Optical 3D Measurement System Research Articles

Experimental investigation on the deformation of CFRP cylinders using piezo-actuators

In this paper, the deformation of cylindrical composite structures employing piezoelectric actuators is investigated. It specifically addresses radial deformations of a composite cylinder generated by macro fibre composites (MFC). The purpose is to experimentally characterise the shape as well as the magnitude of the composite cylinder’s deformation using an optical full-field 3D measurement system. Besides cylinder expansion and contraction under operating conditions, shell bending appeared to contribute significantly to the overall deformation behaviour. With the data provided the development of an adaptive primary aircraft structure is conceivable.

Influence of argon pollution on the weld surface morphology

In this paper the surfaces of butt welded joints in steel tubes were analyzed using an optical 3D measurement system to determine the morphology and topographic parameters. It was established that pollution of the argon shield gas with oxygen did not influence the width of the heat-affected zone. However, the composition of the shield gas significantly influenced the surface asymmetry, Ssk, and its inclination Sku. The measurement of these parameters enabled the selection of a higher quality surface, which was visually proven by the reduction in discoloration of the surface of the weld joint. High quality surfaces eliminate a potential habitat for bacteria and a future source of corrosion as well as providing less resistance to fluid flow.

Improving the capability of a redundant robotic cell for cast parts finishing

PurposePrecision aluminium moulding makes possible the production of large‐size, complex and high‐technology cast parts. However, industrial requirements linked to economic and safety reasons call into question the manual performance of finishing operations. The purpose of this paper is to enhance industrial robot applications by using vision and redundancy optimization to improve their capability.Design/methodology/approachAfter having presented the concepts associated with machine and kinematics capability, the paper first describes the finishing constraints related to the process and the study of inaccuracy factors. Adjusting the trajectory by vision minimizes some inaccuracy factors but does not take into account the structure loading. Therefore, the authors present the optimization, kinematics and precision criteria as well as the multi‐objective method developed by integrating the loading aspect. This method has been verified by simulation and the results validated on industrial parts.FindingsThe paper presents an improvement in machine capacities based on redundancy and an optical 3D measurement system. It develops the strategies, sensors and cell architecture to perform finishing operations.Research limitations/implicationsThe finishing of high‐technology structural cast parts requires the completion of the machining and polishing processes adapted to each part. The choice was made to develop a robotic cell dedicated to integrating specific features, in contrast to machine tools.Practical implicationsThis study was carried out within the framework of the Eureka SANDCAST project in cooperation with the Alcan group, specialized in high‐technology moulded aluminum parts.Originality/valueThe paper presents an approach to robotic cell capability improvement. The robotic cell is dedicated to finishing operations, by machining and polishing large cast aluminum parts; the objectives are to improve machine capability and kinematics capacity with vision and redundancy management.

Rapid Prototyping of Handicraft Based on Reverse Engineering

Reverse Engineering of handicrafts refers to many aspects, such as data collection, data mergence of point clouds, surfaces reconstruction, and rapid prototyping. This paper takes a handicraft horse for example. Once this horse is scanned partially by using non-contact optical 3D measurement system, we can get point clouds data, and accumulate, merge, and combine them into one data file, then build up a three-dimensional picture, and obtain STL format file after slicing. Finally, rapid prototype manufacture can be used. By using this method, handicrafts that are the same as or similar with the mock-ups can be produced.

A Contrast of Generation Sinusoidal Fringe Pattern Method Based on Phase Measurement Profilometry

Optical 3D measurement systems are used in a lot of applications, for instance for quality control and reverse engineering. A structured light active optical 3D measurement method are very often based on projection sinusoidal fringe pattern on the object. The key element of such a shape measurement method is how to generate sinusoidal fringe pattern. The purpose of this paper is to review the method of generation sinusoidal fringe pattern and contrast the two chief method from the specific viewpoint based phase measurement profilmetry. Experiment verification of the performance of each generation method is provided and finally some suggestions on generation method for phase measurement profilometry applications is offered.

A 3D optical deformation measurement system supported by knowledge-based and learning techniques

High accuracy 3D representation and monitoring of objects is receiving increasing interest both in science and industrial applications. Up to now tasks like monitoring of building displacements or deformations were solved by means of artificial targets on the objects of interest, although mature optical 3D measurement and laser scanning tech- niques are available. Such systems can perform their measurements even without targeting. This paper presents a new optical 3D measurement system, based on the fusion between a geodetic image sensor and a laser scanner. The main goal of its develop- ment was the automation of the whole measurement process, including the tasks of point identification and measurement, deformation analysis, and inter- pretation. This was only possible by means of new methods and techniques originally developed in the area of Artificial Intelligence; both point detection and deformation analysis are supported by decision systems that use such techniques. The resulting complex multi-sensor system is able to measure and analyse the deformation of objects, as shown in ex- periments. In this article we focus on specific key components and novel techniques that have been de- veloped, and briefly report on the current stage of the whole system.

Pouring liquid from a pot—kinematics of an everyday task

An experiment was carried out to investigate the effects of handle design on postures in the use of pots. Six combinations of handle (sloping, vertical and curved) and spout designs (long and short) were tested during grasping, lifting and pouring. The fill load was 1000 ml of water at the prevailing room temperature (about 20°C) and three males and three females were involved as subjects. Measurements were made of x- (horizontal), y- (lateral) and z- (vertical) co-ordinates of the wrist, elbow shoulder and hip joints in space throughout the motions, using a CODA MPX30 optical 3D measurement system and both linear and angular displacements of the arm joints and trunk were computed. Very different configurations of arm posture were found to be adopted at the moment of pot lift, and when pouring commences and the subjects’ movement patterns during transfer of the pot to fill vessel showed to be influenced by the configuration of arm posture adopted at the moment of pot lift. For lifting the pot, the vertical handle design proved to be more desirable than either the curved or sloping design, while for pouring from the pot the short spout proved to be more desirable than the long spout, at least when the pot was full. The results are however, not clear on which handle or spout design is best for transferring the pot.

CIRCULAR CODED TARGET FOR AUTOMATION OF OPTICAL 3D-MEASUREMENT AND CAMERA CALIBRATION

One of the primary, but tedious, tasks for the user and developer of an optical 3D-measurement system is to find the homologous image points in multiple images, a task that is frequently referred to as the correspondence problem. Along with the solution, error-free correspondence and accurate measurement of image points are of great importance, on which the qualitative results of succeeding camera calibration and 3D-measurements are immediately dependent. In fact, the automation of measurement processes is getting more important with progresses in production, and hence, is of increasing topical interest. In this paper, we present a circular coded target for automatic image point measurement and identification. The applied image processing method will be described in detail, and we will show some application examples of the circular coded target to optical 3D-measurement techniques.

TV-Holography and holographic interferometry: Industrial applications

A detailed vibration analysis is vital for industry. However, in particular in the automotive industry, one is interested in the acoustical field or in the determination of strain and stress. The acoustical field can easily be measured by microphones or intensity microprobes; however, it is also important to understand by which vibration modes the noise is emanating. TV-Holography, also called electronic speckle interferometry (ESPI), and double or multipulse (three or four) holography are two famous techniques of holography (Marwitz H., Praxis der Holographie, Expert Verlag, 1990). In speckle interferometry two images of the speckle field at different times are recorded directly with a CCD camera and then subtracted from each other by an image processing system. The resulting interference fringes are available in real time. In double pulse holography a ruby laser is triggered such that the interesting object vibration is recorded by two consecutive laser pulses. The interference fringes can be evaluated at reconstruction time by the phase shift technique, if two reference beams are used. The multi-pulse method is very useful for the investigation of operational vibration modes or of transient processes like shock waves. The calculation of the acoustical field and frequency spectrum requires the knowledge of the contour for the generation of boundary elements. The contour data can be taken either from CAD or FEM data or by measurement with optical 3D measurement systems. The acoustical field is calculated by solving the Helmholtz integral. For experimental strain and stress analysis the 3D shape and the 3D displacement are also necessary. For acoustical prediction the component of the displacement, which is perpendicular to the surface, is determined. On the other hand, for strain/stress calculation the tangential components to the surface are used.