Go to Post After all of this is said and done, think about how much more you all will know about the lovely state of Montana and other things not related to robotics. :) - Madison [more]
Home
Go Back   Chief Delphi > Technical > Motors
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
  #16   Spotlight this post!  
Unread 18-02-2012, 01:32
bdbayes bdbayes is offline
Captain
FRC #2927 (Pi Rho Techs)
Team Role: Leadership
 
Join Date: Apr 2011
Rookie Year: 2009
Location: Tacoma, WA
Posts: 75
bdbayes is a jewel in the roughbdbayes is a jewel in the roughbdbayes is a jewel in the rough
Re: How to get maximum output from a Jag?

My team is actively having the same problem. We are currently using 16" wheels with the standard cim gear box and a 3:1 ratio for the chains instead of the standard 2:1 provided with the KoP. I am glad that we are not the only team having this problem.
  #17   Spotlight this post!  
Unread 18-02-2012, 02:47
Kilo Foxtrot 7's Avatar
Kilo Foxtrot 7 Kilo Foxtrot 7 is offline
Small Oily Planetoid
FRC #3673 (C.Y.B.O.R.G. Seagulls)
Team Role: Engineer
 
Join Date: Feb 2011
Rookie Year: 2011
Location: seaside, OR
Posts: 6
Kilo Foxtrot 7 is an unknown quantity at this point
Re: How to get maximum output from a Jag?

Alright so I'm the Mech in question.

let me clear up some things

1. yes we are using 20in wheels and yes they are staggered

2. the drivetrain is running a 5:1 gear ratio on top of the 4.67:1 of the gearboxes so a total of a 23.35:1 ratio

3. i am 98.9% sure that we are not tripping the 40A breakers

4. we are using a fresh battery

so that being said is there any way to keep the jags from triping

Thx

P.S. thund plz get your facts strait before posting it saves me from wasting my valuable sleeping time. %-l
__________________
_____________________________________________

Theory is a nice place, I'd like to go there one day, I hear everything works there.

You can do anything with a hammer and duct tape...
sadly duct tape isn't allowed.
  #18   Spotlight this post!  
Unread 18-02-2012, 08:41
Daniel_LaFleur's Avatar
Daniel_LaFleur Daniel_LaFleur is online now
Mad Scientist
AKA: Me
FRC #2040 (DERT)
Team Role: Engineer
 
Join Date: Apr 2005
Rookie Year: 2003
Location: Peoria, IL
Posts: 1,972
Daniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond reputeDaniel_LaFleur has a reputation beyond repute
Send a message via MSN to Daniel_LaFleur
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Kilo Foxtrot 7 View Post
Alright so I'm the Mech in question.

let me clear up some things

1. yes we are using 20in wheels and yes they are staggered

2. the drivetrain is running a 5:1 gear ratio on top of the 4.67:1 of the gearboxes so a total of a 23.35:1 ratio

3. i am 98.9% sure that we are not tripping the 40A breakers

4. we are using a fresh battery

so that being said is there any way to keep the jags from triping

Thx

P.S. thund plz get your facts strait before posting it saves me from wasting my valuable sleeping time. %-l
Now that we have the real gear ratios, lets go through the numbers (as a teaching exercise).

Freespeed of CIM = 5310 RPM
/60 (min / sec) = 88.5 RPS
/23.35 (gear ratio) = 3.79 RPS (rounded)
20" dia * 3.14 = 62.8" circ
62.8" circ * 3.79 RPS = 238.01" / sec
/12 (in/ft) = 19.83 ft/ sec.

These are theoretical numbers that will never be attained but typically anything over ~16ft/sec in a single speed gearsetup will trip the breakers at startup and while turning (depending on CoF, weight on wheels, wheelbase, etc).

Now lets calculate thrust.

Stall torque (again for theoretical measurements) of cim = 344 in/oz
* 23.35 (gear ratio) = 8032.4 in/oz
/20" (distance of torque) = 401.62 oz
/12 (in/ft) /16 (oz/LB) = 2.09 LBs thrust
* 4 (CIMs) = 8.367 LBf thrust

Thats low, but managable (someone check my math ... I'm terrible in the morning )

All in all your setup might work, but I'd expect tripping of the breakers when turning and in any sort of pushing match.
__________________
___________________
"We are not now that strength which in old days moved earth and heaven; that which we are, we are;
One equal temper of heroic hearts, Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield. "
- Tennyson, Ulysses
  #19   Spotlight this post!  
Unread 18-02-2012, 10:17
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,102
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Daniel_LaFleur View Post
Now lets calculate thrust.

Stall torque (again for theoretical measurements) of cim = 344 in/oz
* 23.35 (gear ratio) = 8032.4 in/oz
/20" (distance of torque) = 401.62 oz
/12 (in/ft) /16 (oz/LB) = 2.09 LBs thrust
* 4 (CIMs) = 8.367 LBf thrust

Thats low, but managable (someone check my math ... I'm terrible in the morning )
Get a cup of coffee :-)

  #20   Spotlight this post!  
Unread 18-02-2012, 11:46
Thundrio Thundrio is offline
Dedicated Racer
FRC #3673
 
Join Date: Feb 2011
Rookie Year: 2010
Location: The Internet
Posts: 67
Thundrio is on a distinguished road
Re: How to get maximum output from a Jag?

Alright I uploaded a video of a drive test from a few weeks ago, although I believe the drive train stuff is all the same (aside from a bit of tightening, but it looks the same). Unfortunately we don't attempt to go over the bump in this video, but here it is.

http://www.youtube.com/watch?v=bGlak6ijWPg
The robot doesn't start moving until about 1:15(I trimmed it with yt but atm the changes are still being processed -_-)

For me the important thing is to find out whether our issue (I know its difficult to discern our exact issue) is one that can be fixed via software/firmware, because I would enjoy people getting off my back so I can program.
__________________
Interested in a new way of playing old games?
visit http://www.speedrunslive.com for a way to make single player games multiplayer!
visit http://www.zeldaspeedruns.com to open up a new world for zelda lovers!
pm me here or at zsr for more information!

Last edited by Thundrio : 18-02-2012 at 12:12.
  #21   Spotlight this post!  
Unread 18-02-2012, 12:09
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,102
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Thundrio View Post
...
You have a high center of gravity and a shorter-than-normal wheelbase (because of the 20" wheels). Even with your present low-torque gearing, you popped a wheelie. What's gonna happen when you go over the bump?

With your high center of gravity and shorter-than-normal wheelbase, you don't need to be geared for 19 feet/sec - it would be very difficult to control at that speed. Change that 5:1 sprocket ratio to 10:1 and you'll cut your amps in half (for a given wheel torque) and still have adequate speed.

If you modify the gearing for more torque, you will have to be extremely careful with the throttle. Adding a slew rate limiter to your joystick would limit your acceleration and help mitigate the wheelie-popping.


PS - You and Kilo Foxtrot 7 need to take your bickering off this forum.



Last edited by Ether : 18-02-2012 at 12:42.
  #22   Spotlight this post!  
Unread 18-02-2012, 12:33
Thundrio Thundrio is offline
Dedicated Racer
FRC #3673
 
Join Date: Feb 2011
Rookie Year: 2010
Location: The Internet
Posts: 67
Thundrio is on a distinguished road
Re: How to get maximum output from a Jag?

I'm not sure how to add that code in.
Code:
change = joystick - limitedJoystick;
if (change>limit) change = limit;
else (if change<-limit) change = -limit;
limitedJoystick += change;
My idea is that just have limitedJoystick created as a joystick in slot 3 (a virtual joystick). Then I basically take the above code and put it right before my robotdrive (which calls the fake limitedJoystick). But it is not working (I didn't suspect it to) even after I created change/limit as a double.

Any help would be appreciated, I would like to get the slew rate limiter tested as soon as possible so it either fixes the issue or we need to try something mechanical (Since the mechs won't do anything to fix it if they think it can be fixed through software).
__________________
Interested in a new way of playing old games?
visit http://www.speedrunslive.com for a way to make single player games multiplayer!
visit http://www.zeldaspeedruns.com to open up a new world for zelda lovers!
pm me here or at zsr for more information!
  #23   Spotlight this post!  
Unread 18-02-2012, 12:46
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,102
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Thundrio View Post
I would like to get the slew rate limiter tested as soon as possible so it either fixes the issue or we need to try something mechanical (Since the mechs won't do anything to fix it if they think it can be fixed through software).
Slew rate limiting will help prevent the wheelie-popping. I don't think it will help you get over the barrier.

What is your wheelbase* measurement, exactly?


* wheelbase: distance between front and rear axles.

  #24   Spotlight this post!  
Unread 18-02-2012, 13:08
ianonavy ianonavy is offline
Programming Mentor/Alumnus
AKA: Ian Adam Naval
FRC #3120 (RoboKnights)
Team Role: Mentor
 
Join Date: Dec 2010
Rookie Year: 2008
Location: Sherman Oaks
Posts: 32
ianonavy is an unknown quantity at this point
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Thundrio View Post
My idea is that just have limitedJoystick created as a joystick in slot 3 (a virtual joystick). Then I basically take the above code and put it right before my robotdrive (which calls the fake limitedJoystick). But it is not working (I didn't suspect it to) even after I created change/limit as a double.
Using pseudo-Java, this would go in an IterativeRobot:
Code:
Joystick joystick = new Joystick(1);
double lastJoystickValue = 0;
// Limit the Joystick to a change of 1% every iteration of the robot. Basically,
// limit the acceleration of the robot.
final double MAX_CHANGE_PER_ITER = 0.01;

public void teleopPeriodic() {
    double currentJoystickValue = joystick.getMagnitude();
    double magnitude = limitRate(currentJoystickValue, lastJoysitckValue); 

    drive(magnitude); // pseudo method
    lastJoystickValue = magnitude;
}

/**
 * Uses the value from the last iteration to limit how much the Joystick can
 * change in one iteration.
 * @param goalValue The ideal value that we ultimately want to reach.
 * @param lastJoystickValue The value of the joystick from the last iteration.
 */
public double limitRate(double goalValue, double lastJoystickValue) {
    double difference = goalValue - lastJoystickValue;
    if (difference > MAX_CHANGE_PER_ITER) {
        return lastJoystickValue + MAX_CHANGE_PER_ITER;
    } else if (difference < -MAX_CHANGE_PER_ITER) {
        return lastJoystickValue - MAX_CHANGE_PER_ITER 
    } else {
        return goalValue;
    }
}
I hope this helps and makes sense. You will need to modify it for your purposes (port to C++, change for your DriveTrain Subsystem, modify for Mecanum drive, or whatever else).
  #25   Spotlight this post!  
Unread 18-02-2012, 13:21
Thundrio Thundrio is offline
Dedicated Racer
FRC #3673
 
Join Date: Feb 2011
Rookie Year: 2010
Location: The Internet
Posts: 67
Thundrio is on a distinguished road
Re: How to get maximum output from a Jag?

The mech lead says the wheelbase is roughly 15 inches (I won't be there for another few hours, I just called him).

Thanks for the pseudo-code ianonavy, I'll give that a try.
__________________
Interested in a new way of playing old games?
visit http://www.speedrunslive.com for a way to make single player games multiplayer!
visit http://www.zeldaspeedruns.com to open up a new world for zelda lovers!
pm me here or at zsr for more information!
  #26   Spotlight this post!  
Unread 18-02-2012, 13:30
Kilo Foxtrot 7's Avatar
Kilo Foxtrot 7 Kilo Foxtrot 7 is offline
Small Oily Planetoid
FRC #3673 (C.Y.B.O.R.G. Seagulls)
Team Role: Engineer
 
Join Date: Feb 2011
Rookie Year: 2011
Location: seaside, OR
Posts: 6
Kilo Foxtrot 7 is an unknown quantity at this point
Re: How to get maximum output from a Jag?

There is a cimple box at 4.67 to 1
and there is a 5:1 reduction from the cimple output to the wheel (12 tooth sprocket to 60 tooth sprocket)

This makes a 23.35 reduction

We need help trying to identify if we can change the ramprate on the jags to a level that prevents it from overloading and do some testing. How do we program a different ramprate in the JAG using Java?

edit: btw, clarksnack is our mentor that Thundrio was talking about in the original post.
__________________
_____________________________________________

Theory is a nice place, I'd like to go there one day, I hear everything works there.

You can do anything with a hammer and duct tape...
sadly duct tape isn't allowed.

Last edited by Kilo Foxtrot 7 : 18-02-2012 at 13:47.
  #27   Spotlight this post!  
Unread 18-02-2012, 13:44
clarksnack clarksnack is offline
Registered User
None #3673
 
Join Date: Feb 2012
Location: Seaside
Posts: 2
clarksnack is an unknown quantity at this point
Re: How to get maximum output from a Jag?

Is there a way to set the ramprate of the Jag in the Java code? We tested one of the motors using the BDC COMM software and placed the ramprate at 1000 and just the one motor appeared to have much more torque available without the Jag internal trip "tripping" How can we program the ramprate in the jag using java?
  #28   Spotlight this post!  
Unread 18-02-2012, 14:24
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,102
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Thundrio View Post
it gets the front wheels over the ramp and cuts out when the bottom ones hit the ramp
Quote:
Originally Posted by Thundrio View Post
The mech lead says the wheelbase is roughly 15 inches
I am having trouble parsing the above two statements.

When you say "ramp", are you referring to the barrier or the bridge?

And what do you mean by "bottom ones"? The rear wheels?


If the wheels are 20" diameter and the wheelbase is 15" diameter, how can the front wheels be "over the ramp" (the barrier) before the "bottom ones" (rear wheels) hit the ramp (barrier)?

Unless by "over the ramp" you mean "on top of the ramp" ??

See the attached PDF.

Attached Files
File Type: pdf 20'' wheel_b.pdf (2.9 KB, 9 views)
  #29   Spotlight this post!  
Unread 18-02-2012, 14:29
Thundrio Thundrio is offline
Dedicated Racer
FRC #3673
 
Join Date: Feb 2011
Rookie Year: 2010
Location: The Internet
Posts: 67
Thundrio is on a distinguished road
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by Ether View Post
I am having trouble parsing the above two statements.

When you say "ramp", are you referring to the barrier or the bridge?
I am referring to the barrier.
Quote:
And what do you mean by "bottom ones"? The rear wheels?
by "bottom ones" I am referring to the rear wheels.

Quote:
Unless by "over the [bold]barrier[/bold]" you mean "on top of the [bold]barrier[/bold]" ??
I did mean on top of the barrier, as they do not go all the way over. It does start to pop a wheelie but we have a wheelie bar in place to stop it

sorry for the confusion. -_-
__________________
Interested in a new way of playing old games?
visit http://www.speedrunslive.com for a way to make single player games multiplayer!
visit http://www.zeldaspeedruns.com to open up a new world for zelda lovers!
pm me here or at zsr for more information!
  #30   Spotlight this post!  
Unread 18-02-2012, 14:30
Ether's Avatar
Ether Ether is offline
systems engineer (retired)
no team
 
Join Date: Nov 2009
Rookie Year: 1969
Location: US
Posts: 8,102
Ether has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond reputeEther has a reputation beyond repute
Re: How to get maximum output from a Jag?

Quote:
Originally Posted by clarksnack View Post
Is there a way to set the ramprate of the Jag in the Java code? We tested one of the motors using the BDC COMM software and placed the ramprate at 1000 and just the one motor appeared to have much more torque available without the Jag internal trip "tripping" How can we program the ramprate in the jag using java?
You can set the ramp rate in the Jag if you are using CAN bus.

If you are using PWM, you can enable the fixed ramp rate of full reverse to full forward in 1/8 second by placing the limit jumpers parallel to the front of the Jag. See Pages 2-3 of this document.

Or you can put the very simple code shown here to limit the rate at which your joystick command is allowed to change. That will limit the rate at which your Jag changes voltage.

You can try it, but I do not think ramp rate is your problem.


Last edited by Ether : 18-02-2012 at 14:34. Reason: added link to Jag Q&A doc
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 13:47.

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