Go to Post If it is good enough for Paul and JVN it's good enough for me. - Vikesrock [more]
Home
Go Back   Chief Delphi > Technical > Programming
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 06-02-2016, 10:46
Ryan_Sciarabba Ryan_Sciarabba is offline
Registered User
FRC #5254
 
Join Date: Jan 2016
Location: New York
Posts: 3
Ryan_Sciarabba is an unknown quantity at this point
Motor is twitching even without input FRC labview

We are trying to program a motor to move but for some reason even without input it's twitching. It works fine with input but without it the motor just moves as if it had a little flash of input. Any solutions to make it stop?
  #2   Spotlight this post!  
Unread 06-02-2016, 11:01
rich2202 rich2202 is offline
Registered User
FRC #2202 (BEAST Robotics)
Team Role: Mentor
 
Join Date: Jan 2012
Rookie Year: 2012
Location: Wisconsin
Posts: 1,275
rich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond reputerich2202 has a reputation beyond repute
Re: Motor is twitching even without input FRC labview

Does it happen when the robot is Disabled? If so, try a new motor controller.

If not, then check your code. Something may be setting motor speed to something other than 0.
  #3   Spotlight this post!  
Unread 06-02-2016, 11:02
Mark McLeod's Avatar
Mark McLeod Mark McLeod is offline
Just Itinerant
AKA: Hey dad...Father...MARK
FRC #0358 (Robotic Eagles)
Team Role: Engineer
 
Join Date: Mar 2003
Rookie Year: 2002
Location: Hauppauge, Long Island, NY
Posts: 8,906
Mark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond reputeMark McLeod has a reputation beyond repute
Re: Motor is twitching even without input FRC labview

While Enabled it's always receiving input, even if that input should be neutral.

Do you call Set Motor in more than one place?

Does the motor continue to twitch if you disconnect the joystick?

Is the motor controller status light solid? (and what kind of motor controller is it?)
__________________
"Rationality is our distinguishing characteristic - it's what sets us apart from the beasts." - Aristotle
  #4   Spotlight this post!  
Unread 06-02-2016, 11:04
Owen Busler's Avatar
Owen Busler Owen Busler is offline
Build Captain
FRC #0303 (Test Team)
Team Role: Leadership
 
Join Date: Aug 2014
Rookie Year: 2014
Location: Bridgewater, NJ
Posts: 147
Owen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant futureOwen Busler has a brilliant future
Re: Motor is twitching even without input FRC labview

If you have it programmed to be controlled by a joystick, one possibility may be that you do not have a "dead band" in your code. Even when the joystick is relaxed in its natural or zero position, it still may be outputting small numbers.

To fix this you may add a simple if statement, or a case structure if you use labview, that says if the absolute value of the joystick input is less than X. You will have to test to see what X works for you.

Again, this is just one problem my team has had in the past.
__________________
2016: Deans List Semi-Finalist/MAR Mount Olive District Engineering Inspiration Award/Buckeye Regional Second Alliance Captain/MAR Montgomery District Event Imagery Award/MAR Championship Gracious Professionalism Award
2015: MAR Mount Olive District Chairman's Award/MAR North Brunswick District Winners/MAR Championship Finalists
2014: MAR Clifton District Chairman's Award/MAR Championship Regional Chairman's Award
  #5   Spotlight this post!  
Unread 06-02-2016, 22:10
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: Motor is twitching even without input FRC labview

What kind of speed controller are you using? I occasionally saw the original Talons "twitch" when something induced noise on the PWM cable.

I have also seen very brief twitches occur using RoboRIO firmware from several years ago when the robot code lost communication for a moment and disabled the PWM outputs at just the right/wrong time to make the speed controller think it had gotten a single "run backwards at high speed" pulse before timing out and shutting off. I thought that undesired behavior was fixed, though.
  #6   Spotlight this post!  
Unread 06-02-2016, 22:16
Greg McKaskle Greg McKaskle is offline
Registered User
FRC #2468 (Team NI & Appreciate)
 
Join Date: Apr 2008
Rookie Year: 2008
Location: Austin, TX
Posts: 4,756
Greg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond reputeGreg McKaskle has a reputation beyond repute
Re: Motor is twitching even without input FRC labview

Just to add one more speculative element. Are you using a Y cable to send the PWM signal to more than one motor controller? If so, jiggle or roll the cable between your fingers to see if that will cause the disabled motor controllers to twitch. If so, fix the cable to get rid of shorts at the Y.

Greg McKaskle
  #7   Spotlight this post!  
Unread 07-02-2016, 00:23
Tom Line's Avatar
Tom Line Tom Line is offline
Raptors can't turn doorknobs.
FRC #1718 (The Fighting Pi)
Team Role: Mentor
 
Join Date: Jan 2007
Rookie Year: 1999
Location: Armada, Michigan
Posts: 2,554
Tom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond reputeTom Line has a reputation beyond repute
Re: Motor is twitching even without input FRC labview

Quote:
Originally Posted by Alan Anderson View Post
What kind of speed controller are you using? I occasionally saw the original Talons "twitch" when something induced noise on the PWM cable.

I have also seen very brief twitches occur using RoboRIO firmware from several years ago when the robot code lost communication for a moment and disabled the PWM outputs at just the right/wrong time to make the speed controller think it had gotten a single "run backwards at high speed" pulse before timing out and shutting off. I thought that undesired behavior was fixed, though.
We struggled with that some last year as well. After we had one of our can-grabbers deploy and almost take off the head-mentors nose, we tried rerouting wires, etc. We never managed to completely beat the twitches though.
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 01:31.

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