Pore Detection in Small Diameter Bores
The University of Michigan, Ann Arbor
NSF Engineering Research Center for
Reconfigurable Manufacturing Systems
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 2
Introduction
Pores above 500 micron inside small bores may cause leakage and other problem
Specifications:• Dimension: Φ 5-15 mm L 100-150 mm ( May be stepped and discontinuous) • Material: Aluminum• Pore Size: Φ < 1 mm
• Surface: Glossy
Φ15mm Φ5mm
100-150 mm
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 3
Project goals
1. In-line inspection of the inner surface of small bores of power train parts
2. Detect and locate pores lager than 1mm diameter inside a small bore
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 4
Progress
• Stage 1. Background investigation (April, 2007 )
• Stage 2. Preliminary study (May, 2007)
• Stage 3. System integration (June, 2007)
• Stage 4. Image processing and porosity analysis (July-Now, 2007)
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 5
Sight Pipe System
X Y motion stage
Z rotary stage
CCD
Sight Pipe
Sample
Side and top view of the system
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 6
“Paper Bore” image
13 mm Diameter
Real Bore image
The shadow lines appears
Scanning results
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 7
Scanning result after alignment
After alignment
Before alignment
Large intensity variance
small intensity variance
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 8
Alignment of Camera and motion stage
• Step1- Focus the camera onto a target point at a close distance and center the target using linear adjustments.
• Step2- Use motion stage to move the camera to the further distance and center the target using angular adjustments.
Step3- Repeat steps 1 and 2 until the targets are centered in the same position.
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 9
Aligning the Bore axis
• Step1-Focus on front of the bore and find the center of the circular opening.
• Step2-Focus on the back of the bore and find the center of a circular ring.
• Step3-Align angular and linear positioning of the bore until the two reference circles are centered with the camera.
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 10
Straightness and angular tolerance for aligning the Bore
• The bore must be properly aligned to provide a low intensity variance for the unwrapping zone.– Straightness should be
within ~0.18 mm in each direction
– Angular error should be within ~670 arcsecs
Standard Deviation due to the Linear Offset
0
2
4
6
8
10
12
14
16
-0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25
Shift Distance (mm)
Sta
ndar
d D
evia
tion
Standard Deviation Due to Angular Offset
0
2
4
6
8
10
12
14
16
-1000 -800 -600 -400 -200 0 200 400
Angular Offset (arcsec)
Sta
ndard
Devia
tion
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 11
Current Work
1. Software interface improvement User-Friendly interface Well organized program with clear comments
2. Porosity analysis using Labview – Detect pores with different size
– Indicate the location of the pores
– Filter the pores as needed (By size, location and so on)
– Provide statistic table
3. Redesign mounting structure for the sight pipe system to add one degree of freedom in vertical direction
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 12
Some Algorithms
Sight Pipe + IMAQ image processing: Finding center polar unwrapping stitching
Motion control : Magnification = real width of line / pixel width of line*Pixel size
Total time of Scan = scanning distance/ motion velocity
Motion velocity= Width of sampling zone*Pixel size*Magnification / Sampling period
Finding the Pore:
Threshold Particle Filter Particle Analysis
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 13
Image Processing
1. A background correction threshold is applied to the entire image.
– Background correction breaks the image up into smaller regions and searches for the darkest areas in each image.
2. The particles are then put through a particle filter based on the major axis of the best fit ellipse.
3. The image saved with particle information are loaded into a screen that allows the user to easily see the pores and their location based on the filter been chosen.
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 14
MINI CCD updating
51 degree field of view with normal lens
Inside view of a bore ( 13 & 30 mm diameter)
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 15
Fiber illumination for the MINI CCD
Fiber
MINI CCD
NSF Engineering Research Center for Reconfigurable Manufacturing SystemsUniversity of Michigan College of Engineering
ERC Presentation Format # 16
Next Steps
• Optimize the pore detection algorithms
• Improve the mounting structure of the sight pipe system
• Increasing the optical magnification to get higher resolution
• Upgrading the CCD and DAQ device for higher speed if necessary
• Continue the Mini CCD research
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