共查询到20条相似文献,搜索用时 234 毫秒
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为了满足纳米级表面形貌样板的高精度非接触测量需求,研制了一种高分辨力光学显微测头。以激光全息单元为光源和信号拾取器件,利用差动光斑尺寸变化探测原理,建立了微位移测量系统,结合光学显微成像系统,形成了高分辨力光学显微测头。将该测头应用于纳米三维测量机,对台阶高度样板和一维线间隔样板进行了测量实验。结果表明:该光学显微测头结合纳米三维测量机可实现纳米级表面形貌样板的可溯源测量,具有扫描速度快、测量分辨力高、结构紧凑和非接触测量等优点,对解决纳米级表面形貌测量难题具有重要实用价值。 相似文献
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Amit K. Sanyal Anthony Bloch N. Harris McClamroch 《Dynamical Systems: An International Journal》2004,19(4):303-343
Multibody systems in planar motion are modelled as two or more rigid components that are connected and can move relative to each other. The dynamics of such multibody systems in planar motion in a central gravitational force field is analysed. The equations of motion of the system include the equations for the orbital motion of the bodies, the orientation (attitude) of the assembly, and the relative orientation (shape) of the bodies with respect to each other. Dynamic coupling between these degrees of freedom gives rise to complex dynamical systems that are usually not integrable. Relative equilibria, corresponding to circular orbits of the multibody system, are obtained. The free dynamics has a symmetry due to a cyclic coordinate. Routh reduction is carried out to eliminate this coordinate and obtain the reduced dynamics. The stability of the relative equilibria is analysed using the Routh stability criterion when it is applicable; an expansion of the Hamiltonian in normal form is used otherwise. We apply the general results to a multibody system consisting of two hinged planar bodies, each modelled as a rigid massless link with a point mass at one end with their other ends connected by a hinge joint. We obtain the relative equilibria of this model, and carry out a stability analysis for the relative equilibria. Numerical simulations using a symplectic integrator are carried out for perturbations to these relative equilibria, to confirm their stability properties. 相似文献
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This paper presents a piezo-driven compliant stage for nano positioning with two degree-of-freedom parallel linear motions. Nano positioning is one of the most important factors in completion of nanotechnologies. It can be accomplished by flexure-based compliant stages driven by piezo-actuators. For compact configuration, the compliant stage is stacked by two-layered compliant mechanisms. The upper layer contains a motion guide mechanism, and the lower layer two displacement amplification mechanisms. The motion guide mechanism consists of four prismatic-prismatic parallel compliant joint chains for two translational motion guides. The displacement amplification mechanism is adopted by a flexure-based flextensional amplification mechanism driven by a stack-type piezo actuator. Due to the parallel compliant joint chains, the stage has the same dynamics in the x and y axes. In this study, through design and analysis, the mechanisms were machined via wire electro-discharge machining and are were then integrated with two stack-type piezoelectric elements for actuation, and two capacitive sensors for ultra-precision displacement measurement. Finally, experiments were carried out to demonstrate the performance of the compliant stage. 相似文献
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悬绳和荷载组成的振动系统的固有频率变化会对控制系统的稳定性和控制性能产生影响,因此针对此问题提出一种低复杂度的鲁棒控制器设计方法。首先,采用干扰观测器导出起重机的线性模型。该模型对于关节摩擦,荷载质量以及旋转速度等参数变化具有鲁棒性。其次,基于该线性模型设计一个含有积分器的状态反馈控制器,其增益通过线性矩阵不等式(LMI)优化算法求出,并且该控制器对于绳长变化具有鲁棒性。最后,比较仿真和实验结果验证所提方法的有效性。通过使用此法可以实现在无测量绳长的传感器系统的情况下容易地操作起重机,从而大大地简化其结构和降低其安装成本。 相似文献
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The advantages of having higher stiffness to weight ratio and strength to weigh ratio that composite materials have resulted in an increasing interest in them. In automotive engineering, weight savings has positive impacts on other attributes like fuel economy, performance and possibly noise, vibration and harshness (NVH). The driveline of an automotive system can be a target for possible weight reduction. This can be done through the use of composite materials. The design of the driveshaft of an automotive system is primarily driven by its natural frequency. This paper presents an exact solution for the vibration of a cross-ply laminated composite driveshaft with an intermediate joint. The joint is modeled as a frictionless internal hinge. The Euler–Bernoulli beam theory is used. Lumped masses are placed on each side of the joint to represent the joint mass. Equations of motion are developed using the appropriate boundary conditions and then solved exactly. 相似文献
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Donno M. Palange E. Di Nicola F. Bucci G. Ciancetta F. 《IEEE transactions on instrumentation and measurement》2008,57(8):1614-1620
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精密直线运动平台在宏微双驱动纳米定位系统中作为宏动台,用于实现大行程工作范围,解析其全工作行程上的振动特征。是微动台实现二级补偿运动的基础.通过构建以Labview软件为核心的虚拟仪器振动测试系统,采用小波变换方法对平台全工作行程运动过程中的振动测试数据进行分析,并与傅里叶变换分析方法进行了比较.由分析结果可知。两种分析方法得出了一致的结论,但小波变换分析方法可得到平台各个精确位置上的振动特性数据.实验证明,将其作为确定控制参数的依据,能改善平台的运动控制性能. 相似文献
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Traceable radius of curvature measurements are critical for precision optics manufacturing. An optical bench measurement is repeatable and is the preferred method for low-uncertainty applications. With an optical bench, the displacement of the optic is measured as it is moved between the cat's eye and the confocal positions, each identified using a figure measuring interferometer. The translated distance is nominally the radius of curvature; however, errors in the motion of the stage add a bias to the measurement, even if the error motions are zero on average. Estimating the bias and resulting measurement uncertainty is challenging. We have developed a new mathematical definition of the radius measurand that intrinsically corrects for error motion biases and also provides a means of representing other terms such as figure error-correction, wave-front aberration biases, displacement gauge calibration and their uncertainties. With this formalism, it is no long necessary to design a high-quality radius bench to carry out a precision measurement; rather a lower quality is adequate, provided that error motions are repeatable and characterized and error motion measurement uncertainties are estimated. 相似文献
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提出一种可恢复功能装配式节点,由可更换耗能铰、约束节点核心区、预制梁柱等组成。可更换耗能铰为人工塑性铰,其滞回性能是装配式节点抗震性能的关键影响因素。将可更换耗能铰设置在装配式节点的预制梁与节点核心区外伸梁端之间,对其进行低周往复荷载作用下的滞回性能试验。在该试验的基础上仅更换耗能铰中破坏的金属阻尼器,进行第二次试验。考察可更换耗能铰的破坏模态、弯矩-转角滞回曲线、骨架曲线、承载能力、延性、能量耗散能力等抗震性能。通过两次试验的对比分析,揭示可更换耗能铰抗震性能的可恢复能力。结果表明:可更换耗能铰弯矩-转角滞回曲线饱满,转动能力与耗能能力强,延性良好,强度退化不明显;可更换耗能铰实现了装配式节点的损伤、破坏集中在耗能铰上,耗能铰耗散的能量占装配式节点耗散总能量的70%以上;两次试验中可更换耗能铰的各项抗震性能基本一致,说明更换破坏的金属阻尼器后,耗能铰抗震性能基本可恢复。 相似文献
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Yunn‐Lin Hwang 《International journal for numerical methods in engineering》2008,73(2):273-295
The aim of this paper is to develop non‐linear recursive formulations for decoupling joint and elastic accelerations, while maintaining the non‐linear inertia coupling between rigid body motion and elastic deformation in deformable mechanical systems. The inertia projection schemes used in most existing recursive formulations for the dynamic analysis of deformable mechanisms lead to dense coefficient matrices in the equations of motion. Consequently, there are strong dynamic couplings between the joint and elastic coordinates. When the number of elastic degrees of freedom increases, the size of the coefficient matrix in the equations of motion becomes large. Consequently, the use of these recursive formulations for solving the joint and elastic accelerations becomes less efficient. In this paper, the non‐linear recursive formulations have been used to decouple the elastic and joint accelerations in deformable mechanical systems. The relationships between the absolute, elastic and joint variables and generalized Newton–Euler equations are used to develop systems of loosely coupled equations that have sparse matrix structure. By using the inertia matrix structure of deformable mechanical systems and the fact that joint reaction forces associated with elastic coordinates do represent independent variables, a reduced system of equations whose dimension is dependent of the number of elastic degrees of freedom is obtained. This system can be solved for the joint accelerations as well as for the joint reaction forces. The use of the approaches developed in this investigation is illustrated using deformable open‐loop serial robot and closed‐loop four‐bar mechanical systems. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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高加速度超精密激光外差干涉测量模型 总被引:2,自引:1,他引:2
为了精确地描述激光外差干涉在高加速度超精密测量中加速度对位移测量精度的影响机理与规律,建立了高加速度超精密激光外差干涉位移测量模型.通过分析测量棱镜三维运动对多普勒频移的影响,推导出高加速度激光外差干涉位移测量模型.理论分析和仿真实验表明,当测量加速度为9m/s2,匀加速运行的位移为500mm时,由于加速度变化引起的相对论性效应对测量精度的影响为5nm.高加速度超精密激光外差干涉位移测量模型的建立,可提高激光外差干涉在高加速度超精密测量中的测量精度,为激光外差干涉在高速和超高速测量领域的应用提供了理论依据. 相似文献
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提出一种异形热态锻件几何尺寸测量方法。基于线激光器、CCD和伺服系统构建线激光扫描测量系统,通过提取图像上被锻件表面轮廓调制的激光条纹二维信息,经过坐标变换及点云三维重构得到锻件三维尺寸信息。针对被测异形锻件形貌特征,建立基于摄像机运动的扫描测量模型,并提出一种基于棋盘参考平面的摄像机光心轨迹求解方法。根据平面上特征点在CCD图像不同帧中的坐标拟合摄像机的运动轨迹,结合扫描测量模型实现对异形锻件完整轮廓尺寸的测量。通过实验对封头进行扫描测量,得到球冠部分截面测量直径误差小于4 mm,满足热态锻件测量要求,验证了该方法的可行性。 相似文献
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介绍了轴对称光学非球面镜超精密加工的新方法.超精密金刚石切削加工机床的刀具进给机构通常由直线导轨实现.由于旋转轴与同等精度的直线导轨相比,具有制造难度小、成本低及结构紧凑等优点,所以采用具有快速伺服机构的金刚石刀架摆臂代替直线导轨进给运动方式.根据非球面方程,快速伺服机构的微进给量根据车刀摆角实时计算.快速伺服机构、工件以及金刚石刀具的同时运动,可以实现轴对称非球面的超精密加工.构建了回转进给工具路径、快速伺服机构运动以及相关的几何模型.通过计算机模拟验证了该加工方法的简便与可靠性,可以降低非球面反射镜加工的设备投入,提高生产效率. 相似文献
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Industrial robots are widely used in various areas owing to their greater degrees of freedom (DOFs) and larger operation space compared with traditional frame movement systems involving sliding and rotational stages. However, the geometrical transfer of joint kinematic errors and the relatively weak rigidity of industrial robots compared with frame movement systems decrease their absolute kinematic accuracy, thereby limiting their further application in ultraprecision manufacturing. This imposes a stringent requirement for improving the absolute kinematic accuracy of industrial robots in terms of the position and orientation of the robot arm end. Current measurement and compensation methods for industrial robots either require expensive measuring systems, producing positioning or orientation errors, or offer low measurement accuracy. Herein, a kinematic calibration method for an industrial robot using an artifact with a hybrid spherical and ellipsoid surface is proposed. A system with submicrometric precision for measuring the position and orientation of the robot arm end is developed using laser displacement sensors. Subsequently, a novel kinematic error compensating method involving both a residual learning algorithm and a neural network is proposed to compensate for nonlinear errors. A six-layer recurrent neural network (RNN) is designed to compensate for the kinematic nonlinear errors of a six-DOF industrial robot. The results validate the feasibility of the proposed method for measuring the kinematic errors of industrial robots, and the compensation method based on the RNN improves the accuracy via parameter fitting. Experimental studies show that the measuring system and compensation method can reduce motion errors by more than 30%. The present study provides a feasible and economic approach for measuring and improving the motion accuracy of an industrial robot at the submicrometric measurement level.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00400-6 相似文献
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G.D. Roumelas W. Gappmair P.J. Gripeos V. Christofilakis 《Journal of Modern Optics》2020,67(8):721-729
ABSTRACTThe research area of optical wireless communication links has attracted significant interest over the last years due to the significant advantages offered by this kind of technology. However, the performance of FSO communication systems depends strongly on the effects, which are related to the atmosphere along the propagation path such FSO links are using. More specifically, the weather conditions and atmospheric turbulence effects can deteriorate considerably the performance characteristics. In this work, we are studying the joint influence of atmospheric turbulence and time jitter effects on the average BER of an FSO link by presenting a new approach for various modulation schemes. Thus new closed-form mathematical expressions are derived for accurate estimation of the BER performance of the optical wireless communication systems. Finally, using the obtained expressions and typical parameter values for FSO links, the numerical results are presented and then verified through Monte Carlo simulations. 相似文献
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Straightness measurement is a very important technique in the field of mechanical engineering. A particular application for straightness measurement is high-accuracy machining on a diamond-turning lathe. We propose a novel, to our knowledge, optical method for measuring the straightness of motion, and its mathematical analysis is outlined. The technique is based on measurement of the lateral displacement of point images by use of reflection confocal optical systems. The advantages of this method are that (i) the lateral displacements in the direction of the two axes perpendicular to the optical axis can be measured, (ii) the rotation angles around all three axes can be measured, and (iii) reflection optical systems are more compact in length than are transmission optical systems. 相似文献