The Player Project

On Feb 23, 2006, at 6:27 PM, Michael Menefee wrote:

> Well, I know everyone is busy with Player 2.0, but if you could =20
> answer a question for me, I=92d appreciate it.  I=92m trying to figure =
=20
> out how the velocities in the position commands are generally =20
> interpreted.  If you set an x velocity of, say, 50mm/s, and a turn =20
> rate of 5 deg/s, is that generally accepted as =93I want to travel =20
> 50mm in the x dir, and the y component of my motion for this second =20=

> will be determined by my turn rate=94, or =93I want to travel along an =
=20
> arc of 5mm turning at a rate of 5 deg/s=94?  Basically, I guess I=92m =20=

> kind of asking if those commands are in world space or local =20
> space.  I could interpret the commands either way, but I=92m just =20
> wondering how most player clients are written.
The latter interpretation is correct.  What you're doing is setting =20
the instantaneous translational and rotational velocities.

So in your example, if you set 50mm/s and 5deg/s, after 1 second a =20
perfect robot will have traveled 50mm counterclockwise along a =20
circular arc.  The curvature of this arc can be computed from the two =20=

velocities.

	brian.

Ah, good deal.  My next question was going to be "what happens if you =
turn
more than 90 deg/s?" if it wasn't that way. :)

Thanks.

-----Original Message-----
From: playerstage-developers-admin@...
[mailto:playerstage-developers-admin@...] On Behalf Of
Brian Gerkey
Sent: Thursday, February 23, 2006 9:11 PM
To: playerstage-developers@...
Subject: Re: [Playerstage-developers] Theory Question


On Feb 23, 2006, at 6:27 PM, Michael Menefee wrote:

> Well, I know everyone is busy with Player 2.0, but if you could =20
> answer a question for me, I'd appreciate it.  I'm trying to figure =20
> out how the velocities in the position commands are generally =20
> interpreted.  If you set an x velocity of, say, 50mm/s, and a turn =20
> rate of 5 deg/s, is that generally accepted as "I want to travel =20
> 50mm in the x dir, and the y component of my motion for this second =20
> will be determined by my turn rate", or "I want to travel along an =20
> arc of 5mm turning at a rate of 5 deg/s"?  Basically, I guess I'm =20
> kind of asking if those commands are in world space or local =20
> space.  I could interpret the commands either way, but I'm just =20
> wondering how most player clients are written.
The latter interpretation is correct.  What you're doing is setting =20
the instantaneous translational and rotational velocities.

So in your example, if you set 50mm/s and 5deg/s, after 1 second a =20
perfect robot will have traveled 50mm counterclockwise along a =20
circular arc.  The curvature of this arc can be computed from the two =20
velocities.

	brian.



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