间在两端面接触。在速度较高时，在两端伴有跳动