Abstract:In nanotechnology research area, since the material and device′s critical dimensional size decrease as well as the geometric structure complexity increase, bringing the continuous challenges in micro/nanometer accuracy measurements. Micro/Nanometer geometric quantity metrology research is the way to keep measurement quantities accuracy, uniformity and all measurement results trace back to international length basic unit. In order to keep the country′s advantages in nanotechnology research and industry area, developed countries have alwaysattached great importance to nanometer geometric quantity metrology research. In China, currently we have also successfully built several micro/nanometer geometric quantity measurement standard devices, which preliminarily established our nation′s nanometer standard traceability framework. The paper reviews the micro/nanometer measurement technologies and measurement standard devices in China, and discusses micro/nanometer metrology′s development for future.

Abstract:Gravimeters, which can obtain the information related to gravity efficiently, have potentially found wide applications in various fields. This kind of instrument plays an irreplaceable supporting role in many industries referring gravimetry. It has been proved by history that the improvement and innovation of the measurement principle employed in gravimeters have significantly increased the performance of such instruments. Firstly, this article introduces the basic concept and classification of gravimeters. Secondly, according to the maturity of measurement principle and the wideness of application field of relevant gravimeters, four typical kinds of gravimeters widely used in the world are selected in this review, including the freefalling body gravimeter, atomic interference gravimeter, spring type gravimeter and superconducting gravimeter. This review presents the measurement principle and development status of each type of gravimeter respectively, and emphasizingly summarizes the specifications related to measurement accuracy. Finally, the present status and future development of the related research on gravimeters both in China and abroad are discussed.

Abstract:Over the past seventeen years, notable advances have occurred in a diverse range of scientific areas following the development of femtosecond optical frequency combs. Frequency comb first establishes a direct link between microwave and optical frequencies, thus enabling the breakthrough of time and frequencydomain research. Frequency stabilization of comb has led to a revolution in frequency metrology and precision measurement. In addition, welldefined temporal coherence across the optical spectrum makes it a unique tool for molecular spectroscopic applications, simultaneously providing high speed measurement, high spectral resolution and broad spectral coverage. This tutorial review provides an introduction to femtosecond optical frequency combs, covering their principles of operation and applications and advance in frequency metrology, absolute distance measurement, precision absorption spectroscopy, high speed nonlinear spectroscopy and microscopy and high precision time and frequency transfer. In this way it aims to demonstrate their potential as a spectroscopic tool that could play a very significant role in future advances in the precision sciences.

Abstract:High precision absolute distance measurement plays an important role in the development of sciences and technology. The traditional methods are gradually unable to meet the increasing requirements. Optical frequency comb is mode locked pulse laser with repetition rate and phase controlled, which has higher temporal, spatial, and frequency resolution. Thus, combbased distance measurement has attracted lots of attention due to its application in high accuracy large scale metrology and satellite flying formation. In this paper, the development and status of combbased distance measurement is summarized, and five measurement principles are introduced in detail, including synthetic wavelength interferometry, multiwavelength interferometry, dispersive interferometry, dualcomb interferometry, and timeofflight method.

Abstract:Precision measurement is the precondition and basis of advanced manufacturing development. As the eyes of intelligent manufacturing, precision measurement greatly improves the production efficiency, reduces the production cost, and directly promotes the development of human society. Under the background of manufacturing informationization, as the pilot technology of advanced manufacturing, precision measurement methods and instrumentation technology must be advanced or synchronized with advanced manufacturing, and provide information support for the precision, integration, intelligent development of the advanced manufacturing. This paper summarizes the current situation and research contents of modern precision measurement technology in industrial production and scientific research, emphatically describes the latest technologies applied in precision measurement, how the precision measurement migrates from laboratory to production line, and the future development trend and direction of precision measurement technology.

Abstract:Articulated coordinate measuring machines (ACMMs) have the advantages of portability, light weight, large measurement range, etc., and are widely applied in the quality inspection fields of automotive industry, aeronautics and astronautics, mold manufacturing, assembly of largescale equipment and etc. ACMMs consist of 6 or 7 rotation joints in series. Force balance mechanism is installed on the joint near the base, which improves the operation capability of ACMMs greatly. The angle measuring systems are achieved with high precision angle encoders installed on the rotation joints. Optical scanning probe is applied on ACMMs to achieve the noncontact and rapid measurement of complicated surface. In order to obtain the more accurate measurement model, several methods for modelling and parameter identification are studied, and the performance evaluation standards of ACMMs are proposed by different international organizations. This paper introduces the key technologies and future development trends of ACMMs.

Abstract:The harm of gear grinding burn is analyzed and a variety of detection methods and characteristics of gear grinding burn are summed up and compared in this paper. These methods can be divided into prior detection methods and post detection methods according to the chronological order of the detection and grinding burn. Prior detection methods include critical constant method, ratio method of grinding force, grinding temperature monitoring, and neural network for predicting grinding burns. Post detection methods include destructive detection methods such as acid corrosion method, the surface microhardness test, metallographic test, metamorphic layer depth and nondestructive detection methods such as visual inspection, Xray diffraction residual stress test, component analysis, eddy current testing, CCD image, magnetoelastic method, online acoustic emission monitoring. The research also investigated the existing detection methods for gear grinding burn, discussed the scope of applications and the limitations, and furthermore revealed the developing direction of detection methods for gear burn.

Abstract:Computer numerical control (CNC) machine tool is a key indicator of the level of the country's manufacturing assembly industry, and its machining accuracy is a key element which reflects the performance and the level of machine tools. Error compensation is one of the main ways and trends to improve the processing accuracy of CNC machine tools. Rapid and accurate measurement of CNC machine volumetric errors is the premise and key of the error compensation and the accuracy improvement of CNC machine tools. How to rapidly and accurately measure all kinds of errors of machine tools has become a research hotspot and focus in the measurement field at home and abroad. Currently, there are many kinds of measuring methods and measuring instruments in this field. Focusing on the measuring instrument and method, as well as the measurement strategy, this work summarizes volumetric geometric errors measurement methods and instruments for CNC machine tools. The principle, pros and cons of them are anaylized and the trends in the fields are discussed.

Abstract:3D shape acquisition of object surface has been widely used in the fields of intelligent manufacturing, aerospace, cultural relics protection, health care, remote education, and so on. Due to the limitation of hardware performance, especially the projection speed of existing digital projection system, 3D shape of object can not be obtained quickly. Hence, the appearance of color imaging and projection system provides a new research direction for 3D imaging system of parallel color channel. This paper reviews the status of 3D shape measurement techniques by projecting and capturing colour fringe pattern images on the object surface in detail. The principle of colour fringe projection technique, the modulation and demodulation of colour fringe pattern, the calibration of 3D imaging system and the directions for future research are analyzed. Moreover, several case studies are illustrated to obtain the 3D shape and colour texture using colour fringe projection techniques. This paper summarizes the 3D shape measurement techniques based on colour fringe pattern images on the object surface elaborately, and the challenging issues and future research directions are also discussed to advance the 3D measurement techniques.

Abstract:Aiming at the current practical problem that the calibration precision of ground test equipment of sensors is inconsistent with the design value, a design scheme for a precision adjusting mechanism is presented with high resolution, high stability and five degree of freedom, in order to meet the higher precision application demand of ground calibration of optical attitude sensors. At first, the influence of conformity error of optical axis on position error of star point is analyzed. With a combination of the technical indicators of attitude sensors, we adopt the independent control method of stacked adjusting hierarchy. Then, the gap elimination method is determined according to the gap form within the mechanism. Besides, an adjusting mechanism structure meeting the calibration requirements for sensors is designed. After that, statics analysis and modal analysis are carried out. Simulation results and test data show that the actual measurement displacement resolution of the adjusting mechanism is better than 0.1μm, and the angular resolution is 0.1 second of arc. During the stability test of star point position, star point position error decreases more than 5″compared with the error value in the test which adopts conventional adjusting mechanisms. It may reduce the influence of conformity error of the optical axis on the calibration precision of sensors and improve reliability of calibration results.

Abstract:The generation of high accuracy calibration force is one of the key factors for high precision measurement of micro thrust. With the advantages of noncontact, structure simplicity, control easiness and etc., electromagnetic force has become an effective method to generate calibration force in micro thrust measurement system. Aimed at the performance requirements of electromagnetic calibration force in micro thrust measurement, the effect of relative position changes between the magnet and the coil on the magnitude of the electromagnetic force is focused. The output characteristics of the electromagnetic force with vertical distance, radial deviation, relative angle changes are obtained by simulation: the electromagnetic force is symmetric along the central axis of the magnet and will become larger when the relative angle and the radial deviation are not zero; the electromagnetic force increases first and then decreases when axial distance increases. Based on the balance weighing method, a 3D adjustable electromagnetic force measurement device is designed and a zero adjustment method of axial distance, radial deviation and relative angle is proposed. Relatively complete mechanical properties are obtained by the piecewise fitting method, the problem of large relative error in small calibration force output is solved. The control relationship between the electromagnetic force and the current is obtained, and the relative position variation range is specified. The new concepts such as insensitive angle, insensitive radial deviation, insensitive axial distance section and etc. are put forward, which provide specific parameters for performance characterization of the electromagnetic force generating device.

Abstract:As the automation and intelligence for power grid and power system improves continuously, the function of power system signal analysis and data processing methods is further highlighted. Compressed sensing is a new signal processing method based on signal sparseness, which transforms the signal sampling process using Nyquist sampling theorem into the observation process based on optimized computation for restoring signal. It is widely used in signal / image processing, medical treatment imaging, wireless communication and etc. Compressed sensingbased power system signal analysis and data processing method has the advantages of low sampling rate, high compression ratio, easy to extract signal characteristics and etc. Therefore, it has a wide application prospect in power system. The main purpose of this paper is to provide a theoretical framework of compressed sensing, and to summarize its applications in power system signal analysis and data processing. The main aspects are as follows: power quality analysis, fault analysis, power system modal identification, power system prediction, data transmission, smart grid and etc, and combined with the development of compressed sensing in power system signal analysis and data processing, its development prospect is expected.

Abstract:To avoid the impact of oilpaper insulation transformers’ aging on its equivalent circuit, the recovery voltage differential spectrum solution method is proposed to determine the number of equivalent circuit’s polarization branches by analyzing the functional relation between the recovery voltage spectrum line and the parameters of the equivalent circuit. The proposed method solves the longtime knotty problem in determining the number of polarized branches of the equivalent circuit, laying a solid foundation for diagnosing the insulation state of the transformer accurately. Case studies show that the number of polarization branches of the equivalent circuit can be determined accurately and the insulation aging condition of the transformer is reflected more accurately by using the recovery voltage differential analysis method. Moreover, the number of the differential spectrum lines and polarization branches becomes larger when the transformer insulation aging becomes worse.

Abstract:In order to solve the problem of noncontact and high precision nondestructive test of aircraft composite material structures, a laser ultrasonic test system based on articulated robot and optoacoustic parameter matching method is proposed. The model of layered anisotropic composite material is built with finite element method, and the characteristics of the asymmetric distribution and beam tilt and distortion of laser ultrasonic induced by the layered anisotropic property of the material are calculated and analyzed. The optoacoustic parameter matching method using laser ultrasonic to characterize the delamination is obtained based on the numerical simulation and experiment results. In the system design, an Nd:YAG pulse laser with 1 064 nm wavelength is used to generate the ultrasonic signal, and the ultrasonic signal is detected by a two wave mixing laser interference system based on photorefractive effect. The exciting and detecting lasers are transmitted by the optical fibers and projected on the surface of the target under test. A precise sixaxis articulated robot is adopted as the Cscan device. The laboratory prototype of the system was built, the Cscan test of the carbon fiber reinforced plastic (CFRP) specimen was realized, and the shape, size and distribution characteristics of the simulated defects in the specimen was obtained. Thus the effectiveness of the test system and parameter matching method is verified. The research results prove that the developed robot assistant laser ultrasonic test system can realize the detection and imaging of the internal delamination with diameter larger than 1 mm in the CFRP composite specimen, and has application prospect in the nondestructive test of aircraft composite material structures.

Abstract:A new parameter identification method for a class of hysteretic nonlinear system is presented. The integration property of the BoucWen model, which plays an important role in later linear and hysteretic parameter identification, is analyzed through constructing appropriate periodic inputs. System states and equivalent disturbance are observed by extended state observer to develop equation set and by solving linear equation set, linear and nonlinear parameters are identified individually. The effectiveness of the method is validated via simulation. Finally, the proposed method is applied to a class of piezoelectric system for identifying hysteretic nonlinear system model, which reflects the characteristics of the real system well.

Abstract:In order to realize unmanned operation of boomtype roadheader, a pose detection method based on UWB ranging technique is proposed. Through analyzing the working conditions of roadheader and local positioning technology principle, a UWB pose detection system is designed. The system uses 4 mobile base station robots equipped with UWB modules to measure the distance from the fuselage nodes to base stations. After calculating the ranging information, the pose parameters of the roadheader are obtained; The UWB ranging accuracy verification experiments in a narrow and closed tunnel were carried out, and the system pose accuracies based on direct analysis algorithm and Caffery algorithm were simulated and analyzed. The study results show that the ranging accuracy of the UWB module can be less than 2 cm in the narrowclosed tunnel. The system threeaxis positioning accuracy increases linearly from 4 mm to 3 cm in the 10~95 m narrowclosed tunnel, and the accuracies of the heading angle, pitch angle and roll angle of the system increase linearly from 0.2° to 1.5°, which satisfies the pose detection accuracy requirement of boomtype roadheader and provides a basis for realizing the autonomous navigation of roadheader.

Abstract:Compared with conventional Cartesian kspace sampling, the nonCartesian sampling can enable higher coverage effeciency of kspace, more efficiently make use of the gradient system performance, and reduce dB/dt to prevent to cause the undesirable human physiological reactions. The combination of nonCartesian kspace sampling and parallel imaging can further accelerate imaging speed, however the artifact pattern in image domain would become much more complicated, which introduces a lot of technical difficulties to nonCartesian parallel MRI reconstruction. In this article, several typical nonCartesian parallel imaging reconstruction techniques including SENSE, CGSENSE, nonCartesian GRAPPA, SPIRiT and newlyemerging compressed sensing are reviewed, their technical details, advantages and disadvantages are discussed. SENSE and CGSENSE can achieve optimal reconstruction results theoretically, but both of them are restricted by the accurate measurement of coil sensitivity distribution. NonCartesian GRAPPA doesn’t rely on coil sensitivity measurement, but can only perform approximate calculation for specified nonCartesian sampling mode. SPIRiT combines the advantages of SENSE and GRAPPA, and can obtain satisfactory result by using iterative optimization algorithm. Taking the advantage of sparse transform characteristic of images, compressed sensing cooperating with existing iterative optimization parallel imaging method can further improve reconstructed image quality, and it will be a hotspot in the future study.

Abstract:Aiming at the 3D measurement and 3D reconstruction of underground pipeline network, a scheme for camera motion estimation and 3D reconstruction of pipeline network based on active stereo omnidirection vision sensor (ASODVS) is presented in this work. A pipe robot equipped with ASODVS travels along the pipeline, obtaining the inpipe panoramic texture images and laser scanning images in real time. The central point of the lasers projected on the inner wall is analyzed and the point cloud data of the pipe crosssection are calculated. Then the panoramic texture images are processed in the following steps. First, the feature points are extracted and matched adopting the SURF algorithm; Second, the wrong matched points are removed using RANSAC method; Third, the motion poses are estimated utilizing the polar geometry principle and optimized with the BA approach; Finally, the point cloud data are converted from the camera coordinate system to the world coordinate system with the motion poses of the camera, completing the 3D reconstruction of the underground pipe network. Experimental results show that the proposed system is capable to estimate the motion poses of the panoramic camera precisely and achieve a realtime 3D reconstruction of the inner pipeline, realizing the synchronization of walking, data acquisition, processing and analysis, 3D modeling for the pipeline inspection robot.

Abstract:A novel point cloud edge extraction algorithm is proposed in this paper based on eight neighbor depth difference. In this algorithm, according to the point clouds of the object features, each feature point is projected vertically along the depth direction, the projection points are divided to grids, and the average of the depths corresponding to the projection points in each grid is calculated and used as the depth of the grid. Then, the depth of each grid is compared with those of its eight neighbor grids; and according to the depth difference, whether edge point exists in the grid or not is determined, and then the sorting method is used to screen out the point cloud edge point of the object in the grid. Aiming at two typical point cloud data containing nonhole and hole, the proposed eight neighbor depth difference algorithm is used to extract the edges of point clouds, which verifies the effectiveness of the algorithm.

Abstract:machine vision; roughness measurement; index assessment; index design; color image

Abstract:A method is introduced for automatic tracking and deformation correction of the measurement error, caused by the parallax deformation of the target object in any position of the visual field. Based on the analysis of parallax deformation, an automatic tracking detection model is proposed to obtain the correction parameters. Through the improvement of SSDA template matching, image binarization and corrosion, centroid coordinate acquisition and contour edge search, the characteristic parameters reflecting the position and pose deviation of the target object are calculated. Thus, the object automatic tracking position and pose deviation correction amount can be obtained. In this paper, the internal thread of arbitrary position pose M4 nut is used as the experimental object. The experimental results show that the automatic tracking correction method is feasible and has good tracking consistency, and achieves better correction effect of parallax distortion.

Abstract:An automobile detector is designed based on tunneling magnetoresistance (TMR) sensor. Key specifications of the automobile detector are determined by theoretical analysis and simulation. The characteristics of the magnetic anomaly signals caused by automobiles are measured and analyzed, and the circuit is developed to detect the signals. Performance of the detector is calibrated and tested, including linearity, noise level, bandwidth, detecting distance, and detection rate. Test results show that the farthest response distance of the detector is up to 4 m, and the detection rate is 100% within 3.5 m. The automobile detector has advantages in precision, linearity, dimensions and power consumption, which can be applied into highly sensitive automobile measurement and detection.

Abstract:A dual parameter fiber sensor based on Long Period Fiber Grating (LPFG) cascaded with Fiber Bragg Grating (FBG) structure for temperature and strain is presented. The proposed fiber sensor is cascaded with LPFG micromachined by the femtosecond laser and FBG, and there are two dips for the transmission spectrum, namely FBG transmission dip at 1 551.9 nm and LPFG transmission dip at 1 559.1 nm with the fringe contrast -12.7 dB. The temperature and strain characteristics of the proposed sensor were measured at 30~70℃ and 0~500 με, respectively. Experimental results show that during the warming process, the FBG shows red shift with increasing wavelength, the sensitivity is 15.00 pm/℃, and the linearity is 0.981 3; The LPFG shows blue shift with decreasing wavelength, the sensitivity is -11.75 pm/℃, and the linearity is 0.945 3. During the cooling process, the FBG shows blue shift with decreasing wavelength, the sensitivity is 18.25 pm/℃, and the linearity is 0.953 8; The LPFG shows red shift with decreasing wavelength, the sensitivity is -15.42 pm/℃, and the linearity is 0.980 2. During the loading process, the FBG shows red shift with increasing wavelength, the sensitivity is 0.93 pm/με, and the linearity is 0.991 5; The LPFG shows blue shift with decreasing wavelength, the sensitivity is -1.51 pm/με, and the linearity is 0.986 3. During the unloading process, the FBG shows blue shift with decreasing wavelength, the sensitivity is 0.92 pm/με, and the linearity is 0.990 9; The LPFG shows red shift with decreasing wavelength, the sensitivity is -1.51 pm/με, and the linearity is 0.972 8. The proposed sensor exhibits high sensitivity and good linearity for dualparameter measurements.

Abstract:Aiming at the measurement errors caused by nonorthogonality, inconsistent sensitivity, zerooffset of the triaxis fluxgate sensor and the position misalignment of two fluxgate sensors composed of the gradiometer, the error model is established in this paper. Based on the invariance principle of total geomagnetic field vector modulus in a short time, the parameter identification of the first fluxgate sensor is performed with linear least squares algorithm; based on the principle of the minimum F norm of the 3 component difference after calibration, the parameter identification of the second fluxgate sensor and the relative position between two fluxgate sensors are conducted with the multiple linear regression method. The experiment results show that the proposed method can reduce the maximum total magnetic field error of two fluxgate magnetometers from 1 194.4 nT to 30.0 nT, and the maximum output error of the three component gradiometer from 529.1 nT to 13.4 nT. The performance of the gradiometer is effectively improved.

Abstract:Micro Electro mechanical Systems (MEMS) gyroscope has been widely used in military and civilian fields due to its low cost and compactness, but there is still issue of insufficient zerobias stability. To improve this performance, a scalable and portable hardware platform with a size of only 45 mm×55 mm×30 mm is designed in this paper. On this platform, multiscale fusion algorithm in wavelet domain is applied to process the original data of the four MEMS gyroscopes by realtime wavelet fusion. The test results show that the system is stable and reliable, and the variance of fused data is reduced by one order of magnitude compared with the original variance.

Abstract:According to the magnetoviscous characteristic of magnetic liquid, the viscosity of the magnetic liquid will increase when a magnetic field with its direction perpendicular to the direction of the vortex vector of the magnetic liquid around the magnetic liquid. Using magnetic liquid as the damping fluid of the vibration damper, the damping radio of the vibration system can be changed by adjusting the magnetic field, so that the purpose of vibration damping is achieved. Based on this property, a piston magnetic liquid damper is proposed. The dynamic model of the magnetic liquid in the damper is built according to the flow equation and continuity equation of magnetic liquid. The formula between damping force and vibration speed of the vibration damper and the damping ratio of the vibration damping system are derived. The experiment was designed. A magnetic liquid vibration damper is installed on the free end of the cantilever beam; a coil is used to exert uniform magnetic field on the vibration damper. The effect of the magnetic liquid vibration damper on the damping ratios of the cantilever beam vibration is studied under different coil currents. The experiment results show good agreement between experiment result and theoretical analysis result under the assumed condition. The experiment result also indicates that the damping effect of the piston magnetic liquid damper is enhanced when the current in the coils increases in a certain range.

Abstract:The largescale integration of renewable energy resources makes the energy storage technology the vital support and breakthrough direction of future energy transitions．In order to reduce the pressure of system adjustment, hybrid energy storage (HES) based on battery and supercapacitor is developed to compensate wind power forecast errors．According to the performance characteristics and the response speed of HES，the decomposition level is determined and the initial allocation for charging/discharging power of HES is realized, utilizing the advantage of obtaining more detailed information by wavelet packet decomposition. Considering capacity constraints of HES in practical applications，a SOC partitioned power control strategy is proposed to modify the power instructions of energy storage devices and an optimized power distribution is achieved, improving compensation effect simultaneously. Application results show that the proposed strategy can compensate wind power forecast errors effectively by taking full advantages of complementary superiorities of HES，ensuring the longterm safe and stable operation of energy storage devices．