MAVS Tire Model

MAVS uses a radial-spring tire model to calculate the normal force on the tire caused by interaction with rough terrain. The radial spring tire model is not used to calculate the lateral and longitudinal friction, which are handled by the VTI model. Rather, the spring tire model is only used to calculate the normal force, taking into account terrain geometry and tire deflection. This is used as input to the VTI model.

The tire model in MAVS is based on the 1975 paper by D.C. Davis, [A radial-spring terrain-enveloping tire model]. In that work, the concept of equivalent deflection is introduced. For an irregular terrain profile and tire position, the overlapping area between the terrain and tire is equated to the area that would produce the same deflection on a flat surface. This equivalent deflection is used to calculate the normal force. 

In the MAVS radial-spring tire model, the overlapping area is converted to an overlapping volume, which is in turn used to calculate an equivalent deflection. This equivalent deflection is then used as a driver to a linear spring-damper system representing the dynamic state of the tire.