Go to Post It isn't what you're given that makes it awesome. It's what you do with it. - JosephC [more]
Home
Go Back   Chief Delphi > FIRST > General Forum
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
Thread Tools Rating: Thread Rating: 2 votes, 5.00 average. Display Modes
  #16   Spotlight this post!  
Unread 23-01-2007, 17:29
Dan_Karol Dan_Karol is offline
Mentor and Coach
AKA: Daniel Karol
FRC #0131 (CHAOS)
Team Role: Mentor
 
Join Date: Dec 2006
Rookie Year: 2004
Location: Southborough MA
Posts: 63
Dan_Karol has a spectacular aura aboutDan_Karol has a spectacular aura about
Send a message via AIM to Dan_Karol
Re: PID How to hold an arm in a fixed position without a locking gear box

This might help you,

This is our team's robot from 2005. On the first stage of the arm we used two of the 6v FP motors (they messed up that year and gave a bunch of teams the wrong motor). On the second stage we used a single van door motor. We used cable and bicycle wheels to gear down the main arm about 18 to 1* and we geared the small arm down to about 9 to 1*. It had no problem holding a single 9 lb tetra 13' out. Here is a link to a picture of the robot.
http://www.chiefdelphi.com/media/photos/21524

As for programming we used a potentiometer on each arm and compared the value they gave us to a target position for the arm. Based on that information we passed a value to the motor to move.

If you have any questions please feel free to ask.

-Dan Karol


*numbers are a guess and may not be what we actually used.
__________________
2004 - 2012: Team 1100
2013 - ????: Team 131

Last edited by Dan_Karol : 23-01-2007 at 17:33. Reason: I didn’t answer all questions
Reply With Quote
  #17   Spotlight this post!  
Unread 23-01-2007, 20:40
Rickertsen2 Rickertsen2 is offline
Umm Errr...
None #1139 (Chamblee Gear Grinders)
Team Role: Alumni
 
Join Date: Dec 2002
Rookie Year: 2002
Location: ATL
Posts: 1,421
Rickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant futureRickertsen2 has a brilliant future
Send a message via AIM to Rickertsen2 Send a message via Yahoo to Rickertsen2
Re: PID How to hold an arm in a fixed position without a locking gear box

While some of the motors may "take the heat", its a good design practice to attempt to minimise the load on the motor when the assembly is static. Counterweights help greatly with this. Another option is gas shocks like the ones used to hold up car trunks and hatchbacks. They not only put out alot of force but provide some dampening. Worm gears are definately a good idea as well. I would highly recomend them. I should note that the gearset in the van door motor is NOT a worm gear set. It is a healical gearset which can be backdriven.

Also, if you plan on using PID, you must make every effort to minimize the amount of backlash in your system or else put the sensor directly on the motor. Chains are especially bad about backlash unless active tensioners are used.
__________________
1139 Alumni
Reply With Quote
  #18   Spotlight this post!  
Unread 23-01-2007, 21:06
Justin M. Justin M. is offline
Mechanical/Driver
FRC #0321 (RoboLancers)
Team Role: Mechanical
 
Join Date: Jan 2005
Rookie Year: 2005
Location: Philadelphia, PA
Posts: 310
Justin M. is on a distinguished road
Send a message via AIM to Justin M.
Re: PID How to hold an arm in a fixed position without a locking gear box

Keep in mind that when you need high-torque motors (like in a programmed non-back drive mode), it helps to use two of them, if possible. If you wire the two motors together (+ to + - to -, then the combined + and - to the victor controlling them), now you are taking two circuits and combining them into one, distributing the power evenly. Not only will the two motors operate in perfect harmony, it will also multiply your torque and stall rating by two.
__________________
Team 321: CHS RoboLancers - Drexel University, CHS Alumni Assn., SDP, Philadelphia Motorsports, Lima Corperation
Reply With Quote
  #19   Spotlight this post!  
Unread 23-01-2007, 21:13
Andrew Blair's Avatar
Andrew Blair Andrew Blair is offline
SAE Formula is FIRST with Gasoline.
FRC #0306 (CRT)
Team Role: Alumni
 
Join Date: Feb 2005
Rookie Year: 2004
Location: Corry
Posts: 1,193
Andrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond reputeAndrew Blair has a reputation beyond repute
Send a message via AIM to Andrew Blair Send a message via Yahoo to Andrew Blair
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Justin M. View Post
Keep in mind that when you need high-torque motors (like in a programmed non-back drive mode), it helps to use two of them, if possible. If you wire the two motors together (+ to + - to -, then the combined + and - to the victor controlling them), now you are taking two circuits and combining them into one, distributing the power evenly. Not only will the two motors operate in perfect harmony, it will also multiply your torque and stall rating by two.
Err, this is illegal as far as CIM's and FP's go. Each must be controlled individually by an independent Victor.
__________________
Reading makes a full man, conference a ready man, and writing an exact man.
-Sir Francis Bacon

"Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius -- and a lot of courage -- to move in the opposite direction."
-Albert Einstein
Reply With Quote
  #20   Spotlight this post!  
Unread 23-01-2007, 21:54
Justin M. Justin M. is offline
Mechanical/Driver
FRC #0321 (RoboLancers)
Team Role: Mechanical
 
Join Date: Jan 2005
Rookie Year: 2005
Location: Philadelphia, PA
Posts: 310
Justin M. is on a distinguished road
Send a message via AIM to Justin M.
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Andrew Blair View Post
Err, this is illegal as far as CIM's and FP's go. Each must be controlled individually by an independent Victor.
Hmm...I had no clue this way illegal. Looks like we'll have to do it in programming then.
__________________
Team 321: CHS RoboLancers - Drexel University, CHS Alumni Assn., SDP, Philadelphia Motorsports, Lima Corperation
Reply With Quote
  #21   Spotlight this post!  
Unread 23-01-2007, 22:58
Alan Anderson's Avatar
Alan Anderson Alan Anderson is offline
Software Architect
FRC #0045 (TechnoKats)
Team Role: Mentor
 
Join Date: Feb 2004
Rookie Year: 2004
Location: Kokomo, Indiana
Posts: 9,113
Alan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond repute
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Andrew Blair View Post
Err, this is illegal as far as CIM's and FP's go. Each must be controlled individually by an independent Victor.
I thought so too, and was about to respond saying so, but I couldn't locate the relevant rule to quote. Can you help me find what I'm certain I'm overlooking? So far, I haven't seen anything in the manual that says each Victor can connect to only one motor. The closest is <R98> which limits Spike relay modules to a single motor. <R91> restricts things in the other direction: "Each motor, actuator, and compressor must be connected to one, and only one, speed controller or relay module." But it doesn't say you can't connect multiple motors to the same speed controller.
Reply With Quote
  #22   Spotlight this post!  
Unread 23-01-2007, 22:59
Alan Anderson's Avatar
Alan Anderson Alan Anderson is offline
Software Architect
FRC #0045 (TechnoKats)
Team Role: Mentor
 
Join Date: Feb 2004
Rookie Year: 2004
Location: Kokomo, Indiana
Posts: 9,113
Alan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond reputeAlan Anderson has a reputation beyond repute
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Justin M. View Post
Looks like we'll have to do it in programming then.
You should have received two Y-connector pwm cables in the Kit of Parts. You can use them to control two Victor speed controllers from the same pwm output on the Robot Controller.
Reply With Quote
  #23   Spotlight this post!  
Unread 23-01-2007, 23:03
Justin M. Justin M. is offline
Mechanical/Driver
FRC #0321 (RoboLancers)
Team Role: Mechanical
 
Join Date: Jan 2005
Rookie Year: 2005
Location: Philadelphia, PA
Posts: 310
Justin M. is on a distinguished road
Send a message via AIM to Justin M.
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Alan Anderson View Post
You should have received two Y-connector pwm cables in the Kit of Parts. You can use them to control two Victor speed controllers from the same pwm output on the Robot Controller.
That will work as well...but I'm starting to think that two motors on one victor is legal. We did this last year with two CIMs in the '06 gearbox...or at least I did - somebody could of changed it.
__________________
Team 321: CHS RoboLancers - Drexel University, CHS Alumni Assn., SDP, Philadelphia Motorsports, Lima Corperation
Reply With Quote
  #24   Spotlight this post!  
Unread 24-01-2007, 01:19
Biff Biff is offline
Registered User
AKA: Tom Cooper
#1227 (Techno Gremlins)
Team Role: Mentor
 
Join Date: Jan 2004
Location: Grand Rapids MI
Posts: 214
Biff is a jewel in the roughBiff is a jewel in the roughBiff is a jewel in the roughBiff is a jewel in the rough
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Ian_Xodus View Post
Thank you for all of your input but my question has still not really been answered.
do you guys build your own gearboxes for the globe motors?
Do you use any special programming to make the motor stay slightly engaged to keep the arm up?
Do you use globe motors, van door, or window?

Sorry... only my second year in first.
In answer to some of your questions, The gearboxes that are on the Globe and the Keyang window motors pretty much match at output speeds. The part that I posted, one end goes on the globe shaft and the other picks up the "gear" on the window motor. The globe was monted to a plate and the plate was mouted to the frame and the window motor. The #25 chain teeth drive chain that is attached to a sprocket that was attached to the last arm. Thus the motors were mounted "nose to nose". The globe gave us the oomph and the window motor helped, and with power off, Held the arm in place. I'm attaching a picture of the last stage you can kindof get an idea of how we did it. You will not need as large a final sprocket as this year your not trying to move a 12 lb tetera. (the vision one). A multi turn pot with a #25 chain sprocket mounted to the frame read the position of the arm. The nice thing about pots with sprockets is you can change the number of teeth on the pot sprocket to get full range out of the pot. Just remember smaller sprockets get more truns on the pot for the same arm angle change. It seems kind of backward but if you work it out you will see.
(Also BTW each motor had it's own victor, although one victor is plenty to drive this setup if this years rules allow it, Also triple check wiring so the motors work together, I tended to label with arrow which way things turned with a marker on the part of the motor showing so I knew if red went to pos or it it was the other way)
Biff
Attached Thumbnails
Click image for larger version

Name:	P2215528.jpg
Views:	63
Size:	62.0 KB
ID:	4929  

Last edited by Biff : 24-01-2007 at 01:27.
Reply With Quote
  #25   Spotlight this post!  
Unread 24-01-2007, 03:03
eugenebrooks eugenebrooks is offline
Team Role: Engineer
AKA: Dr. Brooks
no team (WRRF)
 
Join Date: Jan 2004
Rookie Year: 2001
Location: Livermore, CA
Posts: 601
eugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond reputeeugenebrooks has a reputation beyond repute
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Ian_Xodus View Post
Thank you for all of your input but my question has still not really been answered.
do you guys build your own gearboxes for the globe motors?
Do you use any special programming to make the motor stay slightly engaged to keep the arm up?
Do you use globe motors, van door, or window?
Generally, it is best to design your mechanical system so that continuous motor power is not required to have the arm hold its position. Doing this pretty much boils down to using a worm gear setup to prevent back drive, whether it be one of the motors in the KOP that has a worm gear built into it, or by building your own worm gear setup that is driven by one of the other gear boxes available in the kit such as the banebots unit. We use either of these options, depending on how much power and torque we need to support with the mechanism.

The control software then uses a small dead band window. Once the motor gets the arm into the window the power can be completely shut off in order to prevent overheating. The FP and the motors on the small bane bots gear boxes will overheat quickly if run at stall.

Have fun,
Eugene
Reply With Quote
  #26   Spotlight this post!  
Unread 24-01-2007, 14:32
MrForbes's Avatar
MrForbes MrForbes is offline
Registered User
AKA: Jim
FRC #1726 (N.E.R.D.S.)
Team Role: Mentor
 
Join Date: Feb 2006
Rookie Year: 2006
Location: Sierra Vista AZ
Posts: 6,038
MrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond reputeMrForbes has a reputation beyond repute
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Rickertsen2 View Post
Another option is gas shocks like the ones used to hold up car trunks and hatchbacks. They not only put out alot of force but provide some dampening.
This is looking like a good solution....thanks! McMaster Carr offers a nice selection of "gas springs".
Reply With Quote
  #27   Spotlight this post!  
Unread 24-01-2007, 18:00
petek's Avatar
petek petek is offline
What would Dave do?
AKA: Peter Kieselbach
FRC #3654 (Tech Tigers)
Team Role: Mentor
 
Join Date: May 2002
Rookie Year: 2002
Location: Middletown, CT
Posts: 923
petek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond reputepetek has a reputation beyond repute
Send a message via AIM to petek
Re: PID How to hold an arm in a fixed position without a locking gear box

Quote:
Originally Posted by Alan Anderson View Post
I thought so too, and was about to respond saying so, but I couldn't locate the relevant rule to quote. Can you help me find what I'm certain I'm overlooking? So far, I haven't seen anything in the manual that says each Victor can connect to only one motor. The closest is <R98> which limits Spike relay modules to a single motor. <R91> restricts things in the other direction: "Each motor, actuator, and compressor must be connected to one, and only one, speed controller or relay module." But it doesn't say you can't connect multiple motors to the same speed controller.
Well, that makes at least two of us scratching our heads saying "I could have sworn that was a rule". Here's what I found:
Quote:
<R92> CIM motors and Fisher-Price motors must be connected to speed controllers. They can not be connected to relay modules.
Again, no mention of limit on number of motors per speed controller. From the 2007 Guidelines_Tips_Good Practices.pdf:
Quote:
Only one large motor (CIM, Fisher-Price, Globe or similar motor) should be controlled per speed controller
As far as I know that is only a guideline, not a rule. It goes on to say:
Quote:
In some cases, more than one low current small motor (window/Mabuchi) or actuator may be optionally connected to a single speed controller.
The closest I come to this being a rule is:
Quote:
<R85> ... For examples of acceptable circuit designs, please see the 2007 Robot Power Distribution Diagram.
The Diagram shows just one motor per speed controller.
__________________
Pete Kieselbach
#4

Reply With Quote
  #28   Spotlight this post!  
Unread 25-01-2007, 17:42
Dillon Compton Dillon Compton is offline
Jack-Of-All-Trades
FRC #1391 (Metal Moose)
Team Role: Mentor
 
Join Date: Jan 2005
Rookie Year: 2004
Location: Malvern, PA
Posts: 186
Dillon Compton has much to be proud ofDillon Compton has much to be proud ofDillon Compton has much to be proud ofDillon Compton has much to be proud ofDillon Compton has much to be proud ofDillon Compton has much to be proud ofDillon Compton has much to be proud ofDillon Compton has much to be proud of
Send a message via AIM to Dillon Compton
Re: PID How to hold an arm in a fixed position without a locking gear box

In the past it has been a rule that only one motor may be attached to a Victor 884, however the rules seem to leave that open to interpretation this year. All I can say is that it's a very bad idea, as at stall torque the current draw of two CIMs well exceeds the rating of the Victor 884 and you'd be likely to see magic smoke at least once before the end of a regional...

Ask yourself this: Would you rather buy one extra victor and plan in the few ounces extra, or continually replace burned out victors because they overload and release magic smoke every few matches?

//Dillon Compton
__________________
www.metalmoose.com
Reply With Quote
  #29   Spotlight this post!  
Unread 27-01-2007, 00:30
RoboCoach RoboCoach is offline
Registered User
AKA: John
FRC #0128
Team Role: Mentor
 
Join Date: Feb 2006
Location: Ohio
Posts: 12
RoboCoach is on a distinguished road
Send a message via Yahoo to RoboCoach
Re: PID How to hold an arm in a fixed position without a locking gear box

In the Good Practices manual, section G.6.3.1 V884 Speed Controllers it states "Only one large motor (CIM, Fisher-Price, Globe or similar motor should be controlled per speed controller". Didn't look, but there is probably a similar statement for the Spikes as well.
In any circumstance, the motors should be individually fused.
__________________
Discovery is seeing what everyone else has seen and thinking what no one else has thought. --Albert Szent-Gyorgi
Reply With Quote
  #30   Spotlight this post!  
Unread 28-01-2007, 08:50
KTorak's Avatar
KTorak KTorak is offline
Fire Rescue 47
AKA: Kyle Dersch
FRC #1023 (Bedford Express)
Team Role: Driver
 
Join Date: Jan 2005
Rookie Year: 2005
Location: Montgomery Village, MD
Posts: 899
KTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond reputeKTorak has a reputation beyond repute
Send a message via AIM to KTorak
Re: PID How to hold an arm in a fixed position without a locking gear box

With the motors we have used, we have never done special programming. Usually, they won't back drive with power applied (IE the robot is on). If, however, you turn off the motor, they will backdrive...such as our arm did in 2005. This year however, we made specific checks to make sure our arm will not come crashing down on a robot on our ramp at the end of the match. We also build a custom gearbox to use two motors.
__________________
Kyle D- Myspace - Facebook
2008 Bedford Express Driver & Build & Design (Team) Co-Leader
2007 Bedford Express Driver & Build & Design (Team) Leader
2006 Bedford Express Driver, Build Team Member, & Board of Directors
2005 Bedford Express Rookie, Build Team Member & Robot Operator
-
2008 - GLR Quarter Finalist
2007 - GLR Finalist & Boilermaker Finalist & MARC Off Season Event Winner
2006 - GLR Johnson & Johnson Sportsmanship Award & Archimedes 7th Seed Quarter Finalist
2005 - GLR Finalist & Judges Award.
2004 - GLR Semi Finalist.
2003 - GLR/DTR Quarter Finalist & GLR/NAT'L Rookie All Star.
Reply With Quote
Reply


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

Similar Threads
Thread Thread Starter Forum Replies Last Post
PID without a Ph.D. Joe Johnson Programming 3 07-02-2006 17:37
Drive Straight C Code using Encoders without PID? Chris_Elston Programming 17 15-02-2005 23:41
White Paper Discuss: Locking the Bosch 3360 Drill in low gear CD47-Bot Extra Discussion 4 05-08-2003 02:10
how do you hold pins in? archiver 2001 4 23-06-2002 23:45
How do teams hold their brainstorming meetings? Anton Abaya General Forum 10 03-01-2002 18:02


All times are GMT -5. The time now is 13:52.

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