View Single Post
  #7   Spotlight this post!  
Unread 13-12-2016, 09:20
Chris Hapstack's Avatar
Chris Hapstack Chris Hapstack is online now
Design Mentor
FRC #0342 (Burning Magnetos)
Team Role: Mentor
 
Join Date: Apr 2015
Rookie Year: 2007
Location: Charleston, SC
Posts: 34
Chris Hapstack is a jewel in the roughChris Hapstack is a jewel in the roughChris Hapstack is a jewel in the rough
Re: Robostangs 548 2016 Offseason Swerve - V01 Sidestep

How did you decide on the gearing for your steering motors? It looks like the BAGs are geared at 100:1 (assuming both VP stages are 10:1), which would put you at 130 rpm (unloaded). Is that about standard these days for swerve steering? Never having done a swerve drive myself, I'm curious how you would decide on a target rotational speed. I guess iterative testing would be a good place to start - let the drivers try out different steering speeds and find their sweet spot. My only real reference is the AndyMark Swerve & Steer module which steers at 90 rpm.

Also, when it comes to motor selection for swerve steering, how do you model the steering load? I would be inclined to call it a rotary mechanism, with the arm length being half the width of the wheel and the arm load being the friction force on the wheel. I plugged that into JVN's calculator and got the following. Does that seem like a reasonable way to model it? It seems like a pretty low loading, so I'm inclined to think that friction in the swerve module itself actually plays a pretty big role (potentially bigger than the wheel/ground friction).

However, if this model seems reasonable, then could you potentially get away with using an AndyMark snow blower motor geared at 1:1? (JVN here). That would give you 100 rpm steering in a lighter and much cheaper package (albeit without an easily-integrated VP encoder). Experience makes me hesitant to use a built-in worm gear motor for any mechanism that runs the whole match, but then again I've only used window motors before. I suppose the snow blower motors are designed to run continuously, right? At least a snow blower itself runs continuously while a car window doesn't...
__________________

2017 -------- Team 342 mentor (Charleston, SC)
2015-2016 - Team 85 mentor (Zeeland, MI)
2007-2010 - Team 281 student (Greenville, SC)
Reply With Quote