What could be the reason for a bad phase difference between lateral velocity calculated by a bicycle model and from the measurements?
My cornering stiffnesses and other parameters are correct. The magnitude of yaw rate and lateral velocity that is calculated by the model matches the measurement, and the phase of yaw rate is almost same as the measurement.
The data obtained is from a sinusoidal steer of a car.
In case of a bicycle model, the influence of side angle during cornering has to be considered - similar as it is for motorcycles. This includes mass of vehicle, mass and position of driver, vehicle geometry (eventually under consideration of suspension), and shape of tire. In this way, influences of yaw rate and steering angle are diffentent to those of a car. You might find more information in motorcycle danamics-related literature, eg. the book of Vittore Cossalter (Motorcycle Dynamics), or Gaetano Cocco (How and Why Motorcycle Design and Technology). In addition there is multi-body simulation available, e.g. from simpack.
Kind regards,
Mario
Sorry Mario, but a bicycle model isn't a model of a bicycle! It is a car model, with the width compressed to zero. Roll is ignored, but pitch, yaw, lateral, longitudinal and vertical velocities can all be very close to a full four wheel model.
With regards to the question, the first thing I would check is whether you are measuring the lateral velocity at the same place. Although vehicle dynamics is often measured at the CofG the side-slip is far easier to understand if considered at the rear axle. With yaw it wouldn't matter, but with lateral velocity it does.
Dear Peter,
oops, then I understood the question wrong. A bicycle-car model, which describes a simplified dynamics behavior is known as "single track model" and was introduced by Rieckert and Schunk in 1940. In this model, there are several simplifications assumed, e.g. the center of gravity of the car is at zero z dimension. In this way, there is no vehicle rolling movement considered. Regarding the question of Sampath: If the measured yaw rate corresponds with the calculated one, but the lateral velocity does not, the tire parameter should be observed. In addition, measurement always considers suspension behavior and vehicle rolling, but the single track model does not. In view of side slip behavior evaluation, it sould be distinuished between over steering and under steering vehicle: The singel track model gives a clear definition for both (as function of geometrical dimensions, tire behavior and longitudinal position of the center of gravity in relation to the front and rear axle).
Kind regards,
Mario
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