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dfacchin

Pacejka formula need help

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Hi everybody, I can't understand one thing on the use of pacejka formula. Pacejka gives the longitudinal,lateral and momentum on the tyre(applied to the contact point/patch) with in input longitudinal slip / lateral slipangle and camber(adjusted formula for motrobikes). Now let assume that the wheel is not moving and we are at time 0=t0 and working with a fixed timestep of 500Hz t0: I go and apply a torque to the wheel, pacejka generates no forces becouse the will at time 0 has no slip (bike is not moving and the wheel spin velocity is 0) the wheel will start to spin as it's in the air but generates no force to move the bike t1: now in the next timestep I will apply more torque plus now pacejka will generate a force(let use only the longitudinal force) that is due to the spin of the wheel generated at t0, the force generated by pacejka is opposite to torque evolution direction. The wheel will move with a force equal to pacejka and the total torque to the wheel will be the torque that I applied - the foce generate by pacejka formula. now the wheel rotates with an internal energy of [2*(toque applied)-Pacejka(t1)]. but if my first step is bigger than 500Hz, let's say 100Hz, the Pacejka force at t1 will be calculated with a much bigger longitudinal slip, so it will generate a bigger force. So how do u compute the first longitudinal slip???? Maybe I understood the formula in the wrong way?? One more thing, I'm using a raycast to find the contact point of the wheel and I have no wheel spinning in the simulation. Wich is the best way to controll the wheel spin velocity if I don't really have it? Hope someone can help :D! CIAO

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I will give a look at it, but I think that racer (I already looked at the code) uses a cylinder primitive for wheels, and calculates the longitudinal slip from it somehow...
I'm using a raycast to dimulate the wheel shape, and I guess things have to be different.

tx anyway.
I left a message on ur AC forum with a better explanation of my problem, if u have time to read it :D

cya

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