Hello,
here is a sample ball model I'm using for my simulations. Notice the
<kd> and <kp> params and try to play with their values - they control
how much force
is applied to this specific ball model to prevent it from sinking:
<body:sphere name = "ball_body">
<dampingFactor>0.0001</dampingFactor>
<xyz>0 0 0</xyz>
<rpy>0 0 0</rpy>
<geom:sphere name = "ball_geom">
<xyz>0 0 0.01</xyz>
<rpy>0 0 0 </rpy>
<size>0.02</size>
<mu1>0.3</mu1>
<kp>2e6</kp>
<kd>2e6</kd>
<bounce>120</bounce>
<bounceVel>0.5</bounceVel>
<slip1>0.7</slip1>
<slip2>0.7</slip2>
<mass>0.045</mass>
<visual>
<scale>0.02 0.02 0.02</scale>
<mesh>unit_sphere</mesh>
<material>Gazebo/Robocup_orange</material>
</visual>
</geom:sphere>
</body:sphere>
Also global parameters like step time, erp and cfm does matter, I'm
using those values:
<stepTime>0.002</stepTime>
<erp>0.9</erp>
<cfm>0.01</cfm>
I hope that will help you,
Best regards,
Kamil Muszyński
2011/6/9 Rein Appeldoorn <rein...@gmail.com>:
> I checked those two parameters but nothing changes. Is this a known fact or
> is this just something weird? Here is the world file I'm using:
>
> -----------------------------------------------------------------------------------
>
> <?xml version="1.0"?>
>
> <gazebo:world
> xmlns:xi="http://www.w3.org/2001/XInclude";
> xmlns:gazebo="http://playerstage.sourceforge.net/gazebo/xmlschema/#gz";
> xmlns:model="http://playerstage.sourceforge.net/gazebo/xmlschema/#model";
>
> xmlns:sensor="
> http://playerstage.sourceforge.net/gazebo/xmlschema/#sensor";
> xmlns:window="
> http://playerstage.sourceforge.net/gazebo/xmlschema/#window";
> xmlns:param="http://playerstage.sourceforge.net/gazebo/xmlschema/#param";
>
> xmlns:body="http://playerstage.sourceforge.net/gazebo/xmlschema/#body";
> xmlns:geom="http://playerstage.sourceforge.net/gazebo/xmlschema/#geom";
> xmlns:joint="http://playerstage.sourceforge.net/gazebo/xmlschema/#joint";
>
> xmlns:interface="
> http://playerstage.sourceforge.net/gazebo/xmlschema/#interface";
> xmlns:ui="http://playerstage.sourceforge.net/gazebo/xmlschema/#ui";
> xmlns:rendering="
> http://playerstage.sourceforge.net/gazebo/xmlschema/#rendering";
> xmlns:controller="
> http://playerstage.sourceforge.net/gazebo/xmlschema/#controller";
> xmlns:physics="
> http://playerstage.sourceforge.net/gazebo/xmlschema/#physics"; >
>
> <verbosity>5</verbosity>
>
> <physics:ode>
> <stepTime>0.005</stepTime>
> <gravity>0 0 -9.8</gravity>
> <cfm>0</cfm>
> <erp>0.8</erp>
> <quickStep>true</quickStep>
> <quickStepIters>100</quickStepIters>
> <quickStepW>1.3</quickStepW>
> <contactMaxCorrectingVel>100.0</contactMaxCorrectingVel>
> <contactSurfaceLayer>0.0</contactSurfaceLayer>
> <updateRate>0</updateRate>
> </physics:ode>
>
> <rendering:gui>
> <type>fltk</type>
> <size>800 600</size>
> <pos>0 0</pos>
> </rendering:gui>
>
> <rendering:ogre>
> <ambient>0.8 0.8 0.8 1.0</ambient>
> <sky>
> <material>Gazebo/CloudySky</material>
> </sky>
> <grid>false</grid>
> <shadowTechnique>stencilModulative</shadowTechnique>
> </rendering:ogre>
>
> <!-- The Ground Plane -->
> <model:physical name="groundplane_model">
> <xyz>0 0 0</xyz>
> <rpy>0 0 0</rpy>
> <static>true</static>
>
> <body:plane name="ground_plane_body">
> <geom:plane name="ground_plane_geom">
> <normal>0 0 1</normal>
> <size>1000 1000</size>
> <segments>100 100</segments>
> <uvTile>100 100</uvTile>
> <material>Gazebo/GrassFloor</material>
> <mu1>109999.0</mu1>
> <mu2>1000.0</mu2>
> </geom:plane>
> </body:plane>
> </model:physical>
> <!-- End Ground Plane -->
>
> <!-- The Ball Model -->
> <model:physical name="ball_model">
> <xyz>0.025 0 1</xyz>
> <static>false</static>
>
> <body:sphere name="ball_body">
> <geom:sphere name="ball_geom">
> <xyz>0 0 0</xyz>
> <size>0.015</size>
> <mass>0.02</mass>
>
> <visual>
> <size>0.03 0.03 0.03</size>
> <mesh>unit_sphere</mesh>
> <material>Gazebo/White</material>
> </visual>
> <mu1>109999.0</mu1>
> </geom:sphere>
> </body:sphere>
> </model:physical>
> <!-- End Ball Model -->
>
>
> <!-- The White Point light -->
> <model:renderable name="point_white">
> <xyz>-3 0 5</xyz>
> <static>true</static>
> <light>
> <type>point</type>
> <diffuseColor>0.8 0.8 0.8</diffuseColor>
> <specularColor>0.1 0.1 0.1</specularColor>
> <range>20</range>
>
> <!-- Constant(0-1) Linear(0-1) Quadratic -->
> <attenuation>0.3 0.01 0</attenuation>
> </light>
> </model:renderable>
> <!-- End White Point light -->
>
> </gazebo:world>
>
> -----------------------------------------------------------------------------------
>
> Do you guys get the same behavior? If so, is there any fix or a way to get
> rid of this?
>
> Thanks in advance!
>
> Rein
>
> On Wed, Jun 8, 2011 at 8:33 PM, John Hsu <john...@willowgarage.com> wrote:
>
>> Hi,
>>
>> you can check to see if contactSurfaceLayer is small, e.g.
>>
>> <contactSurfaceLayer>0</contactSurfaceLayer>
>>
>> in addition, you might want to make sure <CFM> is 0.
>>
>> hope this helps.
>>
>> John
>>
>> On Wed, Jun 8, 2011 at 11:00 AM, Rein Appeldoorn <rein...@gmail.com>
>> wrote:
>>
>> > Hi,
>> >
>> > I'm working on a simulation of an autonomous football table. When I model
>> > the ball, it's sinking through the floor. Because the geometry of the
>> ball
>> > is quite small (radius of 0.015), this sinking is not acceptable. Strange
>> > enough, when I check the other objects, they're all sinking a little bit.
>> > Does anybody have an explanation for this?
>> >
>> > A thing I can do is scale up all models, this makes the relative errors
>> > much
>> > less. Does anybody got experience with this fact? Is scaling a good
>> > solution?
>> >
>> > Thanks in advance!
>> >
>> > Regards,
>> >
>> > Rein
>> >
>> >
>> ------------------------------------------------------------------------------
>> > EditLive Enterprise is the world's most technically advanced content
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>> >
>>
>>
>>
>> --
>> John Hsu, Ph.D.
>> Senior Research Engineer
>> Willow Garage Inc.
>> +1-650-475-2809
>>
>> ------------------------------------------------------------------------------
>> EditLive Enterprise is the world's most technically advanced content
>> authoring tool. Experience the power of Track Changes, Inline Image
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