Un algorithme dédié aux Véhicules Légers Tout-Terrain (VLTT) permettant l'estimation et l'anticip... more Un algorithme dédié aux Véhicules Légers Tout-Terrain (VLTT) permettant l'estimation et l'anticipation du renversement est présenté dans ce papier. Il repose sur une estimation temps-réel du Transfert de Charge Latéral (TCL), représentatif des instabilités dynamiques latérales. Le TCL est calculé grâceà un modèle dynamique scindé en deux projections 2D. A partir de ce modèle et d'un système de perception bas-coût, un observateur est proposé. Il permet d'estimer en temps-réel les propriétés du terrain (adhérence et pente), et ainsi d'évaluer avec précision le risque d'instabilité latéraleà l'instant courant. Enfin, un algorithme de prédiction, qui est basé sur l'extrapolation des commandes du conducteur, permet l'anticipation. Ainsi, il est possible de prévenir le pilote d'un risque de renversement, mais aussi d'envisager la création d'un système de sécurité actif.
Proceedings Ieee International Conference on Robotics and Automation, May 3, 2010
Automation in outdoor applications (farming, surveillance, etc.) requires highly accurate control... more Automation in outdoor applications (farming, surveillance, etc.) requires highly accurate control of mobile robots, at high speed, accounting for natural ground specificities (mainly sliding effects). In previous work, predictive control algorithms dedicated to All-Terrain Vehicle lateral stability was investigated. Satisfactory advanced simulation results have been reported but no experimental ones were presented. In this paper, the prevention of a real off-road mobile robot rollover is addressed. First, both rollover dynamic modeling and previous work on a Mixed observer designed to estimate on-line sliding phenomena for path tracking control are recalled. Then, this observer is here used to compute a rollover indicator accounting for sliding phenomena, from a low-cost perception system. Next, the maximum vehicle velocity, compatible with a safe motion over some horizon of prediction, is computed via Predictive Functional Control (PFC), and can then be applied, if needed, to the vehicle actuator to prevent from rollover. The capabilities of the proposed device are demonstrated and discussed thanks to real experimentation.
When designing an accurate automated guidance system for vehicles, a major problem is sliding and... more When designing an accurate automated guidance system for vehicles, a major problem is sliding and pseudosliding effects. This is especially the case in agricultural applications, where five-centimetre accuracy with respect to the desired trajectory is required, although the vehicles are moving on slippery ground.
2007 Ieee Rsj International Conference on Intelligent Robots and Systems, 2007
Most of active devices focused on vehicle stability concerns on-road cars and cannot be applied s... more Most of active devices focused on vehicle stability concerns on-road cars and cannot be applied satisfactorily in an off-road context, since the variability and the non-linearities of the tire/ground contact are often neglected. In previous work, a rollover indicator devoted to light ATVs, accounting for these phenomena has been proposed. It is based on the prediction of the lateral load transfer. Such an indicator requires the online knowledge of the tire cornering stiffness, initially selected from a ground classes network. In this paper, an adapted backstepping observer, making only use of yaw rate measurement, is designed to improve specifically tire cornering stiffness estimation. Capabilities of such an observer are demonstrated and discussed through both advanced simulations and actual experiments.
ABSTRACT Abstrat This paper presents a control algorithm, based on a kinematic model extended wit... more ABSTRACT Abstrat This paper presents a control algorithm, based on a kinematic model extended with additional sliding parameters, in order to accurately guide, forward or backward, the position of a passive towed implement with respect to a planned trajectory. Several experimental results, carried out with an off-road mobile robot and a passive trailer, demonstrate the capabilities of the proposed algorithm.
Proceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453), 2003
A very accurate vehicle guidance is required in numerous agricultural applications, as seeding, s... more A very accurate vehicle guidance is required in numerous agricultural applications, as seeding, spraying, row cropping, . . . Accuracy in vehicle localization can be obtained in realtime from a RTK GPS sensor. Several control laws, relying on this sensor, have been previously designed and provide satisfactory results as long as vehicles do not slide. However, sliding has to occur in agricultural tasks (sloping fields, curves on a wet land, . . .). The challenge addressed in this paper is to preserve vehicle guidance accuracy in such situations. A nonlinear adaptive control law is here designed. Simulation results and field experiments, demonstrating the capabilities of that control scheme, are reported and discussed.
2004 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) (IEEE Cat. No.04CH37566), 2004
When designing an accurate automated guidance vehicle system, a major problem is sliding and pseu... more When designing an accurate automated guidance vehicle system, a major problem is sliding and pseudosliding effects. It is especially the case in agricultural applications, where a five centimeters accuracy with respect to the desired trajectory is required, even if vehicles move on a slippery ground. Previous works have established that RTK GPS was a very suitable sensor to achieve automated guidance with such a high precision: several control laws have been designed for vehicles equipped with that sensor, and provide the expected guidance accuracy as long as vehicles do not slide. Further control developments have been previously proposed to take sliding into account: guidance accuracy in slippery environment has been shown to be preserved, except transiently at beginning/end of curves, ... In this paper, design of such a control law is first recalled and discussed. Model Predictive Control method is then applied in order to preserve guidance accuracy even during these transitions. Finally, the global control scheme is implemented, and improvements with respect to previous guidance laws are demonstrated through full scale experiments.
... thèse propose un algorithme de commande global, exploitant trois domaines connexes de la robo... more ... thèse propose un algorithme de commande global, exploitant trois domaines connexes de la robotique : la modélisation, la perception et la commande. Deux modèles cinématiques étendus sont d'abord proposés afin de caractériser la dynamique du véhicule intégrant les ...
IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004, 2004
Since Global Navigation Satellite Systems are able to supply very accurate coordinates of a point... more Since Global Navigation Satellite Systems are able to supply very accurate coordinates of a point (about 2 cm with a RTK GPS), such a sensor is very suitable to design vehicle guidance system. It is especially the case in agricultural tasks where a centimeter precision is often required (seeding, spraying, ...). To answer to growing high precision agriculture principle demand, several control laws for automated vehicle guidance relying on this sensor have been developed. Such guidance systems are able to supply an acceptable steering accuracy as long as vehicle does not slide (path tracking on even ground with good adherence properties...), what alas inevitably occurs in agricultural tasks. Several principles are here presented to steer vehicle whatever properties of ground and path to be followed are. In this paper a new extended kinematic model with sliding accounted is presented which allows to describe vehicle dynamics in all guidance conditions. Via this model a new non linear control law can be designed, which integrates sliding effects. Its capabilities are investigated through simulations and experimental tests.
2010 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2010
This paper addresses the problem of sliding parameter estimation and lateral control of an off-ro... more This paper addresses the problem of sliding parameter estimation and lateral control of an off-road vehicletrailer system. The aim is to accurately guide the position of the trailer with respect to a planned trajectory, whatever ground conditions and trajectory shape. Relevant sliding parameter estimation is first proposed, based on the kinematic model of the system extended with side slip angles. Then, a vehicle steering control algorithm is presented to move away the vehicle from the reference trajectory in order for the trailer to achieve accurate path tracking. Reported experiments demonstrate the capabilities of the proposed algorithms.
2009 IEEE International Conference on Robotics and Automation, 2009
The active devices dedicated to on-road vehicle stability cannot be applied satisfactorily in an ... more The active devices dedicated to on-road vehicle stability cannot be applied satisfactorily in an off-road context, since the variability and the non-linear features of grip conditions can no longer be neglected. Specific solutions have then to be investigated. In this paper, the prevention of light All-Terrain Vehicle (ATV) rollover is addressed. First, a backstepping observer is designed in order to estimate online a rollover indicator accounting for sliding phenomena, from a low-cost perception system. Next, the maximum vehicle velocity, compatible with a safe motion over some horizon of prediction, is computed via Predictive Functional Control (PFC), and can then be applied, if needed, to the vehicle actuator to prevent from rollover. The capabilities of the proposed device are demonstrated and discussed thanks to an advanced simulation testbed that has proved to supply results very close to experimental ones.
Proceedings 2006 IEEE International Conference on Robotics and Automation, 2006. ICRA 2006., 2006
Automatic devices dedicated to vehicle guidance in off-road conditions are necessarily confronted... more Automatic devices dedicated to vehicle guidance in off-road conditions are necessarily confronted with sliding phenomenon, since it may considerably damage the accuracy of the following task. Control laws taking explicitly into account such a phenomenon have already been designed in previous work. They can actually improve the guidance accuracy. However their efficiency is highly dependent on the sliding parameters estimation (since these parameters cannot be provided by a direct measurement). In this paper, an observer-like estimator is designed, providing sideslip angles from a single exteroceptive sensor, namely a Real Time Kinematic GPS (RTK-GPS). Improvements in guidance accuracy, with respect to previous estimation approaches, is demonstrated through full scale experiments, addressing agricultural applications.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 2005
One of the major current developments in agricultural machinery aims at providing farm vehicles w... more One of the major current developments in agricultural machinery aims at providing farm vehicles with automatic guidance capabilities. With respect to standard mobile robots applications, two additional difficulties have to be addressed: firstly, since farm vehicles operate on fields, sliding phenomena inevitably occurs. Secondly, due to large inertia of these vehicles, small delays introduced by low-level actuators may have noticeable effects. These two phenomena may lower considerably the accuracy of path following control laws.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 2005
High-precision autofarming is rapidly becoming a reality with the requirements of agricultural ap... more High-precision autofarming is rapidly becoming a reality with the requirements of agricultural applications. Lots of research works have been focused on the automatic guidance control of farm vehicles, satisfactory results have been reported under the assumption that vehicles move without sliding. But unfortunately the pure rolling constraints are not always satisfied especially in agriculture applications where the working conditions are rough and not expectable. In this paper the problem of path following control of autonomous farm vehicles in presence of sliding is addressed. To take sliding effects into account, a vehicle-oriented kinematic model is constructed in which sliding effects are introduced as additive unknown parameters of the ideal kinematic model. Based on backstepping method a stepwise procedure is proposed to design an adaptive controller in which sliding effects are learned and compensated by parameter adaptations. It is theoretically proven that for the farm vehicles subject to sliding, the lateral deviation can be stabilized near zero and the orientation errors converge into a neighborhood near the origin. To be more robust to disturbances including external noises and unmodeled time-varying sliding components, the adaptive controller is refined by integrating Variable Structure Controllers (VSC) or projection mappings. Simulation results show that the proposed robust adaptive controllers can reject sliding effects and guarantee high path-following accuracy.
Un algorithme dédié aux Véhicules Légers Tout-Terrain (VLTT) permettant l'estimation et l'anticip... more Un algorithme dédié aux Véhicules Légers Tout-Terrain (VLTT) permettant l'estimation et l'anticipation du renversement est présenté dans ce papier. Il repose sur une estimation temps-réel du Transfert de Charge Latéral (TCL), représentatif des instabilités dynamiques latérales. Le TCL est calculé grâceà un modèle dynamique scindé en deux projections 2D. A partir de ce modèle et d'un système de perception bas-coût, un observateur est proposé. Il permet d'estimer en temps-réel les propriétés du terrain (adhérence et pente), et ainsi d'évaluer avec précision le risque d'instabilité latéraleà l'instant courant. Enfin, un algorithme de prédiction, qui est basé sur l'extrapolation des commandes du conducteur, permet l'anticipation. Ainsi, il est possible de prévenir le pilote d'un risque de renversement, mais aussi d'envisager la création d'un système de sécurité actif.
Proceedings Ieee International Conference on Robotics and Automation, May 3, 2010
Automation in outdoor applications (farming, surveillance, etc.) requires highly accurate control... more Automation in outdoor applications (farming, surveillance, etc.) requires highly accurate control of mobile robots, at high speed, accounting for natural ground specificities (mainly sliding effects). In previous work, predictive control algorithms dedicated to All-Terrain Vehicle lateral stability was investigated. Satisfactory advanced simulation results have been reported but no experimental ones were presented. In this paper, the prevention of a real off-road mobile robot rollover is addressed. First, both rollover dynamic modeling and previous work on a Mixed observer designed to estimate on-line sliding phenomena for path tracking control are recalled. Then, this observer is here used to compute a rollover indicator accounting for sliding phenomena, from a low-cost perception system. Next, the maximum vehicle velocity, compatible with a safe motion over some horizon of prediction, is computed via Predictive Functional Control (PFC), and can then be applied, if needed, to the vehicle actuator to prevent from rollover. The capabilities of the proposed device are demonstrated and discussed thanks to real experimentation.
When designing an accurate automated guidance system for vehicles, a major problem is sliding and... more When designing an accurate automated guidance system for vehicles, a major problem is sliding and pseudosliding effects. This is especially the case in agricultural applications, where five-centimetre accuracy with respect to the desired trajectory is required, although the vehicles are moving on slippery ground.
2007 Ieee Rsj International Conference on Intelligent Robots and Systems, 2007
Most of active devices focused on vehicle stability concerns on-road cars and cannot be applied s... more Most of active devices focused on vehicle stability concerns on-road cars and cannot be applied satisfactorily in an off-road context, since the variability and the non-linearities of the tire/ground contact are often neglected. In previous work, a rollover indicator devoted to light ATVs, accounting for these phenomena has been proposed. It is based on the prediction of the lateral load transfer. Such an indicator requires the online knowledge of the tire cornering stiffness, initially selected from a ground classes network. In this paper, an adapted backstepping observer, making only use of yaw rate measurement, is designed to improve specifically tire cornering stiffness estimation. Capabilities of such an observer are demonstrated and discussed through both advanced simulations and actual experiments.
ABSTRACT Abstrat This paper presents a control algorithm, based on a kinematic model extended wit... more ABSTRACT Abstrat This paper presents a control algorithm, based on a kinematic model extended with additional sliding parameters, in order to accurately guide, forward or backward, the position of a passive towed implement with respect to a planned trajectory. Several experimental results, carried out with an off-road mobile robot and a passive trailer, demonstrate the capabilities of the proposed algorithm.
Proceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453), 2003
A very accurate vehicle guidance is required in numerous agricultural applications, as seeding, s... more A very accurate vehicle guidance is required in numerous agricultural applications, as seeding, spraying, row cropping, . . . Accuracy in vehicle localization can be obtained in realtime from a RTK GPS sensor. Several control laws, relying on this sensor, have been previously designed and provide satisfactory results as long as vehicles do not slide. However, sliding has to occur in agricultural tasks (sloping fields, curves on a wet land, . . .). The challenge addressed in this paper is to preserve vehicle guidance accuracy in such situations. A nonlinear adaptive control law is here designed. Simulation results and field experiments, demonstrating the capabilities of that control scheme, are reported and discussed.
2004 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) (IEEE Cat. No.04CH37566), 2004
When designing an accurate automated guidance vehicle system, a major problem is sliding and pseu... more When designing an accurate automated guidance vehicle system, a major problem is sliding and pseudosliding effects. It is especially the case in agricultural applications, where a five centimeters accuracy with respect to the desired trajectory is required, even if vehicles move on a slippery ground. Previous works have established that RTK GPS was a very suitable sensor to achieve automated guidance with such a high precision: several control laws have been designed for vehicles equipped with that sensor, and provide the expected guidance accuracy as long as vehicles do not slide. Further control developments have been previously proposed to take sliding into account: guidance accuracy in slippery environment has been shown to be preserved, except transiently at beginning/end of curves, ... In this paper, design of such a control law is first recalled and discussed. Model Predictive Control method is then applied in order to preserve guidance accuracy even during these transitions. Finally, the global control scheme is implemented, and improvements with respect to previous guidance laws are demonstrated through full scale experiments.
... thèse propose un algorithme de commande global, exploitant trois domaines connexes de la robo... more ... thèse propose un algorithme de commande global, exploitant trois domaines connexes de la robotique : la modélisation, la perception et la commande. Deux modèles cinématiques étendus sont d'abord proposés afin de caractériser la dynamique du véhicule intégrant les ...
IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004, 2004
Since Global Navigation Satellite Systems are able to supply very accurate coordinates of a point... more Since Global Navigation Satellite Systems are able to supply very accurate coordinates of a point (about 2 cm with a RTK GPS), such a sensor is very suitable to design vehicle guidance system. It is especially the case in agricultural tasks where a centimeter precision is often required (seeding, spraying, ...). To answer to growing high precision agriculture principle demand, several control laws for automated vehicle guidance relying on this sensor have been developed. Such guidance systems are able to supply an acceptable steering accuracy as long as vehicle does not slide (path tracking on even ground with good adherence properties...), what alas inevitably occurs in agricultural tasks. Several principles are here presented to steer vehicle whatever properties of ground and path to be followed are. In this paper a new extended kinematic model with sliding accounted is presented which allows to describe vehicle dynamics in all guidance conditions. Via this model a new non linear control law can be designed, which integrates sliding effects. Its capabilities are investigated through simulations and experimental tests.
2010 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2010
This paper addresses the problem of sliding parameter estimation and lateral control of an off-ro... more This paper addresses the problem of sliding parameter estimation and lateral control of an off-road vehicletrailer system. The aim is to accurately guide the position of the trailer with respect to a planned trajectory, whatever ground conditions and trajectory shape. Relevant sliding parameter estimation is first proposed, based on the kinematic model of the system extended with side slip angles. Then, a vehicle steering control algorithm is presented to move away the vehicle from the reference trajectory in order for the trailer to achieve accurate path tracking. Reported experiments demonstrate the capabilities of the proposed algorithms.
2009 IEEE International Conference on Robotics and Automation, 2009
The active devices dedicated to on-road vehicle stability cannot be applied satisfactorily in an ... more The active devices dedicated to on-road vehicle stability cannot be applied satisfactorily in an off-road context, since the variability and the non-linear features of grip conditions can no longer be neglected. Specific solutions have then to be investigated. In this paper, the prevention of light All-Terrain Vehicle (ATV) rollover is addressed. First, a backstepping observer is designed in order to estimate online a rollover indicator accounting for sliding phenomena, from a low-cost perception system. Next, the maximum vehicle velocity, compatible with a safe motion over some horizon of prediction, is computed via Predictive Functional Control (PFC), and can then be applied, if needed, to the vehicle actuator to prevent from rollover. The capabilities of the proposed device are demonstrated and discussed thanks to an advanced simulation testbed that has proved to supply results very close to experimental ones.
Proceedings 2006 IEEE International Conference on Robotics and Automation, 2006. ICRA 2006., 2006
Automatic devices dedicated to vehicle guidance in off-road conditions are necessarily confronted... more Automatic devices dedicated to vehicle guidance in off-road conditions are necessarily confronted with sliding phenomenon, since it may considerably damage the accuracy of the following task. Control laws taking explicitly into account such a phenomenon have already been designed in previous work. They can actually improve the guidance accuracy. However their efficiency is highly dependent on the sliding parameters estimation (since these parameters cannot be provided by a direct measurement). In this paper, an observer-like estimator is designed, providing sideslip angles from a single exteroceptive sensor, namely a Real Time Kinematic GPS (RTK-GPS). Improvements in guidance accuracy, with respect to previous estimation approaches, is demonstrated through full scale experiments, addressing agricultural applications.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 2005
One of the major current developments in agricultural machinery aims at providing farm vehicles w... more One of the major current developments in agricultural machinery aims at providing farm vehicles with automatic guidance capabilities. With respect to standard mobile robots applications, two additional difficulties have to be addressed: firstly, since farm vehicles operate on fields, sliding phenomena inevitably occurs. Secondly, due to large inertia of these vehicles, small delays introduced by low-level actuators may have noticeable effects. These two phenomena may lower considerably the accuracy of path following control laws.
Proceedings of the 2005 IEEE International Conference on Robotics and Automation, 2005
High-precision autofarming is rapidly becoming a reality with the requirements of agricultural ap... more High-precision autofarming is rapidly becoming a reality with the requirements of agricultural applications. Lots of research works have been focused on the automatic guidance control of farm vehicles, satisfactory results have been reported under the assumption that vehicles move without sliding. But unfortunately the pure rolling constraints are not always satisfied especially in agriculture applications where the working conditions are rough and not expectable. In this paper the problem of path following control of autonomous farm vehicles in presence of sliding is addressed. To take sliding effects into account, a vehicle-oriented kinematic model is constructed in which sliding effects are introduced as additive unknown parameters of the ideal kinematic model. Based on backstepping method a stepwise procedure is proposed to design an adaptive controller in which sliding effects are learned and compensated by parameter adaptations. It is theoretically proven that for the farm vehicles subject to sliding, the lateral deviation can be stabilized near zero and the orientation errors converge into a neighborhood near the origin. To be more robust to disturbances including external noises and unmodeled time-varying sliding components, the adaptive controller is refined by integrating Variable Structure Controllers (VSC) or projection mappings. Simulation results show that the proposed robust adaptive controllers can reject sliding effects and guarantee high path-following accuracy.
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Papers by Roland Lenain