FFB frequency

Ok @pankykapus , i could understand that for physics calculations but what about FFB?
G27 has a maximum of 500hz , 111 is less than 1/4 than that.
I do admit that trying the half rate in AC = 333/2 , i couldn't understand any difference. I just hope that 111hz are enough.

 

If anything it might impact only DD users. Doubt any belt or gear driven wheels is fast and sensitive enough to show the difference.
On DD the worst could happen is bigger stair steps effect in the signal due to missing physics samples.
It can be smoothed with some filtering, so cogging might not be a problem, but some information will be inevitably lost, there is nothing you can do about it unless you match physics and ffb rate.
Still 111 samples in a second is awfully lot.

 

Maybe like this guy they also know what they are doing.

 

It needs 4 samples per second according do Nyquist/Shannon. That's what is taught in communication electronics at the university. That's why CD's have a samplerate of 44100 Hz - a bit more than double of what humans can hear (young people with goooood ears: 20 kHz). I didn't miss that point, I made that point.

 

I doubt my aging nervous system would have much hope of distinguishing between 111 Hz FFB updates and 1 kHz updates.
Moreover, regardless of the rate at which the digital electronics is prepared to accept new FFB data, what really matters is the bandwidth of the power electronics which drive the motor. I have no clue how fast my own G27's electronics run (tho I might now be tempted to try and find out ), but it does seem reasonable that the DD wheels are likely to be quicker. In fact... the OSW system probably has enough data on the web for it to be trivial to find out. Just stepping outside for a moment; I may be some time...

 

It's 333Hz and 111Hz.
You can just go to
Users\asb\Documents\Assetto Corsa\cfg\controls.in
and set

Code:

[FF_SKIP_STEPS]
VALUE=2

I think this is the right number to set, someone correct me if not.

And see if you can detect any difference with your wheel or not. Not apples to oranges but will give you some idea on expected effect.

Some details on what that param does
https://www.assettocorsa.net/forum/index.php?threads/physics-and-ff-frequency.31453/

 

Yeah I know, I was just choosing a "large" frequency to accompany the point I was making But ironically... see below.

I realise I've still never played with that. It's set to 0 right now, but (thanks for the thread link) it does appear safe to set it to at least 0,1,2. I see no reason why I couldn't make it 3 or 4 in fact, at which point I just might be able to feel the difference

And the results are in. Depending on the particular motor, and how clever the motor controller wants to be (I think they are mostly pretty clever), it seems like you should be able to get the torque to change from max CW to max CCW (while you're holding the wheel stationary) in less than half a millisecond.
So... WOW! No game is ever gonna send updates quickly enough for the motor + power electronics to be the limitation. (I haven't yet figured out what the max update rate is for the OSW digital interface though.)

 

I really doubt ANY FFB system could react in ANY way in less than half a millisecond, the electronics, sure, the mechanical bits, motor etc., no way.

 

Well, with the caveat that I don't own one, the calculation is really simple for the case I described: the wheel is being held stationary by the driver (e.g. in a corner, hitting kerbs or whatever) and then the game wants to change the wheel torque - let's say from maximum in one direction to maximum in the other.
The controller receives the command, and the voltage to the motor changes very rapidly to a very large value (like > 200 V), and then only the motor coil inductance limits the time taken for the current to change (at which point the voltage gets really small again). If you throw the numbers into a calculator (couple of hundred volts, 4.5 A max current, 8.8 mH line-line inductance), sub-millisecond is what comes out. Remember that these things were not designed for human interface stuff - they are industrial servo systems.
NB: there's absolutely no physical movement of the wheel in this scenario, which is just one of many relevant scenarios for a sim-racer.
I agree that you'll need to worry about moments of inertia etc. if you want to work out how far/fast the wheel can move in a given amount of time, but that's an entirely different question than the one I'm addressing.

 

That theory only applies if what you're reconstructing the analog signal with has a low-pass filter at the same spot (which soundcards take care of) just sending a 2Hz binary signal to your audio output would make it go 'click' every half second.

 

I follow the reasoning behind the post by panky, but the fact remains that in Iracing, the mod that ups the frequency from 60hz to 120hz was a night and day difference. Suddenly I could actually feel the tires flexing under load!

I could be comparing apples and oranges though, with how ir implements ffb and how ac / acc implements it.

 

It is easy to spot the difference between FF_skipsteps 0 and 1. 1 is higher tick rate than 111Hz will be. Therefore I think it's reasonable to expect some faces.

 

Maybe it's easy for you, with your wheel and whatever car you were using.
I just had a go at playing with different skips. I may have chosen the wrong car tho - I just used the last one I was driving which was a GT86.
I tried skip=2 - felt the same. Skip=6 - felt the same. I thought I was doing it wrong, so I made it 24 (!!!) and then I could finally feel it
Knowing how it felt by this stage, I went back and compared 6 and 0, and still couldn't detect the difference...

However I might need a more responsive car to really make it noticeable.
Perhaps (given that we're talking about ACC, LOL) I should try again in a GT3.
But maybe the G27 just doesn't respond very quickly...

On a different note: ACC might also be using a more clever algorithm than AC for controlling the FFB torque, and that could conceivably make up for a lower update rate.

 

Normal, nothing to be proud or ashamed of. Same as listening high def classical concert via Apple earbuds and trying to distinguish between 128k MP3 and FLAC file.

 

The low pass character of the signal chain is indeed what makes it work, IIRW. Thanks for the addition. For your speaker example: if you increase the click frequency, even the speaker's low pass behaviour would turn that into a wave.

Of course you can't "draw" a pretty sine wave in a diagram with samples=2*frequency.

But not only in digital to analog audio conversion this method is used. Can be used in many D/A scenarios and it should in order to reduce datarates. Dunno about FFB wheels but I'd be impressed if it wasn't. Do you know?

 

@pankykapus

Of course you're right on this but...

..a downside will be still a downside.

 

Unless the gains are bigger than the loses.

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Why do you guys sit around all day, every day, looking for reasons to be sad? Do you really think that Stefano would have chosen whatever number he did if it made the ffb feel like ****? I doubt that Stefano would choose a value that is going to make your thousand dollar placebo generator feel worse than a DFGT. And if he did then get your refund and join an AMS or RF2 league. (or buy a plebe wheel and deal with the fact that you are playing a $50 video game)

 

...its nothing about this Michael.
Its just a question. Nothing more nothing left.

Edit: And if you're interest in the game there should be of course questions

 

Guys next time , before you ask any questions, you need permission from the trolling lawyer and his sharp teeth...

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