Accurate extrinsic calibration method of line structured-light sensor based on standard ball

In large-scale three-dimensional (3D) coordinates measurement, to solve the problem of structured light sensor’s measurement data from different measurement stations unifying to the global coordinate system, a method based on workshop Measuring Position System (wMPS) global controlling is researched to concentrate the structured light sensor’s measurement data to the global coordinate system automatically. According to the measurement principle, two calibration methods are proposed to calibrate the structural parameters based on a standard ball, one is transferring stations based on common points and the other is fitting ball equation. Finally, a platform for experiment is built to verify the two calibration methods. Experimental results show that the average measurement error on 10 points is 0.127 mm according to the laser tracker of the first method and the other average error is 0.101 mm, both the two calibration methods have a high precision to meet the demands of large-scale 3D coordinates measurement.

The ball gear or globular gear is a ball; on the ball there are a series of holes. The ball gear is the key component of the robot’s wrist. As shown in fig.1, by using the ball crowns of two different ball centers as a joint curve surface, and their ball center as a rotational center, the ball gearing can be formed on two ball surfaces with convex teeth and concave teeth engaging each other. The robot’s wrist differs from the wrist of human kind in that, it can transmit rotational movement from the upper arm to the lower arm continuously, while the angle between the upper arm and the lower arm is changing. In the formal papers, the protruding teeth have the shape of a cone, while the concave teeth are the conjugate surface of them. The protruding teeth with straight surface are of cause easy to be machined. But the concave teeth are very hard to be machined. The special machining method such as the electric spark machining has to be employed to deal with this kind of work.KeywordsCone toothballgear MotionPower Transmissionprofile

With the development of the green manufacture, a robotic inspection system is presented to meet the requirement of remanufacturing engineering. It solves the problem of acquiring the information of the three dimensions (3D) shape feature in a timely and effective manner. As to set up this system efficiently, a calibration approach of the main part of the system, the line structured light sensor, based on a six degree of freedom (6-DOF) robot is proposed. This approach takes the advantage of the flexibility of the robot for simplifying the traditional sensor calibration approach and generates the calibration control points with concentric circle to refine the precision of locating its center. The actual experiment demonstrates that this approach is suitable for field calibration with conveniences and good accuracy.

In order to achieve intelligent and flexible welding, complete the extraction and path planning of 3-D complex weld seam of large steel weldment, and solve the problems that in the vision-guided welding process, the scanning path depends on manual teaching, and the offline programming depends on the machining and assembly accuracy of the weldment; a vision-guided method for welding robots based on a line structured-light sensor is proposed. First, the 3-D computer aided design (CAD) model of the weldment is used to build an offline welding knowledge library, and then, the scanning path is planned in combination with the point cloud alignment. Then, the sensor collects the point cloud on the surface of the weldment along the scanning path. Second, different weld seam extraction algorithms are proposed according to different weld types. The random sample consensus (RANSAC) algorithm is used to identify the position of weld feature points, and the three-frame method is used to solve the pose of weld feature points. Finally, the weld seam is generated to guide the welding robot to complete the welding operation. The experimental results show that the proposed method can be used for different types and dimensions of weldments and provides flexible welding operations with better versatility and higher intelligence.

A fully autonomous platform for power measurement of environmental RF sources based on a time domain readout

The quality of machined marine propellers plays a critical role in underwater propulsion performance. Precision casting is the predominant manufacturing technique; however, deformation of wax models and rough blanks during manufacturing frequently cause deviations in the dimensions of final products and, thus, affect propellers’ performance and service life. Current inspection methods primarily involve using coordinate measuring machines and sampling. This approach is time-consuming, has high labor costs, and cannot monitor manufacturing quality in real-time. This study developed a real-time online automated measurement system containing a high-resolution CITIZEN displacement sensor, a four-degree-of-freedom measurement platform, and programmable logic controller-based motion control technology to enable rapid, automated measurement of blade deformation across the wax model, rough blank, and final product processing stages. The measurement data are transmitted in real time to a cloud database. Tests conducted on a standardized platform and real propeller blades confirmed that the system consistently achieved measurement accuracy to the second decimal place under the continual measurement mode. The system also demonstrated excellent repeatability and stability. Furthermore, the continuous measurement mode outperformed the single-point measurement mode. Overall, the developed system effectively reduces labor requirements, shortens measurement times, and enables real-time monitoring of process variation. These capabilities underscore its strong potential for application in the smart manufacturing and quality control of marine propellers.

Since the 1970s, eXpendable BathyThermographs (XBTs) have provided the simplest and most cost-efficient solution for rapid sampling of temperature vs. depth profiles of the upper part of the ocean along ship transects. This manual, compiled by the Ship of Opportunity Program Implementation Panel (SOOPIP) a subgroup of the Global Ocean Observing System (GOOS) Observations Coordination Group (OCG) Ship Observations Team (SOT) together with members of the XBT Science Team, aims to improve the quality assurance of XBT data by establishing best practices for field measurements and promoting their adoption by the global operational and scientific community. The measurement system components include commercially available expendable temperature probes, the launcher, the data acquisition (DAQ) hardware, a Global Navigation Satellite System (GNSS) receiver, an optional satellite transmitter, and a computer with software controls. The measurement platform can be any sea-going vessel with available space for the equipment and operator, and capable of oceanic voyages across the regions of interest. Adoption of a standard methodology in the installation and deployment of the measurement system will lead to data quality improvements with subsequent impact on the computation and understanding of changes in the near surface ocean properties (e.g., heat content), ocean circulation dynamics, and their relationship to climate variability.

The pose measurement of cannon barrel (vertical angle and azimuth angle) is a difficulty and emphasis in the precision analysis of SPAAG fire control system. To solve this problem, this paper presents a contactless measuring method based on computer vision. Before measurement, fix a checked planar faceplate on the cannon barrel as a marker. Firstly, get the coordinate of X corner points using Harris Corner Detection Algorithm to calibrate the camera, and chalk up the cameras intrinsic parameters based on Extended Kalman Filter. Secondly, get the corner points from the image of test position, then calculate the extrinsic parameter matrix of the corresponding position combining with LSE algorithm. Finally, according to the motion model of cannon barrel and the position relative to the marker, derive the constraint equations between extrinsic parameter and vertical angle and azimuth angle, then figure out the two angles. Experiment validate the maneuverability and veracity of this method, and the results indicate that the measuring precision of this method is less than 1mil.

This article presents a high-precision single-camera inertial measurement unit (IMU) extrinsic calibration method by tightly fusing the visual information from other cameras. Specifically, multiple additional cameras are added to the monocular camera-IMU system for assisting calibration as we theoretically prove that more cameras used in calibration can lead to smaller lower bound on the covariance of the estimated extrinsic parameters, which then results in better calibration accuracy. Moreover, we provide two degenerative motion conditions in the resulting multicamera visual-inertial system, which impair the calibration accuracy and should be avoided in real application whenever possible. More importantly, we present the requirement of minimum motion for a reliable extrinsic calibration to provide the practical guideline. Finally, the full validation on both simulation and real-world data is demonstrated. By evaluating the Cramér-Rao lower bound on the covariance, the proposed camera-IMU calibration method is shown to be statistically efficient for accurate calibration with errors less than 0.01 m in translation and 0.5° in rotation, which is consistent with the theoretical analysis in this article.

The measurement of radar performance parameters is the basic work of radar support forces, and the development of simulation training platform has a very good role in promoting this work. This paper describes the current situation of radar parameter measurement, introduces the development of equipment simulation training platform, and combs the development process of radar performance parameter measurement simulation training platform. At last, the practical requirements of the simulation training platform for radar performance parameter measurement are put forward, that is, by building the simulation training platform for radar main parameter measurement, to meet the requirements of the new two-level maintenance system for the parameter measurement of military maintenance personnel.

Accurately calibrate the extrinsic parameters between a camera and an Inertial Measurement Unit (IMU) is a prerequisite for achieving sensor data fusion in visual-inertial navigation systems. Due to delays introduced by triggering, transmission, and other factors, the sampled times of the camera and IMU do not align with the system timestamps, leading to a decrease in the accuracy of extrinsic calibration. Existing calibration methods are unable to avoid the temporal misalignment between the camera and IMU. This paper introduces a novel intermittent calibration sampling method to address temporal misalignment challenges. The approach entails detecting motion-stillness transition points in the IMU data as keyframe segmentation criteria, thereby decoupling data acquisition from system timestamps and aligning it with the sensor’s motion process. Subsequently, the robot hand-eye calibration method is applied to the extrinsic calibration of the Camera-IMU, combining the Random Sample Consensus algorithm to filter the poses of the camera and IMU. This process achieves precise calibration of extrinsic parameters. Experimental validation shows that the algorithm proposed in this paper enhances calibration accuracy when compared to the widely used Kalibr Camera-IMU calibration toolbox. The rotational extrinsic parameter accuracy increased by 181.25%, and the translational extrinsic parameter accuracy improved by 168.33%. These findings provide effective technical means for precise measurement of Camera-IMU extrinsic parameters.

An error compensation method for on-machine measuring blade with industrial robot

“DON’T JUST TELL ME, SHOW ME” is a big part of this chapter as we focus on reliable measurement and verification systems that provide feedback on the key performance indicators defined in the building owner’s goals and targets. Reliable and cost-effective measurement and verification systems connect all the critical elements of smart buildings, equipment, and systems. Understanding the minimum infrastructure required for a reliable measurement and verification platform enables building owners to layer in new sensors and meters as technology develops. In general, technology changes the game in terms of how energy efficiency and indoor environmental quality are delivered and verified. Building performance simulation and smart building infrastructure allow owners to balance building performance against first costs and long-term operating costs. With the help of a technology platform, owners will know what is possible prior to spending construction dollars. Remember, so far we’ve shown you how building science, done properly, enables any existing building to perform like a new one. In this chapter, we will show you how technology will increase your confidence to invest in existing buildings by increasing the knowns and decreasing the unknowns of any building project.

Capturing CO2 from the flue gas of a power plant based on chemical absorption method is an effective way to cut down the emission of CO2. However, the principal components in the solvent are very difficult to be measured online. Therefore an online measurement and control system was designed for the process of capturing CO2 by MEA chemical absorption. The feature selection was done according to Bayesian networks. Furthermore based on the principle of a new sparse support vector machine (SLS-SVM), the measurement of ionic species distribution in the absorption solution was predicted, and the results agreed well with the data obtained by Nuclear Magnetic Resonance (NMR) measurement. The mean square error is 3.8645×10-7. The measurement of solution species distribution was carried out online by using infrared sensors and NMR technology. Meanwhile the sampling system and NMR unit were linked for the online analysis based on variable-temperature and variable-pressure NMR technology. Finally a measurement and control platform was constructed based on VI technology. It shows that the performance of traditional equipment can be improved by the novel system, which will provide a more effective method for CO2 capture process.

To enhance the competence of the product in construction machinery, a proper testing system should be established for the construction machinery hydraulic system. Considering multi-site test and massive control of data processing in most construction machinery hydraulic measurement and control system, a testing platform applicable to different construction hydraulic systems is designed and presented in this paper. Composed of the upper and lower computers, the system is simple and convenient by means of Virtual Instrument Technology. Then it runs very well and proves reliable after debugging operation. Finally, the test-control platform can set manifold experiments in different working conditions.