Robert Schmitt

Uncertainty in measurement for x-ray-computed tomography using calibrated work pieces

This paper presents the principles of industrial x-ray-computed tomography (XCT) and its enormous potentials for the non-destructive 3D measurement and quality assurance of technical parts. Due to many overall factors and many nonlinear factors having an influence on the tomographic imaging process, the reconstructed volume model and thus the measurement results, XCT is a complex technology. Until now for XCT the uncertainty in measurement in general cannot be quantified satisfyingly regarding the traceability to national standards and the comparability to other measurement devices, e.g. tactile coordinate measuring machines. In this work different procedures to determine the uncertainty in measurement are assessed considering their applicability for XCT. The procedure of using calibrated work pieces is regarded as the most promising. This procedure is evaluated for an aluminum test part. The effect of several system parameters, which can be influenced by the operator, on the uncertainty in measurement is analyzed. The possibility of partially minimizing the analysis effort by means of simulation is outlined. In detail, for bore holes the effect of random errors on the measurement result is simulated.

Managing change: quality‐oriented design of strategic change processes

Purpose – The continuous change with which companies are faced, requires an approach to implement the necessary changes to the organizations structure. Existing approaches represent sequential procedures, which do not meet the requirements to deal with the characteristics of continuous change. Furthermore, existing models for managing change only state what has to be done but do not explain how it can be done. Aims to remedy these shortcomings.Design/methodology/approach – Based on existing models and on the criteria of the EFQM model, a control loop for the management of strategic change processes was developed. A quality gate concept was defined to measure the performance of the change process by measurements at the quality gates after each phase of the process.Findings – The integrated methodologies and tools were validated in projects with various companies and adapted to practical needs.Research limitations/implications – A crucial point for the presented procedural model is the applicability of the...

Fast and Accurate 3D Scanning Using Coded Phase Shifting and High Speed Pattern Projection

We describe a structured light phase measuring triangulation technique extending the conventional four-step phase shift sequence with embedded information suited to assist the phase unwrapping process. Using the embedded information, we perform automatic phase unwrapping in the presence of discontinuous or isolated surfaces without extending the length of the phase shift sequence or requiring stereo cameras. We demonstrate the application of the proposed method using a novel structured light projector capable of extraordinarily high projection frequencies and pattern resolution, as well as grayscale quantization. Using high speed cameras, we demonstrate 3D measurements at 20ms total acquisition time for both mono- and stereoscopic camera configurations.

Self-optimising Production Systems

One of the central success factors for production in high-wage countries is the solution of the conflict that can be described with the term “planning efficiency”. Planning efficiency describes the relationship between the expenditure of planning and the profit generated by these expenditures. From the viewpoint of a successful business management, the challenge is to dynamically find the optimum between detailed planning and the immediate arrangement of the value stream. Planning-oriented approaches try to model the production system with as many of its characteristics and parameters as possible in order to avoid uncertainties and to allow rational decisions based on these models. The success of a planning-oriented approach depends on the transparency of business and production processes and on the quality of the applied models. Even though planning-oriented approaches are supported by a multitude of systems in industrial practice, an effective realisation is very intricate, so these models with their inherent structures tend to be matched to a current stationary condition of an enterprise. Every change within this enterprise, whether inherently structural or driven by altered input parameters, thus requires continuous updating and adjustment. This process is very cost-intensive and time-consuming; a direct transfer onto other enterprises or even other processes within the same enterprise is often impossible. This is also a result of the fact that planning usually occurs a priori and not in real-time. Therefore it is hard for completely planning-oriented systems to react to spontaneous deviations because the knowledge about those naturally only comes a posteriori.

Modelling Machine Tools for Self-Optimisation of Energy Consumption

This paper presents a novel approach for modelling machine tools and so preparing the basis for self-optimisation. Based on previous experiments and publications, the main energy consumers in typical machine constructions are identified and machine components are structured in a way that facilitates the definition of the optimisation problem. Also energy saving possibilities are illustrated together with the suggested structure. In addition, further planed research works for the implementation of self-optimised machine behaviour are presented.

Fiber-optical sensor with miniaturized probe head and nanometer accuracy based on spatially modulated low-coherence interferogram analysis

Fiber-optical sensors have some crucial advantages compared with rigid optical systems. They allow miniaturization and flexibility of system setups. Nevertheless, optical principles such as low-coherence interferometry can be realized by use of fiber optics. We developed and realized an approach for a fiber-optical sensor, which is based on the analysis of spatially modulated low-coherence interferograms. The system presented consists of three units, a miniaturized sensing probe, a broadband fiber-coupled light source, and an adapted Michelson interferometer, which is used as an optical receiver. Furthermore, the signal processing procedure, which was developed for the interferogram analysis in order to achieve nanometer measurement accuracy, is discussed. A system prototype has been validated thoroughly in different experiments. The results approve the accuracy of the sensor.

Performance evaluation of iGPS for industrial applications

The performance of Large-Volume Metrology has substantially increased during the last number of years. Systems such as indoor global positioning system (iGPS) provide precise measurements in complete production environments and will eventually lead to the development of new manufacturing principles. The understanding of measurement uncertainty has always been a critical step in the integration of measurement systems in production lines. The laboratory of machine tools and production engineering WZL is addressing this important step by working with a focus on cooperating robot movements to provide a suitable application case. An initial performance evaluation of the iGPS system at WZL is undertaken. Theoretical simulation of the triangulation allows the development of a virtual iGPS. However, at this moment in time parameters are not fully known. Experimental results from a laser tracker for reference measurement are used to validate simulations. An overview of the primary use of the iGPS to control and calibrate robots will show the potential that iGPS possesses to be used in industrial applications, not being limited to robots only.

Morphometric Grading of Osteoarthritis by Optical Coherence Tomography — An Ex Vivo Study

Optical Coherence Tomography (OCT) yields microscopic cross‐sectional images of cartilage in real time and at high resolution. As yet, comprehensive grading of degenerative cartilage changes based on OCT has rarely been performed. This study investigated the potential of quantitative OCT using algorithm‐based image parameters such as irregularity (OII – Optical Irregularity Index), homogeneity (OHI – Optical Homogeneity Index) and attenuation (OAI – Optical Attenuation Index) in the objective grading of cartilage degeneration. Therefore, OCT was used to image and assess 113 human osteochondral samples obtained from total knee replacements. Processing included the analysis of OII (by calculation of the standard deviation with regards to a fitted surface), of OHI (by edge detection of tissue signal changes) and of OAI (by analysis of relative imaging depth). Additionally, samples were subject to macroscopic (Outerbridge grading), biomechanical (elastic stiffness), qualitative OCT and histological evaluation (Modified Mankin grading). Significant correlations were found between all outcome measures. OII and OHI were effective in assessing cartilage surface, integrity and homogeneity, while OAI could discriminate between unmineralized and mineralized cartilage, respectively. Therefore, quantitative OCT holds potential as a diagnostic tool for more reliable, standardized and objective assessment of cartilage tissue properties.

Three-dimensional imaging and analysis of human cartilage degeneration using Optical Coherence Tomography

Optical Coherence Tomography (OCT) is an evolving imaging technology allowing non‐destructive imaging of cartilage tissue at near‐histological resolution. This study investigated the diagnostic value of real time 3‐D OCT in comparison to conventional 2‐D OCT in the comprehensive grading of human cartilage degeneration. Fifty‐three human osteochondral samples were obtained from eight total knee arthroplasties. OCT imaging was performed by either obtaining a single two‐dimensional cross‐sectional image (2‐D OCT) or by collecting 100 consecutive parallel 2‐D OCT images to generate a volumetric data set of 8 × 8 mm (3‐D OCT). OCT images were assessed qualitatively according to a modified version of the DJD classification and quantitatively by algorithm‐based evaluation of surface irregularity, tissue homogeneity, and signal attenuation. Samples were graded according to the Outerbridge classification and statistically analyzed by one‐way ANOVA, Kruskal Wallis and Tukeys or Dunns post‐hoc tests. Overall, the generation of 3‐D volumetric datasets and their multiple reconstructions such as rendering, surface topography, parametric, and cross‐sectional views proved to be of potential diagnostic value. With increasing distance to the mid‐sagittal plane and increasing degeneration, score deviations increased, too. In conclusion, 3‐D imaging of cartilage with image analysis algorithms adds considerable potential diagnostic value to conventional OCT diagnostics.

Perceived quality as a key factor for strategic change in product development

Nowadays technical excellence is not enough to inspire customers for a product. Absolute freedom from error is a basic requirement. But how can customers be rendered enthusiastic about future products? The answer to this question lies in the creation of optimal customer-specific products. Perceived quality of a product is constituted by all visual, tactile, acoustic, gustatory and olfactory impressions. Perceived quality adds customer group specific and subjective perceptible characteristics to the basic understanding of quality. Until now there is no comprehensive systematic approach to close the gap between subjective customer perception and objective product characteristics. To manage these challenges, it is necessary to change the way of thinking within the product development.