Re: [PlayerStage-Gazebo] Differential drive robot inertia in Gazebo

[David M. <mic...@kn...>]

I have already turned the torque way down and experimented with changing
the masses.  I added the additional parameters you suggested as well.
Unfortunately it didn't really change much.  The best that I have been
able to do so far is to keep the velocity low.  In my particular case it
would be better if I could turn some of the physics off for just the
robot's wheels and have it behave more like it does in Stage.  I have
done some experimentation with Microsoft Robotics Developer Studio as
well.  When I modeled the same robot there, they recommended that the
wheels should just be set to a given velocity instead of having the
physics engine try to compute their behavior.

On Thu, 2010-04-01 at 12:58 -0700, Nate Koenig wrote:
> Hello,
> 
> You can reduce the torque parameter, and play with the masses.
> 
> You can also modify the friction of the wheels. To do this add a the
> following parameters to a geom:
> 
> <geom ...>
>   <kp>100000000</kp>
>   <kd>1.0</kd> <!-- Damping constraint -->
>   <bounce>0.0</bounce> <!-- How bouncy the surface is -->
>   <bounceVel>10</bounceVel> <!-- MAx velocity before bounce is applied -->
>   <mu1> BIG NUMBER </mu1>
>   <mu2> BIG NUMBER </mu2>
>   <slip1> small number (0.01) </slip1>
>   <slip2> small number (0.01)</slip2>
> </geom>
> 
> The ODE manual has descriptions of all these parameters.
> 
> -nate
> 
> On Sun, Mar 28, 2010 at 9:41 PM, David Michal <mic...@kn...> wrote:
> > I have modeled a differential drive robot in Gazebo.  The problem is
> > that when I driver the robot from Player it seems to have quite a bit of
> > inertia. When turning to the left or the right it overshoots the target
> > quite a bit.  The real robot uses stepper motors so that once you tell
> > it to stop turning it does.  Is there a way to get Gazebo to better
> > model a stepper motor?  I am using Player 3.0.1, Gazebo 0.9.0, and ODE
> > 0.11.1.
> >
> > Here is what I have in the model file.
> >
> > <body:cylinder name="left_wheel_body">
> >  <xyz>0.0 0.1325 -0.2032</xyz>
> >  <rpy>0 90 90</rpy>
> >  <geom:cylinder name="left_wheel_geom">
> >    <size>.0635 .032</size>
> >    <mass>0.5</mass>
> >    <visual>
> >      <rpy>0 0 90</rpy>
> >      <size>0.127 0.127 0.032</size>
> >      <mesh>drivewheel.mesh</mesh>
> >      <material>Gazebo/Black</material>
> >    </visual>
> >  </geom:cylinder>
> > </body:cylinder>
> >
> > <body:cylinder name="right_wheel_body">
> >  <xyz>0.0 -0.1325 -0.2032</xyz>
> >  <rpy>0 90 90</rpy>
> >  <geom:cylinder name="right_wheel_geom">
> >    <size>.0635 .032</size>
> >    <mass>0.5</mass>
> >   <visual>
> >      <rpy>0 0 90</rpy>
> >      <size>0.127 0.127 0.032</size>
> >      <mesh>drivewheel.mesh</mesh>
> >      <material>Gazebo/Black</material>
> >    </visual>
> >  </geom:cylinder>
> > </body:cylinder>
> >
> > <joint:hinge name="left_wheel_joint">
> >  <body1>left_wheel_body</body1>
> >  <body2>chassis_body</body2>
> >  <anchor>left_wheel_body</anchor>
> >  <anchorOffset>0 0 0</anchorOffset>
> >  <axis>0 1 0</axis>
> >  <erp>0.8</erp>
> >  <cfm>10e-5</cfm>
> > </joint:hinge>
> >
> > <joint:hinge name="right_wheel_joint">
> >  <body1>right_wheel_body</body1>
> >  <body2>chassis_body</body2>
> >  <anchor>right_wheel_body</anchor>
> >  <anchorOffset>0 0 0</anchorOffset>
> >  <axis>0 1 0</axis>
> >  <erp>0.8</erp>
> >  <cfm>10e-5</cfm>
> > </joint:hinge>
> >
> > <controller:differential_position2d name="controller1">
> >  <leftJoint>right_wheel_joint</leftJoint>
> >  <rightJoint>left_wheel_joint</rightJoint>
> >  <wheelSeparation>0.265</wheelSeparation>
> >  <wheelDiameter>0.127</wheelDiameter>
> >  <torque>1</torque>
> >  <interface:position name="position_iface_0"/>
> > </controller:differential_position2d>
> >
> >
> >
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