Publications
95 results found
Wang H, de Boer G, Kow J, et al., 2017, A low-cost soft tactile sensing array using 3D hall sensors, Procedia Engineering, Vol: 168, Pages: 650-653, ISSN: 1877-7058
Tactile sensors are essential for robotic systems to safely interact with the external world and to precisely manipulate objects. Existing tactile sensors are typically either expensive or limited by poor performance, and most are not mechanically compliant. This work presents MagTrix, a soft tactile sensor array based on four 3D Hall sensors with corresponding permanent magnets. MagTrix has the capability to precisely measure triaxis force (1 mN resolution) and to determine contact area. In summary, the presented tactile sensor is robust, low-cost, high-performance and easily customizable to be integrated into a range of robotic and healthcare applications.
de Boer GN, Gao L, Hewson RW, et al., 2016, Heterogeneous multiscale methods for modelling surface topography in EHL line contacts, Tribology International, Vol: 113, Pages: 262-278, ISSN: 1879-2464
A multiscale method for the Elastohydrodynamic Lubrication (EHL) of line contacts is derived based on the Heterogeneous Multiscale Methods.Periodicity applies to the topographical features and lubricant flow, data is homogenised over a range of variables at amicro-scale and coupled into amacro-scalemodel. This is achieved using flow factorsas calculated from metamodels, which themselves evolve with the solution procedure. Results are givenfor an idealised topography and illustrate significant deviationsfrom smooth surface assumptions as quantified by the flow factors. Improvements in the accuracy andefficiency with previous work and large fluctuations due to micro-EHL are also presented.Validation of the multiscale method with a deterministic topography is provided demonstrating good accuracy and efficiency.
Cea Esteban A, 2016, Multiscale Topology Optimization towards 3D PrintedStructures
Wang H, de Boer G, Kow J, et al., 2016, Design methodology for magnetic field-based soft tri-axis tactile sensors, Sensors, Vol: 16, Pages: 1-20, ISSN: 1424-8220
Tactile sensors are essential if robots are to safely interact with the external world and to dexterously manipulate objects. Current tactile sensors have limitations restricting their use, notably being too fragile or having limited performance. Magnetic field-based soft tactile sensors offer a potential improvement, being durable, low cost, accurate and high bandwidth, but they are relatively undeveloped because of the complexities involved in design and calibration. This paper presents a general design methodology for magnetic field-based three-axis soft tactile sensors, enabling researchers to easily develop specific tactile sensors for a variety of applications. All aspects (design, fabrication, calibration and evaluation) of the development of tri-axis soft tactile sensors are presented and discussed. A moving least square approach is used to decouple and convert the magnetic field signal to force output to eliminate non-linearity and cross-talk effects. A case study of a tactile sensor prototype, MagOne, was developed. This achieved a resolution of 1.42 mN in normal force measurement (0.71 mN in shear force), good output repeatability and has a maximum hysteresis error of 3.4%. These results outperform comparable sensors reported previously, highlighting the efficacy of our methodology for sensor design.
Gao L, Hewson RW, 2016, Development of A Wear Model for LubricatedMetal-On-Metal Hip Joints, 5th International Conference on Biomedical Engineering and Biotechnology 2016
de Boer GN, Wang H, Ghajari M, et al., 2016, Force and Topography Reconstruction Using GP and MOR for the TACTIP Soft Sensor System, 17th Annual Conference, TAROS 2016, Publisher: Springer International Publishing, Pages: 65-74, ISSN: 0302-9743
Bach C, Jebari R, Viti A, et al., 2016, Composite stacking sequence optimization for aeroelastically tailored forward-swept wings, Structural and Multidisciplinary Optimization, Vol: 55, Pages: 105-119, ISSN: 1615-1488
A method for stacking sequence optimization and aeroelastic tailoring of forward-swept composite wings is presented. It exploits bend-twist coupling to mitigate aeroelastic divergence. The method is intended for estimating possible weight savings in preliminary aircraft design stages. A structural beam model of the composite wingbox is derived from anisotropic shell theory and the governing aeroelastic equations are presented for a spanwise discretized forward swept wing. Optimization of the system to reduce wing mass is undertaken for sweep angles of -35 degrees to 0 degrees and Mach numbers from 0.7 to 0.9. A subset of lamination parameters (LPs) and the number of laminate plies in each pre-defined direction (restricted to0, +/-45 and 90 degrees}) serve as design variables. A bi-level hybrid optimization approach is employed, making use of a genetic algorithm (GA) and a subsequent gradient-based optimizer. Constraints are implemented to match lift requirements and prevent aeroelastic divergence, excessive deformations, airfoil stalling and structural failure. A permutation GA is then used to match specific composite ply stacking sequences to the optimum design variables with a limited number of manufacturing constraints considered for demonstration purposes. The optimization results in positive bend-twist coupling and a reduced structural mass. Results are compared to an uncoupled reference wing with quasi-isotropic layups and with panel thickness alone the design variables. For a typical geometry and a forward sweep of -25 degrees at Mach 0.7, a wingbox mass reduction of 13% was achieved.
de boer GN, Gao L, Hewson RW, et al., 2016, A multiscale method for optimising surface topography in elastohydrodynamic lubrication (EHL) using metamodels, Structural and Multidisciplinary Optimization, Vol: 54, Pages: 483-497, ISSN: 1615-1488
The frictional performance of a bearing is ofsignificant interest in any mechanical system wherethere are lubricated surfaces under load and in relativemotion. Surface topography plays a major role in determiningthe coefficient of friction for the bearing becausethe size of the fluid film and topography are of a comparableorder. The problem of optimising topography forsuch a system is complicated by the separation in scalesbetween the size of the lubricated domain and that ofthe topography, which is of at least one order of magnitudeor more smaller. This paper introduces amultiscale method for optimising the small scale topographyfor improved frictional performance of the largescale bearing. The approach fully couples theelastohydrodynamic lubrication at both scales betweenpressure generated in the lubricant and deformation ofthe bounding surfaces. Homogenised small scale data isused to inform the large scale model and is representedusing Moving Least Squares metamodels calibrated bycross validation. An optimal topography for a minimumcoefficient of friction for the bearing is identified andcomparisons made of local minima in the response,where very different topographies with similar frictionalperformance are observed. Comparisons of the optimaltopography with the smooth surface model demonstratedthe complexity of capturing the non-linear effect of topographyand the necessity of the multiscale method incapturing this. Deviations from the smooth surface modelwere quantified by the metamodel coefficients andshowed how topographies with a similar frictional performancehave very different characteristics.
Chakladar ND, Gao L, Hewson R, et al., 2016, Evolution of wear and roughness in mixed lubrication regime, The 6th World Tribology Conference
Gao L, Dowson D, Hewson RW, 2016, A numerical study of non-Newtonian transient elastohydrodynamic lubrication of metal-on-metal hip prostheses, Tribology International, Vol: 93, Pages: 486-494, ISSN: 0301-679X
This paper presents a comprehensive numerical study of transient non-Newtonian elastohydrodynamic lubrication of metal-on-metal hip prosthesis subjected to two different gait cycles. The shear-thinning property of the synovial fluid was found to have a significant effect on the lubricating film, in terms of both the magnitude and location of the minimum film thickness, and more generally the film thickness distribution. A range of clearances between the acetabular cup and femoral head was investigated and the shear-thinning effect was more pronounced in the hip replacements with smaller clearances.
Gao L, Dowson D, Hewson RW, 2015, Predictive wear modelling of the articulating metal-on-metal hip replacements, Journal of Biomedical Materials Research - Part B Applied Biomaterials, Vol: 105, Pages: 497-506, ISSN: 1552-4981
The lubrication regime in which artificial hip joints operate adds complexity to the prediction of wear, as the joint operates in both the full fluid film regime, specifically the elastohydrodynamic lubrication (EHL) regime, and the mixed or boundary lubrication regimes, where contact between the bearing surfaces results in wear. In this work a wear model is developed which considers lubrication for the first time via a transient EHL model of metal‐on‐metal hip replacements. This is a framework to investigate how the change in film thickness influences the wear, which is important to further investigation of the complex wear procedure, including tribo‐corrosion, in the lubricated hip implants. The wear model applied here is based on the work of Sharif et al. who adapted the Archard wear law by making the wear rate a function of a relative film thickness nominalized by surface roughness for examining wear of industrial gears. In this work the gait cycle employed in hip simulator tests is computationally investigated and wear is predicted for two sizes of metal-on‐metal total hip replacements. The wear results qualitatively predict the typical wear curve obtained from experimental hip simulator tests, with an initial ‘running‐in period’ before a lower wear rate is reached. The shape of the wear scar has been simulated on both the acetabular cup and femoral head bearing surfaces.
Taherkhani AR, de Boer GN, Gaskell PH, et al., 2015, Aerodynamic drag reduction of emergency response vehicles, Advances in Automobile Engineering, Vol: 4, ISSN: 2167-7670
This paper presents the first experimental and computational investigation into the aerodynamics of emergency response vehicles and focuses on reducing the additional drag that results from the customary practice of adding light-bars onto the vehicles’ roofs. A series of wind tunnel experiments demonstrate the significant increase in drag that results from the light bars and show these can be minimized by reducing the flow separation caused by them. Simple potential improvements in the aerodynamic design of the light bars are investigated by combining Computational Fluid Dynamics (CFD) with Design of Experiments and metamodelling methods. An aerofoil-based roof design concept is shown to reduce the overall aerodynamic drag by up to 20% and an analysis of its effect on overall fuel consumption indicates that it offers a significant opportunity for improving the fuel economy and reducing emissions from emergency response vehicles. These benefits are now being realised by the UK’s ambulance services.
Raske N, Hewson RW, Kapur N, et al., 2015, A predictive model for discrete cell gravure roll coating, 11th European Coating Symposium 2015
Amigo R, Hewson RW, Silva E, 2015, Design of Functionally Graded Adsorption Beds for Gas Storage, 11th World Congress of Structural and Multidisciplinary Optimization
Gao L, de Boer G, Hewson R, 2015, The role of micro cavitation on EHL: A study using a multiscale mass conserving approach, Tribology International, Vol: 90, Pages: 324-331, ISSN: 1879-2464
Amigo RCR, Hewson RW, Silva ECN, 2015, Design of Functionally Graded Adsorption Beds for Gas Storage, 11th World Congress of Structural and Multidisciplinary Optimization
Liu J, Richardson R, Hewson R, et al., 2015, Mechanical Design of Long Reach Super Thin Discrete Manipulator for Inspections in Fragile Historical Environments, 16th Annual Conference on Towards Autonomous Robotic Systems (TAROS), Publisher: SPRINGER-VERLAG BERLIN, Pages: 155-160, ISSN: 0302-9743
de Boer GN, Hewson RW, Thompson HM, et al., 2014, Two-scale EHL: Three-dimensional topography in tilted-pad bearings, TRIBOLOGY INTERNATIONAL, Vol: 79, Pages: 111-125, ISSN: 0301-679X
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- Citations: 17
Berci M, Toropov VV, Hewson RW, et al., 2014, Multidisciplinary multifidelity optimisation of a flexible wing aerofoil with reference to a small UAV, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, Vol: 50, Pages: 683-699, ISSN: 1615-147X
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- Citations: 23
Gao L, Dowson D, Hewson RW, 2014, A numerical study of non-newtonian transient elastohydrodynamic lubrication of metal-on-metal hip prostheses: the effect of lubricant shear-thinning properties, Leeds Lyon Symposium on Tribology
Johns A, Hewson RW, Merson E, et al., 2014, Internal twist drill coolant channel modelling using computational fluid dynamics, 11th World Congress on Computational Mechanics (WCCM XI)
Amigo RCR, Hewson RW, Silva ECN, 2014, On the optimization of adsorption systems, 11th World Congress on Computational Mechanics (WCCM XI)
Gao L, Hewson RW, 2014, A mechanical wear model of metal-on-metal total hip replacements in mixed lubrication conditions., 7th China International Symposium on Tribology (CIST)
Hu R, Hewson R, Morina A, et al., 2013, Influence of material properties and operating conditions on the predicted performance of poroelastic faced bearings, Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, Vol: 228, Pages: 131-139, ISSN: 1350-6501
de Boer GN, Gao L, Hewson RW, et al., 2013, A Two-Scale Method for Incorporating the Effects of ThreeDimensional Surface Topography in an ElastohydrodynamicLine Contact, World Tribology Congress
Gao L, de Boer GN, Hewson RW, 2013, A multiscale framework for lubrication analysis of bearings with textured surface, Advances in Interactions and Multiscale Mechanics, part of the 2013 World Congress in Structural Engineering and Mechanics
Muir M, Muldal C, Kolb E, et al., 2013, The use of MDO and advanced manufacturing to demonstrate rapid, agile construction of a mission optimized UAV, ISSN: 0273-4508
Broad spectrum mission capability for minimal cost is a critical objective for many systems undergoing design and development for use in modern theaters. Through utilization of combinatory and mutually beneficial technologies, a technique has been developed and demonstrated which allows for optimized mission performance characteristics to be achievable and deployable at minimal cost and vastly reduced lead time. Using typical surveillance mission parameters and allowing for variation in deployment zones and atmospheric conditions, multi-method modeling was used to simulate aerodynamic performance characteristics of a NACA6414 based aerofoil. Optimized structural layout was then determined accounting for both structural load cases and the delicate complexities of selected laser sintering and electron beam melting approaches to additive manufacturing. Using the derived structural layout, an iterative aerodynamic optimization using mesh deformation and maximization of elliptical lift distribution was performed, culminating in a design validation analysis and comparison. Export, correction and parameterization of the final design was compiled and delivered to a pre-selected additive manufacturing process ready for automated build. The developed process represents an automated MDO design and manufacturing methodology capable of delivering a uniquely optimized mission capability at a fraction of the time and cost ordinarily required to redevelop already supplied hardware for a bespoke purpose. Furthermore, the process demonstrates how through the combined use of additive manufacturing and structural topology optimization benefits greater than the sum of their parts can be achievable through suitable design parameterization. © 2012 AIAA.
Priest M, Hewson R, 2013, Leeds-Lyon Symposium on Tribology: Great Challenges in Tribology, PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART J-JOURNAL OF ENGINEERING TRIBOLOGY, Vol: 227, Pages: 395-397, ISSN: 1350-6501
Muir M, Muldal C, Kolb E, et al., 2013, The use of MDO and Advanced Manufacturing to Demonstrate Rapid, Agile Construction of a Mission Optimized UAV, 54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
Hewson RW, Kapur N, 2013, Effects of shear thinning on forward roll coating, Chemical Engineering Research and Design, Vol: 91, Pages: 2427-2436, ISSN: 0263-8762
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