TrackFriction

trait TrackFriction:
    .doc: """
    The TrackFriction trait is intended for use to model friction in
    tracked vehicle systems, where friction properties differ
    between the longitudinal and transversal directions of the track.

    The primary_direction defines the longitudinal direction of the track,
    i.e., the forward (tensile/rolling) direction along the track path.

    The secondary_coefficient defines the friction coefficient in the
    transversal (lateral) direction. This direction is orthogonal to both
    the contact normal and the primary_direction, representing the track's
    resistance to sideways motion.

    Example:
    In the example below, the TrackFriction trait is added to the
    DryConstantNormalForceFriction model. This model is the fastest
    friction model from a performance perspective, but other models,
    such as DryBoxFriction, are also suitable.

    MyDryConstantNormalForceFriction is Physics.Interactions.Dissipation.DryConstantNormalForceFriction:
        with Vehicles.TrackSystem.SurfaceContact.Traits.TrackFriction
        secondary_coefficient: 0.1    # Friction coefficient in the transversal direction

        coefficient: 1.0              # Friction coefficient in the longitudinal (track) direction
        normal_force: 1000            # Constant normal force
    """
    secondary_coefficient is Real