I am facing issue using the gazebo differential drive controller. The robot moves however it doesn't exactly move in a straight line when I issue /cmd_vel x="0.05". The robot will start to drift gradually. Appreciate any help thanks. I have tried increasing the mass and also ensuring the inertia is not tilted. Also, when I check the /joint_states topic each of the wheel joint has slightly different position.
<?xml version="1.0" ?>
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<xacro:include filename="$(find alphabot_description)/urdf/materials.xacro" />
<xacro:include filename="$(find alphabot_description)/urdf/alphabot.trans" />
<xacro:include filename="$(find alphabot_description)/urdf/alphabot.gazebo" />
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</inertial>
<visual>
<origin xyz="0.0 0.037 -0.022048" rpy="0 0 0"/>
<geometry>
<mesh filename="package://alphabot_description/meshes/left_wheel_1.stl" scale="0.001 0.001 0.001"/>
</geometry>
<material name="black"/>
</visual>
<collision>
<origin xyz="0.0 0.037 -0.022048" rpy="0 0 0"/>
<geometry>
<mesh filename="package://alphabot_description/meshes/left_wheel_1.stl" scale="0.001 0.001 0.001"/>
</geometry>
</collision>
</link>
<link name="right_wheel_1">
<inertial>
<origin xyz="-3.6087326488468997e-06 -0.005589374587544396 -2.5191228260612597e-06" rpy="0 0 0"/>
<mass value="0.1"/>
<inertia ixx="1.8e-05" iyy="3.1e-05" izz="1.8e-05" ixy="-0.0" iyz="-0.0" ixz="0.0"/>
</inertial>
<visual>
<origin xyz="0.0 0.037 -0.022048" rpy="0 0 0"/>
<geometry>
<mesh filename="package://alphabot_description/meshes/right_wheel_1.stl" scale="0.001 0.001 0.001"/>
</geometry>
<material name="black"/>
</visual>
<collision>
<origin xyz="0.0 0.037 -0.022048" rpy="0 0 0"/>
<geometry>
<mesh filename="package://alphabot_description/meshes/right_wheel_1.stl" scale="0.001 0.001 0.001"/>
</geometry>
</collision>
</link>
<joint name="Rigid 6" type="fixed">
<origin xyz="0.028948 0.04191 0.017048" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="spacer_1_1"/>
</joint>
<joint name="Rigid 7" type="fixed">
<origin xyz="0.028948 -0.04191 0.017048" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="spacer_1_2"/>
</joint>
<joint name="Rigid 8" type="fixed">
<origin xyz="-0.028948 -0.04191 0.017048" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="spacer_1_3"/>
</joint>
<joint name="Rigid 9" type="fixed">
<origin xyz="-0.028948 0.04191 0.017048" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="spacer_1_4"/>
</joint>
<joint name="Rigid 10" type="fixed">
<origin xyz="0.0 0.0 0.029095" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="ultasonic_1"/>
</joint>
<joint name="Rigid 13" type="fixed">
<origin xyz="-0.02225 0.026 -0.003047" rpy="0 0 0"/>
<parent link="battery_case_1"/>
<child link="AA_1"/>
</joint>
<joint name="Rigid 14" type="fixed">
<origin xyz="-0.03775 -0.026 -0.003047" rpy="0 0 0"/>
<parent link="battery_case_1"/>
<child link="AA_2"/>
</joint>
<joint name="Rigid 15" type="fixed">
<origin xyz="0.0 0.0 0.029095" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="battery_case_1"/>
</joint>
<joint name="Rigid 16" type="fixed">
<origin xyz="0.0 0.0 0.029095" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="motor_1"/>
</joint>
<joint name="Rigid 17" type="fixed">
<origin xyz="0.0 0.0 0.029095" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="motor_2"/>
</joint>
<joint name="Rigid 20" type="fixed">
<origin xyz="0.0 0.0 0.040375" rpy="0 0 0"/>
<parent link="spacer_1_3"/>
<child link="top_link_1"/>
</joint>
<joint name="Rigid 21" type="fixed">
<origin xyz="0.02896 0.04191 0.005" rpy="0 0 0"/>
<parent link="top_link_1"/>
<child link="pantilt_1_1"/>
</joint>
<joint name="Rigid 22" type="fixed">
<origin xyz="0.0 0.0 0.002" rpy="0 0 0"/>
<parent link="pantilt_1_1"/>
<child link="servo_emax_1_1"/>
</joint>
<joint name="Rigid 24" type="fixed">
<origin xyz="0.011738 -0.081723 0.0178" rpy="0 0 0"/>
<parent link="servo_1_1"/>
<child link="pantilt_2_1"/>
</joint>
<joint name="Rigid 27" type="fixed">
<origin xyz="0.106503 0.107112 0.088822" rpy="0 0 0"/>
<parent link="pantilt_2_1"/>
<child link="servo_emax_2_1"/>
</joint>
<joint name="Rigid 29" type="fixed">
<origin xyz="-0.125373 0.026 -0.009512" rpy="0 0 0"/>
<parent link="servo_2_1"/>
<child link="pantilt_3_1"/>
</joint>
<joint name="Revolute 30" type="continuous">
<origin xyz="-0.091141 -0.036589 -0.068972" rpy="0 0 0"/>
<parent link="servo_emax_2_1"/>
<child link="servo_2_1"/>
<axis xyz="0.0 1.0 0.0"/>
<dynamics damping="0.1" friction="100"/>
<limit effort="130" lower="-1.57" upper="1.57" velocity="6.98"/>
</joint>
<joint name="Revolute 31" type="continuous">
<origin xyz="0.0 0.0 0.0095" rpy="0 0 0"/>
<parent link="servo_emax_1_1"/>
<child link="servo_1_1"/>
<axis xyz="-0.0 -0.0 1.0"/>
<dynamics damping="0.01" friction="1"/>
<limit effort="130" lower="-1.57" upper="1.57" velocity="6.98"/>
</joint>
<joint name="Rigid 32" type="fixed">
<origin xyz="0.133573 -0.0141 0.020212" rpy="0 0 0"/>
<parent link="pantilt_3_1"/>
<child link="camera_1"/>
</joint>
<joint name="Rigid 43" type="fixed">
<origin xyz="-0.04 -0.0 -0.016548" rpy="0 0 0"/>
<parent link="housing_1"/>
<child link="ball_1"/>
</joint>
<joint name="Rigid 44" type="fixed">
<origin xyz="0.0 0.0 0.024095" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="housing_1"/>
</joint>
<joint name="Rigid 45" type="fixed">
<origin xyz="-0.04 -0.0 -0.016548" rpy="0 0 0"/>
<parent link="housing_2"/>
<child link="ball_2"/>
</joint>
<joint name="Rigid 46" type="fixed">
<origin xyz="0.0 0.0 0.024095" rpy="0 0 0"/>
<parent link="base_link"/>
<child link="housing_2"/>
</joint>
<joint name="Revolute 18" type="continuous">
<origin xyz="-0.0 -0.037 -0.007047" rpy="0 0 0"/>
<parent link="motor_2"/>
<child link="left_wheel_1"/>
<axis xyz="0.0 1.0 -0.0"/>
<dynamics damping="2" friction="2"/>
</joint>
<joint name="Revolute 19" type="continuous">
<origin xyz="-0.0 -0.037 -0.007047" rpy="0 0 0"/>
<parent link="motor_1"/>
<child link="right_wheel_1"/>
<axis xyz="0.0 1.0 -0.0"/>
<dynamics damping="2" friction="2"/>
</joint>
</robot>
gazebo file
<?xml version="1.0" ?>
<robot name="alphabot" xmlns:xacro="http://www.ros.org/wiki/xacro" >
<xacro:property name="blue" value="Gazebo/Blue" />
<xacro:property name="silver" value="Gazebo/Silver" />
<xacro:property name="black" value="Gazebo/Black" />
<xacro:property name="green" value="Gazebo/Green" />
<xacro:property name="gold" value="Gazebo/Gold" />
<xacro:property name="blue_2" value="Gazebo/SkyBlue" />
<gazebo>
<plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
<robotNamespace>/alphabot</robotNamespace>
</plugin>
<plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">
<!-- Plugin update rate in Hz -->
<updateRate>5</updateRate>
<!-- Name of left joint, defaults to `left_joint` -->
<leftJoint>Revolute 18</leftJoint>
<!-- Name of right joint, defaults to `right_joint` -->
<rightJoint>Revolute 19</rightJoint>
<!-- The distance from the center of one wheel to the other, in meters, defaults to 0.34 m -->
<wheelSeparation>0.08</wheelSeparation>
<!-- Diameter of the wheels, in meters, defaults to 0.15 m -->
<wheelDiameter>0.043</wheelDiameter>
<!-- Wheel acceleration, in rad/s^2, defaults to 0.0 rad/s^2 -->
<wheelAcceleration>1.0</wheelAcceleration>
<!-- Maximum torque which the wheels can produce, in Nm, defaults to 5 Nm -->
<wheelTorque>100</wheelTorque>
<!-- Topic to receive geometry_msgs/Twist message commands, defaults to `cmd_vel` -->
<commandTopic>cmd_vel</commandTopic>
<!-- Topic to publish nav_msgs/Odometry messages, defaults to `odom` -->
<odometryTopic>odom</odometryTopic>
<!-- Odometry frame, defaults to `odom` -->
<odometryFrame>odom</odometryFrame>
<!-- Robot frame to calculate odometry from, defaults to `base_footprint` -->
<robotBaseFrame>base_footprint</robotBaseFrame>
<!-- Odometry source, 0 for ENCODER, 1 for WORLD, defaults to WORLD -->
<odometrySource>1</odometrySource>
<!-- Set to true to publish transforms for the wheel links, defaults to false -->
<publishWheelTF>true</publishWheelTF>
<!-- Set to true to publish transforms for the odometry, defaults to true -->
<publishOdom>true</publishOdom>
<!-- Set to true to publish sensor_msgs/JointState on /joint_states for the wheel joints, defaults to false -->
<publishWheelJointState>true</publishWheelJointState>
<!-- Set to true to swap right and left wheels, defaults to true -->
<legacyMode>false</legacyMode>
</plugin>
</gazebo>
<gazebo reference="base_link">
<material>${blue}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
<gravity>true</gravity>
</gazebo>
<gazebo reference="spacer_1_1">
<material>${gold}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="spacer_1_2">
<material>${gold}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="spacer_1_3">
<material>${gold}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="spacer_1_4">
<material>${gold}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="ultasonic_1">
<sensor type="ray" name="TeraRanger">
<pose>0 0 0 0 0 0</pose>
<visualize>true</visualize>
<update_rate>50</update_rate>
<ray>
<scan>
<horizontal>
<samples>10</samples>
<resolution>1</resolution>
<min_angle>-0.14835</min_angle>
<max_angle>0.14835</max_angle>
</horizontal>
<vertical>
<samples>10</samples>
<resolution>1</resolution>
<min_angle>-0.14835</min_angle>
<max_angle>0.14835</max_angle>
</vertical>
</scan>
<range>
<min>0.01</min>
<max>0.2</max>
<resolution>0.02</resolution>
</range>
</ray>
<plugin filename="libgazebo_ros_range.so" name="gazebo_ros_range">
<gaussianNoise>0.005</gaussianNoise>
<alwaysOn>true</alwaysOn>
<updateRate>50</updateRate>
<topicName>sensor/ir_front</topicName>
<frameName>base_ir_front</frameName>
<radiation>INFRARED</radiation>
<fov>0.2967</fov>
</plugin>
</sensor>
<material>${blue_2}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="AA_1">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="AA_2">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="battery_case_1">
<material>${black}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="motor_1">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="motor_2">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="left_wheel_1">
<material>${black}</material>
<mu1>1000</mu1>
<mu2>1000</mu2>
<selfCollide>true</selfCollide>
<kp value="1000.0" />
<kd value="1.0" />
</gazebo>
<gazebo reference="right_wheel_1">
<material>${black}</material>
<mu1>1000</mu1>
<mu2>1000</mu2>
<selfCollide>true</selfCollide>
<kp value="1000.0" />
<kd value="1.0" />
</gazebo>
<gazebo reference="top_link_1">
<material>${blue}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="pantilt_1_1">
<material>${black}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="servo_emax_1_1">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="pantilt_2_1">
<material>${black}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="servo_emax_2_1">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="pantilt_3_1">
<material>${black}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="servo_2_1">
<material>${blue}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="servo_1_1">
<material>${blue}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="camera_1">
<sensor type="camera" name="camera1">
<update_rate>30.0</update_rate>
<camera name="head">
<horizontal_fov>1.3962634</horizontal_fov>
<image>
<width>800</width>
<height>800</height>
<format>R8G8B8</format>
</image>
<clip>
<near>0.02</near>
<far>300</far>
</clip>
<noise>
<type>gaussian</type>
<!-- Noise is sampled independently per pixel on each frame.
That pixel's noise value is added to each of its color
channels, which at that point lie in the range [0,1]. -->
<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>alphabot/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>
<material>${green}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="ball_1">
<material>${silver}</material>
<mu1>0.0001</mu1>
<mu2>0.0001</mu2>
<kp>0.1</kp>
<kd>0.1</kd>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="housing_1">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="ball_2">
<material>${silver}</material>
<mu1>0.0001</mu1>
<mu2>0.0001</mu2>
<kp>0.1</kp>
<kd>0.1</kd>
<selfCollide>true</selfCollide>
</gazebo>
<gazebo reference="housing_2">
<material>${silver}</material>
<mu1>0.2</mu1>
<mu2>0.2</mu2>
<selfCollide>true</selfCollide>
</gazebo>
</robot>
