Go to Post [I] [/I]I think this may be some kind of record. We got through 9 entire posts before someone mangled the spelling of mecanum. [I] [/I] - Ether [more]
Home
Go Back   Chief Delphi > Technical > Technical Discussion
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
 
Thread Tools Rating: Thread Rating: 3 votes, 4.67 average. Display Modes
  #1   Spotlight this post!  
Unread 26-10-2003, 15:41
kmcclary's Avatar
kmcclary kmcclary is offline
Founder 830/1015;Mentor 66/470/1502
FRC #0470 (Alpha Omega Robotics)
Team Role: Engineer
 
Join Date: Aug 2001
Rookie Year: 1994
Location: Ann Arbor, MI
Posts: 491
kmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond reputekmcclary has a reputation beyond repute
How about a custom circuit feedback sensing system?

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.
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).
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.
__________________
Keith McClary - Organizer/Mentor/Sponsor - Ann Arbor MI area FIRST teams
ACTI - Automation Computer Technologies, Inc. (Sponsoring FIRST teams since 2001!)
MI Robot Club (Trainer) / GO-Tech Maker's Club / RepRap-Michigan) / SEMI CNC Club
"Certifiably Insane": Started FIVE FRC teams & many robot clubs (so far)!
2002: 830 "Rat Pack" | 2003-5;14: 1015;1076 "Pi Hi Samurai" | 2005-6: 1549 "Washtenuts"/"Fire Traxx"
2005-(on): 1502 "Technical Difficulties" | 2006-(on): FIRST Volunteer!
2009-(on): 470 "Alpha Omega" | WAFL | Sponsor & "Floating Engineer" for MI Dist 13 (Washtenaw Cnty)
2011: 3638 "Tigertrons" | 2013-(on): 4395 "ViBots" | 2014-(on) 66 "Grizzlies"
"Home" Teams: 66, 470, 1076, 1502, 4395
Local FIRST alumni at or coming to Ann Arbor (UM/EMU/WCC/Cleary)?
...We Want YOU as a Mentor! Please email me for info!
Support CDF Reputation - If a posting helped, thank 'em with rep points!
"It must be FRC build season when your spouse and children become 'Action Items 8 & 9'..."
Closed Thread


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 22:01.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi