Turning Quality Metrics

[JVN]

Originally Posted by IKE

I concur with Chris on there must be an "optimal" amount of scrub.

<SNIP>

Originally Posted by Chris Hibner

My point was that there is an optimal amount of scrub (not just less scrub is better).

<SNIP>

Though it makes me nervous to dissent from my much more experienced colleagues...
I disagree on a purely qualitative basis. In 2011 the Robowranglers built a Nonadrive (4 traction + 5 omni) as Raptor's drivetrain. During initial "live fire" tests, we hypothesized that the side-side wheel wasn't actually much of an advantage. We pulled the circuit breaker from the middle wheel, and zip-tied it up -- performance actually increased. (Note: I still believe the side-side motion is useful in some games, just not 2011).

Our plan was to then swap out the omni-wheels for some medium-traction wheels like kit wheels or Colsons to get the performance as described by others in this thread. What happened next was surprising...

We found that in the 4-omni wheel skid-steer configuration (which we've dubbed "butterfly drive) our driver was able to execute some incredibly smooth, and quite precise maneuvers. He was able to also do some "slide" maneuvers we hadn't anticipated.

I would have never speculated that a "zero-scrub" drive would perform like it did, but with Connor on the sticks the thing performed great, and provide benefits that would not have been present in another system.

That said...

Originally Posted by Jared341

The Nonadrive was a mechanical system that had features that could be used to reduce/eliminate turning overshoot (ex. timely deployment of the traction wheels).

Agreed. "Zero" Scrub to "Infinite" Scrub with the push of a button.
Perhaps Connor's ability to "drop traction - lock heading" helped him avoid over-shoot issues.

My thinking is...
Mechanically balancing scrub to prevent overshoot will help with driver smoothness, but are sacrifices being made to achieve this? What do you give up to help your driver deal with overshoot?

Good discussion.

-John

[IKE]

Originally Posted by JVN

My thinking is...
Mechanically balancing scrub to prevent overshoot will help with driver smoothness, but are sacrifices being made to achieve this? What do you give up to help your driver deal with overshoot?

Good discussion.

-John

I totally agree with your nonadrive experience, but there should probably be a giant * which you eluded to about talented and/or experienced driver.

Less experienced drivers tend to do better with more scrub. that is part of the reason our robots have more scrub at teh start of teh season than the end of the season.

You can set up a front drive car to have slight over steer (likely to spin), and a a driver with reasonable car control on a racetrack will be way faster than one that understeers. That being said, there is a reason why even street performance cars have understeer.

Switchables though get a category of their own. I really enjoyed our 2011 chassis, and I am a huge fan of the 469 style caster drives.

PS, I would love to have watched a talent show between the 217 and 148 drivers in 2010. I got the opportunity to watch a 217 practice, and the speed an maneuverability was absolutely amazing.

[JamesTerm]

Originally Posted by IKE

I totally agree with your nonadrive experience, but there should probably be a giant * which you eluded to about talented and/or experienced driver.

Less experienced drivers tend to do better with more scrub. that is part of the reason our robots have more scrub at the start of the season than the end of the season.

IKE, I'll be curious to see how what you say unfolds... my goal is to make *any* driver look good by making the controls very intruitive for anyone to drive. I'd argue less experienced drivers need any intuitive help they can (e.g. just as Jake has mentioned with the field centric drive for team 1717), and should be able to drive any kind of well defined drive with a virtually identical feel to them.

I cannot completely back up this arguement... just yet, > ; )
but I believe this enough to take a leap of faith and do it.

Oh yes... do you want to share how driving with PID closed loop encoders help with turning performance and latency?

[JVN]

Originally Posted by JamesTerm

IKE, I'll be curious to see how what you say unfolds... my goal is to make *any* driver look good by making the controls very intruitive for anyone to drive. I'd argue less experienced drivers need any intuitive help they can (e.g. just as Jake has mentioned with the field centric drive for team 1717), and should be able to drive any kind of well defined drive with a virtually identical feel to them.

I cannot completely back up this arguement... just yet, > ; )
but I believe this enough to take a leap of faith and do it.

Oh yes... do you want to share how driving with PID closed loop encoders help with turning performance and latency?

James,
This activity seems like it would be very "high effort, low reward" compared to other developments an FRC team could be doing.

I'm going to assume you're going to do some driver drills... if your team isn't the type of team that does driver drills, you're probably not capable of doing what you're describing anyways.

Training drivers isn't that hard. If you're going to run some driver drills you're going to quickly move past the part of the learning curve where this software would matter anyways.

Maybe I'm under-estimating the reward, and over-estimating the effort required for meaningful result.

-John

[James Tonthat]

Originally Posted by JVN

Training drivers isn't that hard. If you're going to run some driver drills you're going to quickly move past the part of the learning curve where this software would matter anyways.

I remember a saying that goes something like

Good robots with bad drivers can lose.
Bad robots with good drivers can win.
Good robots with good drivers can dominate.

That being said, we usually get software to around 80-90% then let the drivers learn to drive the thing. The last 20% takes 80% of the time. (Pareto principle)

[Gregor]

Originally Posted by James Tonthat

I remember a saying that goes something like

Good robots with bad drivers can lose.
Bad robots with good drivers can win.
Good robots with good drivers can dominate.

One that our mentor likes is "a 100% robot with 50% drivers is a 50% robot."

[JamesTerm]

Originally Posted by JVN

James,
This activity seems like it would be very "high effort, low reward" compared to other developments an FRC team could be doing.

I'm going to assume you're going to do some driver drills... if your team isn't the type of team that does driver drills, you're probably not capable of doing what you're describing anyways.

Training drivers isn't that hard. If you're going to run some driver drills you're going to quickly move past the part of the learning curve where this software would matter anyways.

Maybe I'm under-estimating the reward, and over-estimating the effort required for meaningful result.

-John

It was high effort, but now it is a well-defined solution... so it's really an inherited benefit... with no time invested here... but my time invested now is in learning about interfacing with the basics robotics drive itself... gears torque etc... stuff I need to learn no matter what solution we choose. I have gone over your spreadsheet with a fine tooth comb and use this as a simulation. (More on that in the other post on cof tomorrow).

We do driver drills... I listen to the driver's needs and I've talked with Jim Z as I'm very inspired by Team 33's method of drive control. I am not afraid of new innovation. We have to continuously challenge old paradigms and believe and continue to try new things.

For me the reward is that great feeling I saw when we continued to successfully balance the ramp for Rebound Rumble... to make the driver feel like he is at one with how the robot performs. I remember the moment I hesitated when I crashed my car because it was not intuitive to me (I did not know how to quickly react to slow down a standard stick drive). The reward is for a user to not need to worry about what to do when he panics because it is intuitive.

[kramarczyk]

Originally Posted by JVN

We found that in the 4-omni wheel skid-steer configuration (which we've dubbed "butterfly drive) our driver was able to execute some incredibly smooth, and quite precise maneuvers. He was able to also do some "slide" maneuvers we hadn't anticipated.

I would have never speculated that a "zero-scrub" drive would perform like it did, but with Connor on the sticks the thing performed great, and provide benefits that would not have been present in another system.

Do you have a video link showing the awesomeness?

Spoiler for lack of self control.:

John, you don't want no scrub? Scrub from a chassis don't get no love from you? Hanging out field side, watching Wrangler drive, explaining CoF to me.

[JVN]

Originally Posted by kramarczyk

Do you have a video link showing the awesomeness?

Awesomeness is subjective. We like it.
Any match video from 2011 would somewhat show it. In the teaser video you can see some of the drift moves, and you can see Connor kind of whip the robot around a few times (he backs into the rack, then spins the front around to score).

John, you don't want no scrub? Scrub from a chassis don't get no love from you? Hanging out field side, watching Wrangler drive, explaining CoF to me.

I had to google it...