gazebo is not publishing odom tf

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Hi all,

I am trying to simulate a car-like robot with following frame tree: frame tree.png. But gazebo is not publishing the tf from odom to base-footprint and I get the following error in the terminal:

[ERROR] [1472202557.517496142, 40.405000000]: Unable to find odometry for model name /=-1

This is what my launch file looks like:

    <?xml version="1.0"?>
<launch>

      <arg name="paused" default="false"/>
      <arg name="use_sim_time" default="true"/>
      <arg name="gui" default="false"/>
      <arg name="headless" default="false"/>
      <arg name="debug" default="false"/>

<param name="use_sim_time" value="true"/>

  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(find chassis_gazebo)/worlds/chassis.world"/>
    <arg name="debug" value="$(arg debug)" />
    <arg name="gui" value="$(arg gui)" />
    <arg name="paused" value="$(arg paused)"/>
    <arg name="use_sim_time" value="$(arg use_sim_time)"/>
    <arg name="headless" value="$(arg headless)"/>
  </include>

<param name="robot_description" command="$(find xacro)/xacro.py '$(find chassis_description)/urdf/chassis.urdf.xacro'" />

  <!-- push robot_description to factory and spawn robot in gazebo -->
  <node name="chassis_spawn" pkg="gazebo_ros" type="spawn_model" output="screen" 
    args="-urdf -param robot_description -x 28 -y 4 -z 0 -Y 1.57 -model chassis"/>

  <!-- Load joint controller configurations from YAML file to parameter server -->
  <rosparam file="$(find chassis_control)/config/chassis_control.yaml" command="load"/>

  <!-- load the controllers -->
  <node name="controller_spawner" pkg="controller_manager" type="spawner" respawn="false"
output="screen" args="joint1_velocity_controller joint2_velocity_controller front_left_steering_position_controller front_right_steering_position_controller  joint_state_controller"/>

  <!-- convert joint states to TF transforms for rviz, etc -->
  <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher"
    respawn="false" output="screen">
  </node>

</launch>

Does anyone have any advice?

Thank you in advance!