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Unread 28-09-2003, 14:13
DanL DanL is offline
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Re: "Automatic Transmission"

Getting in on the action of this thread, albeit a week or so late, here are my thoughts....

First, I think someone mentioned this before, but I'll say it again: this monster's going to be loud when it's slipping/drill motor turned off to save power. I also can't help wonder how all this slippage and slamming of the plates will hold up. Mechanical things aren't my forte, but it seems that, especially at the CIM's higher RPMs, this is going to cause a lot of wear and breakage, not to mention heat. Rather than 'turning off' the drill motor when going fast, I'd use some more power and put the thing in low so the relative motion decreases and there's less slamming of the plates.


Now for my real problem with this design: from a programmer's point of view, this is a complete nightmare.

Quote:
Originally posted by M. Krass
Well, during that time, so that it doesn't drag on the system, we also want the Chiaphua motor to be spinning -- but we don't want for it to see any load. To accomplish that, we have to employ our second "disconnect," but this time it's an electronic disconnect. By varying the voltage to the Chiaphua via PWM output, we can make it such that its free speed corresponds with the current drill motor speed while under load. This is our electronic clutch.
Something like this cannot easily be determined from motor curves alone. This is going to require testing, testing, and even more testing. You can't wait three, four weeks to build this gearbox and possibly expect the programmers to have the e-clutch figured out in a few days. I've begun thinking of several ways on how to calibrate this, but regardless, the programmers need a lot of trial-and-error time to get the e-clutch working at max efficiency. Another thing, it seems to me the 'golden values' would be different at 12 volts than at 10, 9volts (seeing as more voltage causes the motor to spin faster). Once your voltage begins dropping in those last 60, 45 seconds of the match, it seems to me like the efficiency of the e-clutch will be going down and down.

M, it's an interesting idea, but as I understand it, if anyone implements it, that person better hope he has very talented/patient programmers with plenty of time to find the magic values. Someone correct my ideas if I'm wrong, though - like I said, I'm an electrical guy, not a mechanical one...

[edit]
Thinking about it even more, there seem to be just so many variables to take into account to get it working at max efficiency - the voltage of your battery, the drill motor load rpm vs. the cim no-load rpm (is the relationship linear, or is it complicated?), the actual amount of load or resistance to motion being expierienced, the wear (and so, the changing coefficient of friction) on the clutch plates, differences in individual motors (you'll have to calibrate each side seperately), and probably more to be discovered. If even one of those changes, the programming is going to have to account for that. This idea is going to be like jamming an iron rod through your programmer's face.
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Last edited by DanL : 28-09-2003 at 14:28.
 


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