scholarly journals A Stereo-Vision System for Measuring the Ram Speed of Steam Hammers in an Environment with a Large Field of View and Strong Vibrations

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 996 ◽  
Author(s):  
Ran Chen ◽  
Zhongwei Li ◽  
Kai Zhong ◽  
Xingjian Liu ◽  
Yonghui Wu ◽  
...  
Keyword(s):  
Stereo Vision ◽  
High Speed ◽  
Vision System ◽  
Calibration Method ◽  
Bundle Adjustment ◽  
Field Of View ◽  
Large Field ◽  
Practical Applications ◽  
Accuracy Of Measurements ◽  
Ram Speed

The ram speed of a steam hammer is an important parameter that directly affects the forming performance of forgers. This parameter must be monitored regularly in practical applications in industry. Because of the complex and dangerous industrial environment of forging equipment, non-contact measurement methods, such as stereo vision, might be optimal. However, in actual application, the field of view (FOV) required to measure the steam hammer is extremely large, with a value of 2–3 m, and heavy steam hammer, at high-speed, usually causes a strong vibration. These two factors combine to sacrifice the accuracy of measurements, and can even cause the failure of measurements. To solve these issues, a bundle-adjustment-principle-based system calibration method is proposed to realize high-accuracy calibration for a large FOV, which can obtain accurate calibration results when the calibration target is not precisely manufactured. To decrease the influence of strong vibration, a stationary world coordinate system was built, and the external parameters were recalibrated during the entire measurement process. The accuracy and effectiveness of the proposed technique were verified by an experiment to measure the ram speed of a counterblow steam hammer in a die forging device.

scholarly journals Flexible method for accurate calibration of large-scale vision metrology system based on virtual 3-D targets and laser tracker

2019 ◽  
Vol 16 (6) ◽  
pp. 172988141989351
Author(s):  
Xi Zhang ◽  
Yuanzhi Xu ◽  
Haichao Li ◽  
Lijing Zhu ◽  
Xin Wang ◽  
...  
Keyword(s):  
High Precision ◽  
Stereo Vision ◽  
Large Scale ◽  
Vision System ◽  
Calibration Method ◽  
Field Of View ◽  
Large Field ◽  
Laser Tracker ◽  
Calibration Target ◽  
Pose Tracking

For the purpose of obtaining high-precision in stereo vision calibration, a large-size precise calibration target, which can cover more than half of the field of view is vital. However, large-scale calibration targets are very difficult to fabricate. Based on the idea of error tracing, a high-precision calibration method for vision system with large field of view by constructing a virtual 3-D calibration target with a laser tracker was proposed in this article. A virtual 3-D calibration target that covers the whole measurement space can be established flexibly and the measurement precision of the vision system can be traceable to the laser tracker. First, virtual 3-D targets by calculating rigid body transformation with unit quaternion method were constructed. Then, the high-order distortion camera model was taken into consideration. Besides, the calibration parameters were solved with Levenberg–Marquardt optimization algorithm. In the experiment, a binocular stereo vision system with the field of view of 4 × 3 × 2 m3 was built for verifying the validity and precision of the proposed calibration method. It is measured that the accuracy with the proposed method can be greatly improved comparing with traditional plane calibration method. The method can be widely used in industrial applications, such as in the field of calibrating large-scale vision-based coordinate metrology, and six-degrees of freedom pose tracking system for dimensional measurement of workpiece, as well as robotics geometrical accuracy detection and compensation.

A novel and accurate calibration method for cameras with large field of view using combined small targets

Measurement ◽  
2015 ◽  
Vol 64 ◽  
pp. 1-16 ◽  
Author(s):  
Zhen Liu ◽  
Fengjiao Li ◽  
Xiaojing Li ◽  
Guangjun Zhang
Keyword(s):  
Calibration Method ◽  
Field Of View ◽  
Large Field ◽  
Small Targets

Calibration Method for Large Field of View Image Matching Parameters Based on Non-Metric Correction

2018 ◽  
Vol 38 (8) ◽  
pp. 0815004
Author(s):  
张致远 Zhang Zhiyuan ◽  
刘巍 Liu Wei ◽  
张洋 Zhang Yang ◽  
逯永康 Lu Yongkang ◽  
邸宏图 Di Hongtu ◽  
...  
Keyword(s):  
Image Matching ◽  
Calibration Method ◽  
Field Of View ◽  
Large Field

scholarly journals Automatic Rectification of the Hybrid Stereo Vision System

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3355
Author(s):  
Chengtao Cai ◽  
Bing Fan ◽  
Xin Liang ◽  
Qidan Zhu
Keyword(s):  
Stereo Vision ◽  
Optimization Problem ◽  
Vision System ◽  
Field Of View ◽  
Computation Complexity ◽  
Constrained Optimization Problem ◽  
Projection Model ◽  
Nonlinear Constrained Optimization ◽  
Stereo Vision System ◽  
Dynamic Hybrid

By combining the advantages of 360-degree field of view cameras and the high resolution of conventional cameras, the hybrid stereo vision system could be widely used in surveillance. As the relative position of the two cameras is not constant over time, its automatic rectification is highly desirable when adopting a hybrid stereo vision system for practical use. In this work, we provide a method for rectifying the dynamic hybrid stereo vision system automatically. A perspective projection model is proposed to reduce the computation complexity of the hybrid stereoscopic 3D reconstruction. The rectification transformation is calculated by solving a nonlinear constrained optimization problem for a given set of corresponding point pairs. The experimental results demonstrate the accuracy and effectiveness of the proposed method.

Projector calibration method based on stereo vision system

2017 ◽  
Vol 24 (6) ◽  
pp. 727-733 ◽  
Author(s):  
Shourui Yang ◽  
Miao Liu ◽  
Jiahui Song ◽  
Shibin Yin ◽  
Yin Guo ◽  
...  
Keyword(s):  
Stereo Vision ◽  
Vision System ◽  
Calibration Method ◽  
Stereo Vision System ◽  
Projector Calibration

scholarly journals Architecture and implementation of a high frame-rate stereo vision system

2021 ◽  
Author(s):  
Jamin Islam
Keyword(s):  
Integrated Circuits ◽  
Stereo Vision ◽  
High Speed ◽  
Vision System ◽  
Low Cost ◽  
Cost Effective ◽  
Frame Rate ◽  
Superior Performance ◽  
High Frame Rate ◽  
Stereo Vision System

For the purpose of autonomous satellite grasping, a high-speed, low-cost stereo vision system is required with high accuracy. This type of system must be able to detect an object and estimate its range. Hardware solutions are often chosen over software solutions, which tend to be too slow for high frame-rate applications. Designs utilizing field programmable gate arrays (FPGAs) provide flexibility and are cost effective versus solutions that provide similar performance (i.e., Application Specific Integrated Circuits). This thesis presents the architecture and implementation of a high frame-rate stereo vision system based on an FPGA platform. The system acquires stereo images, performs stereo rectification and generates disparity estimates at frame-rates close to 100 fpSi and on a large-enough FPGA, it can process 200 fps. The implementation presents novelties in performance and in the choice of the algorithm implemented. It achieves superior performance to existing systems that estimate scene depth. Furthermore, it demonstrates equivalent accuracy to software implementations of the dynamic programming maximum likelihood stereo correspondence algorithm.

scholarly journals CAN WE USE LOW-COST 360 DEGREE CAMERAS TO CREATE ACCURATE 3D MODELS?

2018 ◽  
Vol XLII-2 ◽  
pp. 69-75 ◽  
Author(s):  
L. Barazzetti ◽  
M. Previtali ◽  
F. Roncoroni
Keyword(s):  
Laser Scanning ◽  
Low Cost ◽  
Point Clouds ◽  
3D Models ◽  
Bundle Adjustment ◽  
Field Of View ◽  
Large Field ◽  
Single Shot ◽  
New Paradigm ◽  
Image Orientation

360 degree cameras capture the whole scene around a photographer in a single shot. Cheap 360 cameras are a new paradigm in photogrammetry. The camera can be pointed to any direction, and the large field of view reduces the number of photographs. This paper aims to show that accurate metric reconstructions can be achieved with affordable sensors (less than 300 euro). The camera used in this work is the Xiaomi Mijia Mi Sphere 360, which has a cost of about 300 USD (January 2018). Experiments demonstrate that millimeter-level accuracy can be obtained during the image orientation and surface reconstruction steps, in which the solution from 360° images was compared to check points measured with a total station and laser scanning point clouds. The paper will summarize some practical rules for image acquisition as well as the importance of ground control points to remove possible deformations of the network during bundle adjustment, especially for long sequences with unfavorable geometry. The generation of orthophotos from images having a 360° field of view (that captures the entire scene around the camera) is discussed. Finally, the paper illustrates some case studies where the use of a 360° camera could be a better choice than a project based on central perspective cameras. Basically, 360° cameras become very useful in the survey of long and narrow spaces, as well as interior areas like small rooms.

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