scpeters
commented
3 years ago Here is an illustration of normal contact forces for rigid and deformable wheels on a rigid surface
At rest, a deformable wheel may have a symmetric distribution of normal contact pressure, such that the equivalent normal force points directly at the wheel center. While rolling, the wheel deformation may "bunch up" in the direction of travel and bias the pressure distribution, such that the equivalent normal forces is in front of the wheel center. This generates the rolling resistance moment that can be modeled as a friction constraint.
Upstream ODE supports the friction pyramid model with friction force constraints in two tangential directions, as described in gazebo's physics parameters tutorial. In bitbucket pull request 1831, our fork of ODE was modified to support a torsional friction constraint, which constrains the rotational velocity component parallel to the contact normal (see [tutorial]() for more details). After reading a paper entitled "A complementarity-based rolling friction model for rigid contacts" (doi:10.1007/s11012-013-9694-y), I now realize that we can apply the same approach used for torsional friction to implement rolling friction, but applied to rotations about the
fdir1andfdir2axes instead of the normal axis.This will be most useful in modeling rolling resistance of deformable objects on a rigid surface, such as a pneumatic tire on a road.