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A look at what maneuvers (e.g. strafe, turn in place, Ackermann steering, etc.) are possible for most of the possible configurations of a typical FRC swerve drive.
In a holonomic swerve drive, each wheel module is steered and driven independently. This produces a drive system that can perform an outstanding--almost spooky--range of motions. Often in FRC, however, wheel modules are steered and/or powered in groups to simplify the design and reduce the number of motors required. What maneuvers are given up as more and more of these degrees of freedom are tied together?
This is an offshoot of this discussion, where Jared341 suggested a matrix-like classification structure for many of the most popular swerve drive configurations, and began to list the behaviors of each configuration. This document makes use of Ether's nomenclature for some particularly interesting maneuvers.
I hope someone might find this document useful when attempting to make tradeoffs between the degree of maneuverability and the number of controllable degrees of freedom required. When faced with a choice between wheelspeed slip and steering angle slip, steering slip should be preferred, since there will be a less-adverse effect on applied traction.
If you notice errors, please let me know! If you'd like to see any additions... go away 
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swerveConfigurationStudy_revB.pdf
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swerveConfigurationStudy_revB.xlsx
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Discussion
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03-11-2013 10:02 AM
Jared Russell
Re: paper: Possible swerve maneuvers by configuration
Ah, the Unified Field Theory of Swerve.
Great job!
03-11-2013 11:19 AM
Gdeaver
Re: paper: Possible swerve maneuvers by configuration
Our team has done 4 wheel independent steering, 4 wheel independent drive for 4 years now. There have been many discussions of the positive and negative value of swerve in all it's forms to First competitions. However if you have never experienced swerve it is hard to visualize the movement and possibilities. This season we have refined our swerve code to eliminate some problems in the past years. The following link is to our website and down on the right hand side is a video of our driver just messing around testing a new code update. Not really doing anything but the video shows allot of the movements and behavior that are possible. Also the bumpers are not on so wheel position can be observed. This may help with the visualization of the chart posted.
http://wiki.team1640.com/index.php?t...IX_Drive_Train
03-11-2013 11:30 AM
Nate Laverdure
Re: paper: Possible swerve maneuvers by configuration
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Originally Posted by Gdeaver
Our team has done 4 wheel independent steering, 4 wheel independent drive for 4 years now.
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03-11-2013 04:41 PM
viveksridhar
Re: paper: Possible swerve maneuvers by configuration
I have a question about the swerve drive you've built. I'm looking at the drawings you posted on the wiki (http://wiki.team1640.com/images/b/b2/Proto6c.pdf)
I'm a bit confused about which motors are doing what. There seem to be two motors mounted vertically facing upwards, one in line with the wheel and one to the side of the wheel. Which one is driving the wheel itself and which is acting as the pivot, and how do you make a vertical motor drive a wheel in a perpendicular direction? Also, wouldn't it make more sense to have the wheel driving the motor mounted horizontally rather than vertically, and directly drive the wheel?
03-11-2013 04:43 PM
viveksridhar
Re: paper: Possible swerve maneuvers by configuration
Never mind, I just realized there's a more detailed explanation later in that page. Sorry about that!
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