Laser Tracking System Research Articles

Large-scale dimensional metrology (LSDM): from tapes and theodolites to multi-sensor systems

Last decades witness an increasing interest in Large-Scale/Large-Volume Dimensional Metrology (LSDM). Many fields of application, ranging from construction to shipbuilding and aerospace, have shown more and more accurate and versatile systems for geometric control and tolerancing. Especially in the last ten years, optical technology has registered a fundamental step forward both in terms of metrological performances, versatility and convenience of use. This is further demonstrated by the current large diffusion of laser tracker and photogrammetric systems. The growth is also complemented by the development of new standards, even though a comprehensive body specific for LSDM is still lacking. The twofold aim of the present survey is to present a bibliographical and bibliometric analysis of the field and to propose a scheme of classification of the main current approaches. As an output of this paper, a “LSDM Multi-perspective Model” is introduced, according to which dominant technologies and restrictions are analyzed with the aim of individuating current lacks and defining the roadmap for future development of new instruments and systems.

Laser Tracker Error Modeling and Kinematic Calibration Strategy

Calibration of Laser Tracker systems is based most times in the determination of its geometrical errors. Some standards as the ASME B89.4.19 [1] and the VDI 2617-10 [2] describe different tests to calculate the geometric misalignments that cause systematic errors in Laser Tracker measurements. These errors are caused not only because of geometrical misalignments and other sources of error must also be taken in count. In this work we want to state the errors in a kinematic form. Errors will be split in two different components, geometric and kinematic errors. The first ones depend on the offsets, tilts and eccentricity of the mechanical and optical components of the system. Kinematic errors are different for every position of the Laser tracker, so they will be formulated as functions of three system variables: distance (R), vertical angle (V) and horizontal angle (H) usually called d, φ and θ. The goal of this work is to set up an evaluation procedure to determine geometric and kinematic errors of Laser Trackers.

Optogenetic control of selective neural activity in multiple freely moving Drosophila adults

We present an automated laser tracking and optogenetic manipulation system (ALTOMS) for studying social memory in fruit flies (Drosophila melanogaster). ALTOMS comprises an intelligent central control module for high-speed fly behavior analysis and feedback laser scanning (∼40 frames per second) for targeting two lasers (a 473-nm blue laser and a 593.5-nm yellow laser) independently on any specified body parts of two freely moving Drosophila adults. By using ALTOMS to monitor and compute the locations, orientations, wing postures, and relative distance between two flies in real time and using high-intensity laser irradiation as an aversive stimulus, this laser tracking system can be used for an operant conditioning assay in which a courting male quickly learns and forms a long-lasting memory to stay away from a freely moving virgin female. With the equipped lasers, channelrhodopsin-2 and/or halorhodopsin expressed in selected neurons can be triggered on the basis of interactive behaviors between two flies. Given its capacity for optogenetic manipulation to transiently and independently activate/inactivate selective neurons, ALTOMS offers opportunities to systematically map brain circuits that orchestrate specific Drosophila behaviors.

Optimal Method on the Compensation for Inverse Kinematics of Robot

Its hard to define base coordinate of industrial robot because base coordinate of robot in its inner. This article used Laser tracker system (LTS) to test its distance accuracy. Simultaneously, it is hard to must modify the controller of the robot, even though the robot kinematic compensation is high precision. Therefore, it used inverse kinematic compensation to compensate robot error by optimal method. Experiment results demonstrate that it can improve the robot accuracy in the working space, only modifies joint angle.

Algorithm for a high precision contactless measurement system

This paper presents a Monte Carlo simulation of the self-calibration method for the multi laser tracker system (MLTS) which can track a retroreflector mounted on a kinematical system (e.g. positioning stage, robot manipulator etc.). Four laser trackers build up the MLTS. In the first part of the study the required algorithms enabling the MLTS to measure the position of the retroreflector are presented. The algorithms include the localization of the retroreflector, the communication between the laser trackers and the tracking controller as well as the calculation of the Tool Centre Point (TCP) position. In the second part of this study a deeper analysis of the self-calibration algorithm is carried out. A Monte Carlo simulation shows that the quality of the parameter estimation highly depends on the optimal arrangement of the MTLS.

Design of High Accuracy Robot Welding Machine for a Cone Bottom

This paper designed a special welding machine for an aluminum cone bottom workpiece. This machine contains highly accurate positioner system, laser tracking system, and robotic welding devices. It is used to weld the transverse seams and the longitudinal seams of the workpiece. The interaction of welding robot with positioner and the real-time seam correcting can ensure high quality of welding.

Test of Robot Distance Error and Compensation of Kinematic Full Parameters

In order to improve the positioning accuracy of robots in the workspace, the maximum cube of robots is solved according to ISO 9283:1998 standard. In addition, in order to efficiently test and identify the kinematic parameters of robots, a mapping from robot's distance error onto kinematic parameter errors is presented based on Hayati's modified D-H model. Then, by analyzing the condition number of distance error matrix, it is concluded that parameter d i can be deleted when parameter β i is added in the joint of the modified model. Furthermore, by analyzing the relationship among the parameters of the distance error model, it is found that the deletion of some unidentified kinematic parameters may not result in the accuracy decrease of kinematic error model. Finally, some compensation experiments of the proposed model without unidentified kinematic parameters are carried out by using a laser tracker system. The results show that the proposed method effectively reduces the distance error and greatly improves the positioning accuracy of robots.

Design and performance analysis of a novel parallel servo press with redundant actuation

The large capacity servo press is traditionally realized by means of simultaneous actuation of multiple motors. But there exist the over-constraint problem and interference among actuators, which increases the control difficulty and product cost. This paper proposed a novel parallel servo press with redundant actuation, which can avoid the over-constraint and actuation interference. The kinematic and dynamic model of the present servo press are established and thus the kinematic and dynamic performances are obtained under three working modes, i.e. the same and opposite direction modes and non-synchronous mode. The prototype of the active mechanism with the redundant actuators has been manufactured. The kinematic experiments are carried out by using API laser tracking system and the theoretical calculation results agree with the measured data very well, which validates the theoretical model and the present press mechanism.

Применение лазерной системы слежения для управления процессом автоматической MIG/MAG сварки

Применение лазерной системы слежения для управления процессом автоматической MIG/MAG сварки

Analysis and design of prisms using the derivatives of a ray Part I: derivatives of a ray with respect to boundary variable vector

A computational scheme based on differential geometry is proposed for determining the first- and second-order derivative matrices of a skew ray as it is reflected/refracted at a flat boundary surface. In the proposed approach, the position and orientation of the boundary surface in 3D space are described using just four variables. As a result, the proposed method is more computationally efficient than existing schemes based on all six variables. The derivative matrices enable the cross-coupling effects of the system variables on the exit ray to be fully understood. Furthermore, the proposed method provides a convenient means of determining the search direction used by existing gradient-based schemes to minimize the merit function during the optimization stage of the optical system design process. The validity of the proposed approach as an analysis and design tool is demonstrated using a corner-cube mirror and laser tracking system for illustration purposes.

Laser tracker performance quantification for the measurement of involute profile and helix measurements

Standard-conforming measurements for a large involute gear were performed with a manually operated laser tracker system and the corresponding task-specific measurement uncertainties were estimated. Especially, readers using laser trackers for inspecting large involute gears will get information of a taskspecific measurement performance for the first time, which significantly differs from the laser tracker machine specification. To ensure unambiguous and repeatable measurement results, user-friendly auxiliary tools are used, which allows the operator to probe the measurement points according to existing guidelines and standards. Measurements were taken on a robust and highly accurate large involute gear measurement standard of the Physikalisch-Technische Bundesanstalt (PTB) under laboratory conditions. The size of this gear measurement standard complies with those gears used in wind power plants. The external gear materializes a left and a right hand gear as well as a spur gear. The obtained results of profile, helix and surface measurements are presented. These research activities were carried out at the PTB in the department of coordinate metrology.

Research on Preparation Band-Pass Filter by Lon Beam Sputtering

According to the requirement of the filter for laser tracking system, we chose Ta as the target material of high refractive index and SiO2 as the target material of low refractive index, the film system was designed and optimized with the TFCalc software, adopted the double ion sputter coaters by VEECO company for plating system, using two sides of the substrate to broaden the long and short wavelength cut-off band respectively, we improved the peak transmittance and simplified the difficulty of experimental analysis, the filter to meet the demand has been deposited. The average transmittance of the filter at 532nm, 808nm, 1064nm and1550nm wavelength was less than 0.2% and the peak transmittance at 905nm wavelength was 96.3%. The filter can withstand the test of bad environment and satisfy the requirements of the laser tracking system.

General model on polarization compensation in satellite-to-ground quantum communication

A general model in satellite-to-ground quantum communication is proposed by investigating the effect of a laser acquisition, pointing, and tracking (APT) system on the polarization state of single photons. The eccentricity of the general model ranges from 0 to 1, which means that a circular orbit can be introduced reasonably. Moreover, the geocentric-equatorial coordinate system, which can utilize the two-line elements, is used in the general model. Two kinds of simulations are performed, and we found that the rotations of polarization state are obviously influenced by the APT system. Our model could be applied in a realistic satellite-to-ground quantum communication system.

Design of Small Laser Tracking System Based on Four-Quadrant Detector

Returned laser detection is bottleneck in remote active laser detection. A practical small laser tracking system with simple structure based on four-quadrant detector (QD) is presented in this paper. For the volume restriction in weapon systems, design a small laser receiving optical system. An orientation calculation circuit based on the Sum and Difference circuit with Divisional normalization algorithm is designed to decrease the burden on processor. A simple MCU circuit based on high-speed chip C8051F020 is generated, accomplishing AD-conversion and further calculation. Through programming of the electric signals from the orientation calculation circuit with C8051F020, a control signal used by the missile guidance is formed. Laser signal receiving experiment is conducted by the circuit board as presented in this paper. It is possible to achieve the ideal requirements, and provide a good foundation for collaborative processing of other sensor signals to jointly get guided control commands.

Research of Facular Energy Distribution for Pulsed Laser Tracking System

Due to the distortion is always accorded when the laser facular reaches the four-quadrant detection photosensitive surface of the pulsed laser tracking system, resulting in the decline of the target measuring accuracy. Therefore the effect of facular size and energy distribution for the target azimuth measurement accuracy is researched. The calculation method for laser pot offset is discussed, and the formulas and principle circuit are given. The effect analysis of the laser pot size for measuring linear region and sensitivity are carried out, when the laser spot shows a uniform distribution as well as the Gaussian distribution. The performance of the laser pots under the two energy distribution situations are compared, the corresponding simulation curves are obtained. The simulation results show that the linear region of the Gaussian spot is larger than the uniform spot, but its sensitivity is relatively lower than the uniform spot within the effective dynamic range.

Error Correction for Laser Tracking System Using Dynamic Weighting Model

Laser tracking system (LTS) has been widely used in energy industries to meet increasingly high accuracy requirements. However, its measuring accuracy is highly affected by the dynamic uncertainty errors of LTS, and also the current range and angle measurements of LTS are mainly weighted statically, obtaining the dynamic weighting model which is essential for LTS to improve the measuring accuracy. In this paper, a dynamic weighting model that describes not only the dynamic uncertainty but also the geometric variations of LTS is developed, which can be adjusted to the weighting factors of dynamic parameters according to the range observations relative to the angle observations. Intensive experimental studies are conducted to check validity of the theoretical results. The results show that the measuring accuracy of LTS has been increased 2 times after using this technique for correction.

2A1-J06 高速ビジョンを用いたレーザー描画システム(ロボットビジョン(1))

In this study, we developed a 1000-fps stereo laser tracking system that can simultaneously track a fast moving object and draw an arbitrary laser pattern on the surface of the tracked object. Our system can always control the direction of laser beam with a 2-DOF galvano-mirror along a given trajectory on the surface of the tracked object by processing stereo 512X512 images in real time at 1000 fps. The performance was demonstrated by showing an experimental result when a triangle pattern was laser-drawn on the surface of the tracked object moving back-and-forth in three dimensional space.

Identification and Kinematic Calculation of Laser Tracker Errors

Calibration of Laser Tracker systems is based most times in the determination of its geometrical errors. Some standards as the ASME B89.4.19 (2006) and the VDI 2617-10 (2011) describe different tests to calculate the geometric misalignments that cause systematic errors in Laser Tracker measurements. These errors are caused not only because of geometrical misalignments and other sources of error must also be taken in count. In this work we want to express the errors in a kinematic form. Errors will be split in two different components, geometric and kinematic errors. The first ones depend on the offsets, tilts and eccentricity of the mechanical and optical components of the system. Kinematic errors are different for every position of the Laser tracker, so they must be formulated as functions of three system variables: range (R), vertical angle (V) and horizontal angle (H). The goal of this work is to set up an evaluation procedure to determine geometric and kinematic errors of Laser Trackers.

Modeling and simulation of laser tracking systems

PurposeThe purpose of this paper is to properly calibrate the laser tracking system (LTS) prior to using it for metrology and improving the measuring accuracy of LTS.Design/methodology/approachA kinematics model that describes not only the motion but also geometric variations of LTS is developed. Effects of tracking mirror mechanism dimension errors on measured coordinates and target reflector alignment errors on sensor reading are investigated.FindingsThrough error analysis of the proposed model, it is claimed that gimbals axis misalignments and tracking mirror center offset are the key contributors to measure errors of LTS. Intensive simulation studies are conducted to check the validity of the theoretical results and various practical issues are also explored in the simulations. The simulation results demonstrate that under realistic conditions the 10‐parameter model is the minimal and complete model.Research limitations/implicationsThis model, together with its error model which is also presented in this paper, can be used for design, calibration, and control of LTS.Originality/valueThis paper develops a kinematics model that describes not only the motion but also geometric variations of LTS, and demonstrates that gimbals axis misalignments and tracking mirror center offset is the key contributor to measuring errors of LTS.

Accurate and high-resolution boundary conditions and flow fields in the first-class cabin of an MD-82 commercial airliner

Flow fields in commercial airliner cabins are crucial for creating a thermally comfortable and healthy cabin environment. Flow fields depend on the thermo-fluid boundary conditions at the diffusers, in addition to the cabin geometry and furnishing. To study the flow fields in cabins, this paper describes a procedure to obtain the cabin geometry, boundary conditions at the diffusers, and flow fields. This investigation used a laser tracking system and reverse engineering to generate a digital model of an MD-82 aircraft cabin. Even though the measuring error by the system was very small, approximations and assumptions were needed to reduce the workload and data size. The geometric model can also be easily used to calculate the space volume. A combination of hot-sphere anemometers (HSA) and ultrasonic anemometers (UA) were applied to obtain the velocity magnitude, velocity direction, and turbulence intensity at the diffusers. The measured results indicate that the flow boundary conditions in a real cabin were rather complex and the velocity magnitude, velocity direction, and turbulence intensity varied significantly from one slot opening to another. UAs were also applied to measure the three-dimensional air velocity at 20 Hz, which could also be used to determine the turbulence intensity. Due to the instability of the flow, it should at least be measured for 4 min to obtain accurate averaged velocity and turbulence information. It was found that the flow fields were of low speed and high turbulence intensity. This study provides high quality data for validating Computational Fluid Dynamics (CFD) models, including cabin geometry, boundary conditions of diffusers, and high-resolution flow field in the first-class cabin of a functional MD-82 commercial airliner.