An improved vision calibration method for coaxial alignment microassembly

Ye, Xin; Gao, Jun; Zhang, Zhijing; Shao, Chunfu; Shao, Guangyuan

doi:10.1108/aa-10-2013-092

Cited by 14 publications

(5 citation statements)

References 14 publications

(10 reference statements)

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“…The center distance is evaluated by the rotation angle θ and the distribution radius of the bolt holes R (i) . Hence, the optimization model 2 for rotation adjustment calculation is built with θ and R (i) as the variables, and the sum of center distances from all image pairs as the objective function, see (17).…”

Section: Modeling and Calculation Of Rotation Adjustmentmentioning

confidence: 99%

“…Liu et al accomplished the assembly of small parts by utilizing three cameras to detect the posture of the parts and a force sensor to detect the assembly force [16]. Ye et al designed a coaxial alignment assembly system and analyzed the error of the system to achieve the alignment and assembly of small parts with accuracy better than 5um [17], [18]. The specially designed jigs and fixtures with high manufacturing accuracy are generally used to grab the part for the assembly of large parts, hence the position of the part is ensured.…”

Section: Introductionmentioning

confidence: 99%

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A Coaxial Alignment Method for Large Flange Parts Assembly Using Multiple Local Images

Sun

Zhang

2021

IEEE Access

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The large flange parts in aero-engines are usually manually assembled. Collision damage caused by assembly alignment error often occurs in the assembly process, which affects the assembly accuracy and product reliability. The machine vision-based alignment methods usually achieve the highprecision measurement of the parts by obtaining the high-resolution images of the whole parts with a combination of laser distance sensors. Hence, existing methods are high costly and inefficient. In this paper, a new alignment method based on the principle of coaxial alignment for large flange parts is proposed. The proposed method first obtains multiple high-precision image pairs from the local field of views at the fitting surfaces of flanges. The clearance and bolt holes in each image pair are then extracted via edge recognition and Hough Transformation. Two optimization models are built to calculate the translation adjustment and rotation adjustment. The optimization model 1 is built with the translation adjustments of the flange as the variables and the consistency of the clearances as the objective function. The algorithm to solve the model based on the gradient-descent method is proposed. The positions of the bolt holes in the images are subsequently adjusted based on the translation adjustment, and the rotation adjustment is calculated by solving the built optimization model 2. The experiments show that the proposed method can be applied to the assembly process of large flange parts, and the visual servo control model based on this method also has good stability.

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Section: Modeling and Calculation Of Rotation Adjustmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Coaxial Alignment Method for Large Flange Parts Assembly Using Multiple Local Images

Sun

Zhang

2021

IEEE Access

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“…Yang et al (2014) proposed a plane calibration target that can be arbitrarily placed, and they fitted the laser plane according to the trigonometry principle and invariance of the cross-ratio to achieve high-precision calibration. Ye et al (2014) presented a sub-pixel calibration method for a micro assembly system with a coaxial alignment function to reach the micrometer level. Van Crombrugge et al (2021) proposed a method to calibrate the extrinsic parameters of a camera using line-laser projection.…”

Section: Introductionmentioning

confidence: 99%

A unified calibration method of 3D laser profile measurement with different of laser-line lengths

Liu²,

Liu³

2023

RIA

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Purpose Existing calibration methods mainly focus on the camera laser-plane calibration of a single laser-line length, which is not convenient and cannot guarantee the consistency of the results when several three-dimensional (3D) scanners are involved. Thus, this study aims to provide a unified step for different laser-line length calibration requirements for laser profile measurement (LPM) systems. Design/methodology/approach 3D LPM is the process of converting physical objects into 3D digital models, wherein camera laser-plane calibration is critical for ensuring system precision. However, conventional calibration methods for 3D LPM typically use a calibration target to calibrate the system for a single laser-line length, which needs multiple calibration patterns and makes the procedure complicated. In this paper, a unified calibration method was proposed to automatically calibrate the camera laser-plane parameters for the LPM systems with different laser-line lengths. The authors designed an elaborate planar calibration target with different-sized rings that mounted on a motorized linear platform to calculate the laser-plane parameters of the LPM systems. Then, the camera coordinates of the control points are obtained using the intersection line between the laser line and the planar target. With a new proposed error correction model, the errors caused by hardware assembly can be corrected. To validate the proposed method, three LPM devices with different laser-line lengths are used to verify the proposed system. Experimental results show that the proposed method can calibrate the LPM systems with different laser-line lengths conveniently with standard steps. Findings The repeatability and accuracy of the proposed calibration prototypes were evaluated with high-precision workpieces. The experiments have shown that the proposed method is highly adaptive and can automatically calibrate the LPM system with different laser-line lengths with high accuracy. Research limitations/implications In the repeatability experiments, there were errors in the measured heights of the test workpieces, and this is because the laser emitter had the best working distance and laser-line length. Practical implications By using this proposed method and device, the calibration of the 3D scanning laser device can be done in an automatic way. Social implications The calibration efficiency of a laser camera device is increased. Originality/value The authors proposed a unified calibration method for LPM systems with different laser-line lengths that consist of a motorized linear joint and a calibration target with elaborately designed ring patterns; the authors realized the automatic parameter calibration.

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“…In addition, besides the installation error of the camera, its own parameters also affect the assembly accuracy of the parts. Ye et al (2014) proposed a sub-pixel calibration method to reduce the assembly error caused by the lens' distortion of the VAD. Liu et al (2009) put forward a novel camera calibration method of variable focal length, based on the orthogonal rotation matrix.…”

Section: Introductionmentioning

confidence: 99%

Automatic press-fit assembly of small precision interference fitting parts: armature of electro-hydraulic servo valve

Wang

Lou

Xiao-dong

et al. 2019

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Purpose The purpose of this paper is to design an automatic press-fit instrument to realize precision assembly and connection quality assessment of a small interference fitting parts, armature. Design/methodology/approach In this paper, an automatic press-fit instrument was developed for the technical problems of reliable clamping and positioning of the armature, automatic measurement and adjustment of the attitude and evaluation of the connection quality. To compensate for the installation error of the equipment, corresponding calibration method was proposed for each module of the instrument. Assembly strategies of axial displacement and perpendicularity were also proposed to ensure the assembly accuracy. A theoretical model was built to calculate the resistant force generated by the non-contact regions and then combined with the thick-walled cylinder theory to predict the press-fit curve. Findings The calibration method and assembly strategy proposed in this paper enable the press-fit instrument to achieve good alignment and assembly accuracy. A reasonable range of press-fit curve obtained from theoretical model can achieve the connection quality assessment. Practical implications This instrument has been used in an armature assembly project. The practical results show that this instrument can assemble the armature components with complex structures automatically, accurately, in high-efficiency and in high quality. Originality/value This paper provides a technical method to improve the assembly quality of small precision interference fitting parts and provides certain methodological guidelines for precision peg-in-hole assembly.

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An improved vision calibration method for coaxial alignment microassembly

Cited by 14 publications

References 14 publications

A Coaxial Alignment Method for Large Flange Parts Assembly Using Multiple Local Images

A Coaxial Alignment Method for Large Flange Parts Assembly Using Multiple Local Images

A unified calibration method of 3D laser profile measurement with different of laser-line lengths

Automatic press-fit assembly of small precision interference fitting parts: armature of electro-hydraulic servo valve

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