Quote:
Originally Posted by walile
First of all, I sincerely apologize to everyone for 
I have to be honest, I went out for a Tim Hortons coffee and comeback impressed. Makes me wonder if it's the same person. |
Well thanks for your approval and the backhanded complement.
Quote:
Originally Posted by walile
Just want to point out that
- There is at least one active rear differential implementation that track reference signals but the control algorithm is very tightly coupled with the entire AWD system and it's not Mitsubishi. I think we can agree that you can have both feed forward and feed forward + feedback design.
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Go read
this
Quote:
Originally Posted by walile
If Audi Sport Differential is a simple feed forward system, to be honest I am surprised. At thisday and age, it seems a bit primitive. But then again, it doesn't have active center diff to dance with. Might as well KISS.
- I philosophically disagree with the Porsche implementation. Braking system IMHO should be used for reducing vehicle speed or ESP applications, not to help it go faster! Even though I do acknowledge some advantages of that design. Namely the cost and weight saving.
- We certainly have a fundamental philosophical disagreement on system design.
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Simpler is better if the purpose is served, since you are such an expert on control systems, what do you recommend auto makers do? Do you realize how complex the interconnections are, and the fault mechanisms built into CAN? The cost constraints for a mass produced/low margin product are not trivial.
Quote:
Originally Posted by walile
To me, a Torsen or crown gear based system is both primitive and inferior. Sure it's the feed-forward control design that you love so much. But what it really is saying is that hey all the behaviors of the system is programmed mechanically into the design and is passive in its nature.
As you pointed out yourself that ideally you want less power to the front wheels during corning. Well, can the Audi system proactively shift more power to the rear as steering input is detected? NO!
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You have been putting *a lot* of words into my mouth. The torsen is NOT feed forward, what are you talking about? I pointed out that a torsen/mechanical center diff is better at minimizing wheel slip as it does not require any estimation, it just does it. I never said it was better in corners or anything of that nature. Previous versions of Audi vehicles have suffered from understeer horribly. First change was to increase nominal gearing to 40-60, now they have included active rear diff. More torque will naturally go to the rear wheels when accelerating because the vehicle will pitch backwards and there will be more available tractive force. Electronic center diffs are more useful for rally racing, where wheels can go off the ground.
Quote:
Originally Posted by walile
The GTR ATTESA E-TS is an incredible system, certainly did not archive such incredible performance using a simple feed-forward design.
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Huh, wtf does this have to do with feed forward design? The GT-R is built from the ground up to be a race car and the control system is necessarily very advanced and highly tuned. This is not the same system as xdrive which comes on a 320ix 32k car. You pay *a lot* of money to maintain this cars drivetrain.