Modeling and identification of passenger car dynamics using robotics formalism

International audienceThis paper deals with the problem of dynamicmodeling and identification of passenger cars. It presents a new method that is based on robotics techniques for modeling and description of tree-structured multibody systems. This method enables us to systematically obtain the dynamic identification model, which is linear with respect to the dynamic parameters. The estimation of the parameters is carried out using a weighted least squares method. The identification is tested using vehicle dynamics simulation software used by the car manufacturer PSA Peugeot-Citroën in order to define a set of trajectories with good excitation properties and to determine the number of degrees of freedom of the model. The method has then been used to estimate the dynamic parameters of an experimental Peugeot 406, which is equipped with different position, velocity, and force sensors

Identification des paramètres dynamiques d'une voiture

La modélisation est basée sur le formalisme de Denavit et Hartenberg modifié permettant la description géométrique des robots. La voiture est considérée comme une structure arborescente où les roues sont les organes terminaux. Cette description permet de calculer symboliquement, de façon automatique, les modèles géométrique, cinématique et dynamique en utilisant des techniques robotiques ou des outils comme le logiciel SYMORO+. Un tel modèle permet de calculer le modèle dynamique inverse, linéaire par rapport aux paramètres dynamiques à identifier. Les paramètres sont identifiés avec une méthode des moindres carrés pondérés. Les modèles sont testés en simulation puis avec un véhicule réel. L'identification est réalisée en utilisant des trajectoires spécifiques effectuées durant des tests courants avec une voiture instrumentée. La plupart des paramètres dynamiques du châssis sont identifiés, les raideurs de suspension et de barre anti-roulis et les raideurs verticales des pneus aussiThe modelling is based on the modified Denavit-Hartenberg geometric description, which is commonly used in robotics. The car is considered as a tree structure multi body system, where the four wheels are the terminal links. This description allows calculating automatically the symbolic expression of the geometric, kinematics and dynamic models by using robotics techniques or even by using a symbolic software package like SYMORO+. Such a model allows us calculating the inverse dynamic model, which is linear with respect to the dynamic parameters. The identificaion is performed with a weighted least squares method. Models are testing in simulation then with a real car. The identification is realized with common tests with a car equipped with different sensors. Most of the dynamic parameters of the chassis can be identified (inertia matrix, centre of mass position and mass), and also the dynamic parameters of the suspensions, anti-roll bar and vertical stiffness of the tiresNANTES-BU Sciences (441092104) / SudocNANTES-Ecole Centrale (441092306) / SudocSudocFranceF

Intraspecific size shifts in generalist bumblebees and flowers lead to low functional consequences

Body size is a trait that can affect plant–pollinator interaction efficiency and plant reproductive success. We explored the impact of intraspecific size shifts on the interactions between pollinators and flowering plants under controlled conditions. We considered two development conditions leading to the production of large and small individual flowers of Borago officinalis and Echium plantagineum. We also used the natural variability of worker size within bumblebee colonies to isolate small and large workers. We performed a fully crossed experiment with the two flower sizes of each plant species and the two sizes of bumblebee workers. Our results show that the size of both partners did not affect bee foraging behavior in most of the evaluated parameters and both bee sizes were equally efficient in depositing pollen. Significant differences were found only in pollen deposition across the life of a flower in small flowers of B. officinalis, with the greatest quantity of pollen deposited by small bees. We did not find a relationship between pollinator size and plant fitness. Our results suggest that generalist plant–pollinator interactions may be resilient to future potential mismatches in the size of the partners but remain to be tested if they are still resilient under the new environmental conditions resulting from global changes