The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform

Martijn Wisse - One of the best experts on this subject based on the ideXlab platform.

  • IROS - The effect of swing leg retraction on running energy efficiency
    2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011
    Co-Authors: Matt Haberland, J.g. Daniël Karssen, Martijn Wisse
    Abstract:

    Swing leg retraction reduces touchdown energy losses of running by decreasing foot Speed at the moment of ground contact, but does the additional acceleration of the swing leg cost more energy than is saved? To determine whether swing leg retraction can increase the overall energy efficiency of running robots, we find the optimally efficient gaits of a McGeer-like runner over a range of retraction rates. Results show that overall energy usage, including that used to swing the legs, scales with energy loss at touchdown, which is minimized at the retraction rate that zeros foot Tangential Speed at ground contact. Other benefits of swing leg retraction, such as reduced foot slippage and damaging touchdown forces, are realized simultaneously with optimal energy efficiency.

  • The effect of swing leg retraction on running energy efficiency
    2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011
    Co-Authors: Matt Haberland, J.g. Daniël Karssen, Martijn Wisse
    Abstract:

    Swing leg retraction reduces touchdown energy losses of running by decreasing foot Speed at the moment of ground contact, but does the additional acceleration of the swing leg cost more energy than is saved? To determine whether swing leg retraction can increase the overall energy efficiency of running robots, we find the optimally efficient gaits of a McGeer-like runner over a range of retraction rates. Results show that overall energy usage, including that used to swing the legs, scales with energy loss at touchdown, which is minimized at the retraction rate that zeros foot Tangential Speed at ground contact. Other benefits of swing leg retraction, such as reduced foot slippage and damaging touchdown forces, are realized simultaneously with optimal energy efficiency.

Matt Haberland - One of the best experts on this subject based on the ideXlab platform.

  • IROS - The effect of swing leg retraction on running energy efficiency
    2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011
    Co-Authors: Matt Haberland, J.g. Daniël Karssen, Martijn Wisse
    Abstract:

    Swing leg retraction reduces touchdown energy losses of running by decreasing foot Speed at the moment of ground contact, but does the additional acceleration of the swing leg cost more energy than is saved? To determine whether swing leg retraction can increase the overall energy efficiency of running robots, we find the optimally efficient gaits of a McGeer-like runner over a range of retraction rates. Results show that overall energy usage, including that used to swing the legs, scales with energy loss at touchdown, which is minimized at the retraction rate that zeros foot Tangential Speed at ground contact. Other benefits of swing leg retraction, such as reduced foot slippage and damaging touchdown forces, are realized simultaneously with optimal energy efficiency.

  • The effect of swing leg retraction on running energy efficiency
    2011 IEEE RSJ International Conference on Intelligent Robots and Systems, 2011
    Co-Authors: Matt Haberland, J.g. Daniël Karssen, Martijn Wisse
    Abstract:

    Swing leg retraction reduces touchdown energy losses of running by decreasing foot Speed at the moment of ground contact, but does the additional acceleration of the swing leg cost more energy than is saved? To determine whether swing leg retraction can increase the overall energy efficiency of running robots, we find the optimally efficient gaits of a McGeer-like runner over a range of retraction rates. Results show that overall energy usage, including that used to swing the legs, scales with energy loss at touchdown, which is minimized at the retraction rate that zeros foot Tangential Speed at ground contact. Other benefits of swing leg retraction, such as reduced foot slippage and damaging touchdown forces, are realized simultaneously with optimal energy efficiency.

Katherine J. Kuchenbecker - One of the best experts on this subject based on the ideXlab platform.

  • Should haptic texture vibrations respond to user force and Speed?
    2015 IEEE World Haptics Conference (WHC), 2015
    Co-Authors: Heather Culbertson, Katherine J. Kuchenbecker
    Abstract:

    Dragging a tool across a textured surface produces vibrations that convey important perceptual information about the interaction and the underlying qualities of the surface. These vibrations depend on the motions of the tool and respond to both normal force and Tangential Speed. This paper explores various methods of simulating haptic texture interactions by rendering tool vibrations that are based on recorded data. We designed and ran a human-subject study (N=15) to analyze the importance of creating virtual texture vibrations that respond to user force and Speed. Our analysis of data from fifteen textures showed that removing Speed responsiveness did cause a statistically significant decrease in perceived realism, but removing force responsiveness did not. This result indicates that virtual textures aiming to simulate real surfaces should vary the rendered vibrations with user Speed but may not need to vary them with user force.

  • World Haptics - Should haptic texture vibrations respond to user force and Speed
    2015 IEEE World Haptics Conference (WHC), 2015
    Co-Authors: Heather Culbertson, Katherine J. Kuchenbecker
    Abstract:

    Dragging a tool across a textured surface produces vibrations that convey important perceptual information about the interaction and the underlying qualities of the surface. These vibrations depend on the motions of the tool and respond to both normal force and Tangential Speed. This paper explores various methods of simulating haptic texture interactions by rendering tool vibrations that are based on recorded data. We designed and ran a human-subject study (N=15) to analyze the importance of creating virtual texture vibrations that respond to user force and Speed. Our analysis of data from fifteen textures showed that removing Speed responsiveness did cause a statistically significant decrease in perceived realism, but removing force responsiveness did not. This result indicates that virtual textures aiming to simulate real surfaces should vary the rendered vibrations with user Speed but may not need to vary them with user force.

  • One hundred data-driven haptic texture models and open-source methods for rendering on 3D objects
    2014 IEEE Haptics Symposium (HAPTICS), 2014
    Co-Authors: Heather Culbertson, Juan José López Delgado, Katherine J. Kuchenbecker
    Abstract:

    This paper introduces the Penn Haptic Texture Toolkit (HaTT), a publicly available repository of haptic texture models for use by the research community. HaTT includes 100 haptic texture and friction models, the recorded data from which the models were made, images of the textures, and the code and methods necessary to render these textures using an impedance-type haptic interface such as a SensAble Phantom Omni. This paper reviews our previously developed methods for modeling haptic virtual textures, describes our technique for modeling Coulomb friction between a tooltip and a surface, discusses the adaptation of our rendering methods for display using an impedance-type haptic device, and provides an overview of the information included in the toolkit. Each texture and friction model was based on a ten-second recording of the force, Speed, and high-frequency acceleration experienced by a handheld tool moved by an experimenter against the surface in a natural manner. We modeled each texture's recorded acceleration signal as a piecewise autoregressive (AR) process and stored the individual AR models in a Delaunay triangulation as a function of the force and Speed used when recording the data. To increase the adaptability and utility of HaTT, we developed a method for resampling the texture models so they can be rendered at a sampling rate other than the 10 kHz used when recording data. Measurements of the user's instantaneous normal force and Tangential Speed are used to synthesize texture vibrations in real time. These vibrations are transformed into a texture force vector that is added to the friction and normal force vectors for display to the user.

Grazyna Stachowiak - One of the best experts on this subject based on the ideXlab platform.

  • tribo electrochemical behaviour of 316l stainless steel the effects of contact configuration Tangential Speed and wear mechanism
    Corrosion Science, 2015
    Co-Authors: Mobin Salasi, Grazyna Stachowiak
    Abstract:

    Abstract Tribo-electrochemical behaviour of 316L stainless steel was studied using three contact configurations: two-body ceramic counterface (2B-CC), three-body rubber counterface (3B-RC) and three-body ceramic counterface (3B-CC). Electrochemical methods were employed to investigate the effects of Tangential Speed and wear mechanism on the tribo-electrochemical characteristics of the 316L samples at each contact configuration. In both 2B-CC and 3B-RC contacts increasing the Tangential Speed resulted in higher current measured while in the 3B-CC contact the current was an increasing function of time even at a constant rotational Speed. After the abrasion-corrosion tests different repassivation kinetics was found for each contact configuration.

A. Ramalho - One of the best experts on this subject based on the ideXlab platform.

  • Wear modelling in rail–wheel contact
    Wear, 2015
    Co-Authors: A. Ramalho
    Abstract:

    Abstract In rail–wheel transports the maintenance interval for both wheels and rails has become a major issue in reducing costs and increasing safety and has encouraged the development of new numeric procedures for predicting the evolution of wear in order to establish a convenient maintenance schedule. These new tools require the synergy of dynamic analysis and the development of accurate and easy to use wear models. Rail/wheel wear depends on the material properties resulting from contact fatigue and sliding wear. Therefore, all the contact conditions affecting the contact stress distribution will determine the wear behaviour and the contact profiles of wheel and rails. The current research paper investigates the effect of contact conditions on friction and wear behaviour of EN 260 rail steel and R7 wheel steel. Laboratory simulation used twin-disc rolling-sliding tests to study the effect of the creep ratio, contact pressure and Tangential Speed on the resulting traction coefficient and amount of wear. The volume loss was estimated by weighing both specimens before and after the tests. Wear volumes were used to develop a wear equation based on Archard׳s model and considering weighting factors to estimate the influence of creep ratio, contact pressure and Tangential Speed on the specific wear rate. The predicted results were compared with the results of tests performed in the laboratory. Quite small differences between previsions and laboratory tests confirm the reliability of the forecast method. Wear mechanisms were discussed and compared to real rail–wheels sets analysing the fatigue cracks and the strain hardening effects beneath the contact surfaces.

  • Wear modelling in rail-wheel contact
    Wear, 2015
    Co-Authors: A. Ramalho
    Abstract:

    In rail-wheel transports the maintenance interval for both wheels and rails has become a major issue in reducing costs and increasing safety and has encouraged the development of new numeric procedures for predicting the evolution of wear in order to establish a convenient maintenance schedule. These new tools require the synergy of dynamic analysis and the development of accurate and easy to use wear models. Rail/wheel wear depends on the material properties resulting from contact fatigue and sliding wear. Therefore, all the contact conditions affecting the contact stress distribution will determine the wear behaviour and the contact profiles of wheel and rails. The current research paper investigates the effect of contact conditions on friction and wear behaviour of EN 260 rail steel and R7 wheel steel. Laboratory simulation used twin-disc rolling-sliding tests to study the effect of the creep ratio, contact pressure and Tangential Speed on the resulting traction coefficient and amount of wear. The volume loss was estimated by weighing both specimens before and after the tests. Wear volumes were used to develop a wear equation based on Archard's model and considering weighting factors to estimate the influence of creep ratio, contact pressure and Tangential Speed on the specific wear rate. The predicted results were compared with the results of tests performed in the laboratory. Quite small differences between previsions and laboratory tests confirm the reliability of the forecast method. Wear mechanisms were discussed and compared to real rail-wheels sets analysing the fatigue cracks and the strain hardening effects beneath the contact surfaces.

  • Development of Wear Models for Rolling-Sliding Rail-Wheel Contacts
    Proceedings of the Second International Conference on Railway Technology: Research Development and Maintenance, 2014
    Co-Authors: A. Ramalho, P.v. Antunes
    Abstract:

    ? Civil-Comp Press, 2014.Improving the total life cycle costs and safety of trains are current research topics that hold great interest for those who build, maintain and operate trains. The maintenance interval for both wheels and rails has become a major issue for cost reduction while increasing safety. This has encouraged the development of new tools for predicting the evolution of wear and to establish a convenient maintenance schedule. These new tools require the synergy of dynamic analysis and the development of suitable wear models. Rail/wheel wear depends on material properties. Difference in material properties result in competition between contact fatigue and sliding wear mechanisms. Therefore, all the contact conditions affecting the contact stress distribution will govern the wear behaviour. This research paper investigates the effect of contact conditions on the friction and wear behaviour of EN 260 rail steel and R7 wheel steel. A roller-on-roller model was selected to simulate the contact between the wheel (lower specimen) and the rail treads (upper specimen) and, to ensure the compatibility of the results with the real working application. Laboratory simulation used two-disc rolling-sliding tests to study the effect of the creep ratio, contact pressure and the Tangential Speed on the resulting traction coefficient and the amount of wear. The volume loss was estimated by weighing both specimens before and after the tests. Profilometry, integrating the area of the track wear, was performed to assess the wear on the wheel specimens and to compare and validate the results. Wear volumes were used to develop a wear equation based on Archard's model and considering weighting factors to estimate the influence of creep ratio, contact pressure and Tangential Speed on the specific wear rate. The predicted results were compared with the results of tests performed in the laboratory. Quite small differences between the predictions and the laboratory tests confirm the reliability of the forecasting method.