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bmarci

[Car physics] Force feedback and such enjoyment

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bmarci    786

Hi,

I started playing with force feedback wheels, and as I noticed this is the point where most people had already given up or it's just simply out of their interest.

Anyway, I'm having a hard time finding good writings about decent force feedback "simulation", so I have to take the hard way, figuring it out.

Hopefuly some of you are also into this topic :)

 

Here are some notices and questions that arose:

 

- There is a strange behavior even if driving straight, the steering wheel wants to "go slalom", I noticed the same effect with some AAA driving game, but not with Gran Turismo. Maybe it's the toe-in or camber that generates some torque, which are not equal for both wheels and "magnifies" with speed. My quick solution is to have a dead-zone and some damping at the center, so I can release the wheel at 300km/h and not hitting the wall :)

But it feels there is no grip around the center. It builds up as I turn but not instantly.

 

- I'm using the good old Pacejka to get the aligning moment, but it not incorporates the caster angle, is that an important factor, or can that be neglected? Also, where should the Mz curve's peak be? At the peak of Fy's? Or should it go back to zero at Max Fy?

 

- Road surface feedback is what I did yesterday. I'm using constant force for aligning moment, so it seemed obvoius that I should add some "noise" to the current FF force depending on the surface, but it just doesn't make that rumble effect that I expected. Am I on the good way or should I turn my attention to custom FF effects?

 

That's all I can remember now, and thanks for every help, ideas and opinions...ect.

 

 

By the way, this is where I'm now:

http://www.youtube.com/watch?v=sgzUXGlk9Uw

http://www.youtube.com/watch?v=MPhjCDPMizE

http://www.youtube.com/watch?v=WX7x-QIG8sk

 

 

 

 

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lomateron    491

this comment is not about physics but about controls 

 

I don't know why all racing games on PC do not support mouse for steering the wheel, it will be much more accurate than using the keys

So you should add mouse support instead of keys and change that rare tradition

Edited by lomateron

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bmarci    786

I don't know why all racing games on PC do not support mouse for steering the wheel, it will be much more accurate than using the keys

So you should add mouse support instead of keys and change that rare tradition

 

Yes, the Racer does support mouse, and it's pretty weird, but it's only my opinion. :)

The keyboard support is already there and works very nicely, even easier to control the car with keys, but the wheel is much more fun.

I tried the mouse at the early stage, but it didn't work out.

 

mixing keys and mouse might be an exciting idea :D

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bmarci    786


If you move the mouse to the left the wheel will rotate to the left and mantain that position,how can't that work?

Obviously :)

But, in case of mouse you don't have any physical feedback of the steering wheel's whereabout, and that becomes very annoying at high speed.

Even with the FFB wheel, a few percent of dead zone is needed, otherwise the car will never go straight.

 

I played around with the mouse steering for a couple of hours.

I added some dead zone, damping and speed sensitivity, but still having problems with small "correction" steering at high speeds.

Maybe those issues could be overcame in time, though.

Anyway, it was an interesting idea (throttle/brake with keys and steer with mouse)

 

 

But back to the original topic, any idea, anyone? Sim gurus, where are you?? :)

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Hodgman    51234

Sorry to continue the off-topic -- the old version of the CarX demo used to have mouse as lomateron described, which I really enjoyed despite there being no feedback. The new version of the CarX demo tries to simulate feedback by moving the wheel in response to wheel forces, so you have to keep moving the mouse to 'fight' against it. Kinda-sorta works a bit, but I actually prefer their original implementation wink.png

 

I'm not sure what's the cause of the "going slalom" wheel when driving straight -- I have also seen this effect in many sim games. I've never tried it in real life to see if it really occurs laugh.png

I always thought it was a side-effect, caused by momentum in the steering wheel peripheral. That is, the game applies a force to the steering wheel to make it return to centre, but the wheel over-shoots past the centre point and begins to turn in the other direction. This makes the car begin to swerve in the game, and makes the game apply an opposite force to the wheel, making it shoot back in the other direction (and again shoot past the center and continue the swerving motions). As this happens, the car begins to lose grip, so the swerving gets worse and worse...

I'm not at all sure about this hypothesis though.

 

P.S. your project looks very impressive biggrin.png

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bmarci    786

I read somewhere, an old sim (maybe GPL) used some kind of force feedback prediction.

Since the devices have some latency (10-20ms) it could be useful to set the future Mz instead of the current.

 

used_mz = mz + ((mz - last_mz) * prediction_time) / dt;  << or something similar :)

 

I tried this in the weekend and didn't feel much difference. Still damping at the center, so more to the center the wheel gets the less the FFB is set to.

An other idea is to damp the FFB depending on the turning direction instead of the position.

Haven't tried it yet... I'llkeep you updated.

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