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-   -   Most Graceful Mecanum Robots? (http://www.chiefdelphi.com/forums/showthread.php?t=154435)

rlance 02-02-2017 11:46

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Andrew_L (Post 1638179)
Here is a control scheme for omnidirectional robots that I developed earlier that, in my opinion, gives the driver the most useful control over the robot's position and orientation: https://docs.google.com/document/d/1...it?usp=sharing

I'd be happy to answer any questions about it.

What is the "Moon Maneuver"???

We are doing omni this year and are considering adding a button for a pre-programmed evasive maneuver. Is this one of those?

InFlight 02-02-2017 11:53

Re: Most Graceful Mecanum Robots?
 
We used a flight simulator type of joystick for our recycle rush Mecanum Drive. This enables you to control both direction, and rotation (via twist) simultaneously and intuitively. You could use this method for either field centric or robot centric control.

Logitech 963290-0403 is a very reasonably priced PC USB option.

Caleb Sykes 02-02-2017 12:12

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Chris is me (Post 1639454)
For a game like this one, I like having the option to switch between the two mid-match - dip into field centric for fine adjustments and robot centric for long sprints. But this of course requires even more training to be good.

Or have one driver trained with field centric and one trained with robot centric and switch control between the two as needed.

NShep98 02-02-2017 12:16

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by rlance (Post 1639459)
What is the "Moon Maneuver"???

We are doing omni this year and are considering adding a button for a pre-programmed evasive maneuver. Is this one of those?

A moon maneuver is a move in which you "orbit" around a fixed point, often an opposing robot, while facing that point at all times, much like the moon orbiting the Earth.

Chris is me 02-02-2017 12:21

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Caleb Sykes (Post 1639467)
Or have one driver trained with field centric and one trained with robot centric and switch control between the two as needed.

I'm not sure if you're joking, but this is a completely ridiculous idea. This is almost guaranteed to give you worse performance than giving the same driver double the stick time, and the speed lost in switching drivers mid-match completely negates the relatively minor speed advantage of switching between the styles of drive. Don't do this.

Ari423 02-02-2017 12:56

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Chris is me (Post 1639454)
You can also train your drivers to operate a field centric controls in the "tank drive direction" when going on long sprints. It's just a matter of remembering to turn and pointing in the right direction.

For a game like this one, I like having the option to switch between the two mid-match - dip into field centric for fine adjustments and robot centric for long sprints. But this of course requires even more training to be good.

With a bit of feedback control, you should be able to assign a button on the controller to "sprint mode" where driving is still field-centric, but the robot always drives with the front forward. I haven't tried it before, but that should give you the sprinting speed of robot-centric with the ease of control of field-centric.

JesseK 02-02-2017 12:58

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by NShep98 (Post 1639468)
A moon maneuver is a move in which you "orbit" around a fixed point, often an opposing robot, while facing that point at all times, much like the moon orbiting the Earth.

I was staying away from this thread until this. I love driving this maneuver in video games and robot demos. It's pretty fun. However, have yet to see it give an advantage in any FRC match videos.

---

This year Mecanum seems to give the most advantage during line up of receiving a gear and placing a gear. In field-centric mode, it does so by increasing margin of error and intuitiveness to do those tasks. The most graceful Mecanum bots this year will do just that, IMO. Juke moves with Mecanum under-perform 9 times out of 10.

In my experience, Mecanum doesn't seem to reduce the time it takes to do those tasks when compared to a practiced driver on a tank. Time is the differentiator in everything at high levels of play. I'd even say that a tank drive which sprints 16-18ft/s during the straightaways and shifts to a 6-7ft/s low gear for the line-up would still be a faster cycle time than a Mecanum drive at an overall 12-13ft/s.

So "graceful" Mecanum bots who can score well in a reasonable amount of time may find a home on my alliance in early events simply because I set goals for my team to do so well at our singular role that the Mecanum bot will be largely undefended. Or maybe I get that Mecanum bot on my alliance in order to absorb the defense since they're so easy to defend. Who knows :rolleyes:.

Caleb Sykes 02-02-2017 13:02

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Chris is me (Post 1639469)
I'm not sure if you're joking, but this is a completely ridiculous idea. This is almost guaranteed to give you worse performance than giving the same driver double the stick time, and the speed lost in switching drivers mid-match completely negates the relatively minor speed advantage of switching between the styles of drive. Don't do this.

Not joking, that is the control scheme we are currently planning to implement.

We still have plenty of time to abort if we discover this is more trouble than it is worth.

Tom Bottiglieri 02-02-2017 13:04

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Greg Marra (Post 1637813)
What are some of the most graceful examples of mecanum robot driving in the past?

None.

RoboChair 02-02-2017 13:50

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Tom Bottiglieri (Post 1639497)
None.

Something about "Going sideways is a waste of time"?

lenny8 02-02-2017 14:33

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Tom Bottiglieri (Post 1639497)
None.

I agree that we really haven't seen a perfect example YET on how you should drive mecanums but with the constant bashing of the drivetrain ( of people who never even tried it might I add ) it's going be hard to get there.

Kevin Sevcik 02-02-2017 14:42

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Ari423 (Post 1639490)
With a bit of feedback control, you should be able to assign a button on the controller to "sprint mode" where driving is still field-centric, but the robot always drives with the front forward. I haven't tried it before, but that should give you the sprinting speed of robot-centric with the ease of control of field-centric.

This, only I think it'd be better to have it pick the closest of forwards/backwards. Or maybe have that toggleable. It should be straightforward to implement. Hold down the print button, lock out rotation input, apply fixed amount of rotation command CW or CCW in direction of travel based on commanded vector and your current heading. Probably scale it down once you get very close to the correct heading, but capping it to a reasonable amount would probably make driving more stable for large corrections.

Field centric tank drive implemented in this fashion would be an interesting innovation.

CalTran 02-02-2017 14:52

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by lenny8 (Post 1639547)
I agree that we really haven't seen a perfect example YET on how you should drive mecanums but with the constant bashing of the drivetrain ( of people who never even tried it might I add ) it's going be hard to get there.

Can't tell if you're talking in general, or trying to call out 254 on having never tried an omnidirectional drivetrain. If the latter, I'd be immensely surprised if they've never dabbled with it in offseason. I assume their on field performance with a WCD needs no justification.

Caleb Sykes 02-02-2017 15:05

Re: Most Graceful Mecanum Robots?
 
Quote:

Originally Posted by Kevin Sevcik (Post 1639554)
This, only I think it'd be better to have it pick the closest of forwards/backwards. Or maybe have that toggleable. It should be straightforward to implement. Hold down the print button, lock out rotation input, apply fixed amount of rotation command CW or CCW in direction of travel based on commanded vector and your current heading. Probably scale it down once you get very close to the correct heading, but capping it to a reasonable amount would probably make driving more stable for large corrections.

Field centric tank drive implemented in this fashion would be an interesting innovation.

We are implementing this in our code this year, I had this same idea a few years back but haven't had a chance to implement it until now.

Strafing can be pretty useful in many situations, but it is an awful choice for travelling long distances quickly.

NolanGZ3452 02-02-2017 15:52

Re: Most Graceful Mecanum Robots?
 
I might be bias because this is my own team, but i beleave we got the most our of our mecanum drivetrain in 2015. I know its not the same because the games are so different, but i believe if you go with a mecanum drivetrain you need to use its abilities to your advantage or else you might as well just have gone with tank drive.

https://www.youtube.com/watch?v=7FJLMB58eVU


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