Quote:
Originally posted by SuperDanman
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.
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Extremely! (whack whack whack...
) I was wondering about the wear and heating effects, too. That's a LOT of hammering while clutching. (I'd be tempted to add a pneumatic clutch just to reduce the noise and wear on the joint!
)
Quote:
Originally posted by SuperDanman
Now for my real problem with this design: from a programmer's point of view, this is a complete nightmare. Something like this cannot easily be determined from motor curves alone. This is going to require testing, testing, and even more testing. [...] 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).
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Well, I'm not so sure. IMO, the solution to that will be in adding "appropriate feedback sensing" to make it a closed loop system.
The question then becomes:
What data do you need to collect to determine the case, and appropriate control action? In some way, you'll need to know a loading factor per motor, and to sense an imminent motor stall condition.
Off the cuff, current monitoring of the motors may yield enough data to determine the case and close the loop, but you may also the true speed of the motor with either encoders or "PWM off phase generator speed sensing" as well.
Note that to prevent backdriving, you can always include some kind of a mechanical antibackdrive system in each motor's train (like worm gearing, or backdrive pins). Another option would be to wire the coast/brake jumper to switch the Victor into braking mode under program control. I'm just curious though how much back drive the Schottky kickback diodes within the Victor's MOSFETs can safely take before popping!
I agree with you, Dan. Dropping
this one onto the programmers in week 5 (or 6!) without even a proof of concept prototype, and somehow expecting them to "figure it out" would
NOT be a good idea (and possibly suicidal). This is
definitely a case where "off season prototyping" experiments are in order before you even
consider choosing it.
- Keith Mc.