Full vehicle model help

I'm trying to model a full vehicle with 8 dof:

• surge
• sway
• yaw
• roll
• rotation of wheels

I'm using a SAE coordinate system:

• x forward
• y to the right of the driver
• z down

I use Pacejka's formula for the calculation of longitudinal and lateral forces. These are the basics equations:

http://s5.postimg.org/z97j0ieg7/Equazioni1.png

http://s5.postimg.org/6an2dxxnr/Equazioni2.png

As regards notation

• AS is front left
• AD is front right
• PS is rear left
• PD is rear right

Can anyone help me to find out if I made modeling errors and to tune the model?

It seems to me the main problem is longitudinal slip. I do not understand which convention should I use. Inside Pacejka's book I found this:

I also found different formulas for driving condition where at denominator there is r*omega.

I find strange behaviours in the model, for example if I try to plot longitudinal rear force vs longitudinal slip. If I make a simulation without steering I get non zero values for roll angle, yaw rate, lateral velocity.

Now I'm using a step size of 0.001. Before I was using 0.01 and the graphics look like they came from experimental data.

Answer 1

[Steve Miller]

I suggest you look at this model:

https://www.mathworks.com/matlabcentral/fileexchange/110350-vehicle-dynamics-14-dof-model-in-simscape-multibody

--Steve