Joseph Benjamin Ross

Exhaustive detection of manufacturing flaws as abnormalities

Manufacturing flaws of all types, shapes, and sizes can be exhaustively detected as abnormal pixels, if process and noise variations can be learned at every pixel in the inspection area. This statistical template approach to automated visual inspection is extremely fast, effective, and flexible, while achieving false negative rate <10/sup -6/. Critical to this approach are the following novel features: 1) represent both geometry and process information in a model template; 2) align 3D surfaces with subpixel accuracy; compensate for local deformation and texture; 4) estimate bimodal distribution robustly. This novel paradigm was applied to the automatic screening of X-ray images of turbine blades. It has been validated with over 50,000 images and shown to outperform regular inspectors looking at high-pass filtered images.

Challenges faced in applying 3D noncontact metrology to turbine engine blade inspection

3D Non-contact Inspection systems are becoming more capable and affordable, however successful application to complex parts requires understanding the remaining system limitations. Turbine airfoils are key components used in several important industries that present some unique challenges to any metrology application. Issues such as surface finish, complicated shapes and unique geometries exercise many of the key capabilities of a non-contact 3D measurement system. Therefore, many of the short comings of any 3D method become evident in addressing airfoil measurement applications. This paper will address the key challenges posed by complicated shapes such as airfoils, and what gaps still exist in the application of the technology.

Admissible transformation volume for part dimensional quality gauging

Coordinate metrology aims to answer two questions: whether a manufactured part meets design tolerance specifications and how well the manufactured part meets the specifications. Existing methods for analyzing measured coordinate data are not adequate or effective for parts of complex tolerance zones. This paper presents a new approach to dimensional qualification of manufactured parts. In this paper, we view the part qualification problem as an issue of finding an admissible point in transformation space. Based on the concept of admissible point, we develop theories and algorithms for part geometric dimensioning and tolerancing (GD&T) conformance check. A formulation based on containment fit for tolerance check is developed. An admissible transformation volume (ATV) is used to quantitatively characterize the quality of manufactured parts with respect to design tolerance specifications. We examine our approach in three tolerance examples and conclude that admissible transformation volume is an effective metric for part dimensional quality gauging and it is especially useful for multi-tolerance zone check where traditional methods fail to address it effectively.

Material characterization and defect inspection in ultrasound images

The use of ultrasonic imaging to analyze defects and characterize materials is critical in the development of non-destructive testing and non-destructive evaluation (NDT/NDE) tools for manufacturing. To develop better quality control and reliability in the manufacturing environment advanced image processing techniques are useful. For example, through the use of texture filtering on ultrasound images, we have been able to filter characteristic textures from highly textured C-scan images of materials. The materials have highly regular characteristic textures which are of the same resolution and dynamic range as other important features within the image. By applying texture filters and adaptively modifying their filter response, we have examined a family of filters for removing these textures.

A Study of Tracking System Using Multiple Emitter Towers

This paper presents a simple and accurate coordinate transformation method for extending the tracking space of the Intersense IS-900 spatial and motion tracking system using multiple pre-configured emitter towers to form the emitter constellation, but without resorting to the use of a surveyor machine. The proposed approach uses the differences of positional coordinate readings from each emitter tower among a set of commonly viewed spatial points to calculate the parameters needed to define the coordinate transformation. By applying this method, the tracking accuracy using the entire emitter constellation can be achieved by less than 0.5 inches error in most of the working space, and as low as 0.2 inches error in the frontal part of the working space.

Technology enablers for improved aerospace x-ray NDE

In the current climate of reduced Military spending and lower commercial demand for aerospace products, it is of critical importance to allocate scarce technology development resources to meet projected needs. During the past decade, dramatic advances in x-ray nondestructive evaluation (NDE) technology have results in commercially viable digital radiography (DR) and computed tomography (CT) systems. X-ray CT has become an important NDE technique that not only provides data about material integrity, but also valuable volumetric data which is finding applications in reverse engineering, rapid prototyping, process control and 3D metrology. Industrial DR and CT systems have been available for almost 10 years, but are very costly, generally designed for specific applications and have well known limitations for both process development and final inspection. They have inadequate energy/flux to penetrate many large components and structures. In order to support the US Aerospace Industry in its drive towards global competitiveness, it is imperative that key enabling tools such as DR and CT be improved, made affordable, and implemented to meet the anticipated needs of the next decade of aerospace applications. This paper describes a strategy for a consortium of suppliers and users of x-ray NDE systems, academia and national laboratories to work together to attain this goal.

Semiautomatic calibration of robot manipulator for visual inspection task

A semiautomatic procedure to calibrate a robot manipulator for improving positioning accuracy is proposed. An error-correcting transformation is estimated using the point-pairs in the theoretical and actual coordinate frames. The theoretical points are obtained using a 3D model of the inspected part, whereas the actual points are derived with image processing and analytic geometry techniques. The estimation of the error-correcting transformation is based on a leastsquare method. Experimental results are described to illustrate the calibration procedure.