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TECHNICAL PAPERS

Fixtureless Sensor Standoff Control for High-Precision Dimensional Inspection of Freeform Parts

[+] Author and Article Information
Vijay Srivatsan1

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109vsrivats@umich.edu

Reuven Katz, Debasish Dutta

Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109

1

To whom correspondence should be addressed.

J. Manuf. Sci. Eng 129(1), 172-179 (Aug 09, 2006) (8 pages) doi:10.1115/1.2401621 History: Received February 26, 2006; Revised August 09, 2006

High-precision, noncontact dimensional inspection requires sensor standoff control due to the working range limitation posed by high-precision range sensors. Constant sensor standoff with the surface of the part is necessary to ensure accurate measurement. This paper presents a novel computer-aided design (CAD) independent approach to sensor standoff control called “fixtureless sensor standoff control (FSC),” which contrary to current methods does not require a fixture or manual intervention for registration. This approach to sensor standoff control will enable rapid, flexible, and high-precision inspection of freeform parts, thus catering to the needs of future manufacturing systems. In the FSC methodology, the sensor’s position for the next measurement is estimated based on immediate previous measurements. The method was implemented on a four-axis machine used to inspect turbine blades. Results from measurement of an example turbine blade showed the deviation from desired standoff to be significantly smaller than the working range of the sensor.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sensor path for point based sensors

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Figure 2

Flowchart showing fixtureless standoff control for one part orientation

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Figure 3

Standoff control shown for N=4

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Figure 4

Sensor motion during initial phase

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Figure 5

Process of part location

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Figure 6

FSC with seamless sensor motion: (a) next step sensor position calculation for continuous sensor motion and (b) length of sensor motion in one step for continuous sensor motion

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Figure 7

Four-axis turbine blade inspection machine

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Figure 8

Information flow for turbine blade inspection machine

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Figure 11

Validation of FSC with continuous sensor motion shows standoff error significantly smaller than the working range of the sensor

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Figure 10

Turbine blade used for validation experiments

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Figure 9

Effect of user variables on standoff error for discrete implementation on a simulated sinusoidal profile: (a) Plot of RMS sensor positioning error versus number of samples for a sinusoidal profile with amplitude of 1000μm and time period of 10μm for step sizes 3–7 and (b) Plot of RMS sensor positioning error versus step size for a sample size of 5 on a sinusoidal profile with amplitude of 1000μm and T=10μm

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