scholarly journals A New and Direct R-Value Measurement Method of Sheet Metal Based on Multi-Camera DIC System

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1401
Author(s):  
Siyuan Fang ◽  
Xiaowan Zheng ◽  
Gang Zheng ◽  
Boyang Zhang ◽  
Bicheng Guo ◽  
...  
Keyword(s):  
Coordinate System ◽  
Sheet Metal ◽  
Direct Calculation ◽  
Constant Volume ◽  
Thickness Strain ◽  
Measurement Systems ◽  
World Coordinate System ◽  
Random Sample Consensus ◽  
R Value ◽  
Value Measurement

More and more attention has been given in the field of mechanical engineering to a material’s R-value, a parameter that characterizes the ability of sheet metal to resist thickness strain. Conventional methods used to determine R-value are based on experiments and an assumption of constant volume. Because the thickness strain cannot be directly measured, the R-value is currently determined using experimentally measured strains in the width, and loading directions in combination with the constant volume assumption, to determine the thickness strain indirectly. This paper provides an alternative method for determining the R-value without any assumptions. This method is based on the use of a multi-camera DIC system to measure strains in three directions simultaneously. Two sets of stereo-vision DIC measurement systems, each comprised of two GigE cameras, are placed on the front and back sides of the sample. Use of the double-sided calibration strategy unifies the world coordinate system of the front and back DIC measurement systems to one coordinate system, allowing for the measurement of thickness strain and direct calculation of R-value. The Random Sample Consensus (RANSAC) algorithm is used to eliminate noise in the thickness strain data, resulting in a more accurate R-value measurement.

Automated Planning for Stacking of Bent Sheet Metal Parts

1997 ◽  
Author(s):  
Venkateswara R. Ayyadevara ◽  
Robert H. Sturges
Keyword(s):  
Coordinate System ◽  
Sheet Metal ◽  
Computational Efficiency ◽  
Automated Planning ◽  
Automated Generation ◽  
Metal Parts ◽  
Sheet Metal Parts ◽  
World Coordinate System ◽  
Special Part ◽  
The Stability

Abstract This paper deals with the automated generation of stacking plans for bent sheet metal parts which are difficult to stack due to their irregular geometry. A stacking plan consists of a set of homogeneous transformations describing the configuration of each constituent part of the stack with respect to a world coordinate system. Stacks are constructed incrementally by adding parts to an existing stack. The base part is positioned to maximize stability when placed on a special part buffer. Successive parts are added in a configuration minimizing the height of the stack c.g. and ensuring the stability of the stack and the constituent parts. Evaluation of part and stack stability and analysis of part-part interference and part instability are addressed. Three examples demonstrate the advantage of interference analysis, handling of non-90° part orientations, and effect of features like asymmetric flanges and large holes on computational efficiency.

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.

Use of the FITS World Coordinate System by STEREO/SECCHI

Solar Physics ◽  
2009 ◽  
Vol 261 (1) ◽  
pp. 215-222 ◽  
Author(s):  
W. T. Thompson ◽  
K. Wei
Keyword(s):  
Coordinate System ◽  
World Coordinate System

A Self-Calibration Method for Robotic Measurement System

1999 ◽  
Author(s):  
Chunhe Gong ◽  
Jingxia Yuan ◽  
Jun Ni
Keyword(s):  
Coordinate System ◽  
Measurement System ◽  
Calibration Method ◽  
Position Measurement ◽  
Robot Calibration ◽  
Robot System ◽  
Self Calibration ◽  
World Coordinate System ◽  
Robot Accuracy ◽  
Calibration Methods

Abstract Robot calibration plays an increasingly important role in manufacturing. For robot calibration on the manufacturing floor, it is desirable that the calibration technique be easy and convenient to implement. This paper presents a new self-calibration method to calibrate and compensate for robot system kinematic errors. Compared with the traditional calibration methods, this calibration method has several unique features. First, it is not necessary to apply an external measurement system to measure the robot end-effector position for the purpose of kinematic identification since the robot measurement system has a sensor as its integral part. Second, this self-calibration is based on distance measurement rather than absolute position measurement for kinematic identification; therefore the calibration of the transformation from the world coordinate system to the robot base coordinate system, known as base calibration, is not necessary. These features not only greatly facilitate the robot system calibration but also shorten the error propagation chain, therefore, increase the accuracy of parameter estimation. An integrated calibration system is designed to validate the effectiveness of this calibration method. Experimental results show that after calibration there is a significant improvement of robot accuracy over a typical robot workspace.

scholarly journals Status of R value measurement at BESIII

2019 ◽  
Vol 212 ◽  
pp. 04005
Author(s):  
Haiming HU
Keyword(s):  
Systematic Error ◽  
Radiative Correction ◽  
Present Status ◽  
Parameter Tuning ◽  
Initial State ◽  
R Value ◽  
Value Measurement ◽  
Area Law ◽  
Initial State Radiative

The dominant systematic error of R value measurement comes from the hadronic generator simulations. This paper reviews the present status of R value measurement from 2.232 to 3.671 GeV at 14 energy points, especially describes the calculations of initial state radiative correction and the issue of the parameter tuning for the Lund area law generator LUARLW.

Improvement of Image Mosaic Algorithm Based on SURF

2013 ◽  
Vol 427-429 ◽  
pp. 1625-1630
Author(s):  
Xu Lin Long ◽  
Qiang Chen ◽  
Jun Wei Bao
Keyword(s):  
Coordinate System ◽  
Random Sample ◽  
Clustering Algorithm ◽  
Feature Matching ◽  
Consensus Method ◽  
Image Mosaic ◽  
Matching Accuracy ◽  
Speeded Up Robust Features ◽  
Random Sample Consensus ◽  
Improved Algorithm

The present study concerns about feature matching in image mosaic. In order to solve the problems of low accuracy and poor applicability in the traditional speeded up robust features algorithm, this paper presents an improved algorithm. Clustering algorithm based on density instead of random sample consensus method is used to eliminate mismatching pairs. The initial matching pairs are mapped onto a plane coordinate system, which can be regarded as points, by calculating the density of each point to extract the final matching pairs. The results show that this algorithm overcomes the limitations of the traditional speeded up robust features mosaic method, improving the matching accuracy and speed, and the mosaic effect. It has certain theoretical and practical value.

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.

Lane Model and Calculation of Lane Geometric Structure and Vehicle Deviation Angle and Position in Lane for Intelligent Vehicle

2013 ◽  
Vol 274 ◽  
pp. 336-339
Author(s):  
Y. Chen ◽  
M.Y. He
Keyword(s):  
Coordinate System ◽  
Geometric Structure ◽  
Intelligent Vehicle ◽  
Reasonable Assumption ◽  
Deviation Angle ◽  
Boundary Equation ◽  
Change Rate ◽  
World Coordinate System ◽  
Crucial Part ◽  
Camera Coordinate System

Lane model, lane geometric structure calculation, and vehicle deviation angle and position calculation is a crucial part in automatic drive of intelligent vehicle. In this paper, we introduce a lane model and calculation equations of lane geometric structure and vehicle deviation angle and position in lane. Firstly, we establish the world coordinate system and derive the lane boundary equation based on the actual lane alignment. Secondly, we derive the lane boundary equation in the camera coordinate system through the coordinate transformation. Then we build up the image coordinate system and the pixel coordinate system and derive the lane projective parameter model. Finally, we derive the calculation equations of lane geometric structure and vehicle deviation angle and position in lane. For we introduce the camera roll angle, the lane curvature change rate, and the reasonable assumption in the derivation, the lane model and the calculation are more general and accurate.

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