An Orthogonal Wheel Odometer for Positioning in a Relative Coordinate System on a Floating Ground

2021 ◽  
Vol 11 (23) ◽  
pp. 11340
Author(s):  
Zhiguo Lu ◽  
Guangda He ◽  
Ruchao Wang ◽  
Shixiong Wang ◽  
Yichen Zhang ◽  
...  
Keyword(s):  
Coordinate System ◽  
Current Method ◽  
Maximum Error ◽  
Floating Platform ◽  
Time Data ◽  
Sensing System ◽  
World Coordinate System ◽  
Sliding Mechanism ◽  
The World ◽  
Omnidirectional Wheels

This paper introduces a planar positioning sensing system based on orthogonal wheels and encoders for some surfaces that may float (such as ship decks). The positioning sensing system can obtain the desired position and angle information on any such ground that floats. In view of the current method of using the IMU gyroscope for positioning, the odometer data on these floating grounds are not consistent with the real-time data in the world coordinate system. The system takes advantage of the characteristic of the orthogonal wheel, using four vertical omnidirectional wheels and encoders to position on the floating ground. We design a new structure and obtain the position and angle information of a mobile robot by solving the encoder installed on four sets of omnidirectional wheels. Each orthogonal wheel is provided with a sliding mechanism. This is a good solution to the problem of irregular motion of the system facing the floating grounds. In the experiment, it is found that under the condition that the parameters of the four omnidirectional wheels are obtained by the encoder, the influence of the angle change of the robot in the world coordinate system caused by the flotation of the ground can be ignored, and the position and pose of the robot on the fluctuating ground can be well obtained. Regardless of straight or curved motion, the error can reach the centimeter level. In the mobile floating platform experiment, the maximum error of irregular movement process is 2.43 (±0.075) cm and the RMSE is 1.51 cm.

scholarly journals A Novel AVM Calibration Method Using Unaligned Square Calibration Boards

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2265
Author(s):  
Jung Hyun Lee ◽  
Dong-Wook Lee
Keyword(s):  
Coordinate System ◽  
Reference Data ◽  
Side Information ◽  
Reference Sample ◽  
Likelihood Estimation ◽  
Calibration Method ◽  
World Coordinate System ◽  
Sample Data ◽  
The World ◽  
Left And Right

An around view monitoring (AVM) system acquires the front, rear, left, and right-side information of a vehicle using four cameras and transforms the four images into one image coordinate system to monitor around the vehicle with one image. Conventional AVM calibration utilizes the maximum likelihood estimation (MLE) to determine the parameters that can transform the captured four images into one AVM image. The MLE requires reference data of the image coordinate system and the world coordinate system to estimate these parameters. In conventional AVM calibration, many aligned calibration boards are placed around the vehicle and are measured to extract the reference sample data. However, accurately placing and measuring the calibration boards around a vehicle is an exhaustive procedure. To remediate this problem, we propose a novel AVM calibration method that requires only four randomly placed calibration boards by estimating the location of each calibration board. First, we define the AVM errors and determine the parameters that minimize the error in estimating the location. We then evaluate the accuracy of the proposed method through experiments using a real-sized vehicle and an electric vehicle for children to show that the proposed method can generate an AVM image similar to the conventional AVM calibration method regardless of a vehicle’s size.

scholarly journals Structured Light 3D Reconstruction System Based on a Stereo Calibration Plate

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 772
Author(s):  
Meiying Li ◽  
Jin Liu ◽  
Haima Yang ◽  
Wanqing Song ◽  
Zihao Yu
Keyword(s):  
Coordinate System ◽  
Structured Light ◽  
Primary Objective ◽  
Calibration Data ◽  
Complex Objects ◽  
World Coordinate System ◽  
Calibration Methods ◽  
The World ◽  
Stereo Calibration ◽  
Left And Right

Calibration is a critical step in structured light 3D imaging systems. However, in the traditional calibration process, since the calibration plate is based on a two-dimensional model, the flatness of the calibration plate and the angle of the photo will affect the subsequent stitching steps based on the feature points. The number of photos also affects the calibration results. To improve the calibration accuracy, multiple photos need to be taken. The primary objective of this study was to achieve the simple and fast calibration of system parameters, so a method obtaining a large number of calibration data by homography matrix is presented, and a corresponding stereo target is designed in symmetry. First, using the relationship between the corner coordinates of the left and right parts of the stereo calibration plate and the coordinates of the world coordinate system, the homography matrix of the left and right calibration plates from the image coordinates to the world coordinates is calculated. Second, all the pixels in the stereo calibration plate are matched to the world coordinate system by using the homography matrix. In addition, we also compared the results of this method with those of traditional calibration methods. The experimental results show that the 3D geometric surface of the reconstruction result is smooth, it avoids the missing parts and the visual effect is excellent. Furthermore, the error range of small and complex objects can be reduced to 0.03 mm~0.05 mm. This method simplifies the calibration steps, reduces the calibration costs and has practical application value.

scholarly journals Astrometry test of MSCRED IRAF software package

2005 ◽  
pp. 123-125
Author(s):  
R. Popescu ◽  
P. Popescu ◽  
P. Paraschiv ◽  
A. Nedelcu
Keyword(s):  
Coordinate System ◽  
Software Package ◽  
Open Cluster ◽  
Ccd Camera ◽  
Field Size ◽  
World Coordinate System ◽  
The World ◽  
Ccd Observations ◽  
Cassegrain Telescope

Astrometric properties of images obtained using MSCRED IRAF software package are investigated. CCD observations of M35 open cluster were taken in an observation run between October 10 and 17, 2004 at Belogradchick Observatory (Bulgaria) using the 60cm Cassegrain telescope endowed with a 1kX1k Apogee 47P CCD camera, ensuring to a field size of 6.16 square minutes, with a scale of 0.722arcsec/pixel in 2X2 binned mode. Dithered images are resampled and reansambled into a single larger image for which the World Coordinate System (WCS) solution is recomputed and investigated. .

Feature Size Measurement of Multihole Sheet Metal Part Based on HALCON

2013 ◽  
Vol 302 ◽  
pp. 546-549
Author(s):  
Baoan Han ◽  
Hui Yu Xiang ◽  
Zhe Li ◽  
Xiao Zhuang Zhou
Keyword(s):  
Coordinate System ◽  
Sheet Metal ◽  
Contour Extraction ◽  
Size Measurement ◽  
Sheet Metal Part ◽  
Metal Part ◽  
Feature Size ◽  
World Coordinate System ◽  
The World

To realize the target of having a precise feature size measurement of multihole sheet metal part, this paper based on HALCON, first calibrates the camera with HALCON's calibration assistant. After acquiring the image of the multihole sheet metal part, the image coordinates of the center of fitting ellipse and the length of the long and short half shaft (pixel unit) can be gotten by proceeding a series of operations like thresholding, subpixel-precise contour extraction, fitting ellipses and so on. At last, the point coordinates in image are transformed into the plane Z=0 of the world coordinate system through translation and rotation, and the value of each feature size of the sheet metal part can be calculated.

The Research on Camera Axis Perpendicular to the Target Surface and Method to Confirm its Position in Space

2011 ◽  
Vol 317-319 ◽  
pp. 947-955
Author(s):  
Shang Gao ◽  
Xing Long Zhu ◽  
Ji Ping Zhou ◽  
Xin Zhao ◽  
Nan Yin
Keyword(s):  
Coordinate System ◽  
Camera Calibration ◽  
Target Surface ◽  
Optical Center ◽  
Internal Parameters ◽  
World Coordinate System ◽  
The World ◽  
Image Edge ◽  
Relationship Of ◽  
Ccd Image

Confirming the position in space of the camera axis and it perpendicular to the target surface has important significance for simplifying the camera calibration in interior parameters. This article conducted a study on this issue. First, it establishes the relationship of the world coordinate system, the target coordinate system, the camera coordinate system and the image coordinate system. The necessary camera calibration in external parameters and internal parameters are confirmed. Second, the first target coordinate system is adjusted to the same position with the world coordinate system. The adjustment principle of the camera axis perpendicular to the target column end surface is proposed. Namely, whether the camera axis perpendicular to the first target column end surface or not is confirmed by the CCD image edge whether it’s round or not. As the world coordinate system is based on coordinate measuring machines, so the world coordinate of the first target column end surface circle is obtained. Then the second target is placed in between the camera and the first target, and the second target coordinate system is adjusted to the same position with the world coordinate system, and it is adjusted to the same coordinate (except y direction) with the first target column end surface circle’s coordinates. So the images of the first target and the second target column end surface circle in the CCD surely are circles. Third, the method to seek for the camera axis is put forward, namely if the circles of the first target and the second target column end surface circle in the CCD are not concentric, then it shows the optical axis and the joined axis of the first and second target face round are not concentric. By adjusting the CCD camera's position, until the circles of the first target and the second target column end surface circle in the CCD are concentric, such the camera axis can be represented by the joined axis of the first and second target end round. Simultaneously the target circle's center reflects the deviation on CCD coordinate between the optical center and the CCD center. Finally, the camera internal parameters are expressed by the related parameters.

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