Otto Hofmann

Analysis of Lateral Tyre Friction Dynamics

The tyre friction model is a key part of the overall multi-body tyre dynamics model. The LuGre dynamic tyre friction model is analytically linearised for pure cornering conditions. The linearised model parameters are conveniently expressed as functions of static curve slope parameters. The linearised lateral force and self-aligning torque submodels are described by equivalent mechanical systems. The linearised model and equivalent system parameters are analysed for different slip angle and wheel centre speed operating points. An example of the application of linearised tyre friction model to tyre vibration analysis is presented as well.

The yaw torque influence of active systems and smart actuators for coordinated vehicle dynamics controls

This article presents the capability of several active systems and smart actuators to control the vehicle yaw motion for various driving situations. A control concept allowing for a centralised coordination of multiple actuators is described. The additional yaw torque generated through system control interventions is determined taking account of the vehicle side slip angle and the lateral acceleration. Analysis results are illustrated for the active front steering and brake system, active differential and active anti-roll bars. The developed control concept is based on a centralised yaw torque allocation algorithm. The concept comprises the coordination of the considered active systems and the identification of required interventions to control the vehicle yaw motion. A sine with dwell time open-loop manoeuvre is utilised to illustrate the stability and agility improvement achieved by the centralised and coordinated control strategy.

Modeling of Dynamic Tire Friction Potential on Ice Surfaces

It has been shown recently that the tire-ice friction is characterized by a significant dynamic potential for abrupt increases of wheel torque at low vehicle speeds. The paper presents experimental identification and modeling of dynamic tire friction potential (DTFP) on ice surfaces. The model is based on the LuGre tire friction model extended with the DTFP effect. The extension is based on the hypothesis that the DTFP is caused by the bristle dwell time effect. The bristle dwell time process is firstly described by a distributed-parameter model, which is then transformed to a lumped-parameter form based on a definition of average tire-bristle dwell time. The calculated bristle dwell time is used to schedule the maximum static friction parameter of the LuGre model. The extended tire friction model is validated against the experimental data for different operating conditions.Copyright

Beobachtung von Fahrzeugzuständen der Querdynamik mit integrierter reibwertschätzung

Regelungssysteme fur die Fahrdynamik beruhen auf Informationen uber den aktuellen Fahrzeugzustand. Wahrend viele Daten direkt aus Sensorsignalen gewonnen werden konnen, lassen sich wichtige Grosen wie die Fahrzeugquergeschwindigkeit und der zugehorige Strasenreibwert nicht mit der vorhandenen Sensorik erfassen und mussen uber einen Beobachteransatz ermittelt werden. Diese Zustandsschatzung wurde in mehreren Projekten zur integrierten Fahrdynamikregelung am Ford-Forschungszentrum in Aachen erfolgreich eingesetzt.

State estimation of the vehicle lateral dynamic with integrated estimation of the friction between tyre and road

Control systems for vehicle stability require information about the actual vehicle state. While many states can be obtained from sensor signals, some important states, like the lateral velocity and the corresponding tyre-road friction have to be reconstructed by a vehicle state estimator, comprising of a simplified vehicle model. The efficiency of the developed vehicle state estimator has been proven in several projects for integrated vehicle dynamics control at the Ford Research Centre in Aachen.