Definitive FRC Mechanisms

[IKE]

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".

[Madison]

Originally Posted by buildmaster5000

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.

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.

[AdamHeard]

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.

[sanddrag]

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.

[MarkoRamius1086]

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

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

[IKE]

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.

[AustinSchuh]

Originally Posted by IKE

[*]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.)

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.

[Ether]

Originally Posted by AustinSchuh

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.

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?

[ajlapp]

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.

[AustinSchuh]

Originally Posted by Ether

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?

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.

[Billfred]

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.

[Ether]

Originally Posted by AustinSchuh

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.

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 ?

[AustinSchuh]

Originally Posted by Ether

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 ?

Yes, you are. That's definitely a bit clearer than what I originally wrote. 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.

[thefro526]

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.

Originally Posted by Billfred

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.

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.

[Brandon Holley]

Originally Posted by thefro526

You might also want to add Cams to the list, ......though I'm sure there were many more.

Baxter Bomb Squad, 2004.