School of Aerospace, Transport and Manufacturing (SATM)

Permanent URI for this community

https://dspace.lib.cranfield.ac.uk/handle/1826/8736

Browse

Now showing 1 - 20 of 114

Open Access
A complete reinforcement learning based framework for reconfigurable manufacturing system scheduling
(Cranfield University, 2022-11) Tang, Jiecheng; Salonitis, Konstantinos; Emmanouilidis, Christos
Since the last decade of the 20th century, a new kind of manufacturing system paradigm known as the reconfigurable manufacturing system (RMS) has been emerging. The purpose of an RMS is to offer a balanced solution that can swiftly respond to volatile global markets with fluctuating product demand. It achieves this by combining the high throughput of conventional dedicated manufacturing lines (DMLs) with the flexibility of flexible manufacturing systems (FMSs). To instigate the market uncertainty, RMS possesses six core characteristics, namely modularity, integrability, convertibility, scalability, diagnosability, and customisation. These core characteristics are becoming more available with the development of Industry 4.0 technologies. Simulation on digital twins is one of the compelling approach that help RMSs check their status in real time. However, the extended data flow challenges the traditional rule-based scheduling policies and urges a flexible approach to replace ill-suited approaches, then further reveals the potential of an RMS. Reinforcement learning (RL) is a promising decision-making approach which had already led to breakthroughs in a lot of research aspects including game playing, robotics, finance, and autonomous driving. With a monolithic parametric reward function, RL agents addressed a wide range of complex tasks by integrating information from real manufacturing processes. Simulating complex and changeable production systems, like RMS, is an area where RL principles may be applied. An end-to-end deep reinforcement learning framework was developed in this research. The resulting policy is trained to generate a sequence of consecutive actions that can be used as an RMS schedule to manage a fluctuating market simulator in real-time.
Open Access
A framework for business cloud services (BCSS) in SMEs
(Cranfield University, 2022-09) Alsafi, Tariq; Fan, Ip-Shing; McLaughlin, Patrick
The Saudi economy is changing rapidly to move from depending on energy to one with a wide range of indigenous businesses. Successful Small and Medium Enterprises (SMEs) are important in this economic transformation. Many Saudi Arabia SMEs are adopting Cloud Based Enterprise IT Services as the option to grow and sustain due to its cost and agility. However, they are often confused by the large international Cloud Services suppliers and not all SME reap the right business value from their Cloud Services investments. This research aims to create an approach to assist Saudi SMEs based on a strong research understanding. A novel framework is created that takes into account of the different functions of different Business Cloud Services, the different business requirements of each SME and their existing capabilities and readiness. Rather than treating all Cloud Services as the same, the researcher differentiates into three types: Digitalisation, Packaged and Enterprise. The research relates the Technological Resources, Organisation Capabilities, Organisational Requirements and Business Benefits for each of the Cloud Service types and then integrate them into one cohesive framework. This research adopted a pragmatic paradigm. The conceptual framework is developed through literature, contextualised, and improved qualitatively through interviews with 17 experts and 54 practitioners. The model was quantitatively examined with 395 questionnaires. The framework was developed into a readiness assessment tool and validated with three Saudi SMEs, who value the approach as beneficial business advice. The framework contributes to the improved structural knowledge of Cloud Services adoption. The constructs add contextualised factors to understand the business considerations relevant to Saudi SMEs.
Open Access
A framework for sustainable construction project based on BIM environment
(Cranfield University, 2023-06) Alnahdi, Sultan Saleh; Al-Ashaab, Ahmed; Salonitis, Konstantinos
The global construction industry's significant resource consumption and environmental impact underscore the urgency of sustainability. This research emphasizes the intersection of sustainability and construction, focusing on ecological, economic, and social considerations. It highlights Building Information Modelling (BIM) as a key enabler of sustainability within the construction value chain. Construction, vital to economic and societal development, necessitates sustainability as a core project objective. Efficient resource utilization, compliance with evolving sustainability standards, and effective collaboration among stakeholders are crucial. However, communication challenges often impede shared understanding and data integration. BIM emerges as a digital solution, unifying project phases, facilitating collaboration, and informed decision-making. In response to the global sustainability mandate, construction projects worldwide are adopting more effective approaches. BIM plays a pivotal role in enhancing efficiency, performance, and productivity. This research addresses a gap by presenting a framework to assess how building materials impact energy consumption within the BIM environment. The research aims to develop a comprehensive framework for promoting sustainability in construction projects through BIM. This involves investigating sustainable practices, assessing BIM's role in sustainability, selecting optimal engineering calculations, and creating an integrated framework. The framework's effectiveness will be evaluated through a hypothetical case study. Key research questions include BIM's alignment with sustainability, expected improvements in addressing sustainability issues, and the value of sharing sustainability calculations within the construction value chain. The thesis comprises seven chapters, including a literature review on sustainability and BIM, a detailed research methodology, a hypothetical case study, analysis of conduction heat transfer calculations, the development of a sustainable construction framework, and discussions, conclusions, and future directions. This research seeks to empower the construction industry with a practical framework for embedding sustainability within the BIM environment, driving efficiency, environmental responsibility, and societal well-being.
Open Access
A novel railway maintenance robot for inspection and repair
(Cranfield University, 2023-03) Rahman, Miftahur; Durazo-Cardenas, Isidro; Starr, Andrew
Robotics and automation are widely used in various sectors for their economic benefits, accuracy, and efficiency. However, the railway industry has been slow to adopt these technologies for track inspection and repair, despite the increasing demands of asset management. Advances in robotics, computing, sensors, and Industry 5.0 are driving companies to explore innovative inspection and repair methods to optimize resource usage. Mobile manipulators, which combine robot mobility with industrial precision, have the potential to replace humans in risky and tedious tasks. In this research, a Robotic Inspection and Repair System (RIRS) has been developed to establish an improved track inspection method and a robotic repair technique. With a 0.27% error rate in calculating defect positions and 1mm precision in actuation, RIRS demonstrates strong feasibility for railway track maintenance. Later, an improved inspection method has been proposed fusing 3D reconstructed model of the target object from the monocular camera with the large-scale Global Positioning System (GPS) data, medium-scale environment perception from Light Detection And Ranging (LiDAR) and small-scale Colour and Depth (RGB-D) model. Texture of surface and less than 5%-dimensional error of the 3D model compared to the physical model ensures the credibility of the improved inspection technique which provides more information of the target object and sets the foundation for a data-rich digital twin in the future. Finally, the framework of both human-in-the-loop repair task and autonomous simulated repair task have been proposed. Successful delivery of the correct tool based on the detected defect upon receiving command from the human operator and automatic circular trajectory generation demonstrate the prospects of RIRS for assisting human in track repair tasks.
Open Access
A study of control mechanisms in micro and nano system-enhanced polymer nanocomposites under mechanical and electrical stimuli: an experimental and computational investigation
(Cranfield University, 2023-11) Mishra, Raghvendra Kumar; Chianella, Iva; Yazdani Nezhad, Hamed; Goel, Saurav
Nanocomposite materials, particularly those reinforced with graphene nanoplatelets (GNPs) and Barium Titanate (BaTiO₃), have been the focus of extensive study within diverse industries aiming to enhance mechanical and electrical properties. This thesis investigates the intricate relationship between external mechanical and electrical stimuli and the effectiveness of these reinforcing agents within nanocomposites, presenting significant findings and novel contributions, while addressing an unexplored aspect within the field. The research highlights a two-part exploration. The first part of the thesis details the creation of GNP/BaTiO₃ polymer nanocomposite fibrils via mechanical stimulation, specifically cold drawing, emphasising the compatibility of recycled polypropylene (PP)/polyethylene terephthalate (PET) blends. The resulting fibrils, exhibiting a significant aspect ratio disparity of 400:1, have demonstrated substantially improved electrical, thermomechanical, and electromagnetic properties. This in-situ mechanical stimulation (cold drawing) not only alters the morphology but also enhances electrical conductivity, limits polymer chain mobility, and reinforces the PP matrix, significantly improving its electrical, thermomechanical, and electromagnetic interference shielding. In the subsequent second part of the thesis, the study explored the integration of graphene-based materials and BaTiO₃ within epoxy composites. Computational modelling and statistical analysis have revealed the influence of these fillers on DC conductivity, dielectric properties, and thermal behaviour. In addition, a comprehensive examination of variations in filler thickness and volume percentage that seemed to significantly impact material’s behaviour has been investigated for the first time under electric fields. Specifically, the investigation into BaTiO₃ nanoparticles and Si-BaTiO3 in epoxy under electric fields has revealed the interplay between electrical stimuli, material properties, and mechanical behaviour, highlighting ferroelectric and piezoelectric effects observed in BaTiO₃ ceramics.i This comprehensive study not only contributes novel findings but also significantly fills a research gap within the field of nanocomposites by presenting an in-depth examination of mechanical and electrical responsiveness, a study that has not been previously undertaken in such a detailed and exhaustive manner. The research conducted, sheds light on the potential for advanced materials in diverse industrial applications and underscores the importance of material selection, offering a pioneering step towards potential industrial utilisation. Additionally, this research offers guidance for further computational exploration, particularly in selecting GNP and BaTiO₃ materials to enhance the electrical and thermal properties of the epoxy matrix
Open Access
A3 thinking approach to enhance a complaints handling process in the airline sector
(Cranfield University, 2019-07) Alshahrani, Bader Mohammed; Al-Ashaab, Ahmed; McLaughlin, Patrick
A prescription for the business success is a matter of concern for company management, researchers and policy makers. There is an ongoing debate regarding the key tools which can increase business efficiency. For example, one stream of research argued that focusing on short-term goals is enough to boost up business performance. On the other hand, another stream argued that companies should focus on long-term performance by emphasising the importance of continuous improvement to assure the delivery of business sustainability. From this point of view, researchers proposed that problem solving is the key for achieving continuous improvement. Problem solving approaches are essential for maintaining the customer service quality as high as possible given the fact that they (problem solving approaches) focus on preventing the reoccurrence of complaints from customers. However, researcher did not reach a consensus regarding the effectiveness of the ‘traditional’ approaches of problem solving (e.g. the 5 whys). As a result, this study develops an A3 Thinking approach for problem-solving in order to enhance the complaints handling process in the airline sector. This approach is validated by using case studies of Saudi Airlines. One of the main advantages of developing such an approach is that it enables the capture of subsequent provision of useful knowledge gained from each complaint, thus enabling the prevention of the reoccurrence of problems, and supporting decision- making. This study provided a valid evidence on the importance of handling customer complaints in different touchpoints during customer journey (pre-flight, on board and post-flight phases). This study found that breaking down customer journey to touchpoints help company management prevent the reoccurrence of customer complaints by increasing the efficiency of responding to customer complaints. The research contributes to the literature by providing a detailed explanation of the journey encountered by airline customers, and it contributes towards enhanced practitioner outcomes by developing a customised A3 Thinking approach for problem-solving in the airline sector based on a learning cycle.
Open Access
Adoption of product service systems in health care.
(2017-10) Mittermeyer, Stephan Alexander; Tomiyama, Tetsuo; Tiwari, Ashutosh
Health care systems are constantly challenged to deliver better quality of care at lower cost. Product Services Systems (PSS) aim to output a higher value to a customer, while reducing resource input required to achieve such value and sustainability. In the health care market this could help companies increase their focus on value for the patient, but also for the health care system as such. This focus on value can ultimately help drive down health care cost, which is one of the most pressing issues in health care systems today. The potential of PSS to address some of the major challenges in the health care market was recognised early in PSS research, however adoption in this field is still below expectation. Motivated by the potential of PSS in health care this work aims to explore the current status of adoption as well as drivers and barriers to future adoption in this market and evaluates if and how PSS can be designed and implemented by companies active in this market. This work showed that PSS can be feasible and useful in this sector as they address relevant current challenges. Future changes in the health care market will likely make PSS even more relevant. Certain concepts of PSS are already applied in the market without leveraging the benefits of a fully developed PSS. Limitations in how the value for patients and other market actors is determined and made transparent is a major challenge in the adoption of PSS. An assessment method is proposed to enable companies to evaluate the value generation of their PSS offerings. In addition, a guideline for PSS design is proposed based on results of this work and field observations. This thesis contributes to a better understanding of PSS adoption in health care by investigating mechanisms in the health care market to understand if PSS can be implemented in a useful manner and how PSS can be adopted in health care in the future. As PSS consists of a number of separate concepts that may be used by themselves and also outside a PSS concept, a detailed analysis was performed to evaluate how PSS concepts are already utilized by industry, as such partial implementations may be a good starting point for full PSS adoption. Adoption of a PSS in any industry requires a measure to evaluate the success of a system implementation or the quality of PSS offerings. Given the complex market network in health care, metrics for evaluations have been identified, linking different dimensions of clinical utility to PSS. Those metrics enable companies to assess PSS systems or scenarios, but also enable development teams to focus their PSS design efforts, as those assessment metrics provide a framework for PSS requirements engineering in this market. Based on the results of the work outlined above, design guidelines were defined to support the development process of PSS in health care.
Open Access
Advanced uncertainty quantification with dynamic prediction techniques under limited data for industrial maintenance applications.
(Cranfield University, 2021-07) Grenyer, Alex; Erkoyuncu, John Ahmet; Zhao, Yifan
Engineering systems are expected to function effectively whilst maintaining reliability in service. These systems consist of various equipment units, many of which are maintained on a corrective or time-based basis. Challenges to plan maintenance accounting for turnaround times, equipment availability and resulting costs manifest varying degrees of uncertainty stemming from multiple quantitative and qualitative (compound) sources throughout the in-service life. Under or over-estimating this uncertainty can lead to increased failure rates or, more often, unnecessary maintenance being carried out. As well as the quality availability of data, uncertainty is driven by the influence of expert experience or assumptions and environmental operating conditions. Accommodating for uncertainty requires the determination of key contributors, their influence on interconnected units and how this might change over time. This research aims to develop a modelling approach to quantify, aggregate and forecast uncertainty given by a combination of historic equipment data and heuristic estimates for in-service engineering systems. Research gaps and challenges are identified through a systematic literature review and supported by a series of surveys and interviews with industrial practitioners. These are addressed by the development of two frameworks: (1) quantify and aggregate compound uncertainty, and (2) predict uncertainty under limited data. The two frameworks are brought together to produce the Multistep Compound Dynamic Uncertainty Quantification (MCDUQ) app, developed in MATLAB. Results demonstrate effective measurement of compound uncertainties and their impact on system reliability, along with robust predictions under limited data with an immersive visualisation of dynamic uncertainty. The embedded frameworks are each validated through implementation in two case studies. The app is verified with industrial experts through a series of interviews and virtual demonstrations.
Open Access
Advancing the synergy between models and experiments to investigate environmentally and mechanically driven crack propagation
(Cranfield University, 2023-09) Elsherkisi, Mustafa; Castelluccio, Gustavo M.; Gray, Simon
Aero-gas turbine running temperatures are rapidly increasing in order to improve their efficiency, and as a consequence components are subjected to more extreme environ- ments. With higher operational temperatures and improved reliability, there is an in- creased chance of both corrosion and mechanical degradation. In addition to operational temperatures, the environment in which an aircraft flies has a significant effect on the material life. Many contaminants are ingested by the engine and deposited on the turbine blades, which often leads to surface degradation. Depending on the ingested contami- nants, temperature, and applied stresses, cracking can be initiated and propagated rapidly. This is particularly evident in the lower-shank regions of single-crystal nickel-based su- peralloy blades, which have recently experienced significant cracking. This study aims to understand the mechanisms behind crack propagation in single- crystal nickel alloys exposed to intermediate temperatures, and when this propagation is either mechanically or chemically driven. This research started by assessing crack inter- action mechanisms that were hypothesised to be both stagnating and accelerating crack growth, depending on specific length scales and crack formations. This was performed by integrating available experimental data to calibrate a phase field model that could predict the extension of cracks for different crack separations and layouts. The modelling results clearly characterised the length scales needed to encourage crack shielding, and which crack formations would see a stress intensification and consequently crack coalescence. These results informed the decision to revisit the experimental setup to optimise which experiments were performed. Using this newly developed methodology, the salt deposi- tion method was amended with the aim of isolating the deposition sites to minimise crack interaction mechanisms. The hypothesis was that significantly longer cracks would be ob- ii served if this could be achieved. This was performed for both the C-ring (at 550°C), and corrosion-fatigue (at 700°C) tests. In the case of CMSX-4, the results were striking, with the C-ring seeing cracks as much as ten times the size of those previously seen. CMSX-10 however, did not show a significant difference, as such, a microstructural characterisation analysis was conducted, whereby the γ/γ′ structure for the two alloys was replicated from microscopy data and further phase field models were run. The results showed that a more regular structure was more resistant to crack propagation owing to the misalignment of γ′ , which caused stress relaxation in the γ channel and at the interface. Finally, this thesis shows how the model, once calibrated for one material and species, can be used to approximate the response expected for another single-crystal nickel alloy or a change in the embrittling species, while accounting for a degree of uncertainty. This is not to say that modelling can or should replace experiments but rather to highlight that preliminary modelling results can be used to build a test matrix that can reduce the number of experiments that are run. It should be noted that this thesis does not focus on the chemical/corrosive aspects in much detail, but rather investigates the importance of stress. This thesis summarises the importance of integrating modelling, microscopy, and experiments to set and answer hypotheses more efficiently.
Open Access
Alignment measurements uncertainties for large assemblies using probabilistic analysis techniques.
(2017-12) Doytchinov, Iordan; Tonnellier, Xavier P.; Almond, Heather
Big science and ambitious industrial projects continually push forward with technical requirements beyond the grasp of conventional engineering techniques. Example of those are ultra-high precision requirements in the field of celestial telescopes, particle accelerators and aerospace industry. Such extreme requirements are limited largely by the capability of the metrology used, namely, it’s uncertainty in relation to the alignment tolerance required. The current work was initiated as part of Maria Curie European research project held at CERN, Geneva aiming to answer those challenges as related to future accelerators requiring alignment of 2 m large assemblies to tolerances in the 10 µm range. The thesis has found several gaps in current knowledge limiting such capability. Among those was the lack of application of state of the art uncertainty propagation methods in alignment measurements metrology. Another major limiting factor found was the lack of uncertainty statements in the thermal errors compensations applied to assembly’s alignment metrology. A novel methodology was developed by which mixture of probabilistic modelling and high precision traceable reference measurements were used to quantify both measurement and thermal models compensation uncertainty accurately. Results have shown that the suggested methodology can accurately predict CMM specific measurement uncertainty as well as thermal drift compensation made by empirical, FEM and FEM metamodels. The CMM task-specific measurement uncertainties made at metrology laboratory were validated to be of maximum 7.96 µm (1σ) for the largest 2 m assemblies. The analysis of the results further showed how using this method a ‘virtual twins’ of the engineering structures can be calibrated with the known uncertainty of thermal drift prediction behaviour in the micrometric range. Namely, the Empirical, FEM and FEM Metamodels uncertainties of predictions were validated to be of maximum: 8.7 µm (1σ), 11.28 µm (1σ) and 12.24 µm (1σ).
Open Access
Application of fibre lasers in fabrications and processing of thin gauge alloys for engineering applications
(Cranfield University, 2022-10) Coroado, Julio Cristiano Rato Rafael; Ganguly, Supriyo; Williams, Stewart W.
Micro-joining of thin metallic sheets has been growing due to the product weight reduction. Several methods are used to join aluminium and iron-based alloys, but most are limited on the workpiece dimensions, processing time and joint strength. Laser welding was selected as the joining tool for this study as a non-contact, productive and highly flexible process in spatial and temporal resolution of energy application for medical, automotive and aerospace applications. The digital control of the latest multi-pulse pulsed-wave (MPPW) fibre lasers allows different spatial and temporal resolutions to apply low pulse energy at a high repetition rate and narrow pulse width with high precision. However, it isn't easy to control each parameter's effect on the weld profile without understanding the underpinning science of the laser-material interaction. This study aims to predict the material response and establish a relationship between the total applied energy over a spot, the pulse energy, average peak power and pulse duration. The fundamental laser-material interaction parameters (FLMIP), which have proven to characterise the process in continuous-wave (CW) laser welding, have also been investigated in MPPW seam welding. The performance of MPPW and CW laser modes was compared under like-to-like conditions to correlate penetration and melting efficiency, productivity, joining flexibility and defects generation in the similar and dissimilar joining of 5251 H22 aluminium alloy and 304L austenitic stainless steel. In addition to this, an empirical model was applied in both laser modes to achieve a specific weld profile independent of the beam diameter. In MPPW mode, the weld pool profile could be correlated to the power density and interaction time considering the inter-pulse thermal losses. CW processing was revealed to have better flexibility to control the weld shape and joint strength, higher melting efficiency and productivity when compared to MPPW processing.
Open Access
Areal artefact manufacturing using SPDT
(2018-08) Zhao, Junguo; Giusca, Claudiu; Goel, Saurav
With the increasing importance of the surface engineering, surface topography measuring instrument has been used in wider range of applications, which requires trustworthy calibration process to deliver traceability so that the instrument is able to give comparable and reliable measurement. The calibration standard / artefact is designed to transfer traceability easily and reliably. In current market, the feature of the artefact used for evaluation the surface topography measuring process are not sufficiently accurate. This insufficiency may be solved by using certain types of calibration standard specified in ISO standard however they are not commercially produced. In this project, one of the desired types called ‘radial sinusoidal shape’ was produce by SPDT (single point diamond turning) manufacturing method. The feature parameters of the artefact are designed to meet the instrument measurement requirement and the machining path is generated with consideration of the tooling geometry. To assess the repeatability in z direction of the turning machine, a step height experiment was designed and conducted. The measurement result indicates that the repeatability of the machine is unsatisfactory when the feed distance smaller than 100 nm. The wavelength and the amplitude of machined radial sinusoidal shape was measured by stylus profiler, followed by the measurement uncertainty analysis. The measurement result was compared with the design to evaluate quality of the manufacturing process. To estimate the systematic error of the profiler, CCI was used to measure the machined radial sinusoidal shape. The measurement result was also compared with the design.
Open Access
Atmospheric pressure plasma etching of Ti-6Al-4Vusing SF₆
(Cranfield University, 2023-06) Bishop, Alex; Huang, Zhaorong; Giusca, Claudiu; Long See, Tian
Atmospheric pressure plasma (APP) etching using SF₆ has been shown to etch Ti- 6Al-4V (Ti64). Operating parameters for input power, SF₆ concentration and standoff distance were determined through previous work as 1.2 kW, 0.8 L min⁻¹ and 6mm respectively as the optimum values for etching using the Helios 1200 machine. By using various surface characterisation techniques, information over a broad range of spatial frequencies was obtained. By conducting stationary, dynamic and areal etching, the process has been shown a high degree of precision and material removal rates varying from 0.5 mm3 min⁻¹ to 2 mm³ min⁻¹ . This process preferentially etches the BCC β phase of Ti64 over the HPC α phase by∼50 %. It is proposed that this preferential etching of the β phase is due to both the crystal structure strength being weaker than the α phase and the BCC crystal structure being less dense than HPC, making it easier to remove more volume of material. The etching process is highly temperature dependent and preheating of the samples is required to achieve a clean trench. Significant amounts of redeposition also remain on the surface <2 µm which comprise of mostly fluorine and oxygen, but this is easily removed. The surface remains optically opaque after etching due to significant roughening of the surface, however negligible contamination remains. The proposed material removal mechanism is through the formation of volatile VFₓ and TiF₄ compounds.
Open Access
Authoring digital contents for augmented reality in maintenance.
(2018-04) Palmarini, Riccardo; Erkoyuncu, John Ahmet; Roy, Rajkumar
Technicians’ performance is a major driver in maintenance and each process can be prone to time and quality variances as well as errors due to factors such as experience, complexity and environment. Augmented Reality (AR) is an emerging technology that has been applied in a wide variety of disciplines and has been demonstrated to have a role with improving efficiency, effectiveness and decision-making within industrial maintenance. AR has not reached its full potential yet and its implementation in Industry is slowed down by three main limitations: hardware restricted capabilities, object recognition robustness and contents-related issues. This PhD project focuses on easing the implementation of AR by overcoming the AR technology selection challenges and the AR contents-related issues. In order to reach the aim, the student has provided three main contributions to knowledge: 1) a process to select AR technology for maintenance (IPSAR), 2) a method for creating AR step-by-step procedures (FARP) and 3) a method for providing remote assistance (ARRA). FARP and ARRA methods have been developed and tested. The first allows recording procedures in an ad-hoc designed “AR-format” and is able to show “step-by-step” procedures. It aims to support deskilling the maintenance process and reducing the error rate by simplifying the delivery of maintenance with efficient and effective guidance. The second overcomes current remote video-call assistance limitations by improving spatial referencing. ARRA module allows to provide AR-assistance by overlaying virtual objects on the real environment of a remote maintainer. The methods proposed by the student could boost the implementation of AR and open the doors for a bright future in which AR supports technicians thus reducing operational costs and training and improving human performances.
Open Access
Autonomous localization and navigation for a railway inspection and repair system
(Cranfield University, 2023-04) Rahimi, Masoumeh; Durazo Cardenas, Isidro S.; Starr, Andrew
Robotic and autonomous systems have brought numerous benefits to various industries, such as increased accuracy, safety, efficiency, cost-effectiveness, and reduced time. The railway industry has also leveraged robotic technologies for track maintenance jobs, albeit their application is often restricted to specific use cases. This research introduces the Robotic Inspection and Repair System (RIRS), which operates both on and around the railway track. A key consideration for autonomous systems is the need for absolute localization, which is essential for maintenance systems on the railway track. Therefore, this thesis focuses on implementing and developing an autonomous localization and navigation system for the RIRS, using the Global Positioning System (GPS). However, due to the railway environment complexity which includes electromagnetic interferences, tunnels, and dense vegetation, GPS inevitably degrades, making vehicle localization extremely challenging. The RIRS localization system is investigated in two separate modes: off-track and on-track. For the off-track phase, to achieve a higher frequency rate and accurate robot pose estimation even in GPS-denied environments, the Extended Kalman Filter (EKF) filter is applied to fuse continuous data with global pose estimates. This approach's effectiveness is also compared with the Real-Time Appearance-based Mapping (RTAB-Map) approach's odometry based on absolute and relative pose error. For the on-track phase, the RIRS aimed to identify track defects at the absolute level initially, but this is infeasible due to GPS unavailability in almost 20% of the railway network. Therefore, first, the RIRS starts navigating autonomously using GPS odometry. Then track-side object detection and 3D pose estimation is implemented to compensate for the error caused by GPS. The average error of 0.07 m in the vehicle's location demonstrates the reliability of this strategy for a maintenance vehicle.
Open Access
Bead shape control using multi-energy source (mes) for wire-based directed energy deposition (ded) process.
(Cranfield University, 2021-11) Chen, Guangyu; Ding, Jialuo; Williams, Stewart W.
Independent control of layer width and height is essential to achieve a simultaneous high build rate with precision net shape and thermal control independent from deposition shape in the wire-based directed energy deposition (w-DED) process. Bead shape control using a multi-energy source (MES) method was studied to achieve independent control of layer width height of a bead for the w-DED process. This study was carried out in three stages: First, a plasma transfer arc (PTA) energy density measurement was conducted. A split anode calorimeter (SAC) was applied for the measurement of PTA energy density. A laser beam with a well-defined energy profile was used to calibrate the calorimeter without the complications of arc instability. An optimised centred grounded SAC device was introduced to reduce arc distortion. More symmetric arc profiles were obtained. The dynamic thermal characterisation of a scanning laser (SL) was then studied using both experimental and numerical approaches. SL experiments were conducted with different oscillation frequencies and laser beam sizes. An innovative solution dependent convection boundary (SDCB) method was introduced to reduce the element amount of the finite element (FE) model. Results show that the quasi-steady state SL can be applied as an equivalent stationary energy source. Finally, an SL-PTA MES system was introduced to study the MES bead shape control, a PTA was employed in the front to create an initial melt pool and melt the feedstock wire, and an SL was used behind the PTA to reshape the melt pool and precisely control the bead width. A bead shape control strategy was proposed by using the wire feeding rate to control the layer height and the scanning width to control the layer width. The experiment results verified that the SL-PTA MES has independent control of layer width and height.
Open Access
Biomimetic polymer reactor: design and modulation of novel tandem catalysts.
(Cranfield University, 2021-09) Wei, Wenjing; Chianella, Iva; Thakur, Vijay Kumar; Koziol, Krzysztof K. K.
Tandem catalysis can perform multi-step catalytic reactions in one-pot sequentially, which not only improves the efficiency of reactions significantly, but also decreases time, energy and the amounts of reagents needed. However, as there is always more than one active site (catalyst) in tandem reactors, it is critical to separate different sites and ensure each step is conducted individually. Moreover, it is often challenging to control the whole reaction processes due to the complexity of the systems. In this research, several bio-inspired catalytic reactors were proposed and developed to address the two challenges of site separation and smart control of tandem catalysis. First of all, the goal of sites separation has been achieved in this work through an enzyme-inspired molecularly imprinted polymer reactor MIP-Au-NP-BNPC and a core-shell structure catalytic nanoreactor AMPS@AM-Ag. Two molecularly imprinted cavities were created in MIP-Au-NP-BNPC. The different channels of the two catalytic sites in the reactor enabled different catalytic reactions to occur in different regions, resulting in the process of tandem reactions. As a result of the radial distribution of catalytic sites and mass transfer, the core-shell structure of AMPS@AM-Ag enabled the nanoreactor to perform different catalytic processes sequentially. Hence, the nanoreactor demonstrated the ability to conduct tandem catalysis with successful site separation. Then a biomimetic switch was introduced into the reactor to achieve the smart control of the catalytic process. Firstly, a new type of catalytic reactor consisting of a three-layer mussel-inspired polymer, MIP-AgPRS, was developed. The smart switchable layer composed of mussel-inspired self-healing copolymer was prepared between two MIP layers. This middle smart layer was able to react to different temperatures, permitting either simple or tandem reactions by closing and opening the access of the intermediate products. Secondly, a bilayer polymer reactor, DPR, composed of two different temperature-sensitive polymer layers was prepared. The two functional layers were not only able to respond to different specific temperatures, but each also contained different catalytic sites. Because of the two different phase transition processes of the two layers, the polymer reactor demonstrated to be able to perform simple/tandem catalysis in different temperature regions. As a result, this new type of bilayer polymer reactor was capable of achieving smart control of the tandem reactions. Finally, a three-layer switchable polymer reactor, PRS, with two MIP layers and a PNIPAM-PAM switchable layer in the middle was prepared. In an aqueous environment, when the temperature was low (lower than 47 °C), it exhibited an open access (hydrophilic condition), while when the temperature was high (higher than 47 °C), it became closed (hydrophobic condition). Furthermore, a comonomer (AM) was introduced in the middle layer with different ratios to adjust the responsive temperature range, enabling a more comprehensive range of practical uses. Therefore, a fast responsive and stable polymer reactor with self- controlled catalytic property was obtained. By preparing different types of new catalytic reactors, the research carried out here has shown the ability to achieve a smart control of the tandem catalysis while separating the catalytic sites effectively. Therefore, this study has highlighted new solutions to address the challenges present in tandem catalysis and has provided novel inspiration on how to exploit functional polymers while performing complicated catalytic reactions.
Open Access
Broad band anti-reflection 2-16μm coatings on diamond and ZnSe.
(2018-08) Hakim Khalili, Mohammad; Endrino Armenteros, Jose
In this project, Thin Metal Films an optical coating company is requiring the upgrade of a desktop research type radio frequency magnetron sputtering machine which was custom made for a European funded project and was gifted to it after the project completion. As the machine had no usage history, it had to be investigated and its capabilities and characteristics identified. The first part of the project, focused on restoring the machine using a systematic approach by utilising a technique called Plan Do Check Act, where a continuous feedback loop is used to identify problems and finding solution to them. Within the restoration process the aim was to improve the coating uniformity and machine’s repeatability. The restoration of the machine consumed almost the entire project duration leaving a little time for second part of the project. The second part was to use the restored machine, to develop single and multilayer Broad Band Anti-Reflective Coatings for Zinc Selenide and diamond optics. The optics are to be used in Attenuated Total Reflectance accessory units for Infrared spectroscopy. Based on the literature review and multiple decision criteria, yttria and ytterbia were showing promising results in adhering very well to a diamond surface and improving its transmission. Therefore, using Macleod software, a single layer quarter wavelength coating was designed and theoretically examined. It was found that a quarter wavelength ytteria at 5000 nm and a quarter wavelength ytterbia at 3370 nm can increase the transmission on both ZnSe and diamond optics to maximum of 98% and 95% accordingly. The coatings have not actually been deposited on the optics due to both targets breaking before conducting the actual experiments.
Open Access
Caught in the act: The structural pathway of liquid metals to vitrification monitored in situ by synchrotron X-ray diffraction.
(Cranfield University, 2021-09) Stiehler, Martin E.; Georgarakis, Konstantinos; Jolly, Mark R.
When a metallic melt is undercooled fast enough below its liquidus temperature, crystallisation can be avoided and a metallic glass, i.e. a metallic solid with amorphous structure, be formed. This kind of solidification is called vitrification. The prerequisites for this phenomenon are still not clear. An extensive review of the available relevant literature was carried out. To reveal the structural changes taking place at the atomic scale during undercooling and vitrification, data obtained by ultrafast synchrotron X-ray diffraction during aerodynamic-levitation experiments of different metallic-glass forming liquids was analysed. The complete pathway from temperatures well above the liquidus temperature during undercooling and vitrification down to temperatures well below the glass-transition temperature Tg was studied. During undercooling, a non-linear evolution of structural metrics in real as well as in reciprocal space takes place. Especially the height of the first maximum in the structure factor can be described by a structural analogue to the Curie-Weiss law. This behaviour was also found in published data re-analysed here. Indications of universal behaviour among the investigated alloys below a certain temperature as well as for a liquid-liquid crossover in Ti₄₀Cu₃₄Pd₁₄Zr₁₀Sn₂ were found. Small differences in the temperature dependence of the structural behaviour among the different alloys are possibly related to their different glass-forming abilities. To facilitate the analysis of the real-space structure the novel concept of the anti-shell was introduced. Temperature affects different length scales differently. Below Tg the structural behaviour is dominated by the Debye-Waller factor as well as by normal thermal-expansion behaviour. Above Tg an apparent negative thermal expansion of the first nearest-neighbour distance can be attributed to the influence of the structure-forming processes. In addition to short- and medium-range order, a third structural range for distances beyond the third nearest-neighbour is proposed. A disordering of the atomic structure of metallic glasses by the introduction of further alloying elements, facilitated by emergent effects among the components, could be demonstrated. The importance of the influence of global electronic interactions on structure formation was shown as well as their limitation to distances beyond the third nearest-neighbour.
Open Access
A concentrated solar still for community scale desalination.
(2018-08) Bahrami, Mohammadali (Parsa); Sansom, Christopher L.; Tonnellier, Xavier P.
Water and energy are two main basic elements that human lives are dependent on to improve our life standards. Unreliability and a lack of safe drinking water source constitute a major difficulty in developing countries. Among many water purification technologies, solar desalination/distillation has become one of the best solutions as the most attractive and sustainable method to supply drinkable water in remote areas at reasonable cost for future generations. Seawater desalination technologies needed substantial amount of energy in order to convert brackish water into drinkable water. Thus, an extensive research on many desalination technologies has taken place in the last few decades, and solar desalination technology has become one of the most favourable sustainable methods to provide fresh water of sufficiently high quality for human communities. However, this method is not commercialized yet due to its low productivity, but improving this t has become a great source of interest for many researchers. A solar still consumes direct solar energy to produce distilled water through evaporation and condensation process of brackish water. Much research has been conducted in order to increase the productivity, but the outcomes mostly require complex components and a notable increase in cost. Consequently, developing a productive, compact, easy to operate and reasonable cost solar distillation unit was the main challenge in this body of work. A comprehensive literature review is presented in order to illustrate different modifications and their properties on the productivity of solar stills. Even though there are considerations, which cannot be controlled by human intervention (such as meteorological parameters), design and operational factors could make a direct influence on the productivity of the solar still. A novel transportable single basin, double slope shape solar still, enhanced with an internal ventilation fan connected to a copper material heat exchanger, was designed and built without forsaking its basic remit order to increase both evaporation and condensation process. The unit was also designed to use two linear focused Fresnel lenses as a solar radiation concentrator to direct radiation onto the top of solar still basin area. A detailed comparison of theoretical and laboratory experimental results were obtained for the present solar still to find the influence of different modification factors to the present solar still productivity. The temperatures of different parts of the solar still unit such as basin water, top cover glasses, heat exchanger condenser etc. were measured to evaluate different modifications including different fan airflow ratios, with and without a fan shroud, and lava stone effects to the distillate water output. The results presented an increase in productivity of 25.73% in comparison with a conventional solar still, by using a ventilation exhaust fan at its maximum airflow. Also an increase of 16.3% was also achieved by using lava stone as a heat storage material in the basin area.