Registration Of Coordinate Systems Research Articles

Large area robotically assisted optical coherence tomography (LARA-OCT).

We demonstrate large-area robotically assisted optical coherence tomography (LARA-OCT), utilizing a seven-degree-of-freedom robotic arm in conjunction with a 3.3 MHz swept-source OCT to raster scan samples of arbitrary shape. By combining multiple fields of view (FOV), LARA-OCT can probe a much larger area than conventional OCT. Also, nonplanar and curved surfaces like skin on arms and legs can be probed. The lenses in the LARA-OCT scanner with their normal FOV can have fewer aberrations and less complex optics compared to a single wide field design. This may be especially critical for high resolution scans. We directly use our fast MHz-OCT for tracking and stitching, making additional machine vision systems like cameras, positioning, tracking or navigation devices obsolete. This also eliminates the need for complex coordinate system registration between OCT and the machine vision system. We implemented a real time probe-to-surface control that maintains the probe alignment orthogonal to the sample by only using surface information from the OCT images. We present OCT data sets with volume sizes of 140 × 170 × 20 mm3, captured in 2.5 minutes.

Rapid and Precise Measurement Method for Track Static Geometry of Large-Span Bridge Railway

Track geometry is an important parameter reflecting the safety of bridge railway, which is of great significance for the structure control of railway track. The measurement of track geometry is an indispensable part of structural health monitoring for bridge railway. However, existing methods for track static track geometry measurement are inadequate in terms of accuracy and efficiency. In order to improve the measurement method, this paper proposes a rapid and precise measurement method based on IMU/odometer aided by multiple total stations, which has the advantages of high efficiency, high accuracy, and is less affected by the environment. The proposed method uses a track measurement trolley (TMT) integrated with IMU and an odometer to collect railway track data on the bridge, and multiple total stations are used to synchronously measure the three-dimensional coordinates of the TMT. After coordinate system registration and time synchronisation, the data are then fused using a filtering algorithm to finally obtain the static geometry of the railway track. The proposed method was validated on the NanSha Port Railway Bridge across the Xijiang River in Foshan, China, and the results showed that the proposed method can make a single on-orbit measurement of a 1000 m length of large-span bridge railway track within half an hour, with an accuracy on the order of millimetres. The proposed method has obvious advantages in terms of efficiency and accuracy and is therefore an effective new measurement method with practical significance.

A Method to Locate Firing Points by Fusing Double CCD and GIS

The precise positioning of the firing explosion point is an effective means to test the technical performance of artillery weapons and equipment warfare, but when the CCD single pole distance method is directly used to detect the explosion point, it is often affected by the obstacles in the shooting visual area, terrain and landform, and the detection and positioning accuracy is difficult to meet the evaluation requirements. To this end, the double CCD intersection method is first used to locate the explosive point, and the target recognition and positioning algorithm is used to realize the visual explosion point positioning, but this method also has the phenomenon of missing detection of the bomb point and ricochet explosion point. Then, the sensor is used to collect GIS signals at the point of explosion, which can well detect the location of missed bounces and ricochets, but there is also the cost of time registration and spatial coordinate system registration. In order to give full play to the complementary advantages of the two positioning methods, this paper proposes to establish a fusion localization model. Experiments have verified that the fusion positioning method improves the accuracy of the detection of the explosion point of traditional single live shooting, and can provide a reference for the positioning detection of related points of interest.

Digital measurement technique for evaluating aircraft final assembly quality

The geometrical shape of an aircraft (final assembly quality) directly affects the aerodynamic performance, stealth performance, and structural performance of the overall aircraft. This study aims to improve the efficiency and accuracy of the aircraft final assembly quality evaluation. The proposed aircraft final assembly quality evaluation method is based on a fixed digital measurement station. The design of the measurement station that includes constellation, laser scanner, automation equipment, and system software, is reported. Additionally, the relationship between these components and the measurement station is described. Mathematical models of the measurement station (measuring method, system calibration method, and coordinate system registration method) are analyzed. Standard algorithms and the RANSAC-SVD algorithm are used to improve data registration accuracy. The RANSAC-SVD algorithm filters out the set of reference points that are more suited for data recording. The accuracy of model is optimized accordingly. Consequently, the working principle of the system is briefly described, and the main tasks and processes included in the aircraft measurement preparation phase, data acquisition phase, and data analysis processing phase are detailed. Finally, the internal and external parameters of the camera were calibrated and the accuracy of the measurement field was analyzed. The results show that a repeatability of 0.024 mm can be reached, the measurement errors are less than 0.2 mm, and 60% of the measurement data values are less than 0.1 mm.

基于EPNP算法的单目视觉测量系统研究

The method of pose measurement using computer vision is widely used in modern control, navigation, tracking and other fields. A monocular visual pose measurement method was studied and designd based on P4P rectangular distribution of planar target and EPNP algorithm in this paper. Firstly, a single camera was used to obtain the plane target image. After the image processing, the pixel coordinates of the four feature points were obtained, and the EPNP algorithm was used to perform the attitude calculation. Secondly, the simulation analysis of pose error measurement provides theoretical guidance and basis for improving attitude measurement accuracy. Finally, a coordinate system registration method combined with a high-precision two-dimensional turntable was proposed. The method was used to verify the accuracy of the three-direction attitude angles. The experimental results show that the rotation angle around the x and y axes is[-6, 6], the pose measurement error is less than 0.1 to meet the measurement application requirements.

An Indoor Multi-Tag Cooperative Localization Algorithm Based on NMDS for RFID

For radio frequency identification (RFID) system, the location information is very important in many applications, such as Internet of Things, logistics, library management, and so on. Most of traditional RFID localization algorithms can only locate one tag at a time. However, multitag localization is desired in many RFID applications. In this paper, we propose a novel range-free algorithm named nonmetric multidimensional scaling (NMDS)-RFID(F), which combines NMDS algorithm and the fingerprinting localization algorithm to achieve indoor RFID multitag cooperative localization. The NMDS-RFID(F) algorithm firstly uses received signal strength Euclidean distance based on fingerprinting method to get the rank order of the distance for all pairs of tags, and then NMDS algorithm is used to generate the relative coordinates of tags. Finally, due to the coordinates of reference tags are known, we can use the coordinate system registration algorithm to get the absolute coordinates of tags. Simulation results show that the NMDS-RFID(F) algorithm outperforms some previous RFID localization algorithms.

Scanning data reduction and accuracy enhancement through hybrid probing and bicubic surface construction

Reverse engineering demands a fast and accurate measuring method to obtain the surface model of an object when its computer-aided design (CAD) model is not available. Blending the advantages of both contact probes and non-contact scanners has been the trend of reverse engineering development for the past 15 years. Current research on hybrid reverse engineering system focuses on sensor selection, scanning path planning, and coordinate system registration and unification, but lacks of interaction between the data groups from the touch probe and laser sensor. The objective of this research is directed toward improving data accuracy at a reduced amount of data points without complex instrument integration and is accomplished through combining the advantages of contact probes and non-contact scanners and meanwhile offsetting their disadvantages. In this research, data from the laser sensor is strategically selected based on the local surface variation, and a coordinate measuring machine (CMM) touch probe is used to enhance data accuracy. A Cell Merging algorithm is implemented to reduce the amount of data based on a newly proposed concept of Break Points, by which a Hermit bicubic relation is maintained among neighboring sampling points while a hybrid reverse engineering process is going on. At the end of the paper, examples are presented to show the effectiveness of the methodology.