Analysis of optical linear encoders’ errors under vibration at different mounting conditions

The optical linear encoders are the preferred choice sensors for positioning machine tools’ moveable parts. Machine tools’ errors have been traditionally focused on the analysis and performance of the machine tool structure until recent works have treated the encoder itself as a source of error. Encoder error quantification has been done for several mounting conditions in static situations, but there is a lack of information regarding the performance of the encoder under dynamic solicitations. The aim of this work is to analyze the loss of accuracy of the sensor because of vibration for different mounting conditions. A finite element model of encoder has been developed and experimental results have been analyzed using this model.     

基于Vold-Kalman滤波的光栅谐波动态抑制方法

谐波信号失真问题,是影响光栅位移传感器测量精度及分辨力的关键因素之一.针对光栅变速运动情况下的谐波动态抑制难题,探索Vold-Kalman滤波在光栅信号处理中的应用.阐述了 Vold-Kalman滤波的基本原理,建立了基于Vold-Kalman滤波的光栅谐波抑制模型,优化设计了 Vold-Kalman滤波器的权重因子,...     

随机振动下机械产品广义可靠性评估

利用随机振动试验模拟使用环境可时构件进行可靠性考核，通过直接测量可获得薄弱部位的应变、加速度响应规律，再对相同振动条件下构件的可靠性进行评估。应力和应力循环次数是由平均功率谱密度通过离散计算得来，其计算精度由离散点间距、随机振动时间决定，因此获得的应力和应力循环次数具有模糊性。利用普通事件概率表示模糊事件概率，将模糊可靠性计算问题转化为普通可靠性计算。通过定义模糊安全状态的不同形式，建立了以状态变量表示安全状态时的广义可靠性计算模型。结合工程实际给出了算例。     

基于虚拟仪器的旋转轴扭振测试系统的设计与研究

利用虚拟仪器技术设计开发了旋转轴扭振测试系统,并结合ATI2000系列扭振传感器进行了实际测量,实验结果表明该系统可实现传动轴扭振宽频率、宽转速、多通道同时测量及在线分析等功能,且操作方便、灵活性强,为今后测试和研究大型旋转机械的扭振特性及实现扭振在线监测、故障诊断等提供了理论与技术支持.     

光学有效载荷在轨隔振器的设计

为了抑制空间光学载荷的振动,针对大口径、高分辨的光学遥感器设计了一种隔振器,并研究了隔振器的主要结构参数和布置方式。首先,使用有限单元法分析了隔振器主要参数与刚度特性之间的关系。然后,利用BP网络预测隔振器的三向刚度,搜寻了符合条件的隔振器的结构参数。结合光学载荷的一般结构形式,提出一种对称辐射式布置方式,建立了相应的理论模型,并进行了仿真研究。最后,设计、加工出了一套隔振系统原理样机,并对其静态性能及隔振性能进行了测试实验。实验结果显示:隔振系统的基频在5.31Hz左右;对高于25Hz的振动,衰减可以达到20dB以上;仿真和实验结果之差在8%以内。得到的结果表明,设计的隔振器可以有效降低空间飞行器传递给光学载荷的振动。     

精密机床的隔振基础

机床基础底部铺有五层不同材料的防振层的方法来提高机床基础的防振性,能很好的消振和隔离外界振源的影响。该设计主要采用了在机床四周开挖防振沟,通过对设计要素的分析和试验,证明该设计可广泛应用于轧辊磨床的机床基础的设计,提高轧辊磨床的磨削精度。     

随机振动下光学谐振腔腔体形变及变动规律

鉴于复杂环境会使激光陀螺谐振腔产生变形,从而严重影响激光陀螺的性能,本文利用有限元分析软件ANSYS仿真分析了典型随机振动谱(gRMS=6.6 g)下激光陀螺腔镜3个方向的微小形变量,分别为0.342 5″、0.349 4″和0.215 0″,并结合矩阵光学理论定量得到了谐振腔光阑处的形变量。然后定量分析了不同曲率半径、不同腔长、不同入射角对光学四边形环形谐振腔的影响规律。最后,研究了球面镜-球面镜同时变化以及球面镜-平面镜同时变化下谐振光路的变动规律。实验结果表明,单纯考虑谐振腔的抗振性能,当L处于0~1m,R处于1~8m时,球面镜的曲率半径越小,腔长越短,四边形环形光学谐振腔所受外界环境的影响越小,两个腔镜同时变化时按照一定规律等效成单镜变化。本文研究可以为激光陀螺光学谐振腔的设计提供参考。     

复杂旋转机械扭振测量模型与实验研究

基于Newton力学法建立复杂旋转机械扭振的测理模型,正则变换后用Duhamel积分计算各正则坐标的响应,通过与试验测试数据相比较,验证该模型的有效性,为旋转机械的扭振计算提供新途径.     

随机振动下小子样机械产品可靠性评估

针对机械产品使用寿命一般比较长，用于振动试验的产品数量必须很少的特点，提出一种基于经典方法、通过增大产品承受的应力，并结合应力-强度干涉计算，建立适合极小子样产品的可靠性评估方法。研究了过载随机振动试验的实现手段。讨论了过载试验中确定过载系数上限的问题。针对某一高可靠性产品，利用随机振动试验获得薄弱部位的应力响应规律，经可靠性评估表明，如果提高输入功率谱密度约108％，只需选取4～5件进行可靠性试验即可。该方法对试验费用昂贵，小子样产品的可靠性评估，具有工程实用价值。     

基于实验方法的电动机振动特性测试

为防止共振发生,电动机的工作频率应远远小于其固有频率。基于受迫振动理论,本文提出用实验测定电动机的固有频率范围的方法,分析电动机机械振动特征,为电机减振提供有了力支持。重点论述了振动试验的夫具设计及试验过程,并对实验结果进行了分析。实验数据与理论结果较为一致,证明该实验方法是测定电动机的固有频率的有效方法。     

光纤陀螺的振动特性研究

光纤陀螺作为机载导航设备应用时,环境振动对陀螺精度的影响不容忽视。现初步探讨了光纤陀螺的振动特性。通过ANSYS有限元振动模态分析与正弦扫频振动下的陀螺零偏输出实验,研究了单轴光纤陀螺的结构体共振频率以及振动对陀螺性能的影响,并在此基础上,提出了陀螺结构设计的改进方法。     

反复印压作用下光学玻璃的微裂纹交互作用研究

对超声振动辅助磨削加工中BK7光学玻璃材料表面及亚表面的微裂纹扩展过程中的交互作用进行研究,使用维氏金刚石压头进行了BK7光学玻璃二次印压实验来模拟超声振动作用影响下单颗磨粒对光学玻璃的反复印压作用,同时采用界面粘结法获得了不同印压载荷及印压距离下产生的压痕及微裂纹形态特征及分布情况。实验结果表明：在相同载荷加载情况下,第二次印压产生的亚表面中位裂纹扩展最大深度受到侧向裂纹影响减小了30μm,同时侧向裂纹闭合后在光学玻璃材料表面及内部产生破碎。基于压痕断裂力学理论,分析了准静态载荷作用下光学玻璃内部应力场的分布及应力场驱动下微裂纹的扩展机制,对超声振动效应影响下微裂纹扩展的交互作用进行研究。结果表明：磨削过程中使用轴向超声振动辅助,能够有效地降低光学玻璃材料亚表面裂纹的深度,改善亚表面及表面加工质量,同时促进了工件材料的去除。     

Adaptive-randomised self-calibration of electro-mechanical shutters for space imaging

This work describes the self-calibration of a high-precision open-loop mechanism. The self-calibration method is applied to a mechanical shutter for space applications, which was launched onboard the ESA-ROSETTA mission (launch: 2 March 2004). It is based on an adaptive ‘model reference’ and a ‘randomised’ search method which may be generalised to applications in which high performance and functionality are strongly interconnected. The method makes use of an adaptive ‘model-reference’ control approach [K.J. Astrom, B. Wittenmark, On self-tuning regulators Automatica 9 (1973) 185–199 [16]; K.J. Astrom, Theory and application of adaptive control, in: Proceedings of the Eighth IFAC World Conference, Kyoto, Japan, 1981 [17]; D.E. Seborg, S.L. Shah, T.F. Edgar, Adaptive control strategies for process control, AIChE Journal 6(32) (1986) 881–895 [18]] to guarantee mechanism performance. The proposed control system comprises both a deterministic adaptive part and a random-search one [K.L. Clarkson, Applications of random sampling in computational geometry, II, in: Proceedings of the Fourth Annual ACM Symposium on Computational Geometry, 1998, pp. 1–11 [19]; P.K. Agarwal, M. Sharir, Efficient randomised algorithms for some geometric optimisation problems, Discrete Computational Geometry 16 (1996) 317–337 [15]] to guarantee shutter mechanism functionality and performance over testing lifetime (5×10⁴ cycles).     

Edge-lit sine-shape wedged light guides: Design,optical simulation,laser-remelting-based precision fabrication,and optical performance evaluation

Light guiding is an essential functionality of automotive lighting responsible for styling, safety, and artistic effects. The functional performance of optical lighting and illumination products and components depends on novel optical designs and advanced technologies for cost-effective fabrication of tooling with strict surface quality and form geometry accuracy. The present multi-objective study introduces a new design for an edge-lit wedge planar light guide (LG) with sine-shape riblets as well as an advanced microfabrication technology called surface structuring by laser remelting (SSLRM). In the proposed LG design, sine-shape riblets act as optical structures used to redirect - through total internal reflection - the incoming collimated light onto the illuminated surface. Numerical simulations showed that LGs with different amplitudes of sine-shape riblets (e.g., 25 μm, 40 μm, 55 μm) can reach an illumination efficiency of 97.7%. Furthermore, the applicability of SSLRM process for an efficient fabrication of edge-lit LG tooling inserts was demonstrated and several tooling inserts were fabricated with geometric parameters matching the proposed optical designs. Following this, the geometry and surface quality parameters of the fabricated inserts were presented. In addition, functional plastic prototypes of LGs were produced by means of a hot embossing technology that preserved the original form geometry and surface quality characteristics. Their actual optical performance was comparatively evaluated with respect to a LG with a flat-wedged surface and also to LGs with different amplitudes of sine-shape riblets. The maximum actual optical performance was achieved by LGs with a sine-shape amplitude of 55 μm that exhibited a total luminance of 0.1395 cd while the flat wedged LG without light redirecting structures exhibits 0.0006 cd only. It is also demonstrated that the sine-shape amplitude significantly contributes to the overall LG optical performance gaining 1811% improvement with respect to the LG with 25 μm amplitude delivering 0.0073 cd. The results obtained demonstrate the applicability and the high potential of the proposed edge-lit sine-shape wedged LGs as well as that of the SSLRM process used for their high precision microfabrication.     

光盘轴向机械动态特性测量方法的研究

研究了光盘轴向机械动态特性和聚焦伺服系统的关系，系统研究了影响光盘轴向偏摆各分量对总偏摆的影响，据此建立光盘轴向偏摆的数学模型。根据该模型，分析了几种有代表性的测量方法的优缺点并重点研究了它们各自的测量精度，提出了一种全新的基于激光三角法的测量方法。最后给出了测量结果和结果分析。     

径向超声振动辅助锯切光学玻璃

本文通过在锯切用超薄切割砂轮的径向上辅加超声振动的方法,对两种不同物理特性的光学玻璃进行锯切加工实验,探索了径向超声振动对光学玻璃锯切过程的影响。理论分析了超声振动锯切过程中的锯切力和锯切比能,给出了单颗磨粒在普通锯切与超声振动锯切时的切削路径。采用有无超声振动辅助锯切两种方式对K9玻璃和石英玻璃进行锯切实验,分析了超声振动对光学玻璃锯切力和锯切比能的影响。结果表明,相比于普通锯切方式,除了受到加工参数的影响外,超声振动辅助加工时K9玻璃和石英玻璃的锯切力减少幅度分别在30%~50%和50%~65%,锯切比能分别减少了30%~45%和50%~60%。径向超声振动辅助锯切使材料产生微破碎,具有减小锯切力和比能的作用,因此有利于提高光学玻璃材料锯切效率和改善加工质量。     

Design of an optical measurement system for dynamic testing of electrospindles

Dynamic characterization of electrospindles is necessary to ensure long life, reliability and high-tech performance required in many industrial applications. Many diagnostic approaches have been developed with regard to fault detection and dynamic characterization of rotating machinery.     

An improved single-parameter tip-timing method for turbomachinery blade vibration measurements using optical laser probes

This paper presents an improved analysis method for the interpretation of the vibration data measured at turbomachinery blade tips using optical laser probes. A multi-degree-of-freedom numerical simulator, which includes the structural and geometric properties of the bladed-disk assembly, the external forcing terms and the characteristics of the optical probe, has been developed to assess the reliability of the various data processing techniques to identify the natural frequencies and mode shapes of bladed-disk assemblies. It has been demonstrated that the Zablotsky—Korostelev single parameter technique, which is a de-facto standard in the aerospace industries, has inherent limitations associated with it. An improved and more rigorous method is presented for deriving the blade arrival times and a non-linear solution technique is suggested for their numerical determination. Finally, the effect of blade mistuning on the accuracy of the proposed method is also investigated.     

扭振系统中减小振动的阻抗协调法

对于由质量圆盘-扭簧组成的链式扭转振动系统，根据能量波理论，通过协调各组成环阻抗的方法，避免产生共振，达到减小振动强度的目的。     

利用误差谐波补偿法提高金属圆光栅测角精度

提高圆光栅测角精度的方法除了提高分辨率和系统精度以外,广泛采用误差补偿方法。本文通过对新型金属圆光栅的研究,提出了一种基于软件的误差补偿方法——误差谐波补偿法。实验表明该方法可消除一定阶次内幅值和初相位不随时间变化的误差谐波,有效提高测角精度。