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2016-11-25 08:13:41 -0600 commented question URDF Car model: Joint bounces/wobbles

I added the relevant snippet of my URDF

2016-11-25 08:13:21 -0600 received badge  Editor (source)
2016-11-25 05:33:37 -0600 asked a question URDF Car model: Joint bounces/wobbles

Hi there. I'm using Ros Indigo with Gazebo2.

I modeled a car with two fixed rearwheels and two steerable (revolute joints) frontwheels using URDF. When the simulation starts the car falls down in the front. If i reduce the mass of the chassis the car won't fall down in the front anymore but starts to bounce. If I reduce the chassis mass to a small number (1kg) it almost stops bouncing.

My guess is, that this joint can only take a certain amount of weight.

How can I resolve this issue? After all my chassis weighs over 500 kg.

Thanks.

<robot name="erod_macros" xmlns:xacro="http://www.ros.org/wiki/xacro">

<xacro:macro name="wheel" params="wheelname lr fr steerable">



<joint name="wheel_hinge_${wheelname}" type="${steerable}">
    <parent link="chassis"/>
    <child link="wheel_hinge_bearing_${wheelname}"/>
    <origin xyz="${fr*wheel_base/2} ${lr*track_width/2} ${wheel_radius-ground_clearance-chassis_height/2}"  rpy="0 0 0"/>
    <axis> xyz="0 0 1" rpy="0 0 0"
    <limit upper="0" lower="-1.57" velocity="10" effort="1"/>
    </axis>

</joint>

<link name="wheel_hinge_bearing_${wheelname}">
    <inertial>
        <origin xyz="0 0 0" rpy="0 0 0"/>
        <mass value="0.0001"/>
        <inertia ixx="0.001" ixy="0.0" ixz="0.0" iyy="0.001" iyz="0.0" izz="1"/>
    </inertial>
</link>

<!-- Joint: HingeWheel -->
<joint name="wheel_axis_${wheelname}" type="continuous">
  <parent link="wheel_hinge_bearing_${wheelname}"/>
  <child link="wheel_${wheelname}"/>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <axis xyz="0 ${lr} 0" rpy="0 0 0"/>

</joint>

<!-- Link: Wheel -->
<link name="wheel_${wheelname}">
  <collision>
    <origin xyz="0 0 0" rpy="${Pi/2} 0 0"/>
    <geometry>
      <cylinder length="${wheel_width}" radius="${wheel_radius}"/>
    </geometry>
  </collision>
  <visual>
    <origin xyz="0 0 0" rpy="${lr*Pi/2} 0 0"/>
    <geometry>
             <mesh filename="package://meshes/meshes/rad_eRod.dae"/>            </geometry>
  </visual>
  <inertial>
    <origin xyz="0 0 0" rpy="${Pi/2} 0 0"/>
    <mass value="${wheel_mass}"/>
    <inertia ixx="${wheel_I_rr}" ixy="0.0" ixz="0.0" iyy="${wheel_I_yy}" iyz="0.0" izz="${wheel_I_rr}"/>

  </inertial>
</link>


<!-- Transmission: Steer the wheel -->

<!-- Transmission: Rotate the wheel -->

<gazebo reference="wheel_${wheelname}"> <mu1 value="200.0"/> <mu2 value="200.0"/> <material>Gazebo/Black</material> </gazebo>

</xacro:macro>

</robot>

2016-11-19 10:52:41 -0600 asked a question Can't see my model in GZClient

Hi. I'm quite new to Gazebo. I'm using the following system Ubuntu 14.04 ROS Indigo Gazebo 2.2.3

I went trough some tutorials on how to build a gazebo model. I wanted to create a robot (4 wheeled car) but somehow the model doesn't appear in the GUI of Gazebo. There aren't any errors though when using roslaunch to simulate the model.

My robots urdf file looks as follows

<?xml version="1.0"?>
   <robot name="erod" xmlns:xacro="http://www.ros.org/wiki/xacro">

<xacro:property name="wheel_width" value="0.195"/>
<xacro:property name="wheel_radius" value="0.28"/>
<xacro:property name="chassis_width" value="1.22"/>
<xacro:property name="chassis_length" value="3"/>
<xacro:property name="chassis_height" value="0.5"/>
<xacro:property name="wheel_base" value="2.347"/>
<xacro:property name="track_width" value="1.6"/>
<xacro:property name="ground_clearance" value="0.15"/>
<xacro:property name="cg_pos_x" value="0.75"/>
<xacro:property name="cg_pos_z" value="0.5"/>
<xacro:property name="wheel_I_rr" value="1000"/>s
<xacro:property name="wheel_I_yy" value="1000"/>
<xacro:property name="wheel_mass" value="20"/>
<xacro:property name="wheel_mu1" value="200"/>
<xacro:property name="wheel_mu2" value="200"/>
<xacro:property name="chassis_I_xx" value="1000"/>
<xacro:property name="chassis_I_yy" value="1000"/>
<xacro:property name="chassis_I_zz" value="1000"/>
<xacro:property name="chassis_mass" value="520"/>

<xacro:include filename="$(find erod_description)/urdf/erod.gazebo" />
<xacro:include filename="$(find erod_description)/urdf/materials.xacro" />

<link name="footprint" />

<joint name="base_joint" type="fixed">
    <parent link='footprint'/>
    <child link='chassis'/>
</joint>

<link name="chassis">
    <collision> 
            <origin xyz="0 0 ${wheel_radius}" rpy="0 0 0"/> 
            <geometry> 
                <box size="${chassis_length} ${chassis_width} ${chassis_height}"/> 
            </geometry> 
    </collision>
    <visual> 
            <origin xyz="0 0 ${wheel_radius}" rpy="0 0 0"/> 
            <geometry> 
                <box size="${chassis_length} ${chassis_width} ${chassis_height}"/> 
            </geometry> 
            <material name="orange"/>
    </visual>
    <inertia> 
    <origin xyz="0 0 ${wheel_radius}" rpy="0 0 0"/> 
        <mass value="${chassis_mass}"/> 
        <box_inertia m="${chassis_mass}" x="${chassis_length}" y="${chassis_width}" z="${chassis_height}"/>
    </inertia>
</link>

</robot>