Hi all, I built my custom 4wheeler and after spawning it in gazebo, everything worked out just fine. I then decided to bring it alive by including a diff_drive controller. At this point, it all goes wrong. When I spawn the robot, in Gazebo it looks okay. But in RVIZ, there's a complaint about missing transforms between the base_footprint and the rest of the robot. As you can see from the TF diagram attached, the base_footprint link has been displaced by a new connection between the odom frame and the base_link frame. See my Robot URDF bellow

<?xml version = "1.0"?>

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

<xacro:property name="wheel_thickness" value="0.12"/> <xacro:property name="wheel_diameter" value="0.22"/> <xacro:property name="wheel_guide_thickness" value="0.05"/> <xacro:property name="wheel_guide_length" value="0.4"/> <xacro:property name="wheel_guide_height" value="0.1"/> <xacro:property name="body_length" value="0.6"/> <xacro:property name="body_width" value="0.5"/> <xacro:property name="body_height" value="0.3"/> <xacro:property name="camera_width" value="0.01"/> <xacro:property name="wheel_mass" value="0.5"/> <xacro:property name="body_mass" value="1"/> <xacro:property name="guide_mass" value="0.5"/> <xacro:property name="axel_mass" value="0.5"/> <xacro:property name="camera_mass" value="0.1"/> <xacro:property name="kinect_mass" value="0.5"/> <xacro:property name="pi" value="3.1415"/>

<xacro:macro name="default_inertial" params="mass"> <inertial> <mass value="${mass}"/> <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/> </inertial> </xacro:macro>

<xacro:macro name="shape_visual" params="length width height color"> <visual> <pose xyz="0 0 1.0"/> <geometry> <box size="${length} ${width} ${height}"/> </geometry> <material name="${color}"/> </visual> <collision> <geometry> <box size="${length} ${width} ${height}"/> </geometry>
</collision>

</xacro:macro>

<xacro:macro name="camera_visual" params="length width height color"> <visual> <geometry> <box size="${length} ${width} ${height}"/> </geometry> <material name="${color}"/> </visual> <collision> <geometry> <box size="${length} ${width} ${height}"/> </geometry>
</collision>

</xacro:macro>

<xacro:macro name="wheel_guide_macro" params="prefix reflect"> <link name="${prefix}_wheel_guide"> <visual> <origin xyz="0 ${reflect*wheel_guide_thickness/2} 0"/> <geometry> <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/> </geometry> <material name="black"/> </visual> <collision> <geometry> <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/> </geometry>
</collision> <xacro:default_inertial mass="${guide_mass}"/> </link> <joint name="${prefix}_wheel_guide_joint" type="fixed"> <axis xyz="0 1 0" rpy="0 0 0"/> <parent link="base_link"/> <child link="${prefix}_wheel_guide"/> <origin xyz="0 ${reflect*body_width/2} 0" rpy="0 0 0"/> </joint> <gazebo reference="${prefix}_wheel_guide"> <gravity value="true"/> <mindepth>0.00001</mindepth> <material>Gazebo/Grey</material> </gazebo> </xacro:macro>

<xacro:macro name="wheel_axle_macro" params="prefix suffix reflect1 reflect2"> <link name="${prefix}_${suffix}_wheel_axle"> <visual> <origin xyz="0 0 0" rpy="0 ${reflect2*2.0*pi/3} 0"/> <geometry> <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/> </geometry> <material name="black"/> </visual> <collision> <geometry> <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/> </geometry>
</collision> <xacro:default_inertial mass="${axel_mass}"/> </link> <joint name="${prefix}_${suffix}_wheel_axle_joint" type="fixed"> <parent link="${prefix}_wheel_guide"/> <child link="${prefix}_${suffix}_wheel_axle"/> <origin xyz="${reflect2*wheel_guide_length/2} ${reflect1* wheel_guide_thickness/2} ${-wheel_guide_height}" rpy="0 0 0"/> </joint> <gazebo reference="${prefix}_${suffix}_wheel_axle"> <gravity value="true"/> <mindepth>0.00001</mindepth> <material>Gazebo/Grey</material> </gazebo> </xacro:macro>

<xacro:macro name="wheel_position_macro" params="prefix suffix reflect1 reflect2"> <link name="${prefix}_${suffix}_wheel"> <visual> <geometry> <mesh filename="package://learning_tf/meshes/wheels/rubber_wheel_${prefix}.dae"/> </geometry> <material name="black"/> </visual> <collision> <origin xyz="0 0 0" rpy="${pi/2} 0 0"/> <geometry> <cylinder radius="${wheel_diameter/2}" length="${wheel_thickness}"/> </geometry>
<surface> <bounce> <restitution_coefficient>0.0</restitution_coefficient> <threshold>0</threshold> </bounce> </surface>
</collision> <xacro:default_inertial mass="${wheel_mass}"/> </link> <joint name="${prefix}_${suffix}_wheel_joint" type="continuous"> <axis xyz="0 1 0"/> <parent link="${prefix}_${suffix}_wheel_axle"/> <child link="${prefix}_${suffix}_wheel"/> <origin xyz="${reflect2*body_length/6.0} ${reflect1*wheel_thickness/2} -${body_height/4.0}"/> </joint> <gazebo reference="${prefix}_${suffix}_wheel"> <mu1 value="200.0"/> <mu2 value="100.0"/> <kp value="1.0e+6"/> <kd value="1.0"/> <gravity value="true"/> <maxvel>0.0000001</maxvel> <mindepth>0.00001</mindepth> <material>Gazebo/Black</material> </gazebo> <transmission name="${prefix}_${suffix}_wheel_trans"> <type>transmission_interface/SimpleTransmission</type> <actuator name="${prefix}_${suffix}_wheel_motor"> <hardwareinterface>VelocityJointInterface</hardwareinterface> <mechanicalreduction>1</mechanicalreduction> </actuator> <joint name="${prefix}_${suffix}_wheel_joint"> <hardwareinterface>VelocityJointInterface</hardwareinterface> </joint> </transmission> </xacro:macro>

<material name="white"> <color rgba="1 1 1 1"/> </material> <material name="black"> <color rgba="0 0 0 1"/> </material> <material name="blue"> <color rgba="0 0 0.9 1"/> </material> <material name="green"> <color rgba="0 0.8 0 1"/> </material>

<link name="base_footprint"> <visual> <origin xyz="0 0 0"/> </visual> </link> <link name="base_link">

<xacro:shape_visual length="0.6" width="0.5" height="0.3" color="white"/> <xacro:default_inertial mass="${body_mass}"/> </link> <gazebo reference="base_link"> <material>Gazebo/White</material> <mindepth>0.00001</mindepth> <gravity value="true"/> </gazebo> <joint name="base_joint" type="fixed" &gt;="" <parent="" link="base_footprint"/> <child link="base_link"/> <origin xyz="0 0 0.26" rpy="0 0 0"/> </joint>

<xacro:wheel_guide_macro prefix="left" reflect="-1.0"/> <xacro:wheel_guide_macro prefix="right" reflect="1.0"/> <xacro:wheel_axle_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/> <xacro:wheel_axle_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/> <xacro:wheel_axle_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/> <xacro:wheel_axle_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>

<xacro:wheel_position_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/> <xacro:wheel_position_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/> <xacro:wheel_position_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/> <xacro:wheel_position_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>

<link name="camera_link"> <xacro:camera_visual length="0.01" width="${body_width/12.0}" height="${body_width/12.0}" color="black"/> <xacro:default_inertial mass="${camera_mass}"/> </link> <joint name="camera_joint" type="fixed"> <parent link="base_link"/> <child link="camera_link"/> <origin xyz="${body_length/2 + camera_width} 0 0" rpy="0 0 0"/> </joint>

<gazebo reference="camera_link"> <material>Gazebo/Blue</material> <sensor type="camera" name="camera1"> <update_rate>30.0</update_rate> <camera name="head"> <horizontal_fov>1.3962634</horizontal_fov> <image> <width>640</width> <height>480</height> <format>R8G8B8</format> </image> <clip> <near>0.02</near> <far>300</far> </clip> <noise> <type>gaussian</type> <mean>0.0</mean> <stddev>0.007</stddev> </noise> </camera> <plugin name="camera_controller" filename="libgazebo_ros_camera.so"> <alwayson>true</alwayson> <updaterate>0.0</updaterate> <cameraname>camera1</cameraname> <imagetopicname>image_raw</imagetopicname> <camerainfotopicname>camera_info</camerainfotopicname> <framename>camera_link</framename> <hackbaseline>0.07</hackbaseline> <distortionk1>0.0</distortionk1> <distortionk2>0.0</distortionk2> <distortionk3>0.0</distortionk3> <distortiont1>0.0</distortiont1> <distortiont2>0.0</distortiont2> </plugin> </sensor> </gazebo>

<link name="laser_optical_link"/> <joint name="laser_optical_joint" type="fixed"> <axis xyz="0 1 0"/> <parent link="base_link"/> <child link="laser_optical_link"/> <origin xyz="${body_length/2 + camera_width} 0 0.1" rpy="-${pi/2} 0 -${pi/2}"/> </joint>

<link name="hokuyo_link"> <visual> <pose>0 0 0.036 0 0 0</pose>

<geometry>
  <mesh filename="package://learning_tf/meshes/hokuyo.dae"/>
</geometry>

</visual> <collision> <geometry> <cylinder radius="0.01" length="0.01"/> </geometry>
</collision> <xacro:default_inertial mass="${kinect_mass}"/> </link> <joint name="laser_link_joint" type="fixed"> <parent link="base_link"/> <child link="hokuyo_link"/> <origin xyz="-${body_length/2.0 - body_width/4.0} 0 ${body_height/2 + body_height/6}"/> </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>720</samples> <resolution>1</resolution> <min_angle>-1.570796</min_angle> <max_angle>1.570796</max_angle> </horizontal> </scan> <range> <min>0.10</min> <max>30.0</max> <resolution>0.01</resolution> </range> <noise> <type>gaussian</type> <mean>0.0</mean> <stddev>0.01</stddev> </noise> </ray> <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so"> <topicname>/hokuyo/laser/scan</topicname> <framename>hokuyo_link</framename> </plugin> </sensor> </gazebo>

<gazebo> <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so"> <robotnamespace>/</robotnamespace> </plugin> </gazebo> </robot>

Find also below attached my diff_drive YAML file.

type: "diff_drive_controller/DiffDriveController"

publish_rate: 100

left_wheel: ['left_front_wheel_joint','left_back_wheel_joint'] right_wheel: ['right_front_wheel_joint','right_back_wheel_joint']

wheel_separation: 0.50

Odometry covariances for the encoder output of the robot. These values should

be tuned to your robot's sample odometry data, but these values are a good place

to start

pose_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03] twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]

Top level frame (link) of the robot description

base_frame_id: base_link

Velocity and acceleration limits for the robot

linear: x: has_velocity_limits : true max_velocity : 0.2 # m/s has_acceleration_limits: true max_acceleration : 0.6 # m/s^2 angular: z: has_velocity_limits : true max_velocity : 2.0 # rad/s has_acceleration_limits: true max_acceleration : 6.0 # rad/s^2

Note that when I ran this URDF without the diff_drive, all the transforms worked just fine. As soon as I included the diff drive, the TF map changed. As a result of the new link between odom frame and base link frame, my Maps are totally skewed. I get very haphazard maps when running slam-gmapping.

Has anyone experienced this? My information provided may not be as concise as you want... Please ask for clarifications if needed. Thank you.

Hi all, I built my custom 4wheeler and after spawning it in gazebo, everything worked out just fine. I then decided to bring it alive by including a diff_drive controller. At this point, it all goes wrong. When I spawn the robot, in Gazebo it looks okay. But in RVIZ, there's a complaint about missing transforms between the base_footprint and the rest of the robot. As you can see from the TF diagram attached, the base_footprint link has been displaced by a new connection between the odom frame and the base_link frame. See my Robot URDF bellow

<?xml version = "1.0"?>

<geometry>
  <mesh filename="package://learning_tf/meshes/hokuyo.dae"/>
</geometry>

`    type: "diff_drive_controller/DiffDriveController"

Hi all, I built my custom 4wheeler and after spawning it in gazebo, everything worked out just fine. I then decided to bring it alive by including a diff_drive controller. At this point, it all goes wrong. When I spawn the robot, in Gazebo it looks okay. But in RVIZ, there's a complaint about missing transforms between the base_footprint and the rest of the robot. As you can see from the TF diagram attached, the base_footprint link has been displaced by a new connection between the odom frame and the base_link frame. See my Robot URDF bellow

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

<xacro:property name="wheel_thickness" value="0.12"/> <xacro:property name="wheel_diameter" value="0.22"/> <xacro:property name="wheel_guide_thickness" value="0.05"/> <xacro:property name="wheel_guide_length" value="0.4"/> <xacro:property name="wheel_guide_height" value="0.1"/> <xacro:property name="body_length" value="0.6"/> <xacro:property name="body_width" value="0.5"/> <xacro:property name="body_height" value="0.3"/> <xacro:property name="camera_width" value="0.01"/> <xacro:property name="wheel_mass" value="0.5"/> <xacro:property name="body_mass" value="1"/> <xacro:property name="guide_mass" value="0.5"/> <xacro:property name="axel_mass" value="0.5"/> <xacro:property name="camera_mass" value="0.1"/> <xacro:property name="kinect_mass" value="0.5"/> <xacro:property name="pi" value="3.1415"/>

<xacro:macro name="default_inertial" params="mass"> <inertial> <mass value="${mass}"/> <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/> </inertial> </xacro:macro>

<xacro:macro name="shape_visual" params="length width height color"> <visual> <pose xyz="0 0 1.0"/> <geometry> <box size="${length} ${width} ${height}"/> </geometry> <material name="${color}"/> </visual> <collision> <geometry> <box size="${length} ${width} ${height}"/> </geometry>
</collision>

</xacro:macro>

<xacro:macro name="camera_visual" params="length width height color"> <visual> <geometry> <box size="${length} ${width} ${height}"/> </geometry> <material name="${color}"/> </visual> <collision> <geometry> <box size="${length} ${width} ${height}"/> </geometry>
</collision>

</xacro:macro>

<xacro:macro name="wheel_guide_macro" params="prefix reflect"> <link name="${prefix}_wheel_guide"> <visual> <origin xyz="0 ${reflect*wheel_guide_thickness/2} 0"/> <geometry> <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/> </geometry> <material name="black"/> </visual> <collision> <geometry> <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/> </geometry>
</collision> <xacro:default_inertial mass="${guide_mass}"/> </link> <joint name="${prefix}_wheel_guide_joint" type="fixed"> <axis xyz="0 1 0" rpy="0 0 0"/> <parent link="base_link"/> <child link="${prefix}_wheel_guide"/> <origin xyz="0 ${reflect*body_width/2} 0" rpy="0 0 0"/> </joint> <gazebo reference="${prefix}_wheel_guide"> <gravity value="true"/> <mindepth>0.00001</mindepth> <material>Gazebo/Grey</material> </gazebo> </xacro:macro>

<xacro:macro name="wheel_axle_macro" params="prefix suffix reflect1 reflect2"> <link name="${prefix}_${suffix}_wheel_axle"> <visual> <origin xyz="0 0 0" rpy="0 ${reflect2*2.0*pi/3} 0"/> <geometry> <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/> </geometry> <material name="black"/> </visual> <collision> <geometry> <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/> </geometry>
</collision> <xacro:default_inertial mass="${axel_mass}"/> </link> <joint name="${prefix}_${suffix}_wheel_axle_joint" type="fixed"> <parent link="${prefix}_wheel_guide"/> <child link="${prefix}_${suffix}_wheel_axle"/> <origin xyz="${reflect2*wheel_guide_length/2} ${reflect1* wheel_guide_thickness/2} ${-wheel_guide_height}" rpy="0 0 0"/> </joint> <gazebo reference="${prefix}_${suffix}_wheel_axle"> <gravity value="true"/> <mindepth>0.00001</mindepth> <material>Gazebo/Grey</material> </gazebo> </xacro:macro>

<xacro:macro name="wheel_position_macro" params="prefix suffix reflect1 reflect2"> <link name="${prefix}_${suffix}_wheel"> <visual> <geometry> <mesh filename="package://learning_tf/meshes/wheels/rubber_wheel_${prefix}.dae"/> </geometry> <material name="black"/> </visual> <collision> <origin xyz="0 0 0" rpy="${pi/2} 0 0"/> <geometry> <cylinder radius="${wheel_diameter/2}" length="${wheel_thickness}"/> </geometry>
<surface> <bounce> <restitution_coefficient>0.0</restitution_coefficient> <threshold>0</threshold> </bounce> </surface>
</collision> <xacro:default_inertial mass="${wheel_mass}"/> </link> <joint name="${prefix}_${suffix}_wheel_joint" type="continuous"> <axis xyz="0 1 0"/> <parent link="${prefix}_${suffix}_wheel_axle"/> <child link="${prefix}_${suffix}_wheel"/> <origin xyz="${reflect2*body_length/6.0} ${reflect1*wheel_thickness/2} -${body_height/4.0}"/> </joint> <gazebo reference="${prefix}_${suffix}_wheel"> <mu1 value="200.0"/> <mu2 value="100.0"/> <kp value="1.0e+6"/> <kd value="1.0"/> <gravity value="true"/> <maxvel>0.0000001</maxvel> <mindepth>0.00001</mindepth> <material>Gazebo/Black</material> </gazebo> <transmission name="${prefix}_${suffix}_wheel_trans"> <type>transmission_interface/SimpleTransmission</type> <actuator name="${prefix}_${suffix}_wheel_motor"> <hardwareinterface>VelocityJointInterface</hardwareinterface> <mechanicalreduction>1</mechanicalreduction> </actuator> <joint name="${prefix}_${suffix}_wheel_joint"> <hardwareinterface>VelocityJointInterface</hardwareinterface> </joint> </transmission> </xacro:macro>

<material name="white"> <color rgba="1 1 1 1"/> </material> <material name="black"> <color rgba="0 0 0 1"/> </material> <material name="blue"> <color rgba="0 0 0.9 1"/> </material> <material name="green"> <color rgba="0 0.8 0 1"/> </material>

<link name="base_footprint"> <visual> <origin xyz="0 0 0"/> </visual> </link> <link name="base_link">

<xacro:shape_visual length="0.6" width="0.5" height="0.3" color="white"/> <xacro:default_inertial mass="${body_mass}"/> </link> <gazebo reference="base_link"> <material>Gazebo/White</material> <mindepth>0.00001</mindepth> <gravity value="true"/> </gazebo> <joint name="base_joint" type="fixed" &gt;="" <parent="" link="base_footprint"/> <child link="base_link"/> <origin xyz="0 0 0.26" rpy="0 0 0"/> </joint>

<xacro:wheel_guide_macro prefix="left" reflect="-1.0"/> <xacro:wheel_guide_macro prefix="right" reflect="1.0"/> <xacro:wheel_axle_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/> <xacro:wheel_axle_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/> <xacro:wheel_axle_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/> <xacro:wheel_axle_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>

<xacro:wheel_position_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/> <xacro:wheel_position_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/> <xacro:wheel_position_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/> <xacro:wheel_position_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>

<link name="camera_link"> <xacro:camera_visual length="0.01" width="${body_width/12.0}" height="${body_width/12.0}" color="black"/> <xacro:default_inertial mass="${camera_mass}"/> </link> <joint name="camera_joint" type="fixed"> <parent link="base_link"/> <child link="camera_link"/> <origin xyz="${body_length/2 + camera_width} 0 0" rpy="0 0 0"/> </joint>

<gazebo reference="camera_link"> <material>Gazebo/Blue</material> <sensor type="camera" name="camera1"> <update_rate>30.0</update_rate> <camera name="head"> <horizontal_fov>1.3962634</horizontal_fov> <image> <width>640</width> <height>480</height> <format>R8G8B8</format> </image> <clip> <near>0.02</near> <far>300</far> </clip> <noise> <type>gaussian</type> <mean>0.0</mean> <stddev>0.007</stddev> </noise> </camera> <plugin name="camera_controller" filename="libgazebo_ros_camera.so"> <alwayson>true</alwayson> <updaterate>0.0</updaterate> <cameraname>camera1</cameraname> <imagetopicname>image_raw</imagetopicname> <camerainfotopicname>camera_info</camerainfotopicname> <framename>camera_link</framename> <hackbaseline>0.07</hackbaseline> <distortionk1>0.0</distortionk1> <distortionk2>0.0</distortionk2> <distortionk3>0.0</distortionk3> <distortiont1>0.0</distortiont1> <distortiont2>0.0</distortiont2> </plugin> </sensor> </gazebo>

<link name="laser_optical_link"/> <joint name="laser_optical_joint" type="fixed"> <axis xyz="0 1 0"/> <parent link="base_link"/> <child link="laser_optical_link"/> <origin xyz="${body_length/2 + camera_width} 0 0.1" rpy="-${pi/2} 0 -${pi/2}"/> </joint>

<link name="hokuyo_link"> <visual> <pose>0 0 0.036 0 0 0</pose>

<geometry>
  <mesh filename="package://learning_tf/meshes/hokuyo.dae"/>
</geometry>

</visual> <collision> <geometry> <cylinder radius="0.01" length="0.01"/> </geometry>
</collision> <xacro:default_inertial mass="${kinect_mass}"/> </link> <joint name="laser_link_joint" type="fixed"> <parent link="base_link"/> <child link="hokuyo_link"/> <origin xyz="-${body_length/2.0 - body_width/4.0} 0 ${body_height/2 + body_height/6}"/> </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>720</samples> <resolution>1</resolution> <min_angle>-1.570796</min_angle> <max_angle>1.570796</max_angle> </horizontal> </scan> <range> <min>0.10</min> <max>30.0</max> <resolution>0.01</resolution> </range> <noise> <type>gaussian</type> <mean>0.0</mean> <stddev>0.01</stddev> </noise> </ray> <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so"> <topicname>/hokuyo/laser/scan</topicname> <framename>hokuyo_link</framename> </plugin> </sensor> </gazebo>

<gazebo> <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so"> <robotnamespace>/</robotnamespace> </plugin> </gazebo> </robot> ```

Find also below attached my diff_drive YAML file.

` type: "diff_drive_controller/DiffDriveController" publish_rate: 100

left_wheel: ['left_front_wheel_joint','left_back_wheel_joint'] right_wheel: ['right_front_wheel_joint','right_back_wheel_joint']

wheel_separation: 0.50

Odometry covariances for the encoder output of the robot. These values should

be tuned to your robot's sample odometry data, but these values are a good place

to start

pose_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03] twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]

Top level frame (link) of the robot description

base_frame_id: base_link

Velocity and acceleration limits for the robot

linear: x: has_velocity_limits : true max_velocity : 0.2 # m/s has_acceleration_limits: true max_acceleration : 0.6 # m/s^2 angular: z: has_velocity_limits : true max_velocity : 2.0 # rad/s has_acceleration_limits: true max_acceleration : 6.0 # rad/s^2 `

Note that when I ran this URDF without the diff_drive, all the transforms worked just fine. As soon as I included the diff drive, the TF map changed. As a result of the new link between odom frame and base link frame, my Maps are totally skewed. I get very haphazard maps when running slam-gmapping.

Has anyone experienced this? My information provided may not be as concise as you want... Please ask for clarifications if needed. Thank you.

Hi all, I built my custom 4wheeler and after spawning it in gazebo, everything worked out just fine. I then decided to bring it alive by including a diff_drive controller. At this point, it all goes wrong. When I spawn the robot, in Gazebo it looks okay. But in RVIZ, there's a complaint about missing transforms between the base_footprint and the rest of the robot. As you can see from the TF diagram attached, the base_footprint link has been displaced by a new connection between the odom frame and the base_link frame. See my Robot URDF bellow

`

 <robot name="Rover" xmlns:xacro="http://www.ros.org/wiki/xacro">
 
<xacro:property name="wheel_thickness" value="0.12"/>
<xacro:property name="wheel_diameter" value="0.22"/>
<xacro:property name="wheel_guide_thickness" value="0.05"/>
<xacro:property name="wheel_guide_length" value="0.4"/>
<xacro:property name="wheel_guide_height" value="0.1"/>
<xacro:property name="body_length" value="0.6"/>
<xacro:property name="body_width" value="0.5"/>
<xacro:property name="body_height" value="0.3"/>
<xacro:property name="camera_width" value="0.01"/>
<xacro:property name="wheel_mass" value="0.5"/>
<xacro:property name="body_mass" value="1"/>
<xacro:property name="guide_mass" value="0.5"/>
<xacro:property name="axel_mass" value="0.5"/>
<xacro:property name="camera_mass" value="0.1"/>
<xacro:property name="kinect_mass" value="0.5"/>
<xacro:property name="pi" value="3.1415"/>
 
<xacro:macro name="default_inertial" params="mass">
  <inertial>
    <mass value="${mass}"/>
    <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
  </inertial>
</xacro:macro>
 
<xacro:macro name="shape_visual" params="length width height color">
  <visual>
    <pose xyz="0 0 1.0"/>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry>
    <material name="${color}"/>
  </visual>
  <collision>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry> 

  </collision>
 
</xacro:macro>
 
<xacro:macro name="camera_visual" params="length width height color">
  <visual>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry>
    <material name="${color}"/>
  </visual>
  <collision>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry> 

  </collision>
 
</xacro:macro>
 
<xacro:macro name="wheel_guide_macro" params="prefix reflect">
<link name="${prefix}_wheel_guide">
  <visual>
    <origin xyz="0 ${reflect*wheel_guide_thickness/2} 0"/>
    <geometry>
      <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/>
    </geometry>
    <material name="black"/>
  </visual>
  <collision>
    <geometry>
      <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${guide_mass}"/>
</link>
<joint name="${prefix}_wheel_guide_joint" type="fixed">
  <axis xyz="0 1 0" rpy="0 0 0"/>
  <parent link="base_link"/>
  <child link="${prefix}_wheel_guide"/>
  <origin xyz="0 ${reflect*body_width/2} 0" rpy="0 0 0"/>
   
</joint>
<gazebo reference="${prefix}_wheel_guide">
  <gravity value="true"/>
    <mindepth>0.00001</mindepth>
  <material>Gazebo/Grey</material>
</gazebo>
</xacro:macro>
 
<xacro:macro name="wheel_axle_macro" params="prefix suffix reflect1 reflect2"> 
<link name="${prefix}_${suffix}_wheel_axle">
  <visual>
    <origin xyz="0 0 0" rpy="0 ${reflect2*2.0*pi/3} 0"/>
    <geometry>
      <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/>
    </geometry>
   <material name="black"/>
  </visual>
  <collision>
    <geometry>
      <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${axel_mass}"/>
</link>
<joint name="${prefix}_${suffix}_wheel_axle_joint" type="fixed">
  <parent link="${prefix}_wheel_guide"/>
  <child link="${prefix}_${suffix}_wheel_axle"/>
  <origin xyz="${reflect2*wheel_guide_length/2} ${reflect1* wheel_guide_thickness/2} ${-wheel_guide_height}" rpy="0 0 0"/>
</joint>
<gazebo reference="${prefix}_${suffix}_wheel_axle">
  <gravity value="true"/>
    <mindepth>0.00001</mindepth>
  <material>Gazebo/Grey</material>
</gazebo>
</xacro:macro>
 
<xacro:macro name="wheel_position_macro" params="prefix suffix reflect1 reflect2">
<link name="${prefix}_${suffix}_wheel">
  <visual>
    
    <geometry>
      <mesh filename="package://learning_tf/meshes/wheels/rubber_wheel_${prefix}.dae"/>
    </geometry>
    <material name="black"/>
  </visual>
  <collision>
   <origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
    <geometry>
      <cylinder radius="${wheel_diameter/2}" length="${wheel_thickness}"/>
    </geometry> 

    <surface>
      <bounce>
        <restitution_coefficient>0.0</restitution_coefficient>
        <threshold>0</threshold>
      </bounce>
    </surface> 

  </collision>
  <xacro:default_inertial mass="${wheel_mass}"/>
</link>
<joint name="${prefix}_${suffix}_wheel_joint" type="continuous">
  <axis xyz="0 1 0"/>
  <parent link="${prefix}_${suffix}_wheel_axle"/>
  <child link="${prefix}_${suffix}_wheel"/>
  <origin xyz="${reflect2*body_length/6.0} ${reflect1*wheel_thickness/2} -${body_height/4.0}"/>
</joint>
<gazebo reference="${prefix}_${suffix}_wheel">
  <mu1 value="200.0"/>
  <mu2 value="100.0"/>
  <kp value="1.0e+6"/>
  <kd value="1.0"/>
  <gravity value="true"/>
  <maxvel>0.0000001</maxvel>
  <mindepth>0.00001</mindepth>
  <material>Gazebo/Black</material>
</gazebo>

<transmission name="${prefix}_${suffix}_wheel_trans">
    <type>transmission_interface/SimpleTransmission</type>
    <actuator name="${prefix}_${suffix}_wheel_motor">
    <hardwareinterface>VelocityJointInterface</hardwareinterface>
      <mechanicalreduction>1</mechanicalreduction>
    </actuator>
    <joint name="${prefix}_${suffix}_wheel_joint">
      <hardwareinterface>VelocityJointInterface</hardwareinterface>
    </joint>
</transmission>
</xacro:macro>
 
<material name="white">
  <color rgba="1 1 1 1"/>
</material>
<material name="black">
  <color rgba="0 0 0 1"/>
</material>
<material name="blue">
  <color rgba="0 0 0.9 1"/>
</material>
<material name="green">
  <color rgba="0 0.8 0 1"/>
</material>
 
<link name="base_footprint">
  <visual>
   <origin xyz="0 0 0"/>
  </visual>
</link>
<link name="base_link">
 
<xacro:shape_visual length="0.6" width="0.5" height="0.3" color="white"/>
  <xacro:default_inertial mass="${body_mass}"/>
</link>
<gazebo reference="base_link">
  <material>Gazebo/White</material>
    <mindepth>0.00001</mindepth>
  <gravity value="true"/>
</gazebo>
<joint name="base_joint" type="fixed" &gt;="" <parent="" link="base_footprint"/>
   <child link="base_link"/>
   <origin xyz="0 0 0.26" rpy="0 0 0"/>
</joint>
 
<xacro:wheel_guide_macro prefix="left" reflect="-1.0"/>
<xacro:wheel_guide_macro prefix="right" reflect="1.0"/>
<xacro:wheel_axle_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>
<xacro:wheel_axle_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/>
<xacro:wheel_axle_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/>
<xacro:wheel_axle_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>
 
<xacro:wheel_position_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/>
<xacro:wheel_position_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/>
<xacro:wheel_position_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>
<xacro:wheel_position_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>
 
<link name="camera_link">
  <xacro:camera_visual length="0.01" width="${body_width/12.0}" height="${body_width/12.0}" color="black"/>
  <xacro:default_inertial mass="${camera_mass}"/>
</link>
<joint name="camera_joint" type="fixed">
  <parent link="base_link"/>
  <child link="camera_link"/>
  <origin xyz="${body_length/2 + camera_width} 0 0" rpy="0 0 0"/>
</joint>
 
<gazebo reference="camera_link">
    <material>Gazebo/Blue</material>
    <sensor type="camera" name="camera1">
      <update_rate>30.0</update_rate>
      <camera name="head">
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>640</width>
          <height>480</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
        <noise>
          <type>gaussian</type>
          
          <mean>0.0</mean>
          <stddev>0.007</stddev>
        </noise>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwayson>true</alwayson>
        <updaterate>0.0</updaterate>
        <cameraname>camera1</cameraname>
        <imagetopicname>image_raw</imagetopicname>
        <camerainfotopicname>camera_info</camerainfotopicname>
        <framename>camera_link</framename>
        <hackbaseline>0.07</hackbaseline>
        <distortionk1>0.0</distortionk1>
        <distortionk2>0.0</distortionk2>
        <distortionk3>0.0</distortionk3>
        <distortiont1>0.0</distortiont1>
        <distortiont2>0.0</distortiont2>
      </plugin>
    </sensor>
  </gazebo>
 
<link name="laser_optical_link"/>
<joint name="laser_optical_joint" type="fixed">
    <axis xyz="0 1 0"/>
  <parent link="base_link"/>
  <child link="laser_optical_link"/>
  <origin xyz="${body_length/2 + camera_width} 0 0.1" rpy="-${pi/2} 0 -${pi/2}"/>
</joint>
 
<link name="hokuyo_link">
<visual>
    <pose>0 0 0.036 0 0 0</pose>
 
<geometry>
  <mesh filename="package://learning_tf/meshes/hokuyo.dae"/>
</geometry>
 
</visual>
  <collision>
    <geometry>
      <cylinder radius="0.01" length="0.01"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${kinect_mass}"/>
</link>
<joint name="laser_link_joint" type="fixed">
  <parent link="base_link"/>
  <child link="hokuyo_link"/>
  <origin xyz="-${body_length/2.0 - body_width/4.0} 0 ${body_height/2 + body_height/6}"/>
</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>720</samples>
            <resolution>1</resolution>
            <min_angle>-1.570796</min_angle>
            <max_angle>1.570796</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.10</min>
          <max>30.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
       <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicname>/hokuyo/laser/scan</topicname>
        <framename>hokuyo_link</framename>
      </plugin>
    </sensor>
  </gazebo>
 
<gazebo>
  <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
    <robotnamespace>/</robotnamespace>
  </plugin>
</gazebo>
</robot> ``
 
Find also below attached my diff_drive YAML file.
 
`    type: "diff_drive_controller/DiffDriveController"
publish_rate: 100
 
left_wheel:   ['left_front_wheel_joint','left_back_wheel_joint'] 
right_wheel:  ['right_front_wheel_joint','right_back_wheel_joint'] 
 
wheel_separation: 0.50
 
Odometry covariances for the encoder output of the robot. These values should
 
be tuned to your robot's sample odometry data, but these values are a good place
 
to start
 
pose_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]
twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]
 
Top level frame (link) of the robot description
 
base_frame_id: base_link
 
Velocity and acceleration limits for the robot
 
linear:
  x:
    has_velocity_limits    : true
    max_velocity           : 0.2   # m/s
    has_acceleration_limits: true
    max_acceleration       : 0.6   # m/s^2
angular:
  z:
    has_velocity_limits    : true
    max_velocity           : 2.0   # rad/s
    has_acceleration_limits: true
    max_acceleration       : 6.0   # rad/s^2 `
 
Note that when I ran this URDF without the diff_drive, all the transforms worked just fine. As soon as I included the diff drive, the TF map changed. As a result of the new link between odom frame and base link frame, my Maps are totally skewed. I get very haphazard maps when running slam-gmapping.
 
Has anyone experienced this? My information provided may not be as concise as you want... Please ask for clarifications if needed. Thank you.
 

Hi all, I built my custom 4wheeler and after spawning it in gazebo, everything worked out just fine. I then decided to bring it alive by including a diff_drive controller. At this point, it all goes wrong. When I spawn the robot, in Gazebo it looks okay. But in RVIZ, there's a complaint about missing transforms between the base_footprint and the rest of the robot. As you can see from the TF diagram attached, the base_footprint link has been displaced by a new connection between the odom frame and the base_link frame. See my Robot URDF bellow

 
<robot name="Rover" xmlns:xacro="http://www.ros.org/wiki/xacro">
 
<xacro:property name="wheel_thickness" value="0.12"/>
<xacro:property name="wheel_diameter" value="0.22"/>
<xacro:property name="wheel_guide_thickness" value="0.05"/>
<xacro:property name="wheel_guide_length" value="0.4"/>
<xacro:property name="wheel_guide_height" value="0.1"/>
<xacro:property name="body_length" value="0.6"/>
<xacro:property name="body_width" value="0.5"/>
<xacro:property name="body_height" value="0.3"/>
<xacro:property name="camera_width" value="0.01"/>
<xacro:property name="wheel_mass" value="0.5"/>
<xacro:property name="body_mass" value="1"/>
<xacro:property name="guide_mass" value="0.5"/>
<xacro:property name="axel_mass" value="0.5"/>
<xacro:property name="camera_mass" value="0.1"/>
<xacro:property name="kinect_mass" value="0.5"/>
<xacro:property name="pi" value="3.1415"/>
 
<xacro:macro name="default_inertial" params="mass">
  <inertial>
    <mass value="${mass}"/>
    <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
  </inertial>
</xacro:macro>
 
<xacro:macro name="shape_visual" params="length width height color">
  <visual>
    <pose xyz="0 0 1.0"/>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry>
    <material name="${color}"/>
  </visual>
  <collision>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry> 

  </collision>
 
</xacro:macro>
 
<xacro:macro name="camera_visual" params="length width height color">
  <visual>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry>
    <material name="${color}"/>
  </visual>
  <collision>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry> 

  </collision>
 
</xacro:macro>
 
<xacro:macro name="wheel_guide_macro" params="prefix reflect">
<link name="${prefix}_wheel_guide">
  <visual>
    <origin xyz="0 ${reflect*wheel_guide_thickness/2} 0"/>
    <geometry>
      <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/>
    </geometry>
    <material name="black"/>
  </visual>
  <collision>
    <geometry>
      <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${guide_mass}"/>
</link>
<joint name="${prefix}_wheel_guide_joint" type="fixed">
  <axis xyz="0 1 0" rpy="0 0 0"/>
  <parent link="base_link"/>
  <child link="${prefix}_wheel_guide"/>
  <origin xyz="0 ${reflect*body_width/2} 0" rpy="0 0 0"/>
   
</joint>
<gazebo reference="${prefix}_wheel_guide">
  <gravity value="true"/>
    <mindepth>0.00001</mindepth>
  <material>Gazebo/Grey</material>
</gazebo>
</xacro:macro>
 
<xacro:macro name="wheel_axle_macro" params="prefix suffix reflect1 reflect2"> 
<link name="${prefix}_${suffix}_wheel_axle">
  <visual>
    <origin xyz="0 0 0" rpy="0 ${reflect2*2.0*pi/3} 0"/>
    <geometry>
      <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/>
    </geometry>
   <material name="black"/>
  </visual>
  <collision>
    <geometry>
      <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${axel_mass}"/>
</link>
<joint name="${prefix}_${suffix}_wheel_axle_joint" type="fixed">
  <parent link="${prefix}_wheel_guide"/>
  <child link="${prefix}_${suffix}_wheel_axle"/>
  <origin xyz="${reflect2*wheel_guide_length/2} ${reflect1* wheel_guide_thickness/2} ${-wheel_guide_height}" rpy="0 0 0"/>
</joint>
<gazebo reference="${prefix}_${suffix}_wheel_axle">
  <gravity value="true"/>
    <mindepth>0.00001</mindepth>
  <material>Gazebo/Grey</material>
</gazebo>
</xacro:macro>
 
<xacro:macro name="wheel_position_macro" params="prefix suffix reflect1 reflect2">
<link name="${prefix}_${suffix}_wheel">
  <visual>
    
    <geometry>
      <mesh filename="package://learning_tf/meshes/wheels/rubber_wheel_${prefix}.dae"/>
    </geometry>
    <material name="black"/>
  </visual>
  <collision>
   <origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
    <geometry>
      <cylinder radius="${wheel_diameter/2}" length="${wheel_thickness}"/>
    </geometry> 

    <surface>
      <bounce>
        <restitution_coefficient>0.0</restitution_coefficient>
        <threshold>0</threshold>
      </bounce>
    </surface> 

  </collision>
  <xacro:default_inertial mass="${wheel_mass}"/>
</link>
<joint name="${prefix}_${suffix}_wheel_joint" type="continuous">
  <axis xyz="0 1 0"/>
  <parent link="${prefix}_${suffix}_wheel_axle"/>
  <child link="${prefix}_${suffix}_wheel"/>
  <origin xyz="${reflect2*body_length/6.0} ${reflect1*wheel_thickness/2} -${body_height/4.0}"/>
</joint>
<gazebo reference="${prefix}_${suffix}_wheel">
  <mu1 value="200.0"/>
  <mu2 value="100.0"/>
  <kp value="1.0e+6"/>
  <kd value="1.0"/>
  <gravity value="true"/>
  <maxvel>0.0000001</maxvel>
  <mindepth>0.00001</mindepth>
  <material>Gazebo/Black</material>
</gazebo>

<transmission name="${prefix}_${suffix}_wheel_trans">
    <type>transmission_interface/SimpleTransmission</type>
    <actuator name="${prefix}_${suffix}_wheel_motor">
    <hardwareinterface>VelocityJointInterface</hardwareinterface>
      <mechanicalreduction>1</mechanicalreduction>
    </actuator>
    <joint name="${prefix}_${suffix}_wheel_joint">
      <hardwareinterface>VelocityJointInterface</hardwareinterface>
    </joint>
</transmission>
</xacro:macro>
 
<material name="white">
  <color rgba="1 1 1 1"/>
</material>
<material name="black">
  <color rgba="0 0 0 1"/>
</material>
<material name="blue">
  <color rgba="0 0 0.9 1"/>
</material>
<material name="green">
  <color rgba="0 0.8 0 1"/>
</material>
 
<link name="base_footprint">
  <visual>
   <origin xyz="0 0 0"/>
  </visual>
</link>
<link name="base_link">
 
<xacro:shape_visual length="0.6" width="0.5" height="0.3" color="white"/>
  <xacro:default_inertial mass="${body_mass}"/>
</link>
<gazebo reference="base_link">
  <material>Gazebo/White</material>
    <mindepth>0.00001</mindepth>
  <gravity value="true"/>
</gazebo>
<joint name="base_joint" type="fixed" &gt;="" <parent="" link="base_footprint"/>
   <child link="base_link"/>
   <origin xyz="0 0 0.26" rpy="0 0 0"/>
</joint>
 
<xacro:wheel_guide_macro prefix="left" reflect="-1.0"/>
<xacro:wheel_guide_macro prefix="right" reflect="1.0"/>
<xacro:wheel_axle_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>
<xacro:wheel_axle_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/>
<xacro:wheel_axle_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/>
<xacro:wheel_axle_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>
 
<xacro:wheel_position_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/>
<xacro:wheel_position_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/>
<xacro:wheel_position_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>
<xacro:wheel_position_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>
 
<link name="camera_link">
  <xacro:camera_visual length="0.01" width="${body_width/12.0}" height="${body_width/12.0}" color="black"/>
  <xacro:default_inertial mass="${camera_mass}"/>
</link>
<joint name="camera_joint" type="fixed">
  <parent link="base_link"/>
  <child link="camera_link"/>
  <origin xyz="${body_length/2 + camera_width} 0 0" rpy="0 0 0"/>
</joint>
 
<gazebo reference="camera_link">
    <material>Gazebo/Blue</material>
    <sensor type="camera" name="camera1">
      <update_rate>30.0</update_rate>
      <camera name="head">
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>640</width>
          <height>480</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
        <noise>
          <type>gaussian</type>
          
          <mean>0.0</mean>
          <stddev>0.007</stddev>
        </noise>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwayson>true</alwayson>
        <updaterate>0.0</updaterate>
        <cameraname>camera1</cameraname>
        <imagetopicname>image_raw</imagetopicname>
        <camerainfotopicname>camera_info</camerainfotopicname>
        <framename>camera_link</framename>
        <hackbaseline>0.07</hackbaseline>
        <distortionk1>0.0</distortionk1>
        <distortionk2>0.0</distortionk2>
        <distortionk3>0.0</distortionk3>
        <distortiont1>0.0</distortiont1>
        <distortiont2>0.0</distortiont2>
      </plugin>
    </sensor>
  </gazebo>
 
<link name="laser_optical_link"/>
<joint name="laser_optical_joint" type="fixed">
    <axis xyz="0 1 0"/>
  <parent link="base_link"/>
  <child link="laser_optical_link"/>
  <origin xyz="${body_length/2 + camera_width} 0 0.1" rpy="-${pi/2} 0 -${pi/2}"/>
</joint>
 
<link name="hokuyo_link">
<visual>
    <pose>0 0 0.036 0 0 0</pose>
 
<geometry>
  <mesh filename="package://learning_tf/meshes/hokuyo.dae"/>
</geometry>
 
</visual>
  <collision>
    <geometry>
      <cylinder radius="0.01" length="0.01"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${kinect_mass}"/>
</link>
<joint name="laser_link_joint" type="fixed">
  <parent link="base_link"/>
  <child link="hokuyo_link"/>
  <origin xyz="-${body_length/2.0 - body_width/4.0} 0 ${body_height/2 + body_height/6}"/>
</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>720</samples>
            <resolution>1</resolution>
            <min_angle>-1.570796</min_angle>
            <max_angle>1.570796</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.10</min>
          <max>30.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
       <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicname>/hokuyo/laser/scan</topicname>
        <framename>hokuyo_link</framename>
      </plugin>
    </sensor>
  </gazebo>
 
<gazebo>
  <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
    <robotnamespace>/</robotnamespace>
  </plugin>
</gazebo>
</robot> ``
 
Find also below attached my diff_drive YAML file.
 
`    type: "diff_drive_controller/DiffDriveController"
publish_rate: 100
 
left_wheel:   ['left_front_wheel_joint','left_back_wheel_joint'] 
right_wheel:  ['right_front_wheel_joint','right_back_wheel_joint'] 
 
wheel_separation: 0.50
 
Odometry covariances for the encoder output of the robot. These values should
 
be tuned to your robot's sample odometry data, but these values are a good place
 
to start
 
pose_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]
twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]
 
Top level frame (link) of the robot description
 
base_frame_id: base_link
 
Velocity and acceleration limits for the robot
 
linear:
  x:
    has_velocity_limits    : true
    max_velocity           : 0.2   # m/s
    has_acceleration_limits: true
    max_acceleration       : 0.6   # m/s^2
angular:
  z:
    has_velocity_limits    : true
    max_velocity           : 2.0   # rad/s
    has_acceleration_limits: true
    max_acceleration       : 6.0   # rad/s^2 `
 
Note that when I ran this URDF without the diff_drive, all the transforms worked just fine. As soon as I included the diff drive, the TF map changed. As a result of the new link between odom frame and base link frame, my Maps are totally skewed. I get very haphazard maps when running slam-gmapping.
 
Has anyone experienced this? My information provided may not be as concise as you want... Please ask for clarifications if needed. Thank you.
 

Hi all, I built my custom 4wheeler and after spawning it in gazebo, everything worked out just fine. I then decided to bring it alive by including a diff_drive controller. At this point, it all goes wrong. When I spawn the robot, in Gazebo it looks okay. But in RVIZ, there's a complaint about missing transforms between the base_footprint and the rest of the robot. As you can see from the TF diagram attached, the base_footprint link has been displaced by a new connection between the odom frame and the base_link frame. See my Robot URDF bellow

 
<robot name="Rover" xmlns:xacro="http://www.ros.org/wiki/xacro">
 
<xacro:property name="wheel_thickness" value="0.12"/>
<xacro:property name="wheel_diameter" value="0.22"/>
<xacro:property name="wheel_guide_thickness" value="0.05"/>
<xacro:property name="wheel_guide_length" value="0.4"/>
<xacro:property name="wheel_guide_height" value="0.1"/>
<xacro:property name="body_length" value="0.6"/>
<xacro:property name="body_width" value="0.5"/>
<xacro:property name="body_height" value="0.3"/>
<xacro:property name="camera_width" value="0.01"/>
<xacro:property name="wheel_mass" value="0.5"/>
<xacro:property name="body_mass" value="1"/>
<xacro:property name="guide_mass" value="0.5"/>
<xacro:property name="axel_mass" value="0.5"/>
<xacro:property name="camera_mass" value="0.1"/>
<xacro:property name="kinect_mass" value="0.5"/>
<xacro:property name="pi" value="3.1415"/>
 
<xacro:macro name="default_inertial" params="mass">
  <inertial>
    <mass value="${mass}"/>
    <inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
  </inertial>
</xacro:macro>
 
<xacro:macro name="shape_visual" params="length width height color">
  <visual>
    <pose xyz="0 0 1.0"/>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry>
    <material name="${color}"/>
  </visual>
  <collision>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry> 

  </collision>
 
</xacro:macro>
 
<xacro:macro name="camera_visual" params="length width height color">
  <visual>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry>
    <material name="${color}"/>
  </visual>
  <collision>
    <geometry>
      <box size="${length} ${width} ${height}"/>
    </geometry> 

  </collision>
 
</xacro:macro>
 
<xacro:macro name="wheel_guide_macro" params="prefix reflect">
<link name="${prefix}_wheel_guide">
  <visual>
    <origin xyz="0 ${reflect*wheel_guide_thickness/2} 0"/>
    <geometry>
      <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/>
    </geometry>
    <material name="black"/>
  </visual>
  <collision>
    <geometry>
      <box size="${wheel_guide_length} ${wheel_guide_thickness} ${wheel_guide_height}"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${guide_mass}"/>
</link>
<joint name="${prefix}_wheel_guide_joint" type="fixed">
  <axis xyz="0 1 0" rpy="0 0 0"/>
  <parent link="base_link"/>
  <child link="${prefix}_wheel_guide"/>
  <origin xyz="0 ${reflect*body_width/2} 0" rpy="0 0 0"/>
   
</joint>
<gazebo reference="${prefix}_wheel_guide">
  <gravity value="true"/>
    <mindepth>0.00001</mindepth>
  <material>Gazebo/Grey</material>
</gazebo>
</xacro:macro>
 
<xacro:macro name="wheel_axle_macro" params="prefix suffix reflect1 reflect2"> 
<link name="${prefix}_${suffix}_wheel_axle">
  <visual>
    <origin xyz="0 0 0" rpy="0 ${reflect2*2.0*pi/3} 0"/>
    <geometry>
      <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/>
    </geometry>
   <material name="black"/>
  </visual>
  <collision>
    <geometry>
      <cylinder radius="${wheel_guide_height*0.2}" length="${wheel_guide_length/2}"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${axel_mass}"/>
</link>
<joint name="${prefix}_${suffix}_wheel_axle_joint" type="fixed">
  <parent link="${prefix}_wheel_guide"/>
  <child link="${prefix}_${suffix}_wheel_axle"/>
  <origin xyz="${reflect2*wheel_guide_length/2} ${reflect1* wheel_guide_thickness/2} ${-wheel_guide_height}" rpy="0 0 0"/>
</joint>
<gazebo reference="${prefix}_${suffix}_wheel_axle">
  <gravity value="true"/>
    <mindepth>0.00001</mindepth>
  <material>Gazebo/Grey</material>
</gazebo>
</xacro:macro>
 
<xacro:macro name="wheel_position_macro" params="prefix suffix reflect1 reflect2">
<link name="${prefix}_${suffix}_wheel">
  <visual>
    
    <geometry>
      <mesh filename="package://learning_tf/meshes/wheels/rubber_wheel_${prefix}.dae"/>
    </geometry>
    <material name="black"/>
  </visual>
  <collision>
   <origin xyz="0 0 0" rpy="${pi/2} 0 0"/>
    <geometry>
      <cylinder radius="${wheel_diameter/2}" length="${wheel_thickness}"/>
    </geometry> 

    <surface>
      <bounce>
        <restitution_coefficient>0.0</restitution_coefficient>
        <threshold>0</threshold>
      </bounce>
    </surface> 

  </collision>
  <xacro:default_inertial mass="${wheel_mass}"/>
</link>
<joint name="${prefix}_${suffix}_wheel_joint" type="continuous">
  <axis xyz="0 1 0"/>
  <parent link="${prefix}_${suffix}_wheel_axle"/>
  <child link="${prefix}_${suffix}_wheel"/>
  <origin xyz="${reflect2*body_length/6.0} ${reflect1*wheel_thickness/2} -${body_height/4.0}"/>
</joint>
<gazebo reference="${prefix}_${suffix}_wheel">
  <mu1 value="200.0"/>
  <mu2 value="100.0"/>
  <kp value="1.0e+6"/>
  <kd value="1.0"/>
  <gravity value="true"/>
  <maxvel>0.0000001</maxvel>
  <mindepth>0.00001</mindepth>
  <material>Gazebo/Black</material>
</gazebo>

<transmission name="${prefix}_${suffix}_wheel_trans">
    <type>transmission_interface/SimpleTransmission</type>
    <actuator name="${prefix}_${suffix}_wheel_motor">
    <hardwareinterface>VelocityJointInterface</hardwareinterface>
      <mechanicalreduction>1</mechanicalreduction>
    </actuator>
    <joint name="${prefix}_${suffix}_wheel_joint">
      <hardwareinterface>VelocityJointInterface</hardwareinterface>
    </joint>
</transmission>
</xacro:macro>
 
<material name="white">
  <color rgba="1 1 1 1"/>
</material>
<material name="black">
  <color rgba="0 0 0 1"/>
</material>
<material name="blue">
  <color rgba="0 0 0.9 1"/>
</material>
<material name="green">
  <color rgba="0 0.8 0 1"/>
</material>
 
<link name="base_footprint">
  <visual>
   <origin xyz="0 0 0"/>
  </visual>
</link>
<link name="base_link">
 
<xacro:shape_visual length="0.6" width="0.5" height="0.3" color="white"/>
  <xacro:default_inertial mass="${body_mass}"/>
</link>
<gazebo reference="base_link">
  <material>Gazebo/White</material>
    <mindepth>0.00001</mindepth>
  <gravity value="true"/>
</gazebo>
<joint name="base_joint" type="fixed" &gt;="" <parent="" link="base_footprint"/>
   <child link="base_link"/>
   <origin xyz="0 0 0.26" rpy="0 0 0"/>
</joint>
 
<xacro:wheel_guide_macro prefix="left" reflect="-1.0"/>
<xacro:wheel_guide_macro prefix="right" reflect="1.0"/>
<xacro:wheel_axle_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>
<xacro:wheel_axle_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/>
<xacro:wheel_axle_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/>
<xacro:wheel_axle_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>
 
<xacro:wheel_position_macro prefix="left" suffix="front" reflect1="-1.0" reflect2="1.0"/>
<xacro:wheel_position_macro prefix="left" suffix="back" reflect1="-1.0" reflect2="-1.0"/>
<xacro:wheel_position_macro prefix="right" suffix="back" reflect1="1.0" reflect2="-1.0"/>
<xacro:wheel_position_macro prefix="right" suffix="front" reflect1="1.0" reflect2="1.0"/>
 
<link name="camera_link">
  <xacro:camera_visual length="0.01" width="${body_width/12.0}" height="${body_width/12.0}" color="black"/>
  <xacro:default_inertial mass="${camera_mass}"/>
</link>
<joint name="camera_joint" type="fixed">
  <parent link="base_link"/>
  <child link="camera_link"/>
  <origin xyz="${body_length/2 + camera_width} 0 0" rpy="0 0 0"/>
</joint>
 
<gazebo reference="camera_link">
    <material>Gazebo/Blue</material>
    <sensor type="camera" name="camera1">
      <update_rate>30.0</update_rate>
      <camera name="head">
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>640</width>
          <height>480</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
        <noise>
          <type>gaussian</type>
          
          <mean>0.0</mean>
          <stddev>0.007</stddev>
        </noise>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwayson>true</alwayson>
        <updaterate>0.0</updaterate>
        <cameraname>camera1</cameraname>
        <imagetopicname>image_raw</imagetopicname>
        <camerainfotopicname>camera_info</camerainfotopicname>
        <framename>camera_link</framename>
        <hackbaseline>0.07</hackbaseline>
        <distortionk1>0.0</distortionk1>
        <distortionk2>0.0</distortionk2>
        <distortionk3>0.0</distortionk3>
        <distortiont1>0.0</distortiont1>
        <distortiont2>0.0</distortiont2>
      </plugin>
    </sensor>
  </gazebo>
 
<link name="laser_optical_link"/>
<joint name="laser_optical_joint" type="fixed">
    <axis xyz="0 1 0"/>
  <parent link="base_link"/>
  <child link="laser_optical_link"/>
  <origin xyz="${body_length/2 + camera_width} 0 0.1" rpy="-${pi/2} 0 -${pi/2}"/>
</joint>
 
<link name="hokuyo_link">
<visual>
    <pose>0 0 0.036 0 0 0</pose>
 
<geometry>
  <mesh filename="package://learning_tf/meshes/hokuyo.dae"/>
</geometry>
 
</visual>
  <collision>
    <geometry>
      <cylinder radius="0.01" length="0.01"/>
    </geometry> 

  </collision>
  <xacro:default_inertial mass="${kinect_mass}"/>
</link>
<joint name="laser_link_joint" type="fixed">
  <parent link="base_link"/>
  <child link="hokuyo_link"/>
  <origin xyz="-${body_length/2.0 - body_width/4.0} 0 ${body_height/2 + body_height/6}"/>
</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>720</samples>
            <resolution>1</resolution>
            <min_angle>-1.570796</min_angle>
            <max_angle>1.570796</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.10</min>
          <max>30.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
       <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicname>/hokuyo/laser/scan</topicname>
        <framename>hokuyo_link</framename>
      </plugin>
    </sensor>
  </gazebo>
 
<gazebo>
  <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
    <robotnamespace>/</robotnamespace>
  </plugin>
</gazebo>
</robot> 
`
 
Find also below attached my diff_drive YAML file.
 
`   
 type: "diff_drive_controller/DiffDriveController"
publish_rate: 100
 
left_wheel:   ['left_front_wheel_joint','left_back_wheel_joint'] 
right_wheel:  ['right_front_wheel_joint','right_back_wheel_joint'] 
 
wheel_separation: 0.50
 
Odometry covariances for the encoder output of the robot. These values should
 
be tuned to your robot's sample odometry data, but these values are a good place
 
to start
 
pose_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]
twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.03]
 
Top level frame (link) of the robot description
 
base_frame_id: base_link
 
Velocity and acceleration limits for the robot
 
linear:
  x:
    has_velocity_limits    : true
    max_velocity           : 0.2   # m/s
    has_acceleration_limits: true
    max_acceleration       : 0.6   # m/s^2
angular:
  z:
    has_velocity_limits    : true
    max_velocity           : 2.0   # rad/s
    has_acceleration_limits: true
    max_acceleration       : 6.0   # rad/s^2 `rad/s^2`
 
Note that when I ran this URDF without the diff_drive, all the transforms worked just fine. As soon as I included the diff drive, the TF map changed. As a result of the new link between odom frame and base link frame, my Maps are totally skewed. I get very haphazard maps when running slam-gmapping.
 
Has anyone experienced this? My information provided may not be as concise as you want... Please ask for clarifications if needed. Thank you.