[ODE] Best way to achieve this effect

Georg Martius mai99dgf at studserv.uni-leipzig.de
Sat Oct 27 03:39:44 MST 2007


I suggest you have make the skateboard work yourself. I mean write some code 
which is executed every timestep and sorts out the specific things about your 
I suggest the following:
- Have a body (main) without geom, where your wheels/axis are connected with a 
hinge2 each. 
- Have a second body (board) with a geom, which you link with a hinge into the 
main body. The board can tilt left and right. with respect to the main body.
- make the board tilt hard: use dJointGetAngle to obtain current angular 
position. use dJointAddForce  to apply the force you need to keep it in the 
center position. You can use different force profiles, since a linear spring 
implementation might not be what you want. 
- steer the wheels according to the angle: you just got the angular position 
of the board, now apply it to the hinge2 joints with an angularmotor

Have fun!


Am Samstag, 27. Oktober 2007 06:43 schrieb Salik Syed:
> Hi,
> Yes I'm aware that constraints can be set to have a springiness to them
> using the ERP (?CFM) parameters.
> I did read your entire message, and the method you outlined is not what
> I'm looking for, I don't want the
> skateboards trucks to turn simply by a motor or outside force, because
> this is not how a real skateboard
> works. I want to be able to place a body on the deck and when I shift
> that body the deck should
> tilt causing the trucks to turn.In order to do this some kind of joint
> is necessary between the deck and
> the truck in order to cause the deck tilt motion to cause the truck turn
> motion.
>  But i'm not sure what that should be.
> I also thought perhaps a single "link" body with a ball joint connecting
> to the truck and another
> ball joint connected to the deck??? I don't know if this would work
> correctly because I would still need
> to make the hinge joint stiff (so that the truck needs alot of force in
> order to actually rotate)  and I'm not
> sure how to do this
> -Salik
> I think people may not understand exactly how the skateboard works?
> Jon Watte (ODE) wrote:
> > Salik Syed wrote:
> >> What I would like is that the trucks are very hard to spin and only
> >> turn when
> >> a significant force is applied on one  side of the duck to make them
> >> turn.
> >> What is the best way to achieve this effect?  Sort of like a spring
> >> that stretches every time the
> >> deck tilts or the trucks turn, so that a signifcant force is
> >> necessary for either to happen.
> >
> > Did you search for "spring" in the documentation?
> > If so, what don't you understand about the various explanations?
> > What else have you already tried, so we don't have to worry about
> > things that didn't work for you?
> > And did you read the ENTIRE message I sent you on this subject
> > previously?
> > Hint: It actually answers this question, too.
> >
> > Cheers,
> >
> >             / h+

---- Georg Martius,  Tel: +49 177 6413311  -----
------- http://www.flexman.homeip.net ----------
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