07-01-2011 01:31

JVN

Re: pic: Team 2220's Swerve Drive Chasis

Hey,
Good start! Just a friendly word of warning: a swerve drive takes a LOT of effort to get right, especially on the first try. You WILL spend most of the season fighting this design to get it running right, and to keep it running right. You'll spend so much time fighting with it, your driver won't get to use any of the advantages a swerve drive would provide... I promise you this.

I BEG you to not try to use this design without building it in the pre-season and testing it. If you're putting lots of resources (effort) into your drivetrain you're not going to have as much effort available for your mechanism -- the mechanism is where the magic is, and what makes you successful on the field.

Build a simple, reliable, drivetrain, and spend your engineering on the rest of your robot. You'll be much happier. If the summer comes along and you still want to build a swerve drive, try it then.

If you don't have the resources to prototype it in the summer, you might not want to be attempting it anyways. Again, we all have limited resources during the build season -- spend the ones you have on things that will have the biggest payoff...

$0.02
-John

07-01-2011 03:50

Justin Montois

Re: pic: Team 2220's Swerve Drive Chasis

^^ That. Just that.

07-01-2011 07:44

Jedward45

Re: pic: Team 2220's Swerve Drive Chasis

Thanks for the feedback! We have already prototyped the module and found really no problems with it. The big question mark will be attaching the lateral drive and rotational chains. However, we have the resources to build multiple chassis, so we have some room for error. We also built a failsafe into the design. If we cant drive the modules w/swerve, we can lock their positions and drive standard tank.

07-01-2011 07:44

Al Skierkiewicz

Re: pic: Team 2220's Swerve Drive Chasis

From the inspector in me, in looking at the base construction, I think 'what a great place for bumpers'. However, if you use this as a design basis, please double and triple check the bumper rules and FRAME PERIMETER definition if it returns this year. If in doubt, please ask the Q&A after kickoff.

07-01-2011 12:00

JesseK

Re: pic: Team 2220's Swerve Drive Chasis

I too like the I beams as use for a frame -- very creative!

From a maintenance standpoint I would make some strategic holes in the I-beams so you can see what's going on inside the modules in the very likely event of a problem.

To solve the frame perimeter issues (based upon previous years' rules), some stiff foam or lightweight plywood would fit nicely into the I-beam rails.

I'll also echo John's sentiments, yet also add to it that programming a crab drive is just as difficult as building it. Hopefully you have very, very talented programmers since they've probably only seen un-optimized or theoretical code.

07-01-2011 12:24

imac256

Re: pic: Team 2220's Swerve Drive Chasis

That does appear to be a very nice system you guys have designed, but my question is have you guys figured out how you are going to control it and place the sensors on the wheels? A swerve drive needs the sensors to operate and their positioning can be somewhat tricky and has to be designed for.

As for coding a swerve drive, it took my team about a week straight to perfect our swerve drive code, and at least another week of testing before it was stable enough for the drivers to really use, and during that time the frustrations were high. Be sure to give the base to the programmers at least half way through the build time, because trying to program this with people breathing down your necks is not fun. I speak from personal experience there, our 2009 and then our prototype 2010 robot were both swerve drive.

If you guys would like some examples of swerve code, it isn't very nicely structured, our old code is here:
http://coolhub.imsa.edu/cybercollab/...ming-documents
If you have any questions regarding that code send me a PM and I'll try to help

- Ian McInerney
Lead Programmer, Team 2022

07-01-2011 13:02

Ether

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by JesseK I'll also echo John's sentiments, yet also add to it that programming a crab drive is just as difficult as building it. Hopefully you have very, very talented programmers since they've probably only seen un-optimized or theoretical code.

07-01-2011 14:21

Jedward45

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Ether @Jedward45: Are you planning to rig this up as a crab, or do you plan to have independent drive and steering for all 4 wheels?

07-01-2011 15:17

Chris is me

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Jedward45 Thanks for the feedback! We have already prototyped the module and found really no problems with it. The big question mark will be attaching the lateral drive and rotational chains. However, we have the resources to build multiple chassis, so we have some room for error. We also built a failsafe into the design. If we cant drive the modules w/swerve, we can lock their positions and drive standard tank.

07-01-2011 15:36

Ether

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Chris is me swerve is not intuitive to drive no matter how you code it

08-01-2011 00:52

Jedward45

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Chris is me Just remember - mechanical is half the battle. More like a third. A third is control. Swerve is by no means intuitive to control. A third is driving practice - swerve is not intuitive to drive no matter how you code it, so your driver needs a lot of time to get used to it for it to really show its advantages. (Also, the biggest mechanical challenges of swerve come once the module is attached to a full chassis)

08-01-2011 01:25

Chris is me

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Ether I'm not convinced this is true. It seems to me that, with smart enough software, swerve (of the Unicorn variety anyway) should be almost as seamless in its motions as a well-designed mecanum... and without the traction disadvantages of mecanum.

08-01-2011 03:02

artdutra04

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Chris is me A third is driving practice - swerve is not intuitive to drive no matter how you code it, so your driver needs a lot of time to get used to it for it to really show its advantages.

08-01-2011 11:05

Superllama12

Re: pic: Team 2220's Swerve Drive Chasis

That is quite impressive! (hoohoohoo emoticons!!!) From what I understand, Swerve is very difficult to build and use! I hope it works well for you guys!

08-01-2011 20:42

Ether

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Chris is me My "ideal" swerve would have a field centric "point the modules this way" stick and a robot centric everything else... I think.

08-01-2011 20:45

indubitably

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by Ether My ideal swerve would have field-centric Halo-style interface with a pushbutton to align the bot in the direction of motion a la item #4 of this post.

10-01-2011 12:48

gren737

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by JVN Hey, Good start! Just a friendly word of warning: a swerve drive takes a LOT of effort to get right, especially on the first try. You WILL spend most of the season fighting this design to get it running right, and to keep it running right. You'll spend so much time fighting with it, your driver won't get to use any of the advantages a swerve drive would provide... I promise you this. I BEG you to not try to use this design without building it in the pre-season and testing it. If you're putting lots of resources (effort) into your drivetrain you're not going to have as much effort available for your mechanism -- the mechanism is where the magic is, and what makes you successful on the field. Build a simple, reliable, drivetrain, and spend your engineering on the rest of your robot. You'll be much happier. If the summer comes along and you still want to build a swerve drive, try it then. If you don't have the resources to prototype it in the summer, you might not want to be attempting it anyways. Again, we all have limited resources during the build season -- spend the ones you have on things that will have the biggest payoff... $0.02 -John

10-01-2011 19:53

Jedward45

Re: pic: Team 2220's Swerve Drive Chasis

Quote:

Originally Posted by gren737 ^^^ Take it from another mentor this is very good advice! ^^^

10-01-2011 23:31

Gdeaver

Re: pic: Team 2220's Swerve Drive Chasis

Swerve or six wheel drive? That is the question that our team battled tonight. Swerve won. I notified my wife tonight that she may not see me much for the next 6 weeks. This is going to be a very stressful and crazy build. If we pull off our design goals we will have one awesome robot. If we fail we will fail horribly. The programmers have go fever. We'll see how the are in week six and seven and eight...

11-01-2011 15:24

jethrow

Re: pic: Team 2220's Swerve Drive Chasis

swerve drive is harder then you think do not rely on chains.

11-01-2011 16:00

Racer26

Re: pic: Team 2220's Swerve Drive Chasis

1075 did a 2+2 swerve configuration for the last two years (for the 2010 FRC season we designed and built DSSwerve, AFAIK to date the ONLY FRC bot with invertable swerve drive)

Swerve is hard to do well. Our 2010 incarnation of swerve worked fairly well, but we had a driver with 4 years of FRC experience, and our 2010 DSSwerve was derived from our 2009 Swerve.

2010 DSSwerve suffered from throwing chains, bending swerve modules via side-loading when being pushed, and more. The worst part about building a swerve system is that the mechanical complexity of the system makes repairing failed parts significantly more difficult, and can often result in needing to disassemble large portions of the robot, depending on which part has failed.