Hello everyone,

I can't seem to find a working controller for my car-like robot. This is the model I am using:

<?xml version="1.0"?>
<robot name="$(arg roboname)" xmlns:xacro="http://www.ros.org/wiki/xacro">

  <!-- Included URDF/XACRO Files -->
  <xacro:include filename="$(find chassis_description)/urdf/materials.urdf.xacro" />
  <xacro:include filename="$(find chassis_description)/urdf/chassis_wheels.urdf.xacro" />

  <!-- PROPERTY LIST -->
  <!--All units in m-kg-s-radians unit system -->
  <property name="M_PI" value="3.1415926535897931" />

  <!-- Main Body-base -->
  <property name="base_x_size" value="4.68" /> 
  <property name="base_y_size" value="1.27" /> 
  <property name="base_z_size" value="0.2" />
  <property name="base_mass" value="800" /> <!-- in kg-->

  <!--Inertial macros for the box and cylinder. Units are kg*m^2-->
  <macro name="box_inertia" params="m x y z">
    <inertia  ixx="${m*(y*y+z*z)/12}" ixy = "0" ixz = "0"
              iyy="${m*(x*x+z*z)/12}" iyz = "0"
              izz="${m*(x*x+z*z)/12}" /> 
  </macro>

  <!-- BASE-FOOTPRINT -->
  <!-- base_footprint is a fictitious link(frame) that is on the ground right below base_link origin -->
  <link name="base_footprint">
    <inertial>
      <mass value="0.0001" />
      <origin xyz="0 0 0" />
      <inertia ixx="0.0001" ixy="0.0" ixz="0.0"
          iyy="0.0001" iyz="0.0" 
          izz="0.0001" />
    </inertial>
    <visual>
        <origin xyz="0 0 0" rpy="0 0 0" />
        <geometry>
            <box size="0.001 0.001 0.001" />
        </geometry>
    </visual>
  </link>

  <gazebo reference="base_footprint">
    <turnGravityOff>false</turnGravityOff>
  </gazebo>

  <joint name="base_footprint_joint" type="fixed">
  <origin xyz="0 0 ${wheel_radius - base_z_origin_to_wheel_origin}" rpy="0 0 0" />
    <parent link="base_footprint"/>
    <child link="base_link" />
  </joint>

  <!-- BASE-LINK -->
  <!--Actual body/chassis of the robot-->
  <link name="base_link">
    <inertial>
      <mass value="${base_mass}" />
      <origin xyz="0 0 0" />
      <!--The 3x3 rotational inertia matrix. -->
      <box_inertia  m="${base_mass}" x="${base_x_size}" y="${base_y_size}" z="${base_z_size}"/> 
    </inertial>    
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <box size="${base_x_size} ${base_y_size} ${base_z_size}"/>
      </geometry>
      <material name="Grey" />
    </visual>  
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0 " />
      <geometry>
        <box size="${base_x_size} ${base_y_size} ${base_z_size}"/>
      </geometry>
    </collision>     
  </link>
  <gazebo reference="base_link">
    <material>Gazebo/Grey</material>
    <turnGravityOff>false</turnGravityOff>
  </gazebo>

  <!-- WHEELs -->
  <wheel fb="front" lr="right" parent="front_right_wheel_steering_block" translateX="1" translateY="-1" flipY="-1" base_x_origin_to_wheel_origin="1.66"/>
  <wheel fb="front" lr="left" parent="front_left_wheel_steering_block" translateX="1" translateY="1" flipY="-1" base_x_origin_to_wheel_origin="1.66"/>
  <wheel fb="back" lr="right" parent="base_link" translateX="-1" translateY="-1" flipY="-1" base_x_origin_to_wheel_origin="1.14"/>
  <wheel fb="back" lr="left" parent="base_link" translateX="-1" translateY="1" flipY="-1" base_x_origin_to_wheel_origin="1.14"/>

    <joint name="front_right_wheel_joint" type="continuous">
      <parent link="front_right_wheel_steering_block"/>
      <child link="front_right_wheel"/>
      <origin xyz="0 0 0.125" rpy="1.570796 0 0" /> 
      <axis xyz="0 1 0" rpy="0 0 0" />
      <limit effort="100" velocity="100"/>
      <joint_properties damping="0.0" friction="0.0"/>
    </joint>

    <joint name="front_left_wheel_joint" type="continuous">
      <parent link="front_left_wheel_steering_block"/>
      <child link="front_left_wheel"/>
      <origin xyz="0 0 0.125" rpy="-1.570796 0 0" /> 
      <axis xyz="0 1 0" rpy="0 0 0" />
      <limit effort="100" velocity="100"/>
      <joint_properties damping="0.0" friction="0.0"/>
    </joint>

    <joint name="back_left_wheel_joint" type="continuous">
      <parent link="base_link"/>
      <child link="back_left_wheel"/>
      <origin xyz="-1.14 0.785 -0.1" rpy="0 0 0" /> 
      <axis xyz="0 1 0" rpy="0 0 0" />
      <limit effort="100" velocity="100"/>
      <joint_properties damping="0.0" friction="0.0"/>
    </joint>

    <joint name="back_right_wheel_joint" type="continuous">
      <parent link="base_link"/>
      <child link="back_right_wheel"/>
      <origin xyz="-1.14 -0.785 -0.1" rpy="0 0 0" /> 
      <axis xyz="0 1 0" rpy="0 0 0" />
      <limit effort="100" velocity="100"/>
      <joint_properties damping="0.0" friction="0.0"/>
    </joint>

  <link name="front_right_wheel_steering_block">
    <inertial>
      <mass value="1"/>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    </inertial>
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <cylinder length="0.05" radius="0.05"/>
      </geometry>
      <material name="Grey" />
    </visual>  
    <collision name="collision">
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.05" radius="0.05"/>
      </geometry>
    </collision>
  </link>

  <link name="front_left_wheel_steering_block">
    <inertial>
      <mass value="1"/>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
    </inertial>
    <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <cylinder length="0.05" radius="0.05"/>
      </geometry>
      <material name="Grey" />
    </visual>  
    <collision name="collision">
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <cylinder length="0.05" radius="0.05"/>
      </geometry>
    </collision>
  </link>

  <joint name="front_left_steering_joint" type="revolute">
    <parent link="base_link"/>
    <child link="front_left_wheel_steering_block"/>
    <origin rpy="-${M_PI/2} 0 0" xyz="1.66  0.635 -0.1"/>
    <axis xyz="0 1 0"/>
    <limit effort="10.0" lower="-0.604015" upper="0.445345" velocity="0.0"/>
  </joint>

  <joint name="front_right_steering_joint" type="revolute">
    <parent link="base_link"/>
    <child link="front_right_wheel_steering_block"/>
    <origin rpy="${M_PI/2} 0 0" xyz="1.66 -0.635 -0.1"/>
    <axis xyz="0 1 0"/>
    <limit effort="10.0" lower="-0.604015" upper="0.445345" velocity="0.0"/>
  </joint>

<gazebo reference="front_right_steering_link">
   <mu1>0.6</mu1>
   <mu2>0.5</mu2>
                <kp>1000000</kp>
                <kd>0.1</kd>
                <minDepth>0.01</minDepth>
                <maxVel>10.0</maxVel>
</gazebo>

<gazebo reference="front_left_steering_link">
   <mu1>0.6</mu1>
   <mu2>0.5</mu2>
                <kp>1000000</kp>
                <kd>0.1</kd>
                <minDepth>0.01</minDepth>
                <maxVel>10.0</maxVel>
</gazebo>

<!-- motors and transmissions for the two front wheels and steering -->
  <transmission name="tran1">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="front_right_wheel_joint">
      <hardwareInterface>VelocityJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor1">
      <hardwareInterface>VelocityJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <transmission name="tran2">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="front_left_wheel_joint">
      <hardwareInterface>VelocityJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor2">
      <hardwareInterface>VelocityJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <transmission name="rack_and_pinion_left">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="front_left_steering_joint">
      <hardwareInterface>PositionJointInterface</hardwareInterface>
    </joint>
    <actuator name="eps_left">
      <hardwareInterface>PositionJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <transmission name="rack_and_pinion_right">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="front_right_steering_joint">
      <hardwareInterface>PositionJointInterface</hardwareInterface>
    </joint>
    <actuator name="eps_right">
      <hardwareInterface>PositionJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

  <!-- Hokuyo Laser -->
  <link name="hokuyo_link">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="0.1 0.1 0.1"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <!--<box size="0.1 0.1 0.1"/>-->
        <mesh filename="package://chassis_description/meshes/hokuyo.dae"/>
      </geometry>
    </visual>

    <inertial>
      <mass value="1e-5" />
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>

  <joint name="laser_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz="${base_x_size/2-0.05} 0 ${base_z_size/2+0.05}" rpy="0 0 0"/>
    <parent link="base_link"/>
    <child link="hokuyo_link"/>
  </joint>

  <gazebo reference="hokuyo_link">
    <sensor type="ray" name="head_hokuyo_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>true</visualize>
      <update_rate>40</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>2000</samples>
            <resolution>1</resolution>
            <min_angle>-3.141593</min_angle>
            <max_angle>3.141593</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.10</min>
          <max>6</max>
          <resolution>0.02</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <!-- Noise parameters based on published spec for Hokuyo laser
               achieving "+-30mm" accuracy at range < 10m.  A mean of 0.0m and
               stddev of 0.01m will put 99.7% of samples within 0.03m of the true
               reading. -->
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <robotNamespace>/$(arg roboname)</robotNamespace>
        <topicName>/$(arg roboname)/scan</topicName>
        <frameName>hokuyo_link</frameName>
      </plugin>
    </sensor>
  </gazebo>

<gazebo>
  <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
    <robotNamespace>/$(arg roboname)</robotNamespace>
    <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
  </plugin>
</gazebo>

<gazebo>
    <plugin filename="libgazebo_ros_joint_state_publisher.so" name="joint_state_publisher">
      <jointName>back_left_wheel_joint, back_right_wheel_joint, front_left_steering_joint, front_right_steering_joint, front_right_wheel_joint, front_left_wheel_joint</jointName>
      <robotNamespace>/$(arg roboname)</robotNamespace>
      <updateRate>50.0</updateRate>
      <alwaysOn>true</alwaysOn>
    </plugin>
</gazebo>

<gazebo>
  <plugin name="cmdvel_controller" filename="libazcargazebo.so">
      <robotNamespace>/$(arg roboname)</robotNamespace>
  </plugin>
</gazebo>

</robot>

Please can anyone suggest a controller node to me? Any help will be greatly appreciated.

Thank you in advance.