27 research outputs found
The story of Wanderwolf: A contested tale on the re-emergence of 'new wilderness' in the Netherlands
No full textContains fulltext :
221813.pdf (Publisher’s version ) (Open Access)In this chapter, the author studies what the particular wolf has come to signify culturally in the contemporary public imagination and understanding of the Dutch landscape. It suggests that the Wanderwolf 'wandered' into the production of a new landscape ideology, i.e., another genesis of the Dutch landscape, in which it fulfils a different kind, yet equally controversial, iconic role compared to those we know from West-European ethnological and folkloric traditions. The media commotion surrounding the sightings of the Wanderwolf should be seen in the context of a much larger interest and effort to 'rewild' Europe. The visions expressed by the enthusiasts on the apparent return of the wolf reflect strongly those which Cronon has critically analysed in his influential essay on the notion of wilderness. The wolf's adversaries spoke out equally during the Wanderwolf's appearance. As media announced during the Wanderwolf incident, the comeback of the wolf is no longer a fairy tale
Online non-destructive evaluation in automated fibre placement
No full textThe strict quality requirements for aerospace composite structures give rise to costly quality control procedures. In automated fibre placement (AFP) these procedures rely heavily on manualwork and inspection. This research aims at performing preventative non-destructive evaluation of composite laminate quality based on an online geometric analysis of the placed fibre. A robot mounted laser pro le sensor, in combination with robot positional data, is used to create a 3D model of the fibre. These are fused using quaternion coordinate transfer operations with the Robot Operating System, an open source robotics platform. The 3D model is converted into an image for fast processing using open source algorithms from OpenCV. Deviations in part-product quality are identified in real-time including geometric, positioning and buckling defects due to high-radius curvatures in the fibre path. Currently the prototype system will give a non-conformance warning to the operator, and in future work it is planned to develop automated feedback and control algorithms to correct common de fects. The implementation of a preventitive system in an industrial fibre placement process can cut back the time spent on inspection and rework.Aerospace EngineeringAerospace Structures and MaterialsStructural Integrity and Composite
Online Preventative Non-Destructive Evaluation in Automated Fibre Placement
No full textThe strict quality requirements for aerospace composite struc- tures give rise to costly quality control procedures. In automated bre placement (AFP) these procedures rely heavily on manual work and inspection. This research aims at performing preventative non-destructive evaluation of composite laminate quality based on an online geometric analysis of the placed bre. A robot mounted laser pro le sensor, in combination with robot positional data, is used to create a 3D model of the bre. These are fused using quaternion coordinate transfer operations with the Robot Operat- ing System, an open source robotics platform. The 3D model is converted into an image for fast processing using open source algorithms from OpenCV. Deviations in part-product quality are identi ed in real-time including geometric, positioning and buckling defects due to high-radius curvatures in the bre path. Currently the prototype system will give a non-conformance warn- ing to the operator, and in future work it is planned to developStructural Integrity & CompositesAerospace Structures & Computational Mechanic
The effects of local fibre steering: Reducing gaps and overlaps by compensating for tow width fluctuation in automated fibre placement
No full textThe aerospace industry increasingly uses fibre-reinforced plastics that are manufactured using automated fibre placement (AFP). A common problem in AFP is the occurrence of gaps and overlaps that affect the structural perfromance of laminates. Tow width fluctuation is an important cause of gaps and overlaps. Two developments in manufacturing are combined to create a new mitigation method for gaps and overlaps. One development is fibre steering, which harnesses the flexibility of AFP to vary the fibre orientation within the ply. Another development is smart manufacturing which includes responding real-time to changes. The combination is local fibre steering which compensates for tow width fluctuation by placing tows adjacent to each other. In three steps it is assesed how effective local fibre steering is in increasing the structural performance of composite laminates by reducing gaps and overlaps through compensating for tow width fluctuation in automated fibre placement. Firstly, it is determined to what extent gaps and overlaps are reduced by constructing a conventional and a steered laminate. The tow width is modelled using a cubic spline. The steered laminate uses numerical approximations of the equations for parallel parametric curves. Two problems occurs that are: the accumulation of curvature leading to self-intersections and cusps, and large angle deviations. The curvature accumulation is tackled by using smoothing splines and the fibre angle deviation can be limited by taking a weighted average. Secondly, the tow width model is validated by measuring the tow width of two different materials. Thirdly, the effect of the reduction in gaps and overlaps and the fibre angle deviation on the structural performance is determined by using a finite element method based on the defect layer method that calculated the buckling load and the effective stiffness. Results show that gaps and overlaps cannot be completely eliminated but local fibre steering is able to increase the effective stiffness.Aerospace Engineerin
LayLa: An open-source offline programming framework for composite deposition
No full textThe versatility of automated composite technologies granted the possibility of manufacturing laminates with a continuous variation of fiber orientation, also known as Variable Stiffness Laminates (VSL). Despite offering enough dexterity to be adapted for composite deposition, industrial manipulators are nontrivial to integrate into other applications than those originally envisioned, especially when complex curvilinear cartesian paths are desired. Further improvements in layup control and performance are necessary to induce an accurate tracking of fiber tow courses. The goals of this thesis were to a) reduce variability of layup control, b) eliminate experimental iterative steps associated with programming tow courses and c) enforce a constant laydown speed that aids consolidation quality. To achieve such objectives, a framework entitled LayLa (Laying Laminates) was developed as an offline programming tool that automatically computes the series of continuous robot motions to perform a tow course at a desired laydown speed. Experiments with LayLa were conducted for Automated Fiber Placement (AFP) using a six degrees-of-freedom KUKA manipulator, without actual deposition. From a VSL design algorithm, two fiber tow courses with a reduced turning radius were selected to be performed at a laydown speed of 0.1m/s. The overall results revealed reasonably accurate trajectory tracking of both joint and operating space variables, with errors at the end-effector position around 0.05mm and at the laydown speed of 3.2mm/s, corroborating the use of LayLa to create external commands for composite deposition.Aerospace Engineerin
Online preventive non-destructive evaluation for automated fibre placement
No full textThe strict quality requirements for aerospace composite structures give rise to costly quality control procedures. In automated fibre placement (AFP) these procedures rely heavily on manual inspection leading to long machine downtime periods and a slower production process overall. A preventive non-destructive evaluation technique of the composite laminate quality based on an online geometric analysis of the fibre using a laser profile sensor has been developed. This sensor has been mounted on a KUKA KR210 R2700 Extra 10-axis robot and software integration was performed using Robot Operating System (ROS). The robot is equipped with interchangeable end-effectors including an automated fibre placement end-effector, developed at TU Delft. The robot mounted laser profile sensor, in combination with robot positional data, was used to create a 3D model of the fibre. This model can be used in two ways. In real-time it can be used to perform an online assessment of the laminate quality including layup geometry, positioning with respect to a reference location, and detection of in-plane buckling defects. Furthermore the full geometric model obtained can be used to validate mathematical or numerical simulations of the fibre placement process and investigate the effects of process variables on the quality of laminate placement and defect creation. In an industrial process this evaluation method can provide full traceability of the part-product quality. The data can both be used during the qualification of a newly designed laminate, but also for quality assurance during series production.Structural Integrity & Composite
The Impact of Robot Accuracy: Identification of contributors to dimensional variation of assembly products
No full textAt this moment, industrial robot arms are increasingly used to automate manufacturing processes in the aerospace industry. However, these robot arms lack position accuracy to effectively mill parts or assemble products. In this work, this gap is investigated following two approaches; on one hand existing calibration methods of robot arms are evaluated. On the other hand, two methods to define the impact of the robot arm inaccuracy on final dimensional variance of assembly products are compared. It is concluded that at least three extensions to current calibration models improve the accuracy of industrial robot arms. Moreover, multiple advantages and drawbacks of two tolerance analysis methods are given.Aerospace Engineerin
Automated Ultrasonic Inspection using Full Matrix Captureon Composite Materials
No full textThis master thesis focuses on developing an integrated system capable of performing ultrasonic phased array measurement on composite parts in an automated fashion. This could potentially be used in the manufacturing process of fiber laminate composite parts to obtain more accu- rate detection of manufacturing defects. Phased array ultrasonics makes use of an array of ultrasonic elements that will be used to send consecutive pulses with each of the elements which are received with the remaining elements in the array. By taking into account the signal strength of the pulses between each of the elements in the array and their respective timings a two-dimensional image of the area underneath the probe can be reconstructed into an image. This image contains information about the acoustic material properties through the depth of the measured object. By automating this method of inspection and taking consecutive measure- ments of this type it becomes possible to obtain volumetric data of the measured object. This research aims to investigate the feasibility and potential constraints of integrating this type of sensor system with a robotic arm. The benefit of combining this with a robot means it may be used in a repeated fashion, as well as to inspect a large number of possible geometric shapes. The final part of this thesis work will cover the processing of the data that is produced using this method.Since a large amount of data is produced, processing and analysis is needed in order to be able to visualise the data and to be able to draw meaningful conclusions from it.Aerospace Engineerin
The story of Wanderwolf: A contested tale on the re-emergence of 'new wilderness' in the Netherlands
No full textIn this chapter, the author studies what the particular wolf has come to signify culturally in the contemporary public imagination and understanding of the Dutch landscape. It suggests that the Wanderwolf 'wandered' into the production of a new landscape ideology, i.e., another genesis of the Dutch landscape, in which it fulfils a different kind, yet equally controversial, iconic role compared to those we know from West-European ethnological and folkloric traditions. The media commotion surrounding the sightings of the Wanderwolf should be seen in the context of a much larger interest and effort to 'rewild' Europe. The visions expressed by the enthusiasts on the apparent return of the wolf reflect strongly those which Cronon has critically analysed in his influential essay on the notion of wilderness. The wolf's adversaries spoke out equally during the Wanderwolf's appearance. As media announced during the Wanderwolf incident, the comeback of the wolf is no longer a fairy tale
Development of innovative automated solutions for the assembly of multifunctional thermoplastic composite fuselage
No full textIn this study, the development of innovative tooling and end-effector systems for the assembly of a multifunctional thermoplastic fuselage is presented. The increasing demand for cleaner and new aircraft requires utilising novel materials and technologies. Advanced thermoplastic composites provide an excellent material option thanks to their weldability, low density, low overall production cost, improved fracture toughness and recyclability. However, to fully appreciate their potentials in weight, cost and production rate, new manufacturing approaches and techniques are needed. Hence, this project develops three end-effector solutions to demonstrate the feasibility of assembling a full-scale multifunctional integrated thermoplastic lower fuselage shell, including the integration of fully equipped floor and cargo structure. The developed assembly solution comprises three individual yet well-integrated tooling systems that allow housing the skin and assembly; picking, placing and welding of the assembly parts, i.e. clips and stringers; and welding of frames and floor beam sub-assemblies. The process of developing these systems from the end-user requirements, technical challenges, tooling and end-effectors design and manufacturing process are detailed in this paper
