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bronxbomber92

Inputs for Pacejka Magic Formula

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I'm re-implementing the pacejka formula and some car physics, and I just realized a major flaw. How do you actually get the car moving? What I mean by this is that the only inputs to the magic formula are the longitudinal slip and slip angle. These are calculated like so (pseudo comments I wrote):
/* COORDINATE (positive, negative): X IS FORWARD/BACKWARD, Y IS RIGHT/LEFT, Z DOWN/UP
 * To find K (longitudinal slip):
 *		 K = (-Vsx/Vx)
 * 		where Vsx = longitudinal speed of the contact point with respect to woorld coords.
 * 			  Vx  = longitudinal speed of the contact point with respect to the road plane (ground velocity) 
 *		ex.)    (reverse the order of this example, slip_x is what were trying to calculate)
 *			slip_x = k / max_peak_slip;
 *			K = 100.0 * (patch_speed - hub_velocity.x) / denom;
 *
 *			double denom = std::max (std::abs (hub_velocity.x), 3.0);
 *			patch_speed = speed();
 *			hub_velocity = m_velocity;
 *
 *			speed() = (rotational speed of the tire in radians per second) * radius;
 *			m_velocity = m_ground_velocity;
 *
 * To find alpha (slip angle):
 *		alpha = arctan(Vsy/|Vx|)
 *		where Vsy = Vy, and Vy = lateral speed in the contact point with respect to the road plane (ground velocity) 
 * 			  Vx  = longitudinal speed of the contact point with respect to the road plane (ground velocity)
 *		ex.) alpha = -rad_to_deg(atan2(hub_velocity.y, denom))
			
 */
I see nothing in there about any type of acceleration from gas resulting in a torque, or a brake torque, or steering torque. So, my question is, how do I go from the brake, drive, and steer torque to the two slip inputs for the magic formula? Thanks a lot! -Jedd

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