桥式起重机的近景摄影测量方法研究

与常见的桥式起重机变形检测方法相比,近景摄影测量法具有非接触性、瞬间捕获信息量大且数字图像易存储等优点。文中将近景摄影测量与桥式起重机变形检测相结合,通过DLT(直接线性变换)标定非量测相机,采用序贯分析求解其内方位元素;在桥式起重机上合理布置反光标志点,并使用非量测相机获取数字立体像对;通过软件获得数字图像上各个标志点的坐标仪坐标,采用光束平差法求解标志点的物方坐标,构建桥式起重机三维模型,计算主梁变形量。将近景摄影测量法与水准仪、全站仪方法进行对比,证明基于近景摄影测量的桥式起重机变形检测方法能够满足桥式起重机精度要求,为桥式起重机变形检测提供了一种高效的方法。     

激光 ICF 聚变靶丸轮廓测量系统标定方法

针对激光惯性约束聚变靶丸轮廓高精度测量系统的溯源标定问题,提出一种基于激光差动共焦测量原理的标定溯源方法。该方法基于激光差动共焦靶丸测量系统轴向响应曲线过零点精确对应测量系统焦点的性质,首先利用激光差动共焦靶丸测量系统测量经中国计量科学研究院计量检定的标准椭圆块的圆度,其次通过比对测量值和标准椭圆块圆度计量值,得出该系统测量传递系数为1.03,最后通过多次检定验证测量的方法,完成系统的高精度标定。实验结果显示,利用标定完成的系统进行激光聚变靶金属球比对测量,其标准差为37 nm,该标定方法的测量重复性为17 nm,其为靶丸表面轮廓的高精度测量奠定了坚实基础。     

Calibrated Thermal Microscopy of the Tool-Chip Interface in Machining

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool-chip interface during the steady-state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all-reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond-turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control-volume approach; and 2) a simplified finite-difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.     

Calibrated Thermal Microscopy of the Tool–Chip Interface in Machining

This paper presents the results of calibrated, microscopic measurement of the temperature fields at the tool–chip interface during the steady‐state, orthogonal machining of AISI 1045 steel. The measurement system consists of an infrared imaging microscope with a 0.5 mm square target area, and a spatial resolution of less than 5 µm. The system is based on an InSb 128 × 128 focal plane array with an all‐reflective microscope objective. The microscope is calibrated using a standard blackbody source from NIST. The emissivity of the machined material is determined from the infrared reflectivity measurements. Thermal images of steady state machining are measured on a diamond‐turning class lathe for a range of machining parameters. The measurements are analyzed by two methods: 1) energy flux calculations made directly from the thermal images using a control–volume approach; and 2) a simplified finite‐difference simulation. The standard uncertainty of the temperature measurements is ± 52°C at 800°C.     

Analysis of profile measurement techniques employed to surfaces planed by an active machining system

The importance of a reliable and robust surface profile measurement system in the inspection of surface finish is beyond any doubt. For years, visual inspection has been employed in industries to determine the quality of surface finish. Since, in most cases, it fails to ensure a consistent minimum standard of finish quality, mechanical stylus based measurement systems have successfully taken over from human inspection. However, in recent years, the trend is to explore other techniques for conducting surface profile measurements. Non-contact optical methods have emerged as one of the leading candidates. In this paper, capabilities of two optical profile measurement methods (namely, light-sectioning and two-image photometric stereo) have been explored for surfaces machined using an active machining system. These profile measurement results have been compared to the ones obtained from a conventional mechanical stylus instrument. An industry-standard Talysurf CLI system has been used to provide the benchmark, traceable to NPL standards, for the measurements. Suitability of different measurement techniques have been discussed based on the results obtained.     

飞机结构件运动数据的动态视觉测量系统

基于近景摄影测量理论和立体视觉技术,提出并实现了一种针对机身结构件在飞行状态下的轨迹、姿态、位移、变形等多种运动数据的动态视觉测量方法.研究了基于工业近景摄影测量的多相机快速自标定方法;飞行状态下相机动态定位及抖动消除技术;刚性结构件的运动轨迹及姿态的快速求取和通过多相机(≥3)协作实现非编码标志点阵列的精确匹配等多项关键技术.在模拟飞行环境下的实验结果表明,相机标定的重投影误差小于0.03 pixel,系统的运动轨迹姿态测量精度可达0.01 mm/1 m,关键点位移变形测量精度可达0.05 mm/1 m,基本满足飞机测试行业的精度和可靠性测量标准.     

Porosity measurements by X-ray computed tomography: Accuracy evaluation using a calibrated object

Accurate identification and measurement of internal voids and porosity is an important step towards improvement of production processes to obtain high quality materials and products. Recently, the importance of knowing the exact size, shape, volume and location of defects has become even higher as tighter requirements and new standards have been introduced in industry. There are several well-established methods for defects evaluation based on various principles (both destructive and non-destructive). However, all conventional methods have various deficiencies and the information about internal voids/porosity that can be extracted is limited. Most of these drawbacks can be overcome by using X-ray computed tomography (CT). Unlike other methods, CT provides full three-dimensional information about shape, size and distribution of internal voids and porosity; however, the accuracy of measurements is still under investigation. Hence, further evaluations on CT porosity measurements must be performed in order to consider X-ray computed tomography a reliable instrument for the assessment and detection of internal defects.A reference object with artificial defects was used in this research work in order to evaluate the accuracy of porosity measurements by CT. The reference object was manufactured by ultra-precision micro-milling. The object contains dismountable components with embedded internal hemispherical features that simulate internal porosity. The artificial porosity was micro-milled on top surfaces of dismountable cylindrical inserts. The hemispherical calottes were thereafter calibrated by traceable coordinate measuring systems and calibrated values were compared to actual values measured by a CT system. The accuracy of CT porosity measurements was then evaluated based on results obtained on various measurands, using different software tools and measuring procedures, comparing real scans to numerical simulations and investigating the influence of CT system parameters settings on measurement results.     

Comparison of acoustic backscattering techniques for suspended sediments investigation

The aim of this paper is to compare different methods for suspended sediment investigation using the backscattering power of acoustic Doppler current profilers (ADCPs). Different concentration–backscattering models and calibration strategies were compared using two frequencies or only one and accounting or not for sound adsorption due to sediments. Two Teledyne RD Instruments (RDI) ADCPs, working at different frequencies (600 and 1200 kHz), were used simultaneously on the same water column to investigate the suspended sediment concentration and grain size distribution at four cross-sections of a lower Paraná River bifurcation near San Martín city (Argentina). In the same campaign, a Sontek 1000 kHz ADCP previously calibrated with water samples was also used. By applying a mixed electric-acoustical backscatter approach, each RDI ADCP was calibrated on an expected mean concentration, and a homogeneous grain size was fixed among the whole measurement field. Concerning the concentration results, the calibration on the mean value was found to be sufficiently reliable when compared to the previously tested and accepted acoustical backscatter method calibrated against an array of field samples that covered the concentration range of extrapolation. The same electric-acoustic approach was applied for the two frequency method. In this case, the backscatter was calibrated against the expected mean grain size and concentration. Preliminary results concerning the concentration and grain size distribution are consistent with the results of other methods. The quantity and texture of suspended sediments of the Paraná River were found to be consistent with instrument limits in terms of backscattering sensitivity. The wash load did not affect the sound propagation, and sound adsorption due to suspended sand did not perturb the sand concentration assessment.     

Experimental evaluation of HJB optimal controllers for the attitude dynamics of a multirotor aerial vehicle

The present paper is concerned with the design and experimental evaluation of optimal control laws for the nonlinear attitude dynamics of a multirotor aerial vehicle. Three design methods based on Hamilton-Jacobi-Bellman equation are taken into account. The first one is a linear control with guarantee of stability for nonlinear systems. The second and third are a nonlinear suboptimal control techniques. These techniques are based on an optimal control design approach that takes into account the nonlinearities present in the vehicle dynamics. The stability Proof of the closed-loop system is presented. The performance of the control system designed is evaluated via simulations and also via an experimental scheme using the Quanser 3-DOF Hover. The experiments show the effectiveness of the linear control method over the nonlinear strategy.     

User interface for optical multi-sensorial measurements at extruded profiles

Nowadays the process control of concave extruding is a measuring task with rising requirements. A novel optical bi-sensorial measurement system - consisting of a shadow- and a light-section-system - as well as suitable methods of analysis for the in-line inspection are presented. The proposals help to ensure the product quality on a higher level than before. The combination of dimensional accuracy and data-density leads to excellent results. The optical multi-sensor measurement system has to be calibrated and aligned to detect the same surface zone despite of high refresh rates and optical resolutions. The metered characteristics will be coordinate transformed to extrinsic world-coordinates for evaluating form deviations of complex parts. An appropriate user interface enables to re-calculate measurement objects in-line and evaluate the conformity of the part consequently. Finally the real length information assists to influence the process control. After successful test in laboratory the results will be proved in production to the target: measurement uncertainty of better 0.1 mm at every profile.     

Effects of mathematical models and algorithms on quantitative characterization of areal step height with optical and stylus profilometers

Step height characterization is essential for the quality control of various functional components, such as graphene and the step features of semiconductor devices. Two methods are proposed to characterize the areal step heights. The first method extends the two-dimensional characterization in the ISO specification into a three-dimensional one by extracting multiple parallel profiles. The second method calculates the step heights by projecting from the measurement points to the normal vector at the surface centroid. Mathematical models and algorithms of the two methods are introduced and validated by synthetic data. Experiments are conducted by comparing the assessment results of the two methods and of a method proposed in a previous research. The calibrated values of the standards are utilized for validation. The characterization results may differ notably or slightly, depending on the properties of the data and the algorithm.     

Three-dimensional surface characterization for orthopaedic joint prostheses

This study attempts to investigate a range of 'better' methods for the characterization of the three-dimensional (3D) surface topography of orthopaedic joint prostheses. In this paper, a new characterization tool for the comprehensive identification and evaluation of functional features of these surface topographies is presented. For identification, the surface topography is investigated in a space-scale space, by employing wavelet analysis. The roughness, waviness and form involved in surface topography are consequently separated and recovered respectively. The multiscalar topographical features are identified and captured. The errors caused as a consequence of three-dimensional measurement methods can be reduced. After identification, the three-dimensional surface assessment techniques previously reported by Stout and co-workers are used for the quantitative evaluation of various surface roughness features of the orthopaedic joint prostheses. Moreover, the functional properties, such as bearing area, material volume and void volume which are significantly effected by large peaks, pits and scratches are studied and the location of isolated peaks, pits and scratches in the different scales is also clearly characterized. In this work, measurement of the femoral heads and acetabular cups is carried out to demonstrate the applicability of the characterization technique for the three-dimensional surface topography of orthopaedic joint prostheses.     

Noncontact roughness measurement of turned parts using machine vision

The surface roughness of turned parts is usually measured using the conventional stylus type instruments. These instruments, although widely accepted, have several limitations such as low speed measurement, contacting in nature, requiring vibration-free environment, etc. Machine vision methods of roughness measurement are being developed worldwide due to their inherent advantages, including noncontact measurement, high information content, rapid measurement, and surface measurement capability. In past research, area-based light scattering method and gray scale line intensity measurement have been developed for roughness assessment using machine vision. Such methods, however, produced redundant data when applied to measure roughness of turned parts. In this paper, an alternative method of roughness measurement using the 2-D profile extracted from an edge image of the workpiece surface is proposed. Comparison with a stylus type instrument shows a maximum difference of 10% in the measurement of average roughness R _a using the vision method.     

Calibration of step heights and roughness measurements with atomic force microscopes

In this paper we present a method for the vertical calibration of a metrological atomic force microscope (AFM), which can be applied to most AFM systems with distance sensors. A thorough analysis describes the physical z-coordinate of an imaged surface as a function of the observed and uncorrected z-coordinate and the horizontal position. The three most important correction terms in a Taylor expansion of this function are identified and estimated based on series of measurements on a calibrated step height and a flat reference surface. Based on this calibration a number of step heights are calibrated by the AFM with measured values consistent with reference values, where available. Relative standard uncertainty of about 0.5% is achieved for step heights above 200 nm. For step heights below 50 nm, the standard uncertainty is about 0.5 nm. While a calibration of step heights done by AFM and interference microscopy can be compared directly as demonstrated here, this is not straightforward for roughness measurement. To asses this, the exact same area on an important applied surface (a hip joint prosthesis) was measured by both AFM and interference microscopy. Similarities in the images were seen; however, the calculated roughness was significantly different (R_q=3 and 1.5 nm). Applying a low-pass filter with a cut-off wavelength of λ_c=1.5 μm, the appearance of the images and the calculated roughness become almost identical. This strongly suggests that the two methods are consistent, and that the observed differences in shape and roughness in the nanometer range can be explained by the limited lateral resolution of the interference microscope.     

Robust surface fitting—Using weights based on à priori knowledge about the measurement process

Modern surface layouts like automotive cylinder liners, turbine blades or seal faces need high information content. This high information content can only be reached with modern 3D-surface measurement techniques like confocal microscopy or white light interferometry.For an analysis of the surface properties, an antecedent surface fitting is necessary. This surface fit has to be robust and must be based on trustworthy data.According to the optical measurement techniques there are many known effects, which lead to wrong or insecure measuring data. Using à priori knowledge about the measurement process leads to knowledge about surface structures, which otherwise tend to be unsure or wrong. Examples for the confocal microscopy are “bat-wings” at sharp edges, multiple peaks because of oil films or surface coating. White light interferometry also has problems with speckles, when the surface structures have the size close to the interference length of the white light interferometer.Using this knowledgebase for a pre-analysis of the surface data, a confidence level for every single data point could be calculated. That leads to a weighting function, which is usable with the commonly known surface fitting methods.In this work different weighting methods are introduced. Some weighting methods are based on the original measured data and the à priori knowledge about the measurement method. Other weighting methods also use information about the measurement process, for example, the sharpness and skewness of a confocal peak or the signal to noise ratio. The weights could also be based on à priori knowledge about the surface and the structures on the surface, for example, sharp edges or surface areas with bad reflectivity properties.There are combinations with each other, as well as with the already known weights from the common surface fitting methods from the regression analysis. This leads to a regression analysis which based on measured data with a higher reliability. The reducting of the measurement device influence provides a better comparability of surface data.     

Applications of continuous tracking SLDV measurement methods to axially symmetric rotating structures using different excitation methods

This paper presents the latest developments of the continuous-scanning laser Doppler vibrometry (C-SLDV) measurement methods applied to rotating axially symmetric structures such as bladed discs. Measurement of vibrations of rotating structures are still difficult to perform. The main reason is due to the limitations of conventional transducers used for capturing the vibrations, these are often unable to measure and/or transfer a good quality signal remotely. The LDV became an ideal candidate to replace/aid such transducers, but only the introduction of two scanning mirrors in front of a laser head produced a step forward in measurements of vibrations of rotating targets; SLDV systems are now widely used both in industry and academic communities.This work shows how a commercial SLDV system can be used for measurement of vibrations of bladed discs under rotating conditions. The features of the scanning head, which was not modified for this study, were exploited up to the limit to achieve the synchronization between the scanner and a rotating target. The simplest tracking technique is performed when a circle-line scan pattern is synchronized with the rotating bladed disc so as to produce the point tracking measurement method. The extension of such a discrete measurement method to a full-field one is made when the laser beam is capable of tracing continuously either a line (LineScan tracking) or an area (AreaScan tracking) over the surface of the rotating structure. The development of tracking C-SLDV measurement techniques is achieved by the use of the traditional excitation methods and the development of a new excitation system, which will bring the excitation and the measurement to be in the same rotating frame of reference. Several experimental results are provided to illustrate the use of such techniques in turbomachinery industries.     

二维合作目标的单相机空间位姿测量方法

针对空间交会对接的近距离位姿测量要求,提出了一种基于单目视觉的二维合作目标位姿解算算法。为方便空中移动平台的调整以满足特定的位姿关系,引入了一种新的姿态角定义方法,此方法定义的三个姿态角可以作为平台姿态调整的反馈量且不受旋转顺序的限制。平面模型相对于相机坐标系的三个姿态角和位置向量可通过平面单应矩阵直接导出。在测量实验中,算法基于DSP平台实现,合作目标由4个共面LED光源构成,测量值基准由高精度倾角传感器和全站仪获得。对空间位置变化范围为2m×2m,姿态角变化范围为-30°~30°的目标平面进行测量,结果表明,本算法可实现0.88%的相对位置定位误差和最大为0.996°的姿态角测量误差,且单帧算法的解算速度仅为0.25ms。     

Weighted approach for multivariate analysis of variance in measurement system analysis

In a process that is integral to a measurement system, some variation is likely to occur. Measurement system analysis is an important area of study that is able to determine the amount of variation. In evaluating a measurement system's variation, the most adequate technique, once an instrument is calibrated, is gauge repeatability and reproducibility (GR&R). For evaluating multivariate measurement systems, however, discussion has been scarce. Some researchers have applied multivariate analysis of variance to estimate the evaluation indexes; here the geometric mean is used as an agglutination strategy for the eigenvalues extracted from variance–covariance matrices. This approach, however, has some weaknesses. This paper thus proposes new multivariate indexes based on four weighted approaches. Statistical analysis of empirical and data from the literature indicates that the most effective weighting strategy in multivariate GR&R studies is based on an explanation of the percentages of the eigenvalues extracted from a measurement system’ matrix.     

Computer vision algorithms for measurement and inspection of spur gears

Precision measurement of gears plays a vital role in gear measurement and inspection. The current methods of gear measurement are either time consuming or expensive. In addition, no single measurement method is available and capable of accurately measuring all gear parameters while significantly reducing the measurement time. The aim of this paper is to utilize the computer vision technology to develop a non-contact and rapid measurement system capable of measuring and inspecting most of spur gear parameters with an appropriate accuracy. A vision system has been established and used to capture images for gears to be measured or inspected. A software (named GearVision) has been especially developed in-house using Microsoft Visual C++ to analyze the captured images and to perform the measurement and inspection processes. The introduced vision system has been calibrated for metric units then it was verified by measuring two sample gears and comparing the calculated parameters with the actual values of gear parameters. The maximum differences between the calculated parameters and the design values were ±0.101 mm for a spur gear with 156 mm outside diameter. For small gears, higher accuracy could be obtained and as well as small difference.