Go to Post SELECT YOUR STRATEGY BEFORE YOUR ROBOT DESIGN. - Kims Robot [more]
Home
Go Back   Chief Delphi > Technical > Electrical
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Closed Thread
 
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 21-01-2011, 10:21
Jon Stratis's Avatar
Jon Stratis Jon Stratis is online now
Electrical/Programming Mentor
FRC #2177 (The Robettes)
Team Role: Mentor
 
Join Date: Feb 2007
Rookie Year: 2006
Location: Minnesota
Posts: 3,736
Jon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond reputeJon Stratis has a reputation beyond repute
Re: PID on Jaguars is Illegal

Quote:
Originally Posted by Kevin Sevcik View Post
So, first and foremost, there's still some reason to use the CAN-bus. You can still offload some functionality to the Jags, such as limit switches, potentiometers, encoders, and current sensing. Yes, your feedback on encoders and other sensors will be delayed, relative to what you'd get on the cRIO, but it is an option.
Actually, that doesn't seem to be the case. Sure, you can hook up encoders and potentiometers, and send those signals, along with current sensing, to the cRio for processing. That's not offloading functionality though - it's just giving you a few more ports to hook sensors into in addition to those provided by the digital side car and analog breakout. But limit switches? Wouldn't <R62> apply here as well:

Quote:
"...any additional devices on the Ethernet or CAN-bus must not provide command signals that do not originate from the cRIO-FRC."
A limit switch hooked up to the Jaguar would be providing a command signal to stop the motor when it reaches a specific point. In fact, this signal can override the signals sent from the cRio and give you different behavior than the code tells you. If you have an elevator with a limit switch to tell you when it's hit the top, the Jaguar can no longer legally stop the elevator for you - that has to be done in the code. As such, this would seem to disallow hooking limit switches into the Jaguars at all.
  #2   Spotlight this post!  
Unread 21-01-2011, 10:33
gpetilli gpetilli is offline
Registered User
FRC #1559
 
Join Date: Jan 2009
Location: Victor, NY
Posts: 285
gpetilli is a name known to allgpetilli is a name known to allgpetilli is a name known to allgpetilli is a name known to allgpetilli is a name known to allgpetilli is a name known to all
Re: PID on Jaguars is Illegal

is thermal shutdown illegal?
  #3   Spotlight this post!  
Unread 21-01-2011, 10:52
Bryscus's Avatar
Bryscus Bryscus is offline
EE, CpE
AKA: Bryce B.
FRC #0180 (SPAM)
Team Role: Engineer
 
Join Date: Jan 2009
Rookie Year: 1999
Location: Jupiter, FL
Posts: 173
Bryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud ofBryscus has much to be proud of
Re: PID on Jaguars is Illegal

Here are some other things I'd like to mention.

If the GDC wants to limit what can and can't be done in the Jags, they should have TI write new firmware to disallow any possibility of using these functions. I had a long conversation with the Black Jag designer and firmware programmer from TI last year at the Championship about all the good and bad of the closed-loop firmware that TI provided on the Jags. We were one of the teams that decided to take a risk that the CANJaguar software for the cRIO and Jaguar firmware would mature enough to operate properly for last year. If this was disallowed last year, then there were some serious oversights from the GDC. And now that the code has matured to its greatest form to-date it is illegal. Why would FIRST want TI to improve its closed-loop firmware and also sanction a CANJaguar project if the code is not even going to be used?

Also, as someone stated below, distributed computing and control systems is THE FUTURE. How can FIRST claim to be investing in the future if they want to impose archaic designs on teams? We're already using a processor that was introduced almost 20 years ago. Every system around us uses multiple application specific devices. To remove these concepts is shortsighted.

Lastly, the Jags basically have a timeout. They're not supposed to keep functioning if a signal is lost - and this timeout I believe is ?100ms. This is well below the threshold for human comprehension. If there is no signal, the Jag shuts down. So to say that the cRIO is not controlling the Jag has be to based on how long one expects the latency to be between the cRIO and the Jag. For example, if the cRIO commands 90 degrees (in position feedback mode) and the motor is currently at 0 degrees, there will be a time delay between when the motor starts moving and when it reaches 90 degrees. The cRIO must keep commanding 90 degrees in order for the Jag to keep trying to make the motor go to 90 degrees. If at any time a signal is lost, the Jag will stop commanding the motor and everything will stop.

I also hope this ruling is retracted .

One step forward, two steps back.
__________________
The opulence of the front office decor varies inversely with the fundamental solvency of the firm.

Last edited by Bryscus : 21-01-2011 at 11:03.
  #4   Spotlight this post!  
Unread 21-01-2011, 11:13
anthonyttu anthonyttu is offline
Texas Instruments Engineer
AKA: Master Chief
FRC #5417 (Eagle Robotics)
Team Role: Mentor
 
Join Date: Aug 2008
Rookie Year: 2008
Location: Dallas
Posts: 61
anthonyttu has a spectacular aura aboutanthonyttu has a spectacular aura about
Re: PID on Jaguars is Illegal

I don't agree with the statements that the signals are originating from the Jags The CRIO gives a speed/position/current then the Jag following orders. By the same rule <R62> limit switches directly into the jag will also be baned. Thus making the Jag worthless the CAN buss worthless and the whole reason for upgrading the entire control system pointless.
  #5   Spotlight this post!  
Unread 21-01-2011, 11:11
Tim Skloss's Avatar
Tim Skloss Tim Skloss is offline
Dr. Skloss
FRC #0930
Team Role: Parent
 
Join Date: Jan 2002
Rookie Year: 2000
Location: Waukesha, WI, USA
Posts: 73
Tim Skloss is a jewel in the roughTim Skloss is a jewel in the roughTim Skloss is a jewel in the roughTim Skloss is a jewel in the rough
Re: PID on Jaguars is Illegal

Quote:
Originally Posted by Jim Giacchi View Post
My main concern over a rule like this is how would inspectors even check it?
.
Inspectors would see the encoders plugged into the Jaguars.

If you run the encoders to the digital sidecar and do the PID in Labview then that would be LEGAL.
__________________
---------------
FIRST Mentor and Team Leader
C.O.R.E 2062 a NASA, GE Volunteers and Rockwell Automation FRC Team
  #6   Spotlight this post!  
Unread 21-01-2011, 11:32
MikeE's Avatar
MikeE MikeE is offline
Wrecking nice beaches since 1990
no team (Volunteer)
Team Role: Engineer
 
Join Date: Nov 2008
Rookie Year: 2008
Location: New England -> Alaska
Posts: 381
MikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond repute
Re: PID on Jaguars is Illegal

Quote:
Originally Posted by Tim Skloss View Post
Inspectors would see the encoders plugged into the Jaguars.

If you run the encoders to the digital sidecar and do the PID in Labview then that would be LEGAL.
But encoders plugged into the Jaguars are perfectly legal according to <R62-H>. However, unless the inspector has a CANbus monitor or reverse engineers the deployed code, they can't tell whether the readings from the encoders are only sent to the cRio or are interpreted locally on the Jaguar.

So encoders etc. plugged into the Jaguars are a necessary condition for one type of distributed speed control, but not a sufficient condition.
  #7   Spotlight this post!  
Unread 21-01-2011, 11:36
Andrew Schreiber Andrew Schreiber is offline
Data Nerd
FRC #0079
 
Join Date: Jan 2005
Rookie Year: 2000
Location: Misplaced Michigander
Posts: 4,057
Andrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond reputeAndrew Schreiber has a reputation beyond repute
Re: PID on Jaguars is Illegal

Quote:
Originally Posted by Alexander Meyer View Post
Hehe, looks like it's back to the drawing board. I always wanted to know more about how PID loops work--guess I'll be getting up close and personal now. Thankfully the cRio has some serious processing beef.
1114 has a pretty decent description of it here

Quote:
Originally Posted by Bryscus View Post
Lastly, the Jags basically have a timeout. ....
This is only for the FRC Firmware in as far as I am aware.

There is also a signed mode built into the CAN signal so that any arbitrary device cannot inject motor control signals only "trusted" devices.

Quote:
Originally Posted by Tim Skloss View Post
Inspectors would see the encoders plugged into the Jaguars.
.
Which this ruling DID NOT forbid, it merely said we can't use the the PID on the Jag's PID. We can still use them to put sensors onto the CAN bus and reduce wiring complexity.

For reference, I strongly hope they change this rule.
__________________




.
  #8   Spotlight this post!  
Unread 21-01-2011, 15:56
MikeE's Avatar
MikeE MikeE is offline
Wrecking nice beaches since 1990
no team (Volunteer)
Team Role: Engineer
 
Join Date: Nov 2008
Rookie Year: 2008
Location: New England -> Alaska
Posts: 381
MikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond repute
Re: PID on Jaguars is Illegal

Quote:
Originally Posted by Kevin Sevcik View Post
Per GDC Q&A here:
http://forums.usfirst.org/showthread.php?t=16326



Plenty of time later for commentary on this lovely ruling, just wanted to get the word out before people got too invested in tuning and/or ditching PID on the cRIO.
There seems to be a Booth Review in progress. Or CD complaints caused a Challenge Flag to be thrown.

The original link is no longer viewable and the answer no longer appears in the Q&A Robot section http://forums.usfirst.org/forumdisplay.php?f=1481

Last edited by MikeE : 21-01-2011 at 16:00. Reason: clarity and sport metaphors
  #9   Spotlight this post!  
Unread 21-01-2011, 19:23
jhersh jhersh is offline
National Instruments
AKA: Joe Hershberger
FRC #2468 (Appreciate)
Team Role: Mentor
 
Join Date: May 2008
Rookie Year: 1997
Location: Austin, TX
Posts: 1,006
jhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond repute
Re: PID on Jaguars is Illegal

Woohoo... Closed loop control on CAN is legal!!

Update 4

Last edited by jhersh : 21-01-2011 at 19:27.
  #10   Spotlight this post!  
Unread 21-01-2011, 20:05
Alexander Meyer Alexander Meyer is offline
Registered User
FRC #2358 (Bearbotics)
Team Role: Mentor
 
Join Date: Jan 2010
Rookie Year: 2010
Location: Lake Zurich, Illinois
Posts: 36
Alexander Meyer is on a distinguished road
Re: PID on Jaguars is Illegal

Quote:
Originally Posted by jhersh View Post
Woohoo... Closed loop control on CAN is legal!!

Update 4
{fistpump}

I can't tell you how relieved I am..
  #11   Spotlight this post!  
Unread 21-01-2011, 20:12
klmx30302's Avatar
klmx30302 klmx30302 is offline
Is ready for MAYHEM In Merrimack!
AKA: Kevin McCarthy
FRC #0166 (Chop Shop)
Team Role: Mechanical
 
Join Date: Oct 2010
Rookie Year: 2010
Location: Merrimack,NH
Posts: 221
klmx30302 is a jewel in the roughklmx30302 is a jewel in the roughklmx30302 is a jewel in the rough
Re: PID on Jaguars is Illegal

c/p from team update #4:
As long as the CAN bus is wired legally so that the heartbeat from the cRIO is maintained, the closed loop control features of the Jaguar motor controller may be used. (That is, commands originating from the cRIO to configure, enable, and specify an operating point for all Jaguar closed loop modes fit the intent of <R49>.)

(our software subteam breathes a sigh of relief.)
__________________
Unofficial Team 166 Videographer
Our team motto...
"THINK!, There must be a harder way!"



Last edited by klmx30302 : 21-01-2011 at 20:18.
  #12   Spotlight this post!  
Unread 21-01-2011, 20:16
zbanks zbanks is offline
Registered User
AKA: Zach Banks
FRC #0529 (Mansfield Hornets)
Team Role: Leadership
 
Join Date: Feb 2010
Rookie Year: 2008
Location: MA
Posts: 37
zbanks is an unknown quantity at this point
Send a message via AIM to zbanks
Re: PID on Jaguars is Illegal

I'm glad it's legal. I was looking forward to using it this year.

Of course, after reading this thread earlier today, I spent about an hour abstracting and reworking the code.

Although it's still improved, I wish I had known earlier...
  #13   Spotlight this post!  
Unread 21-01-2011, 22:03
MikeE's Avatar
MikeE MikeE is offline
Wrecking nice beaches since 1990
no team (Volunteer)
Team Role: Engineer
 
Join Date: Nov 2008
Rookie Year: 2008
Location: New England -> Alaska
Posts: 381
MikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond reputeMikeE has a reputation beyond repute
Re: PID on Jaguars is Illegal

It's a relief to see the ruling reversed, but a pity the decision was published in the official Q&A in the first place.

Thanks to the positive contributors to this thread for raising awareness and being a part of encouraging a sensible resolution.
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 15:08.

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