• 专利附录
  • 专利说明
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    • 专利摘要:
    The invention relates to a method for controlling a system for assisting the driving of a motor vehicle comprising a trajectory correction function, said method comprising a step of measuring, from a camera equipping the vehicle, the lateral deviation of the vehicle (YL) from a marking on a taxiway and the relative heading angle (ΨL) corresponding to the angle between the longitudinal axis of the vehicle and a line of the taxiway , and a step of activating the trajectory correction function as a function of the lateral deviation and the measured relative heading angle, characterized in that it comprises a step of configuring the triggering of the activation of the trajectory correction function as a function of at least one maximum error found on the measurement of the lateral deviation (eymax) and of a maximum error noted on the measurement of the relative heading angle (emaxΨ).
    公开号:FR3040348A1
    申请号:FR1558106
    申请日:2015-09-01
    公开日:2017-03-03
    发明作者:Nicoleta Minoiu-Enache
    申请人:Renault SAS；
    IPC主号:
    专利说明:

    En référence à la figure 1, la trajectoire de référence est représentée dans un repère absolu {Oa, Xa, Ya }· A chaque instant t, la position du véhicule est repérée par rapport à un point Ot de la trajectoire qui constitue l'origine d’un repère relatif cinématique {Ot, Xt, Yt} dans lequel l'axe Xt est tangent à la trajectoire au point Ot. L’axe X t fait un angle Ψ£) avec l'axe Xa du repère absolu.
    Lorsque le véhicule suit parfaitement sa trajectoire à l'instant t, le centre de gravité CG est confondu avec le point Ot de la trajectoire. Ce n'est pas le cas lorsque le centre de gravité CG est déporté sur l’axe Yt dans le plan de la figure 1 qui est perpendiculaire à l’axe Xt.
    Le centre de gravité CG constitue l’origine d’un repère relatif lié {CG, Xv, Yv} au véhicule dans lequel l’axe Xv est colinéaire à la barre à laquelle le véhicule est assimilé dans le modèle bicyclette. Le repère relatif lié {CG, Xv, Yv} fait un angle Ψι_ avec le repère relatif cinématique {Ot, Xt, Yt}. La valeur de l'angle Ψι_ est nulle dans le cas idéal où le véhicule est dirigé selon la tangente à la trajectoire. Dans le cas contraire, une valeur non nulle de l'angle Ψι_ constitue un écart de trajectoire.
    Par rapport au repère absolu {Oa, Xa, Ya }, le centre de gravité CG se déplace à une vitesse Vcg dont le vecteur, exprimé dans le repère relatif lié {CG, Xv, Yv} fait un angle β avec l'axe Xv.
    On pourra se référer notamment aux demandes de brevet FR2992931, FR2991276 pour une présentation plus détaillée du modèle bicyclette, ainsi qu’à l’ouvrage « Vehicle Dynamics and Control » du Professeur Rajesh Rajamani, aux éditions Springer.
    Cette équation d’état a comme vecteur d’état l’angle de dérive du véhicule β, la vitesse de lacet r, l’angle de cap relatif Ψι_ et l’écart latéral par rapport à l’axe de la voie en avant du véhicule yi_ :
    x = (p,r,wL,yLJ
    Les entrées de ce modèle sont l’angle de braquage des roues avant 5f commandé par le conducteur ou par l’action de la fonction de correction de trajectoire LKA et la courbure de la route pref. Les données mesurées sont la vitesse de lacet r ( mesure fournie par exemple par le gyroscope du véhicule) et l’angle de cap relatif Ψι_ ainsi que l’écart latéral par rapport à l’axe de la voie en avant du véhicule yL, ces deux dernières données étant obtenues à partir de la caméra équipant le véhicule et sont fournies par des algorithmes de traitement d’image coopérant avec la caméra. Cependant, les mesures de Ψι_ et de yL peuvent être erronées et ces erreurs de mesures peuvent générer des activations soit trop tardives, soit trop précoces de la fonction de correction de trajectoire, ou encore un déplacement latéral du véhicule plus important que prévu pendant la mise en œuvre de la correction de trajectoire. Par ailleurs, l’angle de dérive β du vecteur vitesse du véhicule peut être estimé suivant les principes exposés dans le document de brevet WO 2005/061305.
    La description détaillée des paramètres du modèle du véhicule est fournie comme suit :
    Le modèle d’état obtenu comme décrit dans l’équation suivante est linéaire et invariant en temps en considérant une vitesse longitudinale constante. L’entrée de commande est l’angle 5f. La courbure de la route pref peut être considérée comme une entrée de perturbation. x = Ax+BuSf + Bppref, Bu étant le vecteur d’influence de braquage et Bp le vecteur de perturbation.
    On se réfère à la figure 2, qui illustre une représentation du schéma de principe pour la stratégie embarquée de décision d’activation de la fonction de correction de trajectoire LKA conforme à la l’invention.
    Tout d’abord, une phase de calcul dite hors ligne, autrement dit avant utilisation sur le véhicule, est nécessaire. En premier lieu, on calcule le déplacement latéral maximal autorisé du véhicule pendant une correction de trajectoire LKA, en présence des erreurs de mesure de l’écart latéral et de l’angle de cap relatif. Le déplacement latéral maximal est pré-calculé pour un jeu des paramètres de dynamique du véhicule et de géométrie de la voie de circulation comprenant la vitesse, la vitesse de lacet, la courbure maximale de la route et les erreurs de mesure maximales sur la mesure d’angle de cap relatif et sur la mesure de l’écart latéral, et en partant d’un ensemble de points initiaux spécifié. L’objectif de cette phase de calcul hors ligne est de prédéterminer le déplacement latéral maximal du véhicule dmax pendant une correction de trajectoire LKA pour différents jeux de paramètres, partant de l’hypothèse que la caméra équipant le véhicule fournit des mesures erronées pour l’angle de cap relatif et pour l’écart latéral.
    On suppose pour ce faire que l’action de la fonction de correction de trajectoire LKA démarre pour un comportement du véhicule contenu dans un ensemble de points initiaux décrit par des limites comme suit :
    β<βΝ, r<r |ΨΖ|<Ψ^, yL<yNL
    Les sommets de cet ensemble de points initiaux borné sont donnés par l’équation suivante : ζ,=[±/ ",±Λ±<,±>ΐ f
    On cherche plus précisément à calculer les performances de correction de trajectoire d’une loi de commande LKA déjà synthétisée, en ligne droite comme en virage, en présence éventuelle des erreurs de mesure. Cette loi de commande peut s’énoncer comme suit : ôf=Kx = kpfi+krr + kWiyL+kyLyL, les différents coefficients k étant des coefficients de proportionnalité qui peuvent être calculés par différentes méthodes (par exemple par placement des pôles en boucle fermée ou par des optimisations convexes de type LMI (acronyme anglais pour « Linear Matrix Inequalities »), notamment).
    Ces performances peuvent être déterminées par le calcul de l’ensemble atteignable en partant de l’ensemble de points initiaux borné. Une image de l’ensemble atteignable 10 est représentée à la figure 3. Ainsi, l’ensemble atteignable 10 contient toutes les trajectoires possibles en partant de la région de « conduite normale » 11 incluse dans l’ensemble des points initiaux borné défini plus haut. Selon un exemple de réalisation, l’ensemble atteignable 10 peut être approximée par un ensemble invariant ellipsoïdal extérieur à celui-ci. D’autres exemples de réalisation avec d’autres approximations de l’ensemble atteignable peuvent être mises en oeuvre, par exemple par des polytopes, zonotopes ou vecteurs d’intervalle.
    Pour faire l’estimation de l’ensemble atteignable et calculer l’impact de l’erreur de mesure sur le déplacement latéral maximal, on se fixe un jeu de paramètres de calcul pour les paramètres suivants : 1. L’ensemble des points initiaux borné décrit par (βΝ, rN, Ψι_Ν, yi_N) ; 2. Vitesse du véhicule v ; 3. Courbure maximale de la voie de circulation pmax 4. Erreur maximale constatée sur la mesure d’angle de cap relatif e™ et sur la mesure de l’écart latéral eJ"3* . S’agissant de l’erreur maximale constatée sur la mesure d’angle de cap relatif e^et sur la mesure de l’écart latéral e™, ces données sont préférentiellement issues d’une mesure statistique. Ainsi, dans une phase de validation de la caméra équipant le véhicule et de son logiciel de traitement d’image associé, les valeurs des erreurs de mesure de l’écart latéral et de l’angle de cap relatif par la caméra sont calculées de manière statistique au cours de phases de roulage du véhicule. Cette phase de validation est par exemple menée avant la commercialisation du véhicule. Les estimations des erreurs et ^calculées statistiquement sont fournies en tant que paramètres de configuration du véhicule. A noter que d’autres erreurs pourraient être introduites telles que, par exemple, l’erreur sur la vitesse de lacet mesurée.
    Ensuite, pour un jeu de paramètres fixé, on calcule un déplacement latéral maximal dmax de la manière suivante. En supposant la présence d’erreurs de mesure uniquement sur la mesure de l’angle de cap relatif et sur la mesure de l’écart latéral, on peut écrire :
    Wl =Vz+*v et yL =yL+ey L’angle de braquage de consigne des roues avant commandé par l’action de la fonction de correction de trajectoire devient alors : ôf=Kx + kyey +kyLey
    On suppose de plus que les valeurs des erreurs de mesure d’angle de cap relatif et d’écart latéral liées à la caméra, respectivement βψ et ey, sont bornées en valeurs absolues et, en outre, que la valeur maximale absolue de la courbure de la voie, également liée à la caméra, est limitée :
    Ms<“ ^ ; Mso“
    On peut donc écrire ces variables en fonction de trois paramètres normés : |< 1 ; |>v2|< 1 et | w3 < 1 Avec :
    Pref . βψ βγ w, = —— , w2 = —— , w3 = ——
    Pref ey L’angle de braquage de consigne devient alors : ôf=Kx + kVie^w2+kyie^w3 et le système en boucle fermée peut s'écrire de la manière suivante: x = (A + BuK)x + Bukve^w2 + Bukye™w3 + BpP^w,
    Pour ce système en boucle fermée, on cherche une fonction définie positive :
    8V V(x) = xTPx avec P = PTet P>- 0 tel que —<0 pour tous xei 4tel que dx xTPx)l ; w1 ei tel que^^l ; w2gR tel que|>v21 < 1 ; w3 sBtel que|>v3|< 1 A l’aide de la méthode appelée S-Procedure dans la littérature spécialisée, cela revient à dire que l’on cherche V(x) tel que :
    dV — (al(-xTPx) + a2(w[w1 -1 ) + a3(wT2w2 -ï) + aA(wlw3 -1) dx pour des paramètres a, >0 pour i=1,2,3,4.
    Cette même équation s’écrit par ailleurs :
    dV — (ocl -a2-a3-aIl -alxTPx + a2wlwl +a2wT2w2 + a4w3w3 dx
    La première partie de cette équation se développe comme suit : ÔV -T r, T D · -= x Px + x Px = dx lA + B,K)x + B^e~w2+B,kne~w, + Bep™wJpx + χτρΐΑ + Β,Κ)χ + Βχ,β^2+Β^β~νι +i„p“Wl]
    En utilisant les deux inégalités précédentes, on obtient l’inégalité matricielle suivante : dont les inconnues sont la matrice
    Q<0, Q symétrique et Q=P'1 et α,>0 pour i=1,2,3,4. On cherche alors une solution faisable de cette inégalité matricielle. Autrement dit, on cherche l'ensemble invariant qui ne sera pas quitté par la trajectoire corrigée du véhicule malgré les perturbations représentées par les erreurs de mesures et par la courbure de la route. Dans cet ensemble, il faut inclure naturellement la zone de démarrage de la correction de trajectoire. Pour rappel, on estime qu’au moment du déclenchement de l’activation de la fonction de correction de la trajectoire, l’état du véhicule se trouve dans la région de « conduite normale » incluse dans l’ensemble de points initiaux borné tel que défini précédemment (figure 3), définissant cette zone de démarrage. En minimisant l’ensemble invariant contenant cet ensemble de points initiaux, on minimise alors le dépassement de la trajectoire du véhicule en dehors de cette région. L’ensemble de points initiaux borné est défini par des plages avec des valeurs minimales et maximales sur les variables d'état, plages estimées très probables pour le moment d’activation de la correction :
    -βΝ <β<βΝ -rN<r <rN ~Wl ^Wl^Wl -yï ^yL^yï
    Ceci se traduit par des points : zf={±p",±r'‘M,±ylJ,i = 1,....,8 qui doivent être inclus dans l'ensemble invariant référencé 10 sur la figure 3.
    Le problème d’optimisation qui inclut cette contrainte s’écrit de la manière suivante :
    Une fois le problème d’optimisation ci-dessus résolu, on peut calculer le déplacement latéral maximal du véhicule en présence des erreurs de mesure et de la courbure:
    où / = 10,0,2(^-/5),2]
    On prévoit avantageusement d’éliminer tout calcul en ligne et d’utiliser à la place une table de valeurs stockée localement au niveau du véhicule et mémorisant l’ensemble des valeurs de déplacement latéral maximal autorisé pendant l’activation de la fonction de correction de trajectoire, pour différents jeux des paramètres (v, βΝ,ΓΝ, ΨιΛγιΛ pmax ,e™et e™). Ainsi, à titre d’exemple, le problème d’optimisation est à calculer pour des combinaisons (v, βΝ,ΓΝ, ΨιΛγιΛ pmax, e™ et e™ ) comme suit : • V=Vmjn, V=Vmin"*"0-5m/S, V=Vmin"*"1 m/S, ..., V—Vmax ·βΝ=- βΝΓπίη, βΝ=- β^ίη+Ο.δ0, βΝ=- βΝπιίη+1 °,..., βΝ=βΝιτ1Βχ ·ΓΝ=- rNmin, rN=- rNmin+0.57s, rN=- rNmin+17s,..., rN=rNmax .ψ1_Ν=_ψ1_Ν|τιΐηι ψ1_Ν=-ψ1_ΝΓΤΐίη+0.5°, Ψ^-Ψί^ΐη+Ι0,..., ΨίΝ=ΨίΝπΐ3χ .yLN=-yLNmin, yLN=-yi_Nmin+0.1 m, yLN=- γΛηίη+0.2ΓΤΊ,..., yLN= y^max • pmax=0, pmax= 1/1000m, pmax =i/800m, pmax=1/600m pmax=1/50m • eMJmax=-pi/6, evmax =-pi/6+pi/100,... βψ™χ=+ρΐ/6 eymax=-0.5, eymax =-0.5+0.01,... eymax=0.5
    Pour chaque combinaison possible, la valeur dmax est mémorisée dans la table. Par la suite, en temps réel, pendant le roulage du véhicule, à chaque pas de temps, les mesures de (v, β, r, Ψι_, yi_, P, δί) et les erreurs maximales constatées sur les mesure d’angle de cap relatif et d’écart latéral e^et e^ permettent de retrouver et d’extraire de la table de valeurs préalablement mémorisée la valeur dmax. Si la valeur dmax ainsi extraite de la table devient supérieure à une valeur de seuil donnée, par exemple correspondant selon un exemple de réalisation à une demi-largeur de la voie de circulation, l’activation de la correction de trajectoire doit être immédiatement déclenchée pour éviter la sortie de la voie, sauf si le conducteur a mis le clignotant par exemple.
    Ainsi, la stratégie proposée d’activation de la loi de commande déjà synthétisée implémentant la fonction de correction de trajectoire prend en compte les erreurs sur les mesures de l’angle de cap relatif et de l’écart latéral en avant du véhicule fournies par la caméra et son logiciel de traitement d’image associé, en calculant a priori des bornes ou valeurs maximales autorisées pendant la correction pour le déplacement latéral du véhicule, correspondant aux erreurs maximales constatées sur les mesures de l’angle de cap relatif et de l’écart latéral, de sorte que la décision d’activer la correction est déclenchée seulement quand une valeur prédéterminée du déplacement latéral maximal autorisé extraite de la table des valeurs du déplacement maximal en fonction de la dynamique instantanée du véhicule, dépasse un seuil donné.
    Cette stratégie permet ainsi de calculer la dégradation des performances d’une assistance à la conduite de type LKA suite aux erreurs sur les mesures fournies par les algorithmes de traitement d’image associés à la caméra équipant le véhicule. En tenant compte des possibles erreurs de mesures, une valeur de déplacement latéral maximal autorisé de la trajectoire du véhicule pendant la correction est calculée à tout moment et permet de déterminer le moment d’activation de la correction de trajectoire pour empêcher les sorties de voie.
    The invention relates to a method for controlling a driving assistance system for a motor vehicle moving on a driving assistance system for the correction of the trajectory of a motor vehicle. a traffic lane, comprising a trajectory correction function for maintaining the vehicle in the lane. The invention finds a particularly advantageous application in the field of safety and the field of assistance for driving motor vehicles.
    Some vehicles are equipped with a steering system that includes a function controlling, by a control computer, a body that acts on this direction, by delivering a specific assistance torque on the steering to perform a track monitoring aid traffic, which may indicate to the driver a deviation from the normal traffic lane, especially in cases of lack of vigilance, sleepiness or discomfort. These driving assistance functions are known by the terminology "Lane Departure Avoidance" or "Lane Keeping Assist" (LKA).
    The realization of this function is based in particular on the measurement of the position of the vehicle relative to its lane and, in particular, on the measurement of the lateral deviation of the vehicle relative to lateral markings on the ground delimiting the road on which circulates the vehicle and the measurement of the relative heading angle of the vehicle. Typically, these measurements are made using an on-board camera at the front of the vehicle and by means of image processing algorithms associated with the camera, able to detect the white lines on the ground and provide the lateral deviation of the vehicle from these white lines and the relative heading angle of the vehicle. These measures may, however, be erroneous. However, the measurement errors cause either unwanted tripping, too early or too late, the activation of the assistance to correct the trajectory of the vehicle, or the lateral movements of the vehicle during the correction, greater than the waiting.
    The patent document US6556909 discloses an automatic steering control system which, thanks to the combination of several equipment including the rear guide wheels, the management of the distribution of the torque to the wheels or the control of the limited slip differential, makes it possible to remain in a lane without driver intervention.
    The patent document US2007078600 proposes a collision avoidance system using an invariant game based on vehicle states and dynamic characteristics. This system is usable especially for vehicles flying in formation and for completely autonomous vehicles.
    The patent document US8095266 describes a LKA system for maintaining the track equipped with a compensator capable of solving the problems of delay of transmissions of video data supplied by a camera to the control computer, which operates at a higher frequency. . In conventional systems for maintaining the path, video data is repeatedly used by the control computer according to the speed of the image acquisition and processing system.
    However, all these trajectory control methods have precision problems related to the difference between the expected trajectory of the vehicle on its taxiway and the trajectory of the vehicle measured on this lane.
    Also, the object of the invention is in particular to overcome the drawbacks of the state of the art by proposing a method of controlling a driving assistance system for a motor vehicle comprising a vehicle trajectory correction function enabling to correct the trajectory in an optimized way. For this purpose, the invention relates to a method for controlling a driving assistance system for a motor vehicle comprising a function for correcting the trajectory of the vehicle traveling on a traffic lane, said method comprising a step of measuring the lateral deviation of the vehicle relative to a marking on the taxiway and a step of measuring the relative heading angle corresponding to the angle between the longitudinal axis of the vehicle and a line of the taxiway, from at least one camera equipping the vehicle, and a step of activating the function of correcting the trajectory as a function of the lateral deviation and the measured relative heading angle, the method being characterized in that it comprises a step of configuring the triggering of the activation of the function of correction of the trajectory as a function of at least one maximum error noted on the measurement of the lateral deviation and of a maximum error ale found on the measurement of the relative heading angle.
    In this way, the trajectory correction can be activated only at the opportune moment to allow the maintenance of the vehicle in the taxiway despite the presence of measurement errors from the camera.
    According to one embodiment, the step of configuring the triggering of the activation of the trajectory correction function comprises: a step of predetermining a maximum lateral displacement value authorized for said vehicle during the activation of the trajectory correction function, for different sets of vehicle dynamics and taxiway geometry parameters including at least the maximum error found on the measurement of the lateral deviation and the maximum error found on the measurement of the relative heading angle, - a step of storing a table of the predetermined maximum lateral displacement values allowed for each set of parameters set in the predetermination step, the activation of the trajectory correction function being triggered when a maximum allowed lateral displacement value extracted from the table of values previously stored according to conditions co The vehicle's running speed is greater than a given threshold value.
    Advantageously, the maximum errors noted on the measurement of the lateral deviation and on the measurement of the relative heading angle are statistically calculated during a preliminary driving phase of the vehicle.
    Advantageously, the vehicle dynamics parameters comprise at least one parameter among: the speed of the vehicle along the longitudinal axis, the yaw rate, the angle that the front wheels make with the longitudinal axis of the vehicle.
    Advantageously, the geometry parameters of the track comprise at least the maximum curvature of the taxiway.
    Advantageously, the predetermined values of maximum allowed lateral displacement are calculated, for each set of fixed parameters, as a function of an initial state of the vehicle at the initiation of the activation of the function of correction of the trajectory, said initial state being contained in a set of initial points bounded in a reference defined by the relative heading angle and the lateral deviation, and by determining an attainable set of all possible trajectories of the vehicle starting from said initial state of the vehicle.
    Preferably, the determination of said attainable set of all possible trajectories of the vehicle starting from said initial state of the vehicle comprises an approximation of said set achievable by an invariant ellipsoidal set. The invention also relates to a device for controlling a driving assistance system for a motor vehicle traveling on a taxiway, comprising an active steering system, a camera equipping the vehicle, associated with processing means image to provide at least one measurement of the lateral deviation of the vehicle relative to a marking on the taxiway and a measurement of the relative heading angle corresponding to the angle between the longitudinal axis of the vehicle and a taxiway line, a control computer controlling the active steering system to perform a function of correcting the trajectory as a function of the lateral deviation and the measured relative heading angle, characterized in that it comprises means for triggering the activation of the trajectory correction function as a function of at least one maximum error found on the measurement of the lateral deviation and of a maximum error on the measurement of the relative heading angle.
    Advantageously, the device comprises means for storing a table of predetermined maximum lateral displacement values authorized for said vehicle during the activation of the trajectory correction function, for different sets of parameters of vehicle dynamics and of the geometry of the vehicle. taxiway comprising at least the maximum error found on the measurement of the lateral deviation and the maximum error found on the measurement of the relative heading angle, said control computer being designed to trigger the activation of the function for correcting the trajectory when a maximum authorized lateral displacement value provided by the table of values according to current driving conditions of the vehicle is greater than a given threshold value. The invention also relates to a vehicle comprising a device according to the invention. Other features and advantages of the invention will appear on reading the following description of a particular embodiment of the invention, given by way of indication but not limitation, with reference to the appended figures in which: Figure 1 is a representation of the bicycle model applied to a vehicle traveling in a lane; FIG. 2 illustrates a diagram of the principle diagram for the on-board decision strategy for activating the trajectory correction function according to the invention; FIG. 3 illustrates a representation of the approximation of the attainable set of vehicle trajectories from a "normal driving" region and of the relationship with the maximum lateral displacement on the taxiway.
    The variables that will be used in the remainder of the description are listed below: m (kg): Total mass of the vehicle; J (Nm): Inertia of the vehicle around a vertical axis passing through its center of gravity CG;
    If (m): Distance from CG to the front axle of the vehicle; lr (m): Distance from CG to the rear axle of the vehicle; a (m): Average lengths of the front and rear axles of the vehicle;
    Cf (N / rad): Forward drift rigidity; cr (N / rad): Rear drift rigidity; 5f (rad): Steering angle of the front wheels, being the angle of the front wheels with the longitudinal axis of the vehicle; r (rad / s): Yaw rate, ie the speed of rotation of the vehicle around its center of gravity CG along a vertical axis; Ψ (rad / s): Angle of heading of the vehicle in absolute reference; Ψοΐ (rad / s): Angle of heading of the tangent to the reference trajectory in absolute reference; Ψι_ (rad / s): Relative heading angle between the vehicle axis and the tangent to the reference path;
    Ylcg (m): lateral deviation between the vehicle axis and the tangent to the trajectory at the center of gravity of the vehicle; yi_ (m): lateral deviation between the vehicle axis and the tangent to the trajectory in front of the vehicle;
    Is (m): The sighting distance for measuring the lateral deviation in front of the vehicle; β (rad): Angle of drift, which is the angle of the vehicle velocity vector with its longitudinal axis; (vcg) v: vector velocity of the vehicle; v (m / s): Vehicle speed along the longitudinal axis; u (m / s): Vehicle speed along the transverse axis;
    Pref: Curvature of the track; L (m): Width of the taxiway;
    VehWidth (m): Total width of the vehicle; rN (rad / s): Yaw rate delimiting the range where the state vector is usually located for normal driving; '+'i.'Vad / s): Relative heading angle delimiting the area where the state vector is usually located for normal driving; yi_N (m): Lateral deviation defining the domain where the state vector is usually found for normal driving; βΝ (rad): Angle of drift defining the domain where the state vector is usually found for normal driving; e '^ (rad): Maximum error found on the relative heading angle measurement; e ^ (rad): Maximum error found on the measurement of lateral deviation. In order to model the vehicle, we make the following assumptions: H1: The angles β and 5f are small, such that sin (angle) »angle and cos (angle) * 1;
    H2: (vCG) v = (v, u, 0) T = (v, v * (sin β), 0) T * (v, ν * β, 0) T H3: The vehicle is traveling at a longitudinal speed v constant; H4: The contact forces of the tires are linear with the drifts of the tires and depending on the rigidity of the tires; H5: yL * yLCG + ls * Ψι_, where Ψ, _ = Ψ- Ψά The state equation of the "bicycle" model of the vehicle with two steered wheels, as shown in Figure 1, is given below by the following equation:
    With reference to FIG. 1, the reference trajectory is represented in an absolute reference system {Oa, Xa, Ya}. At each instant t, the position of the vehicle is located with respect to a point Ot of the trajectory which constitutes the origin a relative kinematic reference {Ot, Xt, Yt} in which the axis Xt is tangent to the trajectory at the point Ot. The X axis t makes an angle Ψ £) with the axis Xa of the absolute reference.
    When the vehicle perfectly follows its trajectory at time t, the center of gravity CG coincides with the point Ot of the trajectory. This is not the case when the center of gravity CG is offset on the axis Yt in the plane of Figure 1 which is perpendicular to the axis Xt.
    The center of gravity CG constitutes the origin of a relative reference line (CG, Xv, Yv) to the vehicle in which the axis Xv is collinear with the bar to which the vehicle is assimilated in the bicycle model. The relative relative mark {CG, Xv, Yv} makes an angle Ψι_ with the relative kinematic reference {Ot, Xt, Yt}. The value of the angle Ψι_ is zero in the ideal case where the vehicle is directed along the tangent to the trajectory. In the opposite case, a non-zero value of the angle Ψι_ constitutes a trajectory deviation.
    Relative to the absolute coordinate system {Oa, Xa, Ya}, the center of gravity CG moves at a speed Vcg whose vector, expressed in the relative relative coordinate system (CG, Xv, Yv} makes an angle β with the axis Xv .
    We can refer in particular to patent applications FR2992931, FR2991276 for a more detailed presentation of the bicycle model, and the book "Vehicle Dynamics and Control" Professor Rajesh Rajamani, published by Springer.
    This state equation has as a state vector the vehicle drift angle β, the yaw rate r, the relative heading angle Ψι_ and the lateral deviation from the track axis in front of the vehicle yi_:
    x = (p, r, wL, yLJ
    The inputs of this model are the steering angle of the front wheels 5f controlled by the driver or by the action of the LKA trajectory correction function and the curvature of the road pref. The measured data are the yaw rate r (measurement provided for example by the vehicle gyroscope) and the relative heading angle Ψι_ as well as the lateral deviation with respect to the axis of the track in front of the vehicle yL, these last two data being obtained from the camera equipping the vehicle and are provided by image processing algorithms cooperating with the camera. However, the measurements of Ψι_ and yL may be erroneous and these measurement errors may generate activations either too late or too early of the trajectory correction function, or a lateral displacement of the vehicle larger than expected during the setting. implementation of the trajectory correction. Furthermore, the angle of drift β of the vehicle speed vector can be estimated according to the principles set forth in patent document WO 2005/061305.
    The detailed description of the vehicle model parameters is provided as follows:
    The state model obtained as described in the following equation is linear and invariant in time considering a constant longitudinal velocity. The control input is the angle 5f. The curvature of the road pref can be considered as a disturbance entry. x = Ax + BuSf + Bppref, Bu being the steering influence vector and Bp the perturbation vector.
    Referring to Figure 2, which illustrates a representation of the schematic diagram for the on-board decision strategy of activation of the LKA trajectory correction function according to the invention.
    First of all, a so-called offline calculation phase, in other words before use on the vehicle, is necessary. Firstly, the maximum permitted lateral displacement of the vehicle during a LKA trajectory correction is calculated, in the presence of the errors of measurement of the lateral deviation and the relative heading angle. The maximum lateral displacement is pre-calculated for a set of vehicle dynamics and lane geometry parameters including speed, yaw rate, maximum road curvature, and maximum measurement errors on the road measurement. relative heading angle and the measurement of the lateral deviation, and starting from a set of initial points specified. The objective of this offline calculation phase is to predetermine the maximum lateral displacement of the vehicle dmax during an LKA trajectory correction for different sets of parameters, assuming that the camera equipping the vehicle provides erroneous measurements for the vehicle. relative heading angle and lateral deviation.
    It is assumed for this purpose that the action of the LKA trajectory correction function starts for a vehicle behavior contained in a set of initial points described by limits as follows:
    β <βΝ, r <r | ΨΖ | <Ψ ^, yL <yNL
    The vertices of this set of initial bounded points are given by the following equation: ζ, = [± / ", ± Λ ± <, ±> ΐ f
    More precisely, it is sought to calculate the trajectory correction performance of an already synthesized LKA control law, in a straight line as well as in a corner, in the possible presence of measurement errors. This control law can be stated as follows: δf = Kx = kpfi + krr + kwiyL + kyLyL, the different coefficients k being proportionality coefficients that can be calculated by different methods (for example by placing the poles in a closed loop or by convex optimizations of LMI type (acronym for "Linear Matrix Inequalities"), in particular).
    These performances can be determined by calculating the set achievable starting from the set of initial points bounded. An image of the reachable set 10 is shown in FIG. 3. Thus, the reachable set 10 contains all the possible trajectories starting from the "normal driving" region 11 included in the set of initial points bounded defined above. . According to an exemplary embodiment, the reachable assembly 10 may be approximated by an ellipsoidal invariant set outside thereof. Other exemplary embodiments with other approximations of the reachable set can be implemented, for example by polytopes, zonotopes or interval vectors.
    To estimate the achievable set and calculate the impact of the measurement error on the maximum lateral displacement, we set a set of computational parameters for the following parameters: 1. The set of initial points bounded described by (βΝ, rN, Ψι_Ν, yi_N); 2. Vehicle speed v; 3. Maximum curvature of the taxiway pmax 4. Maximum error observed on the relative heading angle measurement e ™ and on the measurement of the lateral deviation eJ "3 *. the measurement of relative heading angle e ^ and the measurement of the lateral deviation e ™, these data are preferably derived from a statistical measurement Thus, in a validation phase of the camera equipping the vehicle and its software associated image processing, the values of the errors of measurement of the lateral deviation and the relative heading angle by the camera are computed statistically during the driving phases of the vehicle.This validation phase is for example pre-marketed vehicle Estimates of errors and ^ calculated statistically are provided as vehicle configuration parameters Note that other errors could be introduced such as, for example, speed error measured lace.
    Then, for a fixed set of parameters, a maximum lateral displacement d max is calculated in the following manner. Assuming the presence of measurement errors only on the measurement of the relative heading angle and the measurement of the lateral deviation, we can write:
    Wl = Vz + * v and yL = yL + ey The set steering angle of the front wheels controlled by the action of the course correction function then becomes: δf = Kx + kyey + kyLey
    It is further assumed that the values of the relative heading angle and lateral deviation measurements related to the camera, respectively βψ and ey, are bounded in absolute values and, furthermore, that the absolute maximum value of the curvature of the way, also related to the camera, is limited:
    Ms <"^; mso "
    We can write these variables according to three normed parameters: | <1;|> v2 | <1 and | w3 <1 With:
    Pref. βψ βγ w, = -, w2 = -, w3 = -
    Pref ey The set steering angle then becomes: δf = Kx + kVie ^ w2 + kyie ^ w3 and the closed-loop system can be written in the following way: x = (A + BuK) x + Bukve ^ w2 + Bukye ™ w3 + BpP ^ w,
    For this closed-loop system, we look for a positive definite function:
    8V V (x) = xTPx with P = PT and P> - 0 such that - <0 for all xei 4 such that dx xTPx) l; w1 ei such that ^^ l; w2gR such that |> v21 <1; w3 sBtel that |> v3 | <1 Using the method called S-Procedure in the specialized literature, this amounts to saying that we are looking for V (x) such that:
    dV - (a ( - xTPx) + a2 (w [w1 -1) + a3 (wT2w2 -i) + aA (wlw3 -1) dx for parameters a,> 0 for i = 1,2,3,4 .
    This same equation is written elsewhere:
    dV - (ocl-a2-a3-aIl -alxTPx + a2wlw1 + a2wT2w2 + a4w3w3 dx
    The first part of this equation develops as follows: ÔV -T r, TD · - = x Px + x Px = dx lA + B, K) x + B ^ e ~ w2 + B, kne ~ w, + Bep ™ wJpx + χτρΐΑ + Β, Κ) χ + Βχ, β ^ 2 + Β ^ β ~ νι + i "p" Wl]
    Using the two previous inequalities, we obtain the following matrix inequality: whose unknowns are the matrix
    Q <0, Q symmetric and Q = P'1 and α,> 0 for i = 1,2,3,4. We then look for a feasible solution of this matrix inequality. In other words, we look for the invariant set which will not be left by the corrected trajectory of the vehicle despite the disturbances represented by measurement errors and the curvature of the road. In this set, naturally include the starting area of the course correction. As a reminder, it is estimated that at the time of initiation of the activation of the trajectory correction function, the state of the vehicle is in the region of "normal driving" included in the set of initial points bounded such that previously defined (Figure 3), defining this start area. By minimizing the invariant set containing this set of initial points, then minimizing the vehicle trajectory beyond this region. The set of initial points bounded is defined by ranges with minimum and maximum values on the state variables, estimated ranges very likely for the moment of activation of the correction:
    -βΝ <β <βΝ -rN <r <rN ~ Wl ^ Wl ^ Wl -yi ^ yL ^ yi
    This results in points: zf = {± p ", ± r'M, ± ylJ, i = 1, ...., 8 which must be included in the invariant set referenced 10 in FIG.
    The optimization problem that includes this constraint is written as follows:
    Once the above optimization problem has been solved, the maximum lateral displacement of the vehicle can be calculated in the presence of measurement errors and curvature:
    where / = 10,0,2 (^ - / 5), 2]
    Advantageously, all on-line calculation is eliminated and a table of values stored locally at the vehicle level is used instead and memorizing the set of maximum lateral displacement values authorized during the activation of the trajectory correction function. , for different sets of parameters (v, βΝ, ΓΝ, ΨιΛγιΛ pmax, e ™ and e ™). Thus, by way of example, the optimization problem is to be calculated for combinations (v, βΝ, ΓΝ, ΨιΛγιΛ pmax, e ™ and e ™) as follows: • V = Vmjn, V = Vmin "*" 0 -5m / S, V = Vmin "*" 1 m / S, ..., V-Vmax · βΝ = - βΝΓπίη, βΝ = - β ^ ίη + Ο.δ0, βΝ = - βΝπιίη + 1 °, .. ., βΝ = βΝιτ1Βχ · ΓΝ = - rNmin, rN = - rNmin + 0.57s, rN = - rNmin + 17s, ..., rN = rNmax .ψ1_Ν = _ψ1_Ν | τιΐηι ψ1_Ν = -ψ1_ΝΓΤΐίη + 0.5 °, Ψ ^ - Ψί ^ ΐη + Ι0, ..., ΨίΝ = ΨίΝπΐ3χ .yLN = -yLNmin, yLN = -yi_Nmin + 0.1m, yLN = - γΛηίη + 0.2ΓΤΊ, ..., yLN = y ^ max • pmax = 0, pmax = 1 / 1000m, pmax = 1 / 800m, pmax = 1 / 600m pmax = 1 / 50m • eMJmax = -pi / 6, evmax = -pi / 6 + pi / 100, ... βψ ™ χ = + ρΐ / 6 eymax = -0.5, eymax = -0.5 + 0.01, ... eymax = 0.5
    For each possible combination, the value dmax is stored in the table. Subsequently, in real time, during the rolling of the vehicle, at each time step, the measurements of (v, β, r, Ψι_, yi_, P, δί) and the maximum errors recorded on the angle measurements of relative heading and lateral deviation e ^ and e ^ make it possible to retrieve and extract from the previously stored value table the value dmax. If the value dmax thus extracted from the table becomes greater than a given threshold value, for example corresponding according to an exemplary embodiment to a half-width of the traffic lane, the activation of the trajectory correction must be immediately triggered for avoid leaving the track, unless the driver has put the flashing light for example.
    Thus, the proposed strategy of activation of the already synthesized control law implementing the trajectory correction function takes into account the errors on the measurements of the relative heading angle and the lateral deviation in front of the vehicle provided by the camera and its associated image processing software, by a priori calculating limits or maximum values allowed during the correction for the lateral displacement of the vehicle, corresponding to the maximum errors found on the measurements of the relative heading angle and the lateral deviation, so that the decision to activate the correction is triggered only when a predetermined value of the maximum allowed lateral displacement extracted from the table of values of the maximum displacement as a function of the instantaneous dynamics of the vehicle, exceeds a given threshold.
    This strategy thus makes it possible to calculate the performance degradation of an LKA-type driving assistance following errors in the measurements provided by the image processing algorithms associated with the camera equipping the vehicle. Taking into account possible measurement errors, a maximum allowed lateral displacement value of the vehicle trajectory during the correction is calculated at any time and makes it possible to determine the moment of activation of the trajectory correction to prevent the lane exits.
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    A method of controlling a driving assistance system for a motor vehicle comprising a function of correcting the trajectory of the vehicle traveling on a taxiway, said method comprising a step of measuring the lateral deviation of the vehicle (YL) relative to a marking on the taxiway and a step of measuring the relative heading angle (Ψι_) corresponding to the angle between the longitudinal axis of the vehicle and a line of the taxiway, from at least one camera equipping the vehicle, and a step of activating the function of correcting the trajectory as a function of the lateral deviation and the measured relative heading angle, the method being characterized in that it comprises a step of configuring the triggering of the activation of the function of correction of the trajectory as a function of at least one maximum error noted on the measurement of the lateral deviation (e ^) and of a maximum error observed on measuring the relative bearing angle (e ™).
    [2" id="c-fr-0002]
    2. Method according to claim 1, characterized in that the step of configuring the triggering of the activation of the trajectory correction function comprises: a step of presetting maximum lateral displacement values (dmax) authorized for said during the activation of the course correction function, for different sets of vehicle dynamics and taxiway geometry parameters including at least the maximum error found on the lateral deviation measurement and the error maximum on the measurement of the relative heading angle, - a step of storing a table of the predetermined maximum lateral displacement values allowed for each set of parameters set in the predetermination step, the activation of the correction of the trajectory being triggered when a maximum allowed lateral displacement value (dmax) is extracted from the tab the value stored beforehand according to the current driving conditions of the vehicle is greater than a given threshold value.
    [3" id="c-fr-0003]
    3. Method according to claim 2, characterized in that the maximum errors found on the measurement of the lateral deviation and on the measurement of the relative heading angle are statistically calculated during a preliminary driving phase of the vehicle.
    [4" id="c-fr-0004]
    4. Method according to any one of claims 2 or 3, characterized in that the vehicle dynamics parameters comprise at least one of: the speed of the vehicle along the longitudinal axis, the yaw rate, the angle that make the front wheels with the longitudinal axis of the vehicle.
    [5" id="c-fr-0005]
    5. Method according to any one of claims 2 to 4, characterized in that the geometry parameters of the path comprise at least the maximum curvature of the traffic lane.
    [6" id="c-fr-0006]
    6. Method according to any one of claims 2 to 5, characterized in that the predetermined maximum permissible lateral displacement values (dmax) are calculated, for each set of fixed parameters, as a function of an initial state of the vehicle on release. the activation of the trajectory correction function, said initial state being contained in a set of initial points bounded (11) in a coordinate system defined by the relative heading angle (Ψι_) and the lateral deviation (yL) , and by determining an achievable set (10) of all possible trajectories of the vehicle from said initial state of the vehicle.
    [7" id="c-fr-0007]
    7. The method of claim 6, characterized in that the determination of said reachable set (10) of all possible trajectories of the vehicle from said initial state of the vehicle comprises an approximation of said set achievable by an invariant ellipsoidal set.
    [8" id="c-fr-0008]
    8. Device for controlling a driving assistance system for a motor vehicle traveling on a taxiway, comprising an active steering system, a camera equipping the vehicle, associated with image processing means for provide at least one measurement of the lateral deviation (YL) of the vehicle relative to a marking on the taxiway and a measurement of the relative heading angle (Ψ | _) corresponding to the angle between the longitudinal axis of the vehicle and a line of the traffic lane, a control computer controlling the active steering system to perform a function of correcting the trajectory as a function of the lateral deviation and the measured relative heading angle, characterized in that it comprises means for triggering the activation of the trajectory correction function as a function of at least one maximum error found on the measurement of the lateral deviation (ej ™ *) and of an error maximum on the measurement of the relative heading angle (e ^).
    [9" id="c-fr-0009]
    9. Device according to claim 8, characterized in that it comprises means for storing a table of predetermined maximum permitted lateral displacement values (dmax) for said vehicle during the activation of the trajectory correction function, for different sets of parameters for vehicle dynamics and taxiway geometry including at least the maximum error found on the measurement of the lateral deviation (ej "3 *) and the maximum error found on the measurement of the relative heading angle (e ^), said control computer being adapted to trigger activation of the course correction function when a maximum allowable lateral displacement value (dmax) provided by the table of values under current conditions vehicle is greater than a given threshold value.
    [10" id="c-fr-0010]
    10. Vehicle comprising a device according to any one of claims 8 or 9.
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    同族专利:
    公开号 | 公开日
    EP3344505A1|2018-07-11|
    EP3344505B1|2019-05-22|
    WO2017037354A1|2017-03-09|
    FR3040348B1|2017-08-11|
    引用文献:
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    CN111942470A|2020-07-01|2020-11-17|浙江大学|Control method for improving deviation rectifying capability of differential wheel steering system of Forklift AGV|
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1558106A|FR3040348B1|2015-09-01|2015-09-01|DEVICE AND METHOD FOR CONTROLLING A DRIVING ASSISTANCE SYSTEM FOR THE TRACK CORRECTION OF A MOTOR VEHICLE.|FR1558106A| FR3040348B1|2015-09-01|2015-09-01|DEVICE AND METHOD FOR CONTROLLING A DRIVING ASSISTANCE SYSTEM FOR THE TRACK CORRECTION OF A MOTOR VEHICLE.|
    PCT/FR2016/051760| WO2017037354A1|2015-09-01|2016-07-08|Device and method for controlling a driver assistance system for correcting the direction of travel of a motor vehicle|
    EP16744815.8A| EP3344505B1|2015-09-01|2016-07-08|Device and method for controlling a driver assistance system for correcting the direction of travel of a motor vehicle|
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