Search

Aiming at the requirements of short-range, high-precision, and high-speed measurement of coaxial helicopter wingtip distance measurement, a millimeter-wave radar wingtip distance measurement scheme is proposed, and the ranging accuracy of frequency-modulated continuous wave millimeter-wave radar is improved by optimizing the frequency estimation method and the beat-frequency signal processing process. The multi-antenna data coherent superposition method and the correlation search for the estimated frequency are used to shorten the measurement period, and at the same time, the ranging accuracy of the millimeter-wave radar can be improved, and the single measurement time can be guaranteed. Based on frequency refinement, frequency offset method, phase method, amplitude method and fitted approximation method, the frequency estimation of millimeter wave radar differential frequency signal is combined with the influence of bandwidth, measured target shape and material on ranging to improve millimeter wave radar ranging performance comprehensively. Through simulations and experiments, the accuracy, stability, time consuming and application conditions of the optimized algorithm are comprehensively evaluated, and the feasibility of millimeter wave radar wingtip ranging is verified.

Optical and visual measurement technology is used widely in fields that involve geometric measurements, and among such technology are laser and vision-based displacement measuring modules (LVDMMs). The displacement transformation coefficient (DTC) of an LVDMM changes with the coordinates in the camera image coordinate system during the displacement measuring process, and these changes affect the displacement measurement accuracy of LVDMMs in the full field of view (FFOV). To give LVDMMs higher accuracy in the FFOV and make them adaptable to widely varying measurement demands, a new calibration method is proposed to improve the displacement measurement accuracy of LVDMMs in the FFOV. First, an image coordinate system, a pixel measurement coordinate system, and a displacement measurement coordinate system are established on the laser receiving screen of the LVDMM. In addition, marker spots in the FFOV are selected, and the DTCs at the marker spots are obtained from calibration experiments. Also, a fitting method based on locally weighted scatterplot smoothing (LOWESS) is selected, and with this fitting method the distribution functions of the DTCs in the FFOV are obtained based on the DTCs at the marker spots. Finally, the calibrated distribution functions of the DTCs are applied to the LVDMM, and experiments conducted to verify the displacement measurement accuracies are reported. The results show that the FFOV measurement accuracies for horizontal and vertical displacements are better than ±15 µm and ±19 µm, respectively, and that for oblique displacement is better than ±24 µm. Compared with the traditional calibration method, the displacement measurement error in the FFOV is now 90% smaller. This research on an improved calibration method has certain significance for improving the measurement accuracy of LVDMMs in the FFOV, and it provides a new method and idea for other vision-based fields in which camera parameters must be calibrated.

The measurement of input and output torque of a precision reducer, the core component of an industrial robot, plays a vital role in evaluating the robot's performance. The TMSIS and TMSOS of a vertical cylindrical high-precision reducer detector were designed and investigated in this study to realize the accurate measurement of input and output torque of the reducer. Because a transmission chain connects the torque transducer and the reducer, the characteristics of the inevitable additional torque are analyzed in detail. A torque calibration device is developed to realize the calibration of the torque measurement system. The readings of the torque calibration device are compared with the data of the instrument’s torque measurement system to realize the instrument's torque calibration. The improved particle swarm optimization and Levenberg–Marquardt algorithm-based radial basis function neural network is used to compensate for the error of the torque measurement system. The parameters of the RBF neural network are settled according to the characteristics of the additional torque and the torque calibration results. The experimental results show that the torque measurement accuracy of the torque measurement system can reach 0.1% FS after torque calibration and error compensation.

Optical metrology has experienced a fast development in recent years—cross laser-pattern has become a common cooperative measuring marker in optical metrology equipment, such as infrared imaging equipment or visual 3D measurement system. The rapid and accurate extraction of the center point and attitude of the cross-marker image is the first prerequisite to ensure the measurement speed and accuracy. In this paper, a cross laser-pattern is used as a cooperative marker, in view of the high resolution of the cross laser-pattern image in the project and the vulnerability to adverse environmental effects, such as stray light, smoke, water mist and other interference in the environment, resulting in poor contrast, low signal-to-noise ratio (SNR), uneven energy distribution. As a result, a method is proposed to detect the center point and attitude of cross laser-pattern image based on Gaussian fitting and least square fitting. Firstly, the distortion of original image is corrected in real time, the corrected image is smoothed by median filter, and the noise is suppressed while preserving the edge sharpness and detail of the image. In order to adapt to different environments, the maximum inter-class variance method of threshold automatic selection is used to determine the threshold of image segmentation to eliminate the background interference caused by different illumination intensities. To improve the real-time performance of the algorithm, the four cross laser edge pixels are obtained by line search, and then fitted by least square. With the edge lines, the transverse and portrait line of the cross-laser image are separated, then we calculate Gaussian center points of all Gaussian sections of transverse and portrait lines based on Gaussian fitting method, respectively. Based on the traditional line fitting method, the sub-pixel center of the transverse and portrait laser strip images are fitted by removing the Outlying Points, and the center coordinates and attitude information of the cross laser-pattern are calculated by using the center equation of the laser strip, realizing cross laser-pattern center and attitude accurate positioning. The results show that the method is robust, the center positioning accuracy is better than 0.6 pixels, the attitude positioning accuracy is better than ±15” under smoke and water mist environment and the processing speed is better than 0.1 s, which meets the real-time requirements of the project.

In order to achieve the rejection of the ocean current disturbances and fast convergence in the depth positioning process of the deep-sea self-holding intelligent buoy (DSIB), a finite-time boundedness (FTB) depth control strategy based on over shoot estimation in pole placements (OEIPP) method has been proposed in which variable gains are adjusted for the DSIB closed-loop system. In this paper, the system parameters have been investigated including depth error, transient time, control gains and current disturbances. The mathematical model for the DSIB dynamic motion is established by combining the pressure hull deformation and the current disturbances model. At the same time, as the DSIB closed-loop system need be established by the finite-time transformation matrix, the establishment process on the FTB depth control strategy with a OEIPP method has been proofed. Finally, to observe the transient state of the DSIB closed-loop control system in finite time, an adjustment rule of the control gains under different current disturbances based on the FTB depth control method is analyzed. The performance of the control strategy is validated through simulations and at-sea experiments, and its feasibility established. The results show that the proposed control strategy can guarantee that the DSIB reaches the allowable depth errors of a target depth under the ocean current disturbances within a finite time. They also provide a useful guide for establishing an adjustment rule for the control gains under various current disturbances within a finite time.

Net buoyancy changes affect hovering performance and increase the extra energy consumption of deep–sea intelligent floats (DIFs) at different submergence depths. To improve the adjustment efficiency of net buoyancy changes and solve the extra energy consumption problem at different submergence depths, this study proposes a combination model of ballasting weight (BW) and minimum oil content for DIFs based on the BW method. The proposed model is accurately designed by combining an exponential function model of actual density distribution in the oceans and the deformation of a DIF hull that resulted from compressibility and thermal expansibility. Given that the adjustment process of the net buoyancy changes should be approximated for actual deployment, the model establishes the compressibility balanced relationship between the DIF hull and actual seawater. The feasibility of the proposed model is validated through hyperbaric tank system and at–sea experiments. Experimental results show that the relationship between the net buoyancy changes of DIF and pressure is nonlinear. The BW changes fluctuate between 0.05 and 0.15 g by increasing the diving depth by 1 m. For the influence of the BW on the submergence depth error, the scope of the depth error ratio is 2.2% to 2.8% from the predefined depth of 100–4200 m. Analysis results provide a basis for the establishment of an optimal net buoyancy adjustment scheme for DIFs.

High precision reducer is the core component of industrial robot. Its performance test is the key to improve product quality and ensure the accuracy of robot operation. One of the basic geometric parameters in performance test is the angle, which refers to the angular displacement of the input or output of the tested reducer. Based on a vertical instrument, angular measurement systems are designed in this article. In order to ensure the precision of results, the angle encoder is as close as possible to the measured object, which shortens the measurement chain and reduces the number of error sources. A cylindrical and disk structure improves the structural stiffness, ensures regular deformation patterns, and minimizes the angular errors caused by weak stiffness supports in the conventional instrument. Another system consisting of an autocollimator and a regular polyhedron, whose output is taken as angular standard, calibrates absolute circular gratings in the instrument. The model based on back propagation neural network can compensate the errors over the whole circumference, and finally get the angular displacement of input and output of the tested reducer in the drive process accurately. After compensation, the angular measurement errors of the instrument are within ±2 arc seconds.

In rotating machines, misaligned shafts increase vibrations and friction, which can increase the energy consumption considerably and cause premature bearing and seal damage. Laser-based alignment systems can realize quick shaft alignment with high accuracy, consisting of laser transmitting unit, charge-coupled device (CCD) or position sensitive detector (PSD) receiving unit and display unit. Their resolution can reach 1 μm or higher, and the accuracy can be even up to ± (0.5%|L| + 1 resolution). In the paper, the principle of a laser-based alignment system is presented. In order to calibrate laser-based alignment systems, a set of measurement device is established. The receiving unit is fixed on a high precision one-dimensional linear stage, while the transmitting unit remains stationary. So, the relative displacement between the two units can be measured. A laser interferometer is used as the standard value of the linear stage displacement, which is traceable to the definition of meter. The layout of the calibration system is complied with Abbe's principle, reducing the measurement error. In addition, several key influencing factors for calibration are given. At last, the uncertainty of the calibration result is analyzed. The result indicates that the calibration apparatus is practical and efficient during the routine work.

The performance of a high precision reducer determines the accuracy and efficiency of the mechanical motion, particularly in the field of industrial robots. To meet the requirements of scientific research and the expansion of industrial production, comprehensive performance testing of high precision reducers has become an important focus in related fields. This review article summarizes the main test parameters, analyzes the characteristics of existing methods, and proposes requirements according to the aspects of the mechanical structure, metrology principles, and engineering applications. Moreover, measurement methods for basic physical quantities and specific calibration techniques are presented, and the load technology is summarized. Scientific research orientations and technical routes are emphasized for achieving high-precision measurements, which can appropriately determine the performance of high precision reducers.

The trajectory of guideway influences spatial position and pose of a moving workpiece. Laser beam and visual image are used for joint measurement to continuously track a specified point on moving guideway. Meanwhile, the geodetic datum is established in the reference plane formed by structured light, which is emitted by an electronic leveling device. Further, the trajectory of a specified point on moving guideway in the world coordinate system is determined, providing effective geometric information for assembly. This paper takes a two-axis guideway system in an instrument for testing precision reducer as an example. The trajectory is obtained by the proposed method. Based on measurement results, it provides a practical application. Assembly experiments prove that the proposed method is useful. The guideway is in a universal application and this feasible method can be applied to other similar industrial fields.

Structural health monitoring is a topic of great concern in the world, and tunnel deformation monitoring is one of the important tasks. With the rapid developments in tunnel traffic infrastructure construction, engineers need a portable and real-time system to obtain the tunnel deformation during construction. This paper reports a novel method based on laser and machine vision to automatically measure tunnel deformation of multiple interest points in real time and effectively compensate for the environment vibration, and moreover it can overcome the influence of a dusty and dark tunnel environment in low visibility. An automatic and wireless real-time tunnel deformation monitoring system, which is based on laser and machine vision and can give early warnings for tunnel collapse accidents, is proposed. The proposed system uses a fixed laser beam as a monitoring reference. The image acquisition modules mounted on the measured points receive the laser spots and measure the tunnel accumulative deformation and instantaneous deformation velocity. Compensation methods are proposed to reduce measurement errors caused by laser beam feasibility, temperature, air refraction index, and wireless antenna attitude. The feasibility of the system is verified through tunnel tests. The accuracy of the detection system is better than 0.12 mm, the repeatability is less than 0.11 mm, and the minimum resolution is 10 &mu, m, therefore, the proposed system is very suitable for real-time and automatic detection of tunnel deformation in low visibility during construction.

A fiber-capacitive drop analyzer is an instrument which monitors a growing droplet to produce a capacitive opto-tensiotrace (COT). Each COT is an integration of fiber light intensity signals and capacitance signals and can reflect the unique physicochemical property of a liquid. In this study, we propose a solution analytical and concentration quantitative method based on multivariate statistical methods. Eight characteristic values are extracted from each COT. A series of COT characteristic values of training solutions at different concentrations compose a data library of this kind of solution. A two-stage linear discriminant analysis is applied to analyze different solution libraries and establish discriminant functions. Test solutions can be discriminated by these functions. After determining the variety of test solutions, Spearman correlation test and principal components analysis are used to filter and reduce dimensions of eight characteristic values, producing a new representative parameter. A cubic spline interpolation function is built between the parameters and concentrations, based on which we can calculate the concentration of the test solution. Methanol, ethanol, n-propanol, and saline solutions are taken as experimental subjects in this paper. For each solution, nine or ten different concentrations are chosen to be the standard library, and the other two concentrations compose the test group. By using the methods mentioned above, all eight test solutions are correctly identified and the average relative error of quantitative analysis is 1.11%. The method proposed is feasible which enlarges the applicable scope of recognizing liquids based on the COT and improves the concentration quantitative precision, as well.

To obtain a method for measuring thread functional diameter, a new probe based on the synthetic measurement principle is designed to quantify the practical effect of each parameter in all axial sections. The probing element is an axial slice of a standard thread with a certain thickness; hence, the slice has a determined lead angle and curvature radius. When threads with different diameters are measured by slices, the maximum error caused by the lead angle and curvature radius can approach 99 μm according to the simulation results. To solve this problem, a measurement error model is established by analyzing the relationship between the contact points of the measuring tip and thread. By simulations and experiments, our results show that most of the effect of lead angle and curvature radius can be compensated. Using six slices with different pitches, a precise detection of 192 kinds of threads is achieved after error compensation within the range of M65–M300.

The calibration and error compensation techniques for an Articulated Arm Coordinate Measuring Machine (AACMM) with two parallel rotational axes are proposed. An improved six-parameter D–H model is established. The reversal techniques are used to calibrate the parallelism errors, arm lengths and zero position of the AACMM. The effects of the bending and torsion deformations caused by the gravity of the arms are removed. The experiments prove that the calibration method is simple and the measurement expanded uncertainty ( 2 u c ) of the developed AACMM with a measuring range of (∅200–∅1000 mm) × 250 mm is less than 10 μm after error compensation.

A coordinate measuring machine (CMM) with two linear axes and an articulated arm has been developed for on machine in situ measurement of just machined workpieces. Some techniques for calibrating the CMM parameters, such as the arm and stylus lengths, offsets, parallelism and squareness errors between axes, as well as zero positions of the articulated arm and stylus, have been worked out, which are essential for assuring high accuracy of the CMM. The effectiveness of the proposed calibration techniques has been proved by experiments and practice.

The Precision Micro-Assembly Machine was developed to manufacture the ICF targets, which have submillimeter-sized components with micrometer sized features. The machine provides simultaneous manipulation of three objects in a 3-cm3 operating arena and can stitch together multiple millimeter-scales operating arenas over distances spanning tens of centimeters with micrometer-level accuracy. In this report, we will discuss the technologies that are merged to help assist the research community with micro-component fabrication. Furthermore, we also present the design of the online monitoring system, which contains two kinds of non-contact measurement system, microscopic image and laser confocal. The online monitoring system can characterize the positions of the target components during the assembly process. The effect and mathematic model of on-line measuring was analyzed. The results of target assembly experiments show position tolerance of the assembly is not more than 10μm.

In order to set up a controller of good dynamic response for the laser tracking system, special requirements of laser tracking system to its controller are analyzed in this article. One is exact position track and the other is rapid and steady speed response. The overall design strategy of the control system is put forward on the condition that the startup torque and Coulomb torque difference a lot and the system works at relative low speed (typically -10rpm to 10rpm). It is pointed out that the PWM method is effective to reduce system startup torque and increase steadiness of startup. In position loop a fuzzy PI controller is designed to decrease the position overshoot to 1.5mm and increase the smoothness of the tracking. The experimental results show that the tracking control system can accurately and rapidly follow movement of the target.

Considering the measurement system for the suspended position of the transparent film in the water, an image processing method based on watershed transform for contour detection has been proposed. The difference between the film and water has been researched by obtaining the image information through the image sensor under special light source. An algorithm of watershed which uses minima imposition to solve the problem of over segmentation for the detection is applied. Depending upon the improved algorithm, which aims to obtain the contour of the film, the target areas in the image integrate together. The result of the position is gained by the image processing technology, which provides the technical basis for automatic operation of catching film in the water.

A method for measuring bodies of rotation in the cylindrical coordinate system is considered. This method possesses many advantages such as high efficiency and high reliability. However cylindrical CMMs suffer from some specific problems due to their complexity in construction and long structural loops. Error compensation gains special importance in cylindrical CMMs. To limit these deficiencies, new techniques for compensating the parallelism errors between the measuring column axes and the rotary axis, and for compensating thermal errors utilizing reference object measurements and bidirectional measurements have been developed. The effectiveness of the proposed techniques is proven by experiment and practice.

A method for measuring the angle of two elements separated at a large distance by using a common optical reference is proposed. A common light plane or several parallel light planes are projected on these elements. The angles between these elements and the projections of light planes are measured and thereafter the angle between these two elements is determined. A practical example of measuring the angle formed by two elements separated at a distance of 7 m is shown. Its calibration method is also discussed.

To ensure that the liquid drop is slowly delivered under quasi-equilibrium condition in drop analysis, a microflow feeding pump actuated by a single stepping motor and controlled by the computer software is improved. The function of switching and injecting can be effectively realized and the cost is reduced. It can exclude the influence of bubbles. The photo signal of an embedded photoelectric sensor is used to control the movement of the syringe so as to avoid the step-missing condition. The computer software is used to solve the possible problems caused by the accidental mechanical block or sudden power cut. A kind of one-time syringe is designed for some liquids difficult to clean. Average method in the dynamic drop monitoring process is used to smooth the signals with high-frequency noise. A representation of the liquid drop fingerprint based on equivalent drop volume percentage is developed by normalizing the capacitive signal to solve the problem of magnification variation.

To achieve the aim of precise measurement of a target micro‐sphere, approximately 0.2 mm in diameter, a laser confocal probe was designed. To improve the output signal, a mathematical model of the photoelectric signal was proposed. The diameter of the pinhole was determined, and the optical path was adjusted; the oscillating units were designed. The performance of the probe was validated by experiments using gauge blocks combined with a micro‐motion measuring mount model. Besides, a more accurate signal processing method was suggested.

To achieve the aim of precise position measurement of a target micro-sphere, approximately 0.2mm in diameter, a laser confocal probe, on an active focus adjusting principle, was introduced in this paper. For finding the effect way to improve the output signal, a mathematical modal of the photoelectric signal was proposed. Based on the mathematical modal, the diameter of the pinhole was decided and the optical path was adjusted, which forward the performance of the probe. The tuning fork stimulating, inductive coils and the pinhole adjuster device were designed according to the theoretical analysis, which were more convenient to the measure task. The stability of the intact oscillating unit was tested; and the optical and mechanical performance of the probe was validated by experiments using gage blocks combining with a calibrated micro-driven table. Besides, a more accurate signal processing method was suggested in this paper.

Dual-wavelength optical signals are injected into the liquid drop through optical fibers in order to study the light intensity variation during the drop growth. Modulation and demodulation are used to reduce the influence of ambient light on the valuable optical signals. HA17555 chip composes the oscillating circuit for light modulation, with different high oscillating frequency for different light source. The light signal collected by a fiber detector after propagation inside the drop is changed into electric signal through the OPA2111 photoelectric circuit. The second-order band-pass filter composed of MAX275 chip is used for signal-separation. The high-pass filter is used to prevent the low frequency signal of ambient light. The valuable signal related to the drop is demodulated by a linear demodulation circuit including a half-wave rectifier, full-wave composition and low-pass filter.

CCD camera is used in the liquid signature analyzer system to capture images of the liquid drop of the tested sample. The digital image processing work is presented. CCD camera records the variation of the liquid drop during growth. The outline information of the drop is available through image processing. The instantaneous volume of the liquid drop can be gained through mathematical calculation. With the use of CCD camera, the information of the tested sample we can get during the measurement is enhanced. The function of the liquid signature analyzer is enriched and the discrimination ability of this technology is improved.

An instrumental method for measuring the properties of liquids has been developed. The instrument, called the fiber-capacitive drop analyzer (FCDA), is based on a specially designed drop sensor by means of the fiber drop analyzing technology and the capacitive drop analyzing technology, and produces a volume-based fiber drop trace (VFDT), which shows the relation between the light intensity passing through the liquid drop and the instant drop volume. Preliminary experiments have been carried out and these prove that VFDT externalizes the overall properties of tested liquids and is suitable for fine discrimination among different kinds of liquids. In this paper, a multi-wavelength drop analysis (MWDA) method is described. In this case, the light source of the FCDA is developed from a single wavelength to a multi-wavelength. A special filter is employed to sort out the signals from the mixed multi-wavelength signals and it becomes possible to get two or three VFDT with different light wavelength at the same time. As one knows, a material will absorb the light on certain wavelengths. It means that, for a mixed liquid, one can get different VFDTs by MWDA at the same time. By this way, the resolution capability of a FCDA is enhanced very much due to more information including in those VFDTs. A special signal process circuit, the key technology of the MWDA, is described in this paper. The test results show that the new circuit had satisfied the MWDA method well and will be very useful to an instrument of the FCDA with MWDA.

The liquid drop fingerprint (LDF) can be obtained from fiber‐capacitive drop analysis. LDF is unique and specific for a certain liquids. LDF makes the time‐based fiber drop trace independent from the speed of drop growth and the volatility of liquids. Identification and linear interpolation are used to normalize the fingerprint data, to make LDFs of different liquids comparable. A correlation comparison method is used to describe LDF quantitatively, by using the geometric correlation coefficient, the vector correlation coefficient, the scale correlation coefficient, and the distance correlation coefficient. The mathematical correlation functions are introduced in detail. Some experimental graphs and data results are presented.

A single‐wavelength liquid signature analyzer can only reveal a part of the characteristics of some liquids, because the same liquid has different absorption in the light signal with different wavelengths and different liquids have different absorption in the light signal with the same wavelength. So dual‐wavelength light signals from two LEDs are introduced into the liquid drop. In the processing circuit, two light signals are modulated with different high frequencies. The collected signal is separated by band‐pass filters and demodulated by a linear precision demodulation circuit. Bubbles make the drop shape and volume become unstable, so a seal cavity is specially designed. The drop sensor is separable, thus, the drop head can be cleaned thoroughly, which reduces the mutual interference among different tested liquids. The penetration depth of fibers into the liquid drop can be adjusted quantitatively. Furthermore fibers, diodes, and the preamplifier circuit are integrated into the liquid drop ...

Fiber drop analysis reveals the variation regularity of the light signal passing through the liquid drop during the drop growth. The coupled light signal reflects mechanical and optical properties of the tested liquids, but it is not only dependent on the profile and volume of the drop, but it is also dependent on the liquid absorption. Thus, spectral drop analysis is introduced into the drop analyzer to study the liquid composition by studying the absorption spectrum of the multi‐wavelength light signal passing through the liquid. A three‐dimensional (3‐D) liquid drop fingerprint (LDF) can be obtained by merging the light intensity signal from the fiber drop sensor, the drop volume signal from the capacitive drop sensor or CCD image processing, and the absorption spectrum signal from the fast Fourier transform (FFT) infrared spectrum analyzer. The 3‐D LDF covers a more extensive range of physical and chemical properties of liquids, and it enhances the capability of drop analysis for fine discrim...

An instrument called the liquid signature analyzer (LSA) has been developed for liquid property studies. The LSA is based on fiber‐capacitive drop analysis and produces a liquid drop fingerprint (LDF) which shows the variation of the coupled light signal inside the drop along with the drop formation. The LDF reflects multiple properties of the tested liquids and it is unique under certain conditions. A fiber‐capacitive drop sensor is designed through which a satiated and uniform drop is formed. A micro‐flow feeding pump, actuated by a single stepper motor and controlled by the computer software, is devised to ensure that the drop is slowly delivered under quasi‐equilibrium conditions. Modulation and demodulation are used to exclude the possible influence of ambient light in the fiber signal processing circuit. Three methods are presented in capacitive signal measurement; they are frequency modulation, differential frequency method, and transformer bridge method. A computer interface for the LSA h...

A low cost confocal probe based on time difference measurement has been developed. A tuning fork is used to modulate the focal length of the probe. An auxiliary arm is introduced to the optical system. This arm can be utilized for carrying out lateral measurement or for providing a reference signal. The position of the surface is determined by measuring the time difference between two successive peak intensities of the measuring signal or that between peak intensities of measuring and reference signals. Some key problems in probe design are discussed. A correlation based technique for determining the time difference between two peak pulses is developed. Error compensation technique for nonlinearity and other errors is introduced. The excellent performance of the probe has been proven by experiments.

A photoelectric multiple‐wavelength liquid drop sensor (PMWLDS) is introduced in this paper. Being employed in the liquid signature analyzer (LSA), the PMWLDS has improved much of LSAs characteristics, compared to the previous models. The PMWLDS is constructed of two integrated parts and can be separated during its cleaning. When separated, all the surfaces contacting liquid samples become open surfaces, by which the liquid head can be cleaned easily. A small chamber is designed for the elimination of the bubbles existing in the test liquid. Otherwise, the unique drop forming process will be destroyed and the LSAs test results will become meaningless. Due to a multiple‐wavelength light source integrated into the sensor, liquid drop traces can be obtained based on different light wavelengths. Being a newly developed drop sensor, PMWLDS shortens the length of the fiber sensor, makes an adjustable couple between liquid drop and fiber sensor, avoids the capacitor sensor's signature loss, etc. All the...

A new drop analysis method for liquid property study, called image drop analysis (IDA), with CCD, has been developed and its abilities to monitor the drop growth and to measure the drop volume by image acquisition and digital image processing technology are introduced. The remarkable advantage of IDA is that there is no need to determine the dielectric constant of the tested liquid and it can be used for measuring unknown liquids. Image drop analysis provides not only the volume, but also the shape information for the drop during its growth. By merging IDA and fiber drop analysis (FDA) into a fiber‐image drop analyzer (FIDA), a volume‐based fiber drop trace (VFDT) is obtained; it is independent of the speed of drop growth and the volatility of liquids. Graphic results are presented.

A flexible coordinate measuring system based on multi-lateration with tracking laser Interferometers has been built. The problems related to the optimal design of the system are studied. The principle of redundancy and its application in self-calibration, error compensation, system optimization, lost Information recovery, and measuring range extension are discussed. A new tracking system with Independent drives and a new design of the cat's eye are proposed. The optimal arrangement of the multi-lateration system, which is essential for improving its accuracy, is studied in detail. All the studies combine computer simulations and experiments.

In the process of microtarget assembling, the geometrical parameters of the microtarget need to be measured in real-time by the online detection system with four-axis linkage. So the moving performance and positioning accuracy of every motorized axis are crucial to the measurement. This paper proposed a new motion control technique for linear translation stages with stepper motor. The control algorithm was realized on field programmable gate array (FPGA) and digital signal processor (DSP), and met the high-efficiency and high-precision measurement requirements. An efficient and optimized speed control performance was achieved by using a method that was based on speed-difference driving and speed-table supplying, and a high-precision, closed-loop positioning control performance which has an error less than +0.3μm was achieved by using a method that was based on position feedback, position-window restriction and time-window restriction.