How can i import a ".tir" Pacejka file which has PAC2002 file format.

Question

I have a Pacejka tire model file (".tir") and i am trying to import it into VPP. I've read your instructions about "Converting an existing Pacejka set to VPP" (Blocks->Tires). However it is not so clear for me what "x" represents there and what kind of graph i should have so i can fit a graph with toying the parameters which VPP accepts.

Thanks in advance.

Answer 1

x is the variable in the function. Following the instructions in the documentation, you have to compose a function y = f(x) where everything are constant values except the x, then draw it.

That x represents the tire slip velocity in m/s. For the longitudinal formula x is the tire's longitudinal slip velocity. For the lateral formula x is is the lateral slip velocity. This way the each function yields a coefficient of friction based on the slip.

Once you have the function drawn you should be able to identify the key parts, such as the peak friction and its x,y position in the graph. You can then use those values to approximate the function in the VPP Tire Friction inspector.

Comments

- If i didn't get it wrong i will have 2 graphs for lateral slip velocity and longitudinal slip velocity. How will i combine them?

- And i have min allowed wheel load and max allowed wheel load in the pacejka model. Which one should i use as "N"?

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- Current tire model in VPP is isotropic, that is, uses only a single curve that is applied in all directions. I'd use an intermediate curve, biased to one or another based on the specific behavior expected.

- For N I'd choose the weight to be supported by the tire when the car is at rest.