Estimating Tire Parameters Using GPS
Accurate estimation of tire force-slip characteristis requires
measurement of vehicle acceleration, velocity and wheelspeeds. Until
recently it has been difficult to measure absolute vehicle velocity,
estimation schemes relied on some sort of state observers and intertial
sensors. Recent work here at Stanford uses GPS velocity to directly
measure absolute velocity accurate to 2 [cm/s].
Several research groups propose that tire longitudinal stiffness at low
values of slip may indicate the tire to road friction coefficient and thus
the peak value of the force slip curve. Our work here shows that
longitudinal stiffness estimates exhibit considerable sensitivity to tire
inflation pressure, normal loading, tread depth and temperature. This suggests
that any analysis which seeks to identify these properties must carefully account
for at least these test conditions.