Re: prismatic joints

Hi Mithila,

I don't know that much about the joints in breve, because I am working on 
swarm robotics and to speed up the simulation I am currently using no 
physics. But as I understood the documentation you should use the 
set-joint-velocity method for controlling the joint. And additionally the 
set-joint-damping method to set the friction of the joint. This may prevent 
the joint from falling to the ground. You can find those methods in the Joint 
class. 

\Marc

On Wednesday, 20. April 2005 13:56, Mithila Patwardhan wrote:
> Hi,
>
> Thanks for that extremely detailed answer to my query, Marc. I wanted to
> know exactly that.
> I have another question - this one is about prismatic joints in breve. I
> have used prismatic joints in my gripper design. When I run the
> simulation, the links sort of fall to ground. I thought I should use
> set-joint-limits but I get a compiler error when I try to do that. There
> is a get-joint-position method but no set-joint-position method. How can
> one control the joint?
>
> Regards,
> Mithila
>
> Marc Szymanski wrote:
> >Hi,
> >
> >you could write a method in the controller class that returns the pointer
> > to the body.
> >
> >Control : myController {
> >	+ variables:
> >		body, gripper (object).
> >	...
> >	+ to get-gripper:
> >		return gripper.
> >
> >	+ to get-body:
> >		return body.
> >}
> >
> >You could now access the body and the gripper in every other class with
> >"(controller get-body) method-of-body." or "(controller get-gripper)
> >method-of-gripper.".
> >
> >An ohter way would be, if you want to have several bodies with grippers
> > that belong to each other, to initialize the gripper with the body.
> >
> >Real : Gripper {
> >	+ variables:
> >		myBody (object).
> >
> >	+ to init-with body theBody (object):
> >		myBody = theBody.
> >		# the following line is very important.
> >		return self.
> >}
> >
> >I think this would be the most elegant way. Cause you have a typical
> >OO-connection like a "gripper has a body". You could create the gripper in
> >the init method of the body. I think this is much cleaner than statics or
> >friends even C++ because it defines their connection. Did you read the
> > stuff about the Multibody? Because you need to link the gripper with the
> > body if you want to move the gripper when moving the body.
> >
> >I hope I understood your question.
> >
> >\Marc
> >
> >On Wednesday, 20. April 2005 04:38, Mithila Patwardhan wrote:
> >>Hi,
> >>
> >>I have a question about accessing items outside a class. I am trying to
> >>build a vehicular robot with a gripper. I have a class for the body of
> >>the robot and another for the gripper. I want to use an object which
> >>belongs to the class for the body inside the iterate procedure in the
> >>gripper class.
> >>
> >>I have read through the breve documentation and was unable to come up
> >>with a way of doing this. In fact, what is a clean way of referring to
> >>objects from other classes without instantiating the class (something
> >>along the lines of static members or friend functions?)
> >>
> >>Thanks,
> >>Mithila
> >>_______________________________________________
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> >>[email protected]
> >>http://lists.spiderland.org/mailman/listinfo/breve
>
> _______________________________________________
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-- 
--------------------------------------------------------------------------
Dipl.-Inform. Marc Szymanski
Institute for Process Control and Robotics(IPR), Universität Karlsruhe(TH)
Kaiserstr. 12, D-76128 Karlsruhe, Germany
Phone: +49 721 608 6694, Fax: +49 721 608 7141
WWW http://wwwipr.ira.uka.de/~szymansk

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