Research Papers

Visual-Based Automation of Peg-in-Hole Microassembly Process

[+] Author and Article Information
R. J. Chang

C. Y. Lin, P. S. Lin

Department of Mechanical Engineering,  National Cheng Kung University, No. 1, University Road, Tainan, Taiwan, R. O. C.

J. Manuf. Sci. Eng 133(4), 041015 (Aug 16, 2011) (12 pages) doi:10.1115/1.4004497 History: Received July 22, 2010; Revised June 24, 2011; Published August 16, 2011; Online August 16, 2011

An automatic visual-servo microassembly system is installed and tested. With a compliant polyurethane microgripper, a visual-servo system is implemented for micropeg alignment, micropeg transportation, and peg-in-hole assembly. The microassembly process is controlled by developing dynamic position-based servo through image calibration, regional-scanning with edge-fitting, and shadow-aided positioning algorithm. The main specifications of the system are gripping range of 60–90 μm, working space of 7 mm × 5.74 mm × 15 mm, and system bandwidth of 25 Hz. In performance test, cylindrical copper micropegs of diameter 80 μm and 88 μm are automatically aligned, gripped, transported, and assembled to a stainless rod with a mating hole of 100 μm.

Copyright © 2011 by American Society of Mechanical Engineers
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Figure 1

CCD installation and coordinate systems for visual servo (CCD axis is in longitudinal direction)

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Figure 2

Visual-servo framework

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Figure 3

System hardware with control framework

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Figure 4

Searching of micropeg and calibration in DPBS-IC

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Figure 5

Step response and error response in DPBS-IC

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Figure 6

Scanning direction and pixels errors between scanning edge and fitting line

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Figure 7

Search boundary and convergence in RSEF algorithm

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Figure 8

Geometric optics in SAP algorithm

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Figure 9

Positioning and alignment between micropeg and hole in SAP algorithm: (1) Get the positioning information of micropeg and hole by RSEF. (2) Positioning micropeg in the negative xw -axis. (3) Positioning micropeg along v(3) -axis with 50 pixels under the center of mating hole. (4) Positioning the mating tip of micropeg in u(3) . (5) Positioning between the mating tip of micropeg and the center of mating hole in v(3) .

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Figure 10

Micropeg alignment and positioning by needle manipulator (Left: Image from CCD1; Right: Window from human–machine interface and final slope = −0.037)

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Figure 11

Operational procedure in microassembly automation (CCD channel switching time is ignored)

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Figure 12

Search micropeg and perform calibration for the DPBS-IC algorithm

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Figure 13

Alignment between micropeg, held by microgripper, and mating hole in zw -axis

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Figure 14

Final step to proceed micropeg-in-hole assembly

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Figure 15

Finishing micropeg-in-hole assembly (clearance ratio = 0.15)



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