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

Abstract

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.