Go to Post 'We're back to square one! and while we're at it, let's redesign square one.' - Bethie42 [more]
Home
Go Back   Chief Delphi > Technical > Programming > Java
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 11-01-2017, 22:15
abigailthefox's Avatar
abigailthefox abigailthefox is offline
Registered User
FRC #1711 (Raptors)
Team Role: Programmer
 
Join Date: Feb 2015
Rookie Year: 2015
Location: Traverse City
Posts: 59
abigailthefox has a spectacular aura aboutabigailthefox has a spectacular aura about
Holonomic Drive WPILIBJ Support

My team has decided to go with a holonomic drivetrain this year, specifically four omni wheels mounted in the corners of the base, at 45 degree angles.
I am the lead programmer for our team, but I have not previously worked on programming a drivetrain with omni wheels (I am also one of only two veterans on the programming sub team, and the other also does not have experience with this).
I saw on another thread (from several years ago) a note about using the mecanumDrive_Cartesian method in the WPILIBJ to control a holonomic drive similar to the one we are using. However, the poster only mentioned that the wheels were at 45 degree angles, and although the OP was talking about omni wheels and I have never heard of someone mounting mecum wheels at 45 degree angles to the base, I wondered if anyone had experience with/has used this method with a holonomic omni drive like I have described.
If it doesn't work, I would also be interested in some pointers on working out the math for this myself, and where to start.
Reply With Quote
  #2   Spotlight this post!  
Unread 12-01-2017, 08:53
MuskieProgramme MuskieProgramme is online now
Registered User
FRC #6420
Team Role: Programmer
 
Join Date: Dec 2016
Rookie Year: 2014
Location: Muscatine, IA
Posts: 19
MuskieProgramme is an unknown quantity at this point
Re: Holonomic Drive WPILIBJ Support

I am new to WPILIB so there may be a better way, but I have created a holonomic drive in FIRST Tech Challenge.

You have two joystick inputs (x and y)
You have four outputs (a, b, c, and d) arranged like so:
a b
c d

The formula will look something like this:

a = y + x
b = -y + x
c = y - x
d = -y - x

...assuming that positive power to each rotates the robot clockwise.

This isn't the "ideal" formula for holonomic driving - I have since moved on to something better at scaling. However, it is the simplest to understand and easiest to implement. If you want to understand the logic behind it, draw each wheel as a force vector, with a proposed direction. Cancel any opposing force and you can see how this particular formula works.
Reply With Quote
  #3   Spotlight this post!  
Unread 12-01-2017, 09:02
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: Holonomic Drive WPILIBJ Support

Quote:
Originally Posted by abigailthefox View Post
My team has decided to go with a holonomic drivetrain this year, specifically four omni wheels mounted in the corners of the base, at 45 degree angles.

I saw on another thread (from several years ago) a note about using the mecanumDrive_Cartesian method in the WPILIBJ to control a holonomic drive similar to the one we are using.
Yes, the mecanum method in WPILib will work with the omni drive you described above.

What gear ratio (from motor to wheel) are you planning to use?

What diameter omni wheels?



Reply With Quote
  #4   Spotlight this post!  
Unread 12-01-2017, 12:21
abigailthefox's Avatar
abigailthefox abigailthefox is offline
Registered User
FRC #1711 (Raptors)
Team Role: Programmer
 
Join Date: Feb 2015
Rookie Year: 2015
Location: Traverse City
Posts: 59
abigailthefox has a spectacular aura aboutabigailthefox has a spectacular aura about
Re: Holonomic Drive WPILIBJ Support

Quote:
Originally Posted by Ether View Post
What gear ratio (from motor to wheel) are you planning to use?

I don't know yet, we're between a few options.

Quote:
Originally Posted by Ether View Post
What diameter omni wheels?

6" omni wheels.
Reply With Quote
  #5   Spotlight this post!  
Unread 12-01-2017, 13:14
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: Holonomic Drive WPILIBJ Support

Quote:
Originally Posted by abigailthefox View Post
I don't know yet, we're between a few options.

6" omni wheels.
Well, whatever you choose, do yourself a big favor and choose based on doing some math.

If you need help, ask. There are lots of easy-to-use drivetrain spreadsheets available.


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


All times are GMT -5. The time now is 12:33.

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