What is default Mu for Vehicle Body 3 DOF block?

The 3 DOF Vehicle Body block in the Vehicle Dynamics Blockset uses in its forces equations, but I can't find the default value for this parameter anywhere.

I see the option to enable specifying as an input, but I want to know what μ will be if I don't explicitly pass it.

I also see mu, which is a friction scale factor, but that's not the same thing.

Does anyone know what the default value is or how to figure it out?

Answer 1

[Paul]

As best I can tell, if the [mu_r, mu_f] vector is not specified externally, then the block uses the parameter specified in

Nominal friction scaling factor, mu

for both mu_r and mu_f as long as Axle forces is set to one of these options:

• External longitudinal velocity
• External longitudinal forces

You can test this by first specifying a value for "Nominal friction scaling factor, mu" and simulating and then turning External friction — Mu input port to 'on' and using the same value as in step 1 in a two-element Constant vector as the external input and simulate again. When I did this with constant xdotin and WhlAngF inputs I got identical results for the inertial displacement in the Info bus.

[Daniel]

Hm, that does seem to be the case, but is very shocking to me. No realistic tire will have a friction coefficient of 1, so I was thinking the nominal friction scaling factor had to be just some other scale factor, not an actual coefficient of friction.