Definitive FRC Mechanisms
 

I was thinking about things I could do to further familiarize my team members with the history of FRC robot design and considered creating a presentation that is a look at the best of the best mechanical and control systems designs.

I thought it might be a fun exercise to debate who and what would be in this presentation here on CD. The notion is simple -- for any or each of the following items, select a robot that, in your opinion, represents the best-in-class in that sort of function. Defend your choice. Add pictures when possible.

This list is not comprehensive. Some of the terms are quite generalized, some are not. Feel free to suggest additional terms.

DRIVE SYSTEMS

• 2WD
• 3WD
• 4WD
• 6WD
• Treads
• Omnidirectional
• Swerve
• Mecanum
• Articulated/Suspension
• Steering
• Cantilevered Wheels
• Live Axle
• Dead Axle
• Brakes
• Stair Climber
• Ramp Climber
• Other

GEARBOXES

• 1 Speed
• 2 Speed
• 3+ Speed
• Continuously Variable Transmission
• Worm Drive
• Clutches
• Winch
• One-Way/Ratchet
• Power Take Off
• Other

MANIPULATORS

• Elevator
• Single Jointed Arm
• Double Jointed Arm
• Triple+ Jointed Arm
• Roller Claw
• Pincer Claw
• Crane Claw
• Vacuum System
• Helix
• Shooter
• Turret
• Linkage
• Lifter
• Balancing
• Hanging
• Grabbing Pipes
• Defense
• Other

CONTROLS

• Robot Control
• Manipulator Control
• Custom Dashboard
• Motor positioning
• Path finding
• Machine Vision
• Other

Re: Definitive FRC Mechanisms
 

Perhaps include mecanum under DRIVE SYSTEMS since that has been the subject of much interest on CD.

I mention this only because I notice that you have Omnidirectional listed, which would be a superset of mecanum, but you also have swerve listed, which is a subset of omnidirectional.

Re: Definitive FRC Mechanisms
 

I've added it back. I may have replaced it with omnidirectional when I meant to add them both. Oops.

Re: Definitive FRC Mechanisms
 

I'm going to think on this one for a while before responding...

-Brando

Re: Definitive FRC Mechanisms
 

Team 16 the Bomb Squad for 3wd swerve, couldn't find any pictures of it.

Re: Definitive FRC Mechanisms
 

I'd probably personally expand on "linkages" a lot more. Four bar paralellograms in arms are practically ubiquitous, but past that there's so much more you can do with them and so many other robots that use varying linkages for different applications that I think special emphasis should be added on four bar arms.

Re: Definitive FRC Mechanisms
 

I'm going to say 254/60/968 and the West Coast Drive (6WD) is the best all-around drive (i.e., does everything well). 118's coaxial swerves are probably the best in the "standard" 4-wheel swerve. Plenty of pictures of 254/60/968 on CD-Media (visible under the hopper in http://www.chiefdelphi.com/media/photos/23573, http://www.chiefdelphi.com/media/photos/26141, http://www.chiefdelphi.com/media/photos/27537). 118's swerves are better seen in the Behind the Design books, but the one from 2007 is at http://www.chiefdelphi.com/media/photos/27221, though poorly visible.

The transmission from 254/968 in 2007 (http://www.chiefdelphi.com/media/photos/27018, http://www.chiefdelphi.com/media/photos/28070) is one of the best 2-speed trannies in FRC, but it's tough to make (and AM sells plenty of 2-speed trannies). It weighs just over 1 lb without the motors, and their robot was plenty good to go with it.

Re: Definitive FRC Mechanisms
 

IMO, 1771 gets a tip of the hat for vacuums (they even got the Championship Xerox Creativity Award!). From the 2008 season.



1771 in 2008
Impeller
1771 2008 Scrimmage Video

Re: Definitive FRC Mechanisms
 

If the goal is to familiarize your team members with the history of FRC robot design get the kids to do the research! Using blue alliance, chief delphi maybe even youtube the students would get more out of actually doing the research than being told what is good.

I conducted a similar activity recently with our strategy pre-season sub-team where we looked more at performance than at design. However this gave the new students an opportunity to get familiar with certain teams and this process could easily be adapted to fit your design idea. Pick a topic and ask each team to research and present on it, this could be done in an hour or so or more time depending on how in depth you want the information to be.

I hope this helps, if not sorry for not answering your question :)

Re: Definitive FRC Mechanisms
 

I completely agree with that statement, but this thread will ensure the kids find the "right" answers.

Re: Definitive FRC Mechanisms
 

I agree, but it depends who your students are. Are they freshman with no knowledge, seniors with design experience, or even freshman who know more about different teams than you do? Unless they are seniors and juniors who have knowledge of previous machines from teams I will show them the best in each section so I know that they have all seen one of the top machines or parts of a robot.

I really like using thebluealliance for showing match strategy and design in action because then you can show kids a match where omnis are useful in some ways, but all the other times when you will be pushed out of the way by defense. It is one thing to tell, tell, tell; however, show and tell is the best option IMHO.

Re: Definitive FRC Mechanisms
 

there are many "right answers"! Also I think that students at any level are fully capable of finding "right" answers to these questions.

in addition to the resources I have already mentioned FIRST hands out design awards. These teams win these awards for a reason!

also look at teams that performed really well like the finalists at championships these teams made it that far for a reason!

Re: Definitive FRC Mechanisms
 

Part of this exercise will, I hope, get people to look beyond award and event winners. Award winning designs are rarely notable and it's likely that there are some great subsystem designs that are strapped to mediocre robots.

I have not yet fully conceptualized what my presentation will look like. I want it to be more than a history lesson, but I also want to be armed with good examples of great system design to present to them as a great benchmark.

Re: Definitive FRC Mechanisms
 

A good starting place on much of what you want has been provided by AM here. It covers the basics of a lot of the topics you mention, but perhaps not to the same depth you desire. Reguardless, they are good resources for teaching new team members.

Re: Definitive FRC Mechanisms
 

I know I might sound like someone tooting their own horn (although I was not on the team at the point), but in 2008, 1178 built Manny, a robot with scissor lift elevator. You can look it up on thebluealliance.net, but here is a basic summary: 2 motor six wheel (West Coast) drive, where each motor only powers the center wheel. 2 tusks (leasing to the name) powered by a window motor to pick up the ball and load it onto the scissor lift. Worked well in competition, from what I hear, it was one of the most reliable robots we have, still worked until we had an issue with the controller (but will soon be updated with a C-RIO). Although it had a few problems (could have been slightly more powerful and maybe a little bit taller) it was an impressive robot, and a team favorite.

Re: Definitive FRC Mechanisms
 

A possible bonus category would be:

Innovative Buzzer Beaters: Ways teams have scored points even after the clock stpped.

Also, Ways to Hang as this is a periodic bonus that many vetrans get a significant advantage having seen numerous "ways to hang".

Re: Definitive FRC Mechanisms
 

Thanks.

I have my own opinions about a lot of these categories, but am interested in reading what others have to say about them as well. I've been around FRC for nearly as long as some of my students have been alive, so I've seen a robot or two in my time. :)

Re: Definitive FRC Mechanisms
 

I agree with the buzzer beat mentality; 1717's ramps were hands down the BEST in 07, and they heavily inspired their own hanger this year.

I think this season also pointed out a very useful and effective variant of the roller claw; the pinching roller claw using a clutch. I remember in the past we had done this in software in some cases, the clutch is a very elegant mechanical solution.

This is quite a stretch, but while we're on design, acquisition and scoring area/angle is a big one. Whatever the system is, it should allow as much driver error as possible while acquiring and scoring.

Re: Definitive FRC Mechanisms
 

Team 60 in 2002 is one of the really dominant robots that I'll never forget.

On the topic of intricate details in mechanism design, there were many features of the 2004 team 60/254 robot I really liked, including the single-piston 3-jaw claw and the level-winder for the winch. I think I even recall custom-printed heat-shrink tubing on the team 60 robot that year.

Re: Definitive FRC Mechanisms
 

This is the kind of thing I am always keeping my eyes open for!::rtm::

If I could add two cents, I think adding a small section on frame materials would be marvelous! One of the most frequent questions I get from people is what a robot is made of. Aluminum, Steel, wood, 1/4th, 1/8th, 1/16th, square tube, C channel, plates...

True experience only comes from seeing and believing. Thats what seperates the men from the boys, the alumni from the freshmen. However, knowing what you're seeing, while your seeing it, is priceless.

Really hope to see this final version!
Sincerely,
Petrie

Re: Definitive FRC Mechanisms
 

I wouldn't mind taking a stab at a couple of these:

I was not around in the really early days when everything had to be custom. Because of that, I am trying to throw in mixes of really cool custom stuff and really cool COTS stuff.

GEARBOXES[*]1 Speed: The various ways to get a 1-speed from a FP-gearbox, and Banebot planetaries.
[*]2 Speed: AM Super shifter vs. 254/968 custom (it keeps getting better each year)
[*]3+ Speed: 3 speed: NBD-Whitepaper 4 speed: KB33-white paper (2004? I think)
[*]Continuously Variable Transmission- Does the 217 Crazy Chicken Drive Count?
[*]Worm Drive: Window and Van-door Motors. [*]Clutches: I really liked the clutches used on grippers this year (71 used some nice COTs clutches from McMaster, and a bunch of teams used belts as slip clutches.)
[*]Winch
[*]One-Way/Ratchet: NBD with clutch pins installed.
[*]Power Take Off: 254/968 2010 lifter.
[*]Other-Belt drive systems. There were a whole bunch in 2009 I think I liked 234 that year.

Re: Definitive FRC Mechanisms
 

You would never have known it by just looking, but 971 used a software clutch this year on our front (and back) roller. Current loop on the roller worked very well, cost nothing, and weighed nothing. Another tool to throw in the back of tricks.

Re: Definitive FRC Mechanisms
 

How did you close the loop on current? Did you use a Jag in current mode to drive the motor? Or did you have a current sensor and close the loop in your cRIO code?

Re: Definitive FRC Mechanisms
 

Elevator
Wildstang, 111, 1997, 1998, 1999
The best two-sided interlocking lifters ever. Their lift in 1997 went way higher than should have been possible given the available materials.

Roller Claw and Multi-joint Arm
TechnoKats, 45, "Skycat" maybe....
Telescoping arm section with turret, an upper joint and a really simple roller claw.

Telescoping Arm
Pink, 233, 2005
Three sections of telescoping art.

Shooter
HOT, 2006
Unusual shooter that shot balls into an arc that generated backspin. It had some issues, but it scores high for creativity and execution.

Defense
Juggernauts, 1, 2000
Most underrated robot ever...possibly. This was one of the most rugged, well-devised robots I have ever seen. They dominated the double ramp all season, but didn't get picked at worlds. :(

Suspension
Robonauts, 118, 2010
Their hump buster was pretty amazing. Lots of suspension travel and a truly robust design.

I could do this all night. :eek:

Re: Definitive FRC Mechanisms
 

We tried both methods. We used CAN, so we had a loop on the cRIO for SVR, and used the Jag current loop for nationals. One concern with using the Jag in current mode was that we wouldn't be able to feed forward our drivetrain commands to the roller. (Backup tended to rip the ball out of the roller.) The solution to that ended up being to add the feed forward to the goal of the current loop.

Re: Definitive FRC Mechanisms
 

Brakes: 25 had the market cornered on this for a number of years. A servo mounted above that picture would push a rod into the brass gear there, locking the entire drivetrain up. Neat trick.

Re: Definitive FRC Mechanisms
 

I'm trying to parse the above. What I think I hear you saying is this:

Since backing up the robot tended to rip the ball out of the roller mechanism, you realized you needed more torque on the roller when backing up (and perhaps less torque when going forward?). So instead of using a constant setpoint for the current command, you subtracted some fraction of the drivetrain command from the roller current setpoint. Clever. Am I understanding it correctly ?

Re: Definitive FRC Mechanisms
 

Yes, you are. That's definitely a bit clearer than what I originally wrote. :p We originally did this by adding some more to the voltage that the current loop on the cRIO was sending to the jaguar.

I'm not totally sure if the real issue is that you need more torque when backing up, but that the ball would roll on the ground when backing up. This would require us to spin the roller up, but still have the same torque applied to the ball from the roller. The acceleration of the roller due to the current loop wasn't fast enough to react to this correctly, so our little bit of extra umph would help that out.

Re: Definitive FRC Mechanisms
 

You might also want to add Cams to the list, 148/217 in 2010 come to mind, though I'm sure there were many more.

This is quite the nifty feature. I've always wanted to try it out but the 25 mechanism seems to only work in Gear Based Drivetrains.

Re: Definitive FRC Mechanisms
 

Baxter Bomb Squad, 2004.

Re: Definitive FRC Mechanisms
 

I couldn't find much info on the bot, but Team 997 used treads very effectively in 2010.

http://www.chiefdelphi.com/media/photos/35069

Re: Definitive FRC Mechanisms
 

They're designed and produced by Outback Manufacturing of Bend, OR and have been used on robots since at least 2007.

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103 has used this a few times, but most effectively in our 2007 robot. I do not have any pictures of this, but almost no team was able to move us when we engaged the breaks. And the best part about the brakes is that it did not put any stress on the motors. Its quite a nifty trick that is nice to have, but if we are overweight, its the first thing to go.

Re: Definitive FRC Mechanisms
 

... Titanium... :rolleyes:

Re: Definitive FRC Mechanisms
 

Wildstang (111) in 2003 is still my favorite bots of all time.

A full description of it can be found here
http://www.wildstang.org/2003/inventor/main.html

The Swerve drive, wings and StangPS made this robot king of the hill.

It could plant itself to the ramp and turn on a dime.

It was great to watch it take over Reliant Stadium.