Multi-Camera-Based Universal Measurement Method for 6-DOF of Rigid Bodies in World Coordinate System.

Zuoxi Zhao,Yuchang Zhu,Yangfan Luo,Yuanhong Li,Zhi Qiu,Chaoshi Xie,Zhuangzhuang Zhang

doi:10.3390/s20195547

Zuoxi Zhao, Yuchang Zhu + Show 5 more

Open Access

https://doi.org/10.3390/s20195547

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Abstract

The measurement of six-degrees-of-freedom (6-DOF) of rigid bodies plays an important role in many industries, but it often requires the use of professional instruments and software, or has limitations on the shape of measured objects. In this paper, a 6-DOF measurement method based on multi-camera is proposed, which is accomplished using at least two ordinary cameras and is made available for most morphological rigid bodies. First, multi-camera calibration based on Zhang Zhengyou’s calibration method is introduced. In addition to the intrinsic and extrinsic parameters of cameras, the pose relationship between the camera coordinate system and the world coordinate system can also be obtained. Secondly, the 6-DOF calculation model of proposed method is gradually analyzed by the matrix analysis method. With the help of control points arranged on the rigid body, the 6-DOF of the rigid body can be calculated by the least square method. Finally, the Phantom 3D high-speed photogrammetry system (P3HPS) with an accuracy of 0.1 mm/m was used to evaluate this method. The experiment results show that the average error of the rotational degrees of freedom (DOF) measurement is less than 1.1 deg, and the average error of the movement DOF measurement is less than 0.007 m. In conclusion, the accuracy of the proposed method meets the requirements.

Highlights

The measurement of six-degrees-of-freedom (6-degrees of freedom (DOF)) is important in industrial production and the 6-DOF of a measured object represents its position information, which will help the machine to operate efficiently, 6-DOF measurements are often used in fields such as precision machining, spacecraft docking, and manufacturing assembly [1]
The 6-DOF of a rigid body include the rotational degrees of freedom (Ψ, θ, φ) around the x, y, and z axes as well as the movement degrees of freedom (Tx, T y, Tz ) along the x, y, and z axes
In order to evaluate the performance of the proposed method, this paper takes two cameras as an example and takes the shovel of a paddy field grader as the measured rigid body

Summary

Introduction

The measurement of six-degrees-of-freedom (6-DOF) is important in industrial production and the 6-DOF of a measured object represents its position information, which will help the machine to operate efficiently, 6-DOF measurements are often used in fields such as precision machining, spacecraft docking, and manufacturing assembly [1].The 6-DOF of a rigid body include the rotational degrees of freedom (Ψ, θ, φ) around the x, y, and z axes as well as the movement degrees of freedom (Tx , T y , Tz ) along the x, y, and z axes. The commonly used measuring instruments or methods include laser, Hall sensor, inertial measurement unit (IMU), total station, and vision. Laser measurement methods, which include laser interferometer [2], laser tracker [3], and laser collimation method [4], have high accuracy, but a special optical path needs to be designed using a lens [5,6,7]. As a result, it has requirements on the size or range of motion of the measured object.

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