Your new slip ratio method is very similar to the classic relaxation method (referred as SAE950311) Somehow that one didn't work out for me, even I spent about 20 bucks on that ?
Your traction forces (yellow lines) seem a bit off, at this speed they mustn't be that “chunky”, especially on the front wheels. Also, not sure, but the pacejka graphs seem too steep, at low speed they shouldn't reach the max “instantly” (I have to double-check with mine). Apart from that the low speed oscillations are there, but they instantly vanish when the car starts rolling. You should plot the longitudinal pacejkas as well ?
Lewa said: What i noticed is that if i manually override the lateral velocity of the front tires to 0 during this U turn maneuvers the car “corrects” itself which looks more natural. I have no idea if that's expected behaviour with the current implementation or if i maybe read out/apply the tire forces incorrectly via the bullet api.) For me it looks like during turning the tire forces at the front should be reversed. (Maybe the inertia is not accounted for if velocities of localpoints are retrieved via the physics API.)
The lateral velocities look perefctly fine for me. The direction of forces also look correct, the lateral amplitude is ok, but the longitudinal jumps are too much, they should be gradual at this speed.
You can also try “disconnecting” the engine when you reached enough speed, and see what happens. Engine torque can easily trick you in real life, if you suddenly lift of the throttle you get snap oversteer and spin out at once.
So, it turns out that the method i'm using also exhibit issues depending on what value is used as “B”. If you set the value too high (like 0.91) it fixes the oscillation issue but the sideeffect is that the car doesn't have full traction during acceleration (i noticed this the most if it park my car on a slope and start accelerating. The wheels start out with almost no traction, start spinning really fast and thus loose traction due to the pacejka curve after its peak tractionforce.) Which in turn means it can't move up a slope from standstill. Setting the value lower (like 0.091) fixes the traction issue but it then starts having the oscillation issue with the tire rotation again. (Maybe it's possible to find the perfect value of “B” for a the given cars parameters but it's not a universal solution.)
CasualKyle said:
You've probably already checked this but in the off chance you haven't, while your car is turning, are all four tires on the ground?
I ask because I actually encountered this oscillation situation with my rudimentary car physics. I noticed while I'm cornering say to the right (although it happened in both directions), the front right tire and back right tire lifted off from the ground. This caused the car to not turn as much since only two tires were applying friction forces on the car. During the turn eventually gravity would pull the car down and all four tires would make contact which would causes an overall greater cornering force so the car would then turn a bit faster. But this overall greater cornering force then caused the front right and back right tires to lift off again. This loop caused the car to kind of of oscillate back and forth during turning.
I fixed it by simply changing where I apply the friction forces. In the picture below I used to apply them at point A, right where the suspension ray cast (green line) attaches to the car. Now I changed the position to point B. By raising the point up to be in line with the center of the car, any lateral friction forces will not cause the car roll.
Perhaps I could've also fixed the problem by giving the car more mass but my rudimentary physics engine isn't quite setup for rigid bodies with masses yet.
Anyway, this is just what happened with me so sorry if none of this applies to your problem.
Have to try that out. I apply the velocities directly at the contactpoint of the raycast (where the tire hits the road/ground.)
I ended up removing the suspension force from the equation as no matter how much i was tweaking it the car was either understeering or heavily oversteering. (Making it really hard to finetune the handling for an acceptable driving behaviour.) So now the suspension has no influence on the cars traction.
