Introducing a novel mesh following technique for approximation-free robotic tool path trajectories

Modern tools for designing and manufacturing of large components with complex geometries allow more flexible production with reduced cycle times. This is achieved through a combination of traditional subtractive approaches and new additive manufacturing processes. The problem of generating optimum tool-paths to perform specific actions (e.g. part manufacturing or inspection) on curved surface samples, through numerical control machinery or robotic manipulators, will be increasingly encountered. Part variability often precludes using original design CAD data directly for toolpath generation (especially for composite materials), instead surface mapping software is often used to generate tessellated models. However, such models differ from precise analytical models and are often not suitable to be used in current commercially available path-planning software, since they require formats where the geometrical entities are mathematically represented thus introducing approximation errors which propagate into the generated toolpath. This work adopts a fundamentally different approach to such surface mapping and presents a novel Mesh Following Technique (MFT) for the generation of tool-paths directly from tessellated models. The technique does not introduce any approximation and allows smoother and more accurate surface following tool-paths to be generated. The background mathematics to the new MFT algorithm are introduced and the algorithm is validated by testing through an application example. Comparative metrology experiments were undertaken to assess the tracking performance of the MFT algorithms, compared to tool-paths generated through commercial software. It is shown that the MFT tool-paths produced 40% smaller errors and up to 66% lower dispersion around the mean values

Robotic path planning for non-destructive testing - a custom MATLAB toolbox approach

The requirement to increase inspection speeds for non-destructive testing (NDT) of composite aerospace parts is common to many manufacturers. The prevalence of complex curved surfaces in the industry provides motivation for the use of 6 axis robots in these inspections. The purpose of this paper is to present work undertaken for the development of a KUKA robot manipulator based automated NDT system. A new software solution is presented that enables flexible trajectory planning to be accomplished for the inspection of complex curved surfaces often encountered in engineering production. The techniques and issues associated with conventional manual inspection techniques and automated systems for the inspection of large complex surfaces were reviewed. This approach has directly influenced the development of a MATLAB toolbox targeted to NDT automation, capable of complex path planning, obstacle avoidance, and external synchronization between robots and associated external NDT systems. This paper highlights the advantages of this software over conventional off-line-programming approaches when applied to NDT measurements. An experimental validation of path trajectory generation, on a large and curved composite aerofoil component, is presented. Comparative metrology experiments were undertaken to evaluate the real path accuracy of the toolbox when inspecting a curved 0.5 m2 and a 1.6 m2 surface using a KUKA KR16 L6-2 robot. The results have shown that the deviation of the distance between the commanded TCPs and the feedback positions were within 2.7 mm. The variance of the standoff between the probe and the scanned surfaces was smaller than the variance obtainable via commercial path-planning software. Tool paths were generated directly on the triangular mesh imported from the CAD models of the inspected components without need for an approximating analytical surface. By implementing full external control of the robotic hardware, it has been possible to synchronise the NDT data collection with positions at all points along the path, and our approach allows for the future development of additional functionality that is specific to NDT inspection problems. For the current NDT application, the deviations from CAD design and the requirements for both coarse and fine inspections, dependent on measured NDT data, demand flexibility in path planning beyond what is currently available from existing off-line robot programming software

Robotic path planning for non-destructive testing of complex shaped surfaces

The requirement to increase inspection speeds for non-destructive testing (NDT) of composite aerospace parts is common to many manufacturers. The prevalence of complex curved surfaces in the industry provides significant motivation for the use of 6 axis robots for deployment of NDT probes in these inspections. A new system for robot deployed ultrasonic inspection of composite aerospace components is presented. The key novelty of the approach is through the accommodation of flexible robotic trajectory planning, coordinated with the NDT data acquisition. Using a flexible approach in MATLAB, the authors have developed a high level custom toolbox that utilizes external control of an industrial 6 axis manipulator to achieve complex path planning and provide synchronization of the employed ultrasonic phase array inspection system. The developed software maintains a high level approach to the robot programming, in order to ease the programming complexity for an NDT inspection operator. Crucially the approach provides a pathway for a conditional programming approach and the capability for multiple robot control (a significant limitation in many current off-line programming applications). Ultrasonic and experimental data has been collected for the validation of the inspection technique. The path trajectory generation for a large, curved carbon-fiber-reinforced polymer (CFRP) aerofoil component has been proven and is presented. The path error relative to a raster-scan tool-path, suitable for ultrasonic phased array inspection, has been measured to be within ± 2mm over the 1.6 m2 area of the component surface

Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.

BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden

The development of a fast inspection system for complex aerospace composite structure

The increasing use of composite materials across a range of industries is well documented. In the aerospace industry this has been driven by a desire to build lighter structures, to improve corrosion, impact and fatigue resistance and to reduce the cost of manufacture. Although great strides have been made in these areas, manufacturing costs are still a concern. This is partly due to the cost of raw materials, but also due to the historically labour intensive method of manufacture. The industry requirement to inspect every part can result in the Non-Destructive Testing process becoming a bottleneck resulting in reduced production throughput. The continued development of ever more complex composite geometries will add to the inspection cost burden. IntACom is a development project with the aim of reducing the time taken for inspection of complex geometry composite components by a factor of four. It will do this by addressing three areas: (1) Automation of current manual inspection; (2) Enhancement of existing semi-automated systems through the use of multiple transducers and Ultrasonic phased array technology (PAUT); (3) Software enhancement through the use of techniques such as assisted defect recognition and scan display management. The heart of the system is an inspection cell comprising two 6-axis robotic arms each capable of working independently and cooperatively. The arms deploy end effectors carrying ultrasonic transducers coupled to state of the art Phased Array Ultrasonic Testing (PAUT) or full matrix capture (FMC) acquisition systems. A single operator interface will control all aspects from initial loading of part data, through scanning of the part to data analysis. Currently about three quarters complete, this paper will give an overview of the progress to date and the planned outcomes

Computer-aided tool path generation for robotic non-destructive inspection

Compared to manual Non-Destructive Testing (NDT) for inspection of engineering components, automated robotic deployment of the same NDT techniques offers an increase in accuracy, precision and speed of inspection while reducing production time and associated labour costs. Traditionally, the robot tool path is either taught or programmed manually. Automation of NDT tool path generation, as presented in this paper, offers further significant time reduction, and an increase in the flexibility of inspection planning compared to manual robot teaching and programming. Moreover, such a solution helps to maintain a controlled probe orientation with respect to the scanned surface, and thus which can dramatically reducing lift-off noise. In this work we present the reverse engineering of complex shape test-pieces which have no CAD documentation, and the computer-aided tool scan path generation of such test-pieces as deployed by means of six-axis KUKA robotic arms. Both the use of commercial software and a custom MATLAB toolbox are explored. The tool-paths generated by commercial software are used for robotic scanning of a titanium fan blade by means of Swept Frequency Eddy Current (SFEC) method. Investigations for the future potential for integrating robotic NDT and in-line metrology are also presented

Rapid inspection of composite and additive manufactured components using advanced ultrasonic techniques

To build lighter, more fuel efficient aircraft, industry has rapidly adopted new technologies. Lighter, stronger, corrosion resistant structures are possible using advanced composite materials, while the shortage of metals such as titanium drives the development of additive manufacturing methods. These technologies enable the manufacture of intricate shapes and variation of material properties throughout the part to meet local loading conditions. This presents challenges for Non-Destructive Testing. Intricate geometries can require time consuming manual inspection. Varying properties invariably mean that components are highly anisotropic making ultrasonic testing difficult due to changing acoustic velocities and high levels of structural noise. Combined with the need to inspect every part the process can become a bottleneck to production throughput. This paper describes the development of a robotic inspection system aimed at reducing the time to inspect components with complex geometry. The heart of the system comprises two 6-axis robotic arms capable of working independently and cooperatively. By reading in CAD data the system is able to manipulate transducers around highly complex shapes accurately at high speed. Phased array ultrasonic testing or full matrix capture (FMC) algorithms have been developed that allow wide swathes of data to be acquired in a single pass, while simultaneously coping with surface curvature and features such as radii. Custom software allows the inspection of parts with highly variant thickness by referencing each A-scan to the CAD data where front and rear interfaces cannot be reliably detected. An algorithm combining aspects of FMC and the synthetic aperture focusing technique reduces the effects of coherent noise and acoustic velocities that vary with angle. Analysis and sentencing is made easier by displaying 3D data wrapped around a CAD image. In addition to A and B-scans, a rotatable and zoomable image shows features mapped in 3D and displayed within the part

Advances in Damage Monitoring Techniques for the Detection of Failure in SiCf/SiC Ceramic Matrix Composites

From a disruptive perspective, silicon carbide (SiC)-based ceramic matrix composites (CMCs) provide a considerable temperature and weight advantage over existing material systems and are increasingly finding application in aerospace, power generation and high-end automotive industries. The complex structural architecture and inherent processing artefacts within CMCs combine to induce inhomogeneous deformation and damage prior to ultimate failure. Sophisticated mechanical characterisation is vital in support of a fundamental understanding of deformation in CMCs. On the component scale, “damage tolerant” design and lifing philosophies depend upon laboratory assessments of macro-scale specimens, incorporating typical fibre architectures and matrix under representative stress-strain states. This is important if CMCs are to be utilised to their full potential within industrial applications. Bulk measurements of strain via extensometry or even localised strain gauging would fail to characterise the ensuing inhomogeneity when performing conventional mechanical testing on laboratory scaled coupons. The current research has, therefore, applied digital image correlation (DIC), electrical resistance monitoring and acoustic emission techniques to the room and high-temperature assessment of ceramic matrix composites under axial tensile and fatigue loading, with particular attention afforded to a silicon carbide fibre-reinforced silicon carbide composite (SiCf/SiC) variant. Data from these separate monitoring techniques plus ancillary use of X-ray computed tomography, in-situ scanning electron microscopy and optical inspection were correlated to monitor the onset and progression of damage during mechanical loading. The benefits of employing a concurrent, multi-technique approach to monitoring damage in CMCs are demonstrated