Theory Question

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Theory Question

Michael C. Menefee

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

 

Thanks,

Michael Menefee

 

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Re: Theory Question

Brian Gerkey

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

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

        brian.



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RE: Theory Question

Michael C. Menefee
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: [hidden email]
[mailto:[hidden email]] On Behalf Of
Brian Gerkey
Sent: Thursday, February 23, 2006 9:11 PM
To: [hidden email]
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  
> answer a question for me, I'd appreciate it.  I'm trying to figure  
> out how the velocities in the position commands are generally  
> interpreted.  If you set an x velocity of, say, 50mm/s, and a turn  
> rate of 5 deg/s, is that generally accepted as "I want to travel  
> 50mm in the x dir, and the y component of my motion for this second  
> will be determined by my turn rate", or "I want to travel along an  
> arc of 5mm turning at a rate of 5 deg/s"?  Basically, I guess I'm  
> kind of asking if those commands are in world space or local  
> space.  I could interpret the commands either way, but I'm just  
> wondering how most player clients are written.
The latter interpretation is correct.  What you're doing is setting  
the instantaneous translational and rotational velocities.

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

        brian.



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<a href="http://sel.as-us.falkag.net/sel?cmd=k&kid0944&bid$1720&dat1642">http://sel.as-us.falkag.net/sel?cmd=k&kid0944&bid$1720&dat1642
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