Surface Profiling of Drywalls for
Automated Sanding
Dony Alex Dr. Mohamed Al-Hussein Dr. Saeed Behzadipour
Hole School of Construction Engineering
Dept. of Civil & Environmental Engineering
University of Alberta
Canada
June 29th, 2011
Outline
●Introduction
●Surface Profiling Techniques
●Proposed Methodology
●Algorithms
●Case Study
●Conclusion
Current Challenges in Construction
●Declining Productivity
●Hazardous Working Conditions
●Shortage of Skilled Workers
●10 -15% increase in overall productivity
●Reduce exposure to hazardous environment
●Better quality
●Higher standards of work
How Automation Helps?
Challenges in Construction
sources: Euroconstruct, Eurostat, ACEA)
The Sanding Process
●Ensures smooth surface
●Exposure to dust - at least 10
times the Permissible Exposure
Limits (PEL)
●Integration of robotics - a relatively
new concept
Tape Coat Drywall
Tape
Block
Coat
Skim
Coat
Sanding
Image: http://home.howstuffworks.com/drywall4.htm
Surface Profiling
●Process of identifying the surface
geometry.
●Identifies irregularities
●Currently performed manually.
Surface Profiling Techniques
Classification
●Contact Based
●Non-contact Based
Sensor Accuracy Cost Complexity
Stylus High Medium High
Ultrasonic High High Low
Shadow
Profilometry
Medium Low Low
Capacitance Medium Low High
Shadow Profilometry
●Technique of tracing a surface profile using shadows
●When a plane of light is made to intersect with an irregular surface at
an angle, the resultant intersection line follows the topography of the
surface.
Shadow scanner for evaluating surface smoothness in wood industry (Sandak and Tanaka, 2005).
Proposed Methodology – Test Setup
Test Setup
oVirtual test environment setup in 3DS Max
oComprises of surface (1) , curtain (2), light source (3) and
camera (4)
oCaptures image of the shadow profile over the surface cross
section
oCaptures location at which shadow edge is formed
Case Study
H
D1
D1 = Distance at which Shadow edge is formed.
H = Height of curtain from the surface.
H= 6cm
Angle of Incidence (α)= 450
Case Study 2 – Nail Hole
Maximum Error = 0.3 cm
Average Error = 0.02 cm
Accuracy of the reconstructed profile
Case 3 – Curved Elevation
Maximum Error = 0.1 cm
Average Error = 0.04 cm
Accuracy of the reconstructed profile
Conclusions - Contributions
●Introduction of shadow profilometry as a method of profiling
the drywall surface
●Successful simulation of shadow profilometry for surface
profiling
●Successful 3D reconstruction of the surface
Conclusion – Limitations and Future Scope
● The research treats the drywall as a single
surface
●Accuracy greatly depends on sharpness of the
shadow
●Experimental implementation and validation
●Robot task planning based on the surface profile
●Integration of sensor into a robotic arm
Limitations
Future Scope