Documents disponibles écrits par cet auteur

Handwheel Force Feedback for Lanekeeping Assistance: Combined Dynamics and Stability / Switkes, Joshua P. in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 128 N° 3 (Septembre 2006) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 128 N° 3 (Septembre 2006) . - 532-542 p. Titre : Handwheel Force Feedback for Lanekeeping Assistance: Combined Dynamics and Stability Titre original : Rétroaction de force de volant de commande pour l'aide de Lanekeeping : Dynamique et stabilité combinées Type de document : texte imprimé Auteurs : Switkes, Joshua P., Auteur ; Coe, Ian A. ; Rossetter, Eric J., Auteur ; Gerdes, Christian J., Auteur Article en page(s) : 532-542 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Lanekeeping  Ruelle  Rétroaction  Contrôleur  Conducteur  Véhicule  Stabilité  Atténuation  artificielle  Injection  Gain  stable Résumé : Lanekeeping assistance could save thousands of lives each year by maintaining lane position in the absence of driver steering commands. In order to work smoothly with the driver, handwheel force feedback must be an integral part of such a system. Here we combine force feedback with a lanekeeping controller based on lateral and heading error. In addition to force feedback replicating the feel in a conventional vehicle, the force can be based on the level of lanekeeping assistance being given. This coupling of the force feedback and assistance systems can destabilize the vehicle if not designed properly. Linear modeling verified by experiments shows the effect of varying the gains on both the force feedback and the lanekeeping assistance itself. In this analysis we show that within a range of values that feel reasonable to the driver, changes to the lanekeeping controller or force feedback can have marked effects on the response of the vehicle. It also shows that stability of the system can be ensured by injecting artificial damping or reproducing the on-center characteristics of a conventional vehicle. The analysis allows the force feedback designer to determine a range of stable force feedback gains, from which a set most acceptable to the driver can be chosen. L'aide de Lanekeeping a pu sauver des milliers des vies tous les ans en maintenant la position de ruelle en l'absence des commandes de direction de conducteur. Afin de fonctionner facilement avec le conducteur, la rétroaction de force de volant de commande doit être une partie intégrale d'un tel système. Ici nous combinons la rétroaction de force avec un contrôleur lanekeeping basé sur la partie latérale et dirigeant l'erreur. En plus de la rétroaction de force repliant la sensation dans un véhicule conventionnel, la force peut être basée sur le niveau de l'aide lanekeeping étant donnée. Cet accouplement des systèmes de rétroaction et d'aide de force mettent en boîte déstabilisent le véhicule si non conçu correctement. Modeler linéaire vérifié par des expériences montre l'effet de changer les gains sur la rétroaction de force et l'aide lanekeeping elle-même. Dans cette analyse nous prouvons que dans une marge des valeurs qui se sentent raisonnables au conducteur, les changements au contrôleur lanekeeping ou la rétroaction de force peuvent avoir marqué des effets sur la réponse du véhicule. Il prouve également que la stabilité du système peut être assurée l'atténuation artificielle d'injection ou en reproduisant des caractéristiques de sur-centre d'un véhicule conventionnel. L'analyse permet au concepteur de rétroaction de force de déterminer une gamme des gains stables de rétroaction de force, desquels un ensemble le plus acceptable pour le conducteur peut être choisi. En ligne : switkesj@stanford.edu [article] Handwheel Force Feedback for Lanekeeping Assistance: Combined Dynamics and Stability = Rétroaction de force de volant de commande pour l'aide de Lanekeeping : Dynamique et stabilité combinées [texte imprimé] / Switkes, Joshua P., Auteur ; Coe, Ian A. ; Rossetter, Eric J., Auteur ; Gerdes, Christian J., Auteur . - 532-542 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 128 N° 3 (Septembre 2006) . - 532-542 p. Mots-clés : Lanekeeping  Ruelle  Rétroaction  Contrôleur  Conducteur  Véhicule  Stabilité  Atténuation  artificielle  Injection  Gain  stable Résumé : Lanekeeping assistance could save thousands of lives each year by maintaining lane position in the absence of driver steering commands. In order to work smoothly with the driver, handwheel force feedback must be an integral part of such a system. Here we combine force feedback with a lanekeeping controller based on lateral and heading error. In addition to force feedback replicating the feel in a conventional vehicle, the force can be based on the level of lanekeeping assistance being given. This coupling of the force feedback and assistance systems can destabilize the vehicle if not designed properly. Linear modeling verified by experiments shows the effect of varying the gains on both the force feedback and the lanekeeping assistance itself. In this analysis we show that within a range of values that feel reasonable to the driver, changes to the lanekeeping controller or force feedback can have marked effects on the response of the vehicle. It also shows that stability of the system can be ensured by injecting artificial damping or reproducing the on-center characteristics of a conventional vehicle. The analysis allows the force feedback designer to determine a range of stable force feedback gains, from which a set most acceptable to the driver can be chosen. L'aide de Lanekeeping a pu sauver des milliers des vies tous les ans en maintenant la position de ruelle en l'absence des commandes de direction de conducteur. Afin de fonctionner facilement avec le conducteur, la rétroaction de force de volant de commande doit être une partie intégrale d'un tel système. Ici nous combinons la rétroaction de force avec un contrôleur lanekeeping basé sur la partie latérale et dirigeant l'erreur. En plus de la rétroaction de force repliant la sensation dans un véhicule conventionnel, la force peut être basée sur le niveau de l'aide lanekeeping étant donnée. Cet accouplement des systèmes de rétroaction et d'aide de force mettent en boîte déstabilisent le véhicule si non conçu correctement. Modeler linéaire vérifié par des expériences montre l'effet de changer les gains sur la rétroaction de force et l'aide lanekeeping elle-même. Dans cette analyse nous prouvons que dans une marge des valeurs qui se sentent raisonnables au conducteur, les changements au contrôleur lanekeeping ou la rétroaction de force peuvent avoir marqué des effets sur la réponse du véhicule. Il prouve également que la stabilité du système peut être assurée l'atténuation artificielle d'injection ou en reproduisant des caractéristiques de sur-centre d'un véhicule conventionnel. L'analyse permet au concepteur de rétroaction de force de déterminer une gamme des gains stables de rétroaction de force, desquels un ensemble le plus acceptable pour le conducteur peut être choisi. En ligne : switkesj@stanford.edu

Lyapunov Based Performance Guarantees for the Potential Field Lane-Keeping Assistance System / Rossetter, Eric J. in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 128 N° 3 (Septembre 2006) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 128 N° 3 (Septembre 2006) . - 510-522 p. Titre : Lyapunov Based Performance Guarantees for the Potential Field Lane-Keeping Assistance System Titre original : Lyapunov basé sur des garanties de bonne fin pour la ruelle potentielle de champ gardant le système d'aide Type de document : texte imprimé Auteurs : Rossetter, Eric J., Auteur ; Gerdes, Christian J., Auteur Article en page(s) : 510-522 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Système  ruelle-garant  Conducteur  Champs  potentiel  Enerigie Résumé : Active lane-keeping assistance systems hold the potential to save thousands of lives every year, but require an approach that can simultaneously work cooperatively with the driver and provide a guaranteed level of safety. One approach that meets these dual demands is to passively couple the vehicle to the environment using the paradigm of "artificial" potential fields. This paper develops such a controller and demonstrates that with appropriate choice of a preview or look-ahead distance, the lateral and yaw dynamics effectively decouple, enabling a tight energy-based bound on lateral error. Since this control scheme does not attempt to track a desired trajectory, disturbances encountered during normal driving (such as road curvature) will alter the path of the vehicle. However, the energy theoretic framework can be used to develop a Lyapunov-based bound that handles general time-varying disturbances. This technique provides bounds on the lateral motion of the vehicle that are sufficiently tight to use as a design tool. Experimental results verify that this bound, and the system structure itself, work well in practice, providing guaranteed assistance in a cooperative manner. Les systèmes ruelle-gardants actifs d'aide tiennent le potentiel de sauver des milliers des vies chaque année, mais exigent une approche qui peut simultanément fonctionner coopérativement avec le conducteur et fournissent un niveau garanti de la sûreté. Une approche qui satisfait ces demandes duelles est de coupler passivement le véhicule à l'environnement en utilisant le paradigme des champs potentiels "artificiels". Cet article développe un tel contrôleur et démontre cela avec le choix approprié d'une prévision ou regarde-en avant la distance, la partie latérale et la dynamique de lacet découple efficacement, permettant une limite fortement énergie-basée sur l'erreur latérale. Puisque cet arrangement de commande n'essaye pas de dépister une trajectoire désirée, les perturbations produites pendant la normale conduisant (comme la courbure de route) changeront le chemin du véhicule. Cependant, le cadre théorétique d'énergie peut être employé pour développer une limite Lyapunov-basée qui manipule des perturbations temps-variables générales. Cette technique fournit les limites sur le mouvement latéral du véhicule qui sont suffisamment serrées pour employer comme outil de conception. Les résultats expérimentaux vérifient que cette limite, et la structure de système elle-même, fonctionnent bien dans la pratique, fournissant l'aide garantie d'une façon coopérative. En ligne : ejross@stanfordalumni.org, gerdes@stanford.edu [article] Lyapunov Based Performance Guarantees for the Potential Field Lane-Keeping Assistance System = Lyapunov basé sur des garanties de bonne fin pour la ruelle potentielle de champ gardant le système d'aide [texte imprimé] / Rossetter, Eric J., Auteur ; Gerdes, Christian J., Auteur . - 510-522 p. Génie Mécanique Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 128 N° 3 (Septembre 2006) . - 510-522 p. Mots-clés : Système  ruelle-garant  Conducteur  Champs  potentiel  Enerigie Résumé : Active lane-keeping assistance systems hold the potential to save thousands of lives every year, but require an approach that can simultaneously work cooperatively with the driver and provide a guaranteed level of safety. One approach that meets these dual demands is to passively couple the vehicle to the environment using the paradigm of "artificial" potential fields. This paper develops such a controller and demonstrates that with appropriate choice of a preview or look-ahead distance, the lateral and yaw dynamics effectively decouple, enabling a tight energy-based bound on lateral error. Since this control scheme does not attempt to track a desired trajectory, disturbances encountered during normal driving (such as road curvature) will alter the path of the vehicle. However, the energy theoretic framework can be used to develop a Lyapunov-based bound that handles general time-varying disturbances. This technique provides bounds on the lateral motion of the vehicle that are sufficiently tight to use as a design tool. Experimental results verify that this bound, and the system structure itself, work well in practice, providing guaranteed assistance in a cooperative manner. Les systèmes ruelle-gardants actifs d'aide tiennent le potentiel de sauver des milliers des vies chaque année, mais exigent une approche qui peut simultanément fonctionner coopérativement avec le conducteur et fournissent un niveau garanti de la sûreté. Une approche qui satisfait ces demandes duelles est de coupler passivement le véhicule à l'environnement en utilisant le paradigme des champs potentiels "artificiels". Cet article développe un tel contrôleur et démontre cela avec le choix approprié d'une prévision ou regarde-en avant la distance, la partie latérale et la dynamique de lacet découple efficacement, permettant une limite fortement énergie-basée sur l'erreur latérale. Puisque cet arrangement de commande n'essaye pas de dépister une trajectoire désirée, les perturbations produites pendant la normale conduisant (comme la courbure de route) changeront le chemin du véhicule. Cependant, le cadre théorétique d'énergie peut être employé pour développer une limite Lyapunov-basée qui manipule des perturbations temps-variables générales. Cette technique fournit les limites sur le mouvement latéral du véhicule qui sont suffisamment serrées pour employer comme outil de conception. Les résultats expérimentaux vérifient que cette limite, et la structure de système elle-même, fonctionnent bien dans la pratique, fournissant l'aide garantie d'une façon coopérative. En ligne : ejross@stanfordalumni.org, gerdes@stanford.edu

Physics-based modeling and control of residual-affected HCCI engines / Shaver, Gregory. M. in Transactions of the ASME . Journal of dynamic systems, measurement, and control, Vol. 131 N°2 (Mars/Avril 2009) 

Public ISBD [article]  in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 131 N°2 (Mars/Avril 2009) . - 12 p. Titre : Physics-based modeling and control of residual-affected HCCI engines Type de document : texte imprimé Auteurs : Shaver, Gregory. M., Auteur ; Gerdes, Christian J., Auteur ; Roelle, Matthew, J., Auteur Année de publication : 2009 Article en page(s) : 12 p. Note générale : dynamic systems Langues : Anglais (eng) Mots-clés : physics;  pressure;  combustion;  control  equipment;  engines;  valves;  compression;  cycles;  cylinders;  exhaust  systems;  model  validation;  homogeneous  charge  compression  ignition  engines Résumé : Homogeneous charge compression ignition (HCCI) is a novel combustion strategy for IC engines that exhibits dramatic decreases in fuel consumption and exhaust emissions. Originally conceived in 1979, the HCCI methodology has been revisited several times by industry but has yet to be implemented because the process is difficult to control. To help address these control challenges, the authors here outline the first generalizable, validated, and experimentally implemented physics-based control methodology for residual-affected HCCI engines. Specifically, the paper describes the formulation and validation of a two-input, two-state control-oriented system model of the residual-affected HCCI process occurring in a single engine cylinder. The combustion timing and peak pressure are the model states, while the inducted gas composition and effective compression ratio are the model inputs. The resulting model accurately captures the system dynamics and allows the simultaneous, coordinated control of both in-cylinder pressure and combustion timing. To demonstrate this, an H2 optimal controller is synthesized from a linearized version of the model and used to dictate step changes in both combustion timing and peak pressure within about four to five engine cycles on an experimental test bed. The application of control also results in reductions in the standard deviation for both combustion timing and peak pressure. The approach therefore provides accurate mean tracking, as well as a reduction in cyclic dispersion. Another benefit of the simultaneous coordination of both control inputs is a reduction in the control effort required to elicit the desired response. Instead of using a peak pressure controller that must compensate for the effects of a combustion timing controller, and vice versa, the coordinated approach optimizes the use of both control inputs to regulate both outputs. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://dynamicsystems.asmedigitalcollection.asme.org/issue.aspx?journalid=117&is [...] [article] Physics-based modeling and control of residual-affected HCCI engines [texte imprimé] / Shaver, Gregory. M., Auteur ; Gerdes, Christian J., Auteur ; Roelle, Matthew, J., Auteur . - 2009 . - 12 p. dynamic systems Langues : Anglais (eng) in Transactions of the ASME . Journal of dynamic systems, measurement, and control > Vol. 131 N°2 (Mars/Avril 2009) . - 12 p. Mots-clés : physics;  pressure;  combustion;  control  equipment;  engines;  valves;  compression;  cycles;  cylinders;  exhaust  systems;  model  validation;  homogeneous  charge  compression  ignition  engines Résumé : Homogeneous charge compression ignition (HCCI) is a novel combustion strategy for IC engines that exhibits dramatic decreases in fuel consumption and exhaust emissions. Originally conceived in 1979, the HCCI methodology has been revisited several times by industry but has yet to be implemented because the process is difficult to control. To help address these control challenges, the authors here outline the first generalizable, validated, and experimentally implemented physics-based control methodology for residual-affected HCCI engines. Specifically, the paper describes the formulation and validation of a two-input, two-state control-oriented system model of the residual-affected HCCI process occurring in a single engine cylinder. The combustion timing and peak pressure are the model states, while the inducted gas composition and effective compression ratio are the model inputs. The resulting model accurately captures the system dynamics and allows the simultaneous, coordinated control of both in-cylinder pressure and combustion timing. To demonstrate this, an H2 optimal controller is synthesized from a linearized version of the model and used to dictate step changes in both combustion timing and peak pressure within about four to five engine cycles on an experimental test bed. The application of control also results in reductions in the standard deviation for both combustion timing and peak pressure. The approach therefore provides accurate mean tracking, as well as a reduction in cyclic dispersion. Another benefit of the simultaneous coordination of both control inputs is a reduction in the control effort required to elicit the desired response. Instead of using a peak pressure controller that must compensate for the effects of a combustion timing controller, and vice versa, the coordinated approach optimizes the use of both control inputs to regulate both outputs. DEWEY : 629.8 ISSN : 0022-0434 En ligne : http://dynamicsystems.asmedigitalcollection.asme.org/issue.aspx?journalid=117&is [...]

Release of major elements from recycled concrete aggregates and geochemical modelling / Gerdes, Christian J. in Cement and concrete research, Vol. 39 N° 5 (Mai 2009) 

Public ISBD [article]  in Cement and concrete research > Vol. 39 N° 5 (Mai 2009) . - pp. 446–459 Titre : Release of major elements from recycled concrete aggregates and geochemical modelling Type de document : texte imprimé Auteurs : Gerdes, Christian J., Auteur ; Hans A. van der Sloot, Auteur Année de publication : 2009 Article en page(s) : pp. 446–459 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : pH;  Hydrate  phases;  Leaching;  Equilibrium;  Geochemical  modelling Résumé : The pH dependent leaching characteristics were assessed for different types of recycled concrete aggregates, including real construction debris and crushed fresh concrete samples prepared in laboratory. Carbonation effects were identified from the characteristic pH dependent leaching patterns for the major constituents Al, Ca, Fe, Mg, Si and SO42–. The original particle size ranges were different for the samples investigated and this factor influenced the cement paste content in the samples which in turn controlled the leachable contents. Cement paste contents for concrete samples with fine particle size fractions (0–4 mm) were found to be higher than the originally present amount in the hardened concrete. Geochemical speciation modelling was applied over the entire pH range using the speciation and transport modelling framework ORCHESTRA, for which mineral saturation, solution speciation and sorption processes can be calculated based on equilibrium models and thermodynamic data. The simulated equilibrium concentrations by this model agreed well with the respective measured concentrations. The main differences between the fresh and aged materials were quantified, described and predicted by the ORCHESTRA. Solubility controlling mineral phase assemblages were calculated by the model as function of pH. Cement hydrate phases such as calcium silicate hydrate, calcium aluminate hydrate (AFm and AFt) and hydrogarnet were predominating at the material pH. The concentration of carboaluminates was found to be strongly dependent on the available carbonates in the samples. As the pH was decreased these phases decomposed to more soluble species or precipitates were formed including iron- and aluminium hydroxides, wairakite and amorphous silica. In the most acid region most phases dissolved, and the major elements were approaching maximum leachability, which was determined by the amount of cement paste. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000477 [article] Release of major elements from recycled concrete aggregates and geochemical modelling [texte imprimé] / Gerdes, Christian J., Auteur ; Hans A. van der Sloot, Auteur . - 2009 . - pp. 446–459. Génie Civil Langues : Anglais (eng) in Cement and concrete research > Vol. 39 N° 5 (Mai 2009) . - pp. 446–459 Mots-clés : pH;  Hydrate  phases;  Leaching;  Equilibrium;  Geochemical  modelling Résumé : The pH dependent leaching characteristics were assessed for different types of recycled concrete aggregates, including real construction debris and crushed fresh concrete samples prepared in laboratory. Carbonation effects were identified from the characteristic pH dependent leaching patterns for the major constituents Al, Ca, Fe, Mg, Si and SO42–. The original particle size ranges were different for the samples investigated and this factor influenced the cement paste content in the samples which in turn controlled the leachable contents. Cement paste contents for concrete samples with fine particle size fractions (0–4 mm) were found to be higher than the originally present amount in the hardened concrete. Geochemical speciation modelling was applied over the entire pH range using the speciation and transport modelling framework ORCHESTRA, for which mineral saturation, solution speciation and sorption processes can be calculated based on equilibrium models and thermodynamic data. The simulated equilibrium concentrations by this model agreed well with the respective measured concentrations. The main differences between the fresh and aged materials were quantified, described and predicted by the ORCHESTRA. Solubility controlling mineral phase assemblages were calculated by the model as function of pH. Cement hydrate phases such as calcium silicate hydrate, calcium aluminate hydrate (AFm and AFt) and hydrogarnet were predominating at the material pH. The concentration of carboaluminates was found to be strongly dependent on the available carbonates in the samples. As the pH was decreased these phases decomposed to more soluble species or precipitates were formed including iron- and aluminium hydroxides, wairakite and amorphous silica. In the most acid region most phases dissolved, and the major elements were approaching maximum leachability, which was determined by the amount of cement paste. ISSN : 0008-8846 En ligne : http://www.sciencedirect.com/science/article/pii/S0008884609000477