Jafar Jamshidi

Manufacturing and assembly automation by integrated metrology systems for aircraft wing fabrication

Abstract Discrepancies of materials, tools, and factory environments, as well as human intervention, make variation an integral part of the manufacturing process of any component. In particular, the assembly of large volume, aerospace parts is an area where significant levels of form and dimensional variation are encountered. Corrective actions can usually be taken to reduce the defects, when the sources and levels of variation are known. For the unknown dimensional and form variations, a tolerancing strategy is typically put in place in order to minimize the effects of production inconsistencies related to geometric dimensions. This generates a challenging problem for the automation of the corresponding manufacturing and assembly processes. Metrology is becoming a major contributor to being able to predict, in real time, the automated assembly problems related to the dimensional variation of parts and assemblies. This is done by continuously measuring dimensions and coordinate points, focusing on the products key characteristics. In this paper, a number of metrology focused activities for large-volume aerospace products, including their implementation and application in the automation of manufacturing and assembly processes, are reviewed. This is done by using a case study approach within the assembly of large-volume aircraft wing structures.

Key characteristics management in product lifecycle management: A survey of methodologies and practices

Key characteristics (KCs) play a significant role in product lifecycle management (PLM) and in collaborative and global product development. Over the last decade, KCs methodologies and tools have been studied and practiced in several domains of the product lifecycle, and many world-class companies have introduced KCs considerations into their product development practices. However, there has been no systematic survey of KCs techniques, methodologies, and practices in this respect. This paper aims to give a comprehensive survey of KCs methodologies, and practices from the perspective of enterprise integration and PLM. The paper firstly presents a holistic framework of KCs methodologies and practices through the product lifecycle, and summarizes the fundamentals of KCs including their definition and classification, KC flowdown, and the identification and selection of KCs. A review of the KCs methods and practices in the product lifecycle is then presented, particularly in engineering design, manufacturing planning, production and testing as well as information and knowledge management respectively. Finally, the problems and challenges for future research on KCs techniques are discussed.

Indoor GPS: system functionality and initial performance evaluation

Indoor GPS (iGPS) is a newly developed laser based measuring system for large scale metrology. The relative portability, reconfigurability and ease of installation make the iGPS suitable for many industries manufacturing large scale products. The system performance depends on both the components characteristics and their physical configuration. Hence, an important consideration for the iGPS is to characterise its real capabilities, pointing out how they can be influenced by the systems configuration and setup. In this paper, the system is introduced and the technical aspects are briefly described. Then, an initial test is performed to establish its repeatability, reproducibility and accuracy.

Estimation of uncertainty in three-dimensional coordinate measurement by comparison with calibrated points

This paper details a method of estimating the uncertainty of dimensional measurement for a three-dimensional coordinate measurement machine. An experimental procedure was developed to compare three-dimensional coordinate measurements with calibrated reference points. The reference standard used to calibrate these reference points was a fringe counting interferometer with a multilateration-like technique employed to establish three-dimensional coordinates. This is an extension of the established technique of comparing measured lengths with calibrated lengths. Specifically a distributed coordinate measurement device was tested which consisted of a network of Rotary-Laser Automatic Theodolites (R-LATs), this system is known commercially as indoor GPS (iGPS). The method was found to be practical and was used to estimate that the uncertainty of measurement for the basic iGPS system is approximately 1 mm at a 95% confidence level throughout a measurement volume of approximately 10 m × 10 m × 1.5 m.

Study of the uncertainty of angle measurement for a rotary-laser automatic theodolite (R-LAT)

Abstract This paper shows how the angular uncertainties can be determined for a rotary-laser automatic theodolite of the type used in (indoor-GPS) iGPS networks. Initially, the fundamental physics of the rotating head device is used to propagate uncertainties using Monte Carlo simulation. This theoretical element of the study shows how the angular uncertainty is affected by internal parameters, the actual values of which are estimated. Experiments are then carried out to determine the actual uncertainty in the azimuth angle. Results are presented that show that uncertainty decreases with sampling duration. Other significant findings are that uncertainty is relatively constant throughout the working volume and that the uncertainty value is not dependent on the size of the reference angle.

A comparison of two distributed large-volume measurement systems: the mobile spatial co-ordinate measuring system and the indoor global positioning system

Abstract Advances in the area of industrial metrology have generated new technologies that are capable of measuring components with complex geometry and large dimensions. However, no standard or best-practice guides are available for the majority of such systems. Therefore, these new systems require appropriate testing and verification in order for the users to understand their full potential prior to their deployment in a real manufacturing environment. This is a crucial stage, especially when more than one system can be used for a specific measurement task. In this paper, two relatively new large-volume measurement systems, the mobile spatial co-ordinate measuring system (MScMS) and the indoor global positioning system (iGPS), are reviewed. These two systems utilize different technologies: the MScMS is based on ultrasound and radiofrequency signal transmission and the iGPS uses laser technology. Both systems have components with small dimensions that are distributed around the measuring area to form a network of sensors allowing rapid dimensional measurements to be performed in relation to large-size objects, with typical dimensions of several decametres. The portability, reconfigurability, and ease of installation make these systems attractive for many industries that manufacture large-scale products. In this paper, the major technical aspects of the two systems are briefly described and compared. Initial results of the tests performed to establish the repeatability and reproducibility of these systems are also presented.

A New Data Fusion Method for Scanned Models

This paper introduces a high- and low-resolution data integration method for scanning systems. The high-resolution data captured by a touch probe on a CMM, in the form of geometric features, and the low-resolution laser scanned model, in the form of triangulated mesh, are sent to a CAD software. The two model types are first integrated into a unique coordinate system and then unified into a precise CAD model. Depending on the part complexity, some or all of the modelling process can be done automatically. This data fusion method enhances the flexibility of scanning while maintaining the accuracy of the results.

Verification of the indoor GPS system by comparison with points calibrated using a network of laser tracker measurements

This paper details a method of determining the uncertainty of dimensional measurement for a three dimensional coordinate measurement machine. An experimental procedure was developed to compare three dimensional coordinate measurements with calibrated reference points. The reference standard used to calibrate these reference points was a fringe counting interferometer with the multilateration technique employed to establish three dimensional coordinates. This is an extension of the established technique of comparing measured lengths with calibrated lengths. Specifically a distributed coordinate measurement device was tested which consisted of a network of Rotary-Laser Automatic Theodolites (R-LATs), this system is known commercially as indoor GPS (iGPS). The method was found to be practical and able to establish that the expanded uncertainty of the basic iGPS system was approximately 1 mm at a 95% confidence level.

Rapid and accurate data integration method for Reverse Engineering Applications

In many cases it is desirable to precisely extract the design information and to generate a full CAD model from an existing part or prototype to be able to analyse its functionality or to replicate it using available manufacturing techniques. The process of Reverse Engineering(RE) helps generate design information from a part, for which such information is unavailable or mislaid. Various scanning systems are available for use in RE that can be divided into contact, and non-contact systems. Contact systems like Coordinate Measurement Machines(CMM) with touch-trigger probe are highly accurate but time consuming and costly when the number of required data-points is high. Laser Scanners(LS), as non-contact systems, are fast but less accurate or expensive if in higher resolution versions. Also higher resolution equals higher level of noise in cloud-data, requiring extensive modelling operations. Moreover feature extraction from cloud-data is always an approximation of the actual feature, which might not be ideal for precision engineering applications. In this paper a data integration method for these two types of data is introduced. The accurate data captured by CMM touch-trigger probe is used to accurately create geometric features and the low-resolution data gained from the non-sensitive features by LS are used to fill the gaps between the accurate features. This method enhances the speed and flexibility of scanning while maintaining the accuracy of the results. Experimental results for method verification are presented. This method can be employed automatically, fully or partially, depending on the complexity of the component.

High accuracy laser scanned view registration method for reverse engineering using a CMM generated CAD model

Complete CAD modelling by 3D digitizers comprises of full coverage scanning of the part from a number of views in the Reverse Engineering process. Different scanned views are required to be registered into a cohesive coordinate system to generate a practical CAD model. In this paper a high accuracy registration method is introduced in which the preregistered views, obtained by a conventional registration method are used as a base for fine registration. This is based on the relationships of the scanned views in the Laser Scanned model and the scanned features created by the Coordinate Measurement Machine. This method is most suitable for Reverse Engineering of precision parts with accurate and standard machined geometric features and complex but less accurate casting features. Experimental results of the method application on two components are presented.© 2006 ASME