I've been building a 4 wheel differential drive robot (all 4 wheels have motors) and I've noticed that when I control the robot, in Gazebo it barely turns while in RViz it turns a lot more. This causes a lot of desync and I've been trying to solve it for quite some time now.

I'm working on a VM, VMWare Workstation 16 running Ubuntu 22.04.3 LTS. I have ROS2 Iron and I'm using ros2_control for moving the robot. For now, I'm using RViz2 and Gazebo to simulate the robot (I don't know which version of Gazebo I have, it auto-installed based on my ROS2 version).

You can find all the code here https://github.com/ClauPan/Vox/tree/main/src

Here is my urdf for the robot structure (the numbers for the different parameters are based on the dimensions of my real robot, which I plan to use this code for):

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">
    <xacro:include filename="colors.xacro"/>

    <!-- BASE LINK -->

    <link name="base_link"></link>

    <!-- BASE FOOTPRINT LINK -->
    <joint name="base_footprint_joint" type="fixed">
        <parent link="base_link"/>
        <child link="base_footprint"/>
        <origin xyz="0 0 0" rpy="0 0 0"/>
    </joint>

    <link name="base_footprint"></link>

    <!-- CHASSIS LINK -->

    <joint name="chassis_joint" type="fixed">
        <parent link="base_link"/>
        <child link="chassis"/>
        <origin xyz="-0.105 0 0"/>
    </joint>

    <link name="chassis">
        <parent link="chassis_joint"/>
        <visual>
            <geometry>
                <box size="0.21 0.135 0.0475"/>
            </geometry>
            <material name="white"/>
        </visual>
        <collision>
            <geometry>
                <box size="0.21 0.135 0.0475"/>
            </geometry>
        </collision>
        <inertial>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <mass value="0.67"/>
            <inertia 
                ixx="${(1/12) * 0.67 * (0.135*0.135+0.0475*0.0475)}" ixy="0.0" ixz="0.0"
            iyy="${(1/12) * 0.67 * (0.21*0.21+0.0475*0.0475)}" iyz="0.0"
                izz="${(1/12) * 0.67 * (0.21*0.21+0.135*0.135)}"
            />
        </inertial>
    </link>

    <gazebo reference="chassis">
        <material>Gazebo/White</material>
    </gazebo>

    <joint name="front_left_wheel_joint" type="continuous">
        <parent link="chassis"/>
        <child link="front_left_wheel"/>
        <origin xyz="-0.08 0.1145 0" rpy="-${pi/2} 0 0"/>
        <axis xyz="0 0 1"/>
    </joint>

    <link name="front_left_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.06" length="0.06"/>
            </geometry>
            <material name="blue"/>
        </visual>
        <collision>
            <geometry>
                <!-- <cylinder radius="0.06" length="0.06"/> -->
                <sphere radius="0.06"/>
            </geometry>
        </collision>
        <inertial>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <mass value="0.17"/>
            <inertia 
                ixx="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" ixy="0.0" ixz="0.0"
            iyy="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" iyz="0.0"
                izz="${(1/12) * 0.17 * (0.06*0.06)}"
            />
        </inertial>
    </link>

    <gazebo reference="front_left_wheel">
        <material>Gazebo/Blue</material>
    </gazebo>

    <joint name="front_right_wheel_joint" type="continuous">
        <parent link="chassis"/>
        <child link="front_right_wheel"/>
        <origin xyz="-0.08 -0.1145 0" rpy="${pi/2} 0 0"/>
        <axis xyz="0 0 -1"/>
    </joint>

    <link name="front_right_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.06" length="0.06"/>
            </geometry>
            <material name="blue"/>
        </visual>
        <collision>
            <geometry>
                <!-- <cylinder radius="0.06" length="0.06"/> -->
                <sphere radius="0.06"/>
            </geometry>
        </collision>
        <inertial>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <mass value="0.17"/>
            <inertia 
                ixx="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" ixy="0.0" ixz="0.0"
            iyy="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" iyz="0.0"
                izz="${(1/12) * 0.17 * (0.06*0.06)}"
            />
        </inertial>
    </link>

    <gazebo reference="front_right_wheel">
        <material>Gazebo/Blue</material>
    </gazebo>

    <joint name="back_left_wheel_joint" type="continuous">
        <parent link="chassis"/>
        <child link="back_left_wheel"/>
        <origin xyz="0.08 0.1145 0" rpy="-${pi/2} 0 0"/>
        <axis xyz="0 0 1"/>
    </joint>

    <link name="back_left_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.06" length="0.06"/>
            </geometry>
            <material name="blue"/>
        </visual>
        <collision>
            <geometry>
                <!-- <cylinder radius="0.06" length="0.06"/> -->
                <sphere radius="0.06"/>
            </geometry>
        </collision>
        <inertial>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <mass value="0.17"/>
            <inertia 
                ixx="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" ixy="0.0" ixz="0.0"
            iyy="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" iyz="0.0"
                izz="${(1/12) * 0.17 * (0.06*0.06)}"
            />
        </inertial>
    </link>

    <gazebo reference="back_left_wheel">
        <material>Gazebo/Blue</material>
    </gazebo>

    <joint name="back_right_wheel_joint" type="continuous">
        <parent link="chassis"/>
        <child link="back_right_wheel"/>
        <origin xyz="0.08 -0.1145 0" rpy="${pi/2} 0 0"/>
        <axis xyz="0 0 -1"/>
    </joint>

    <link name="back_right_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.06" length="0.06"/>
            </geometry>
            <material name="blue"/>
        </visual>
        <collision>
            <geometry>
                <!-- <cylinder radius="0.06" length="0.06"/> -->
                <sphere radius="0.06"/>
            </geometry>
        </collision>
        <inertial>
            <origin xyz="0 0 0" rpy="0 0 0"/>
            <mass value="0.17"/>
            <inertia 
                ixx="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" ixy="0.0" ixz="0.0"
            iyy="${(1/12) * 0.17 * (3*0.06*0.06 + 0.06*0.06)}" iyz="0.0"
                izz="${(1/12) * 0.17 * (0.06*0.06)}"
            />
        </inertial>
    </link>

    <gazebo reference="back_right_wheel">
        <material>Gazebo/Blue</material>
    </gazebo>

</robot>

This is the urdf for my ros2_control:

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

    <ros2_control name="GazeboSystem" type="system">
        <hardware>
            <plugin>gazebo_ros2_control/GazeboSystem</plugin>
        </hardware>
        <joint name="front_left_wheel_joint">
            <command_interface name="velocity">
                <param name="min">-10</param>
                <param name="max">10</param>
            </command_interface>
            <state_interface name="velocity"></state_interface>
            <state_interface name="position"></state_interface>
        </joint>
        <joint name="back_left_wheel_joint">
            <command_interface name="velocity">
                <param name="min">-10</param>
                <param name="max">10</param>
            </command_interface>
            <state_interface name="velocity"></state_interface>
            <state_interface name="position"></state_interface>
        </joint>
        <joint name="front_right_wheel_joint">
            <command_interface name="velocity">
                <param name="min">-10</param>
                <param name="max">10</param>
            </command_interface>
            <state_interface name="velocity"></state_interface>
            <state_interface name="position"></state_interface>
        </joint>    
        <joint name="back_right_wheel_joint">
            <command_interface name="velocity">
                <param name="min">-10</param>
                <param name="max">10</param>
            </command_interface>
            <state_interface name="velocity"></state_interface>
            <state_interface name="position"></state_interface>
        </joint>
    </ros2_control>

    <gazebo> 
        <plugin name="gazebo_ros2_control" filename="libgazebo_ros2_control.so">
            <parameters>$(find vox)/config/my_controllers.yaml</parameters>
        </plugin>
    </gazebo>
</robot>

This is my .yaml file for the controller:

controller_manager:
  ros__parameters:
    update_rate: 30
    use_sim_time: true

    diff_cont:
      type: diff_drive_controller/DiffDriveController

    joint_broad:
      type: joint_state_broadcaster/JointStateBroadcaster

diff_cont:
  ros__parameters:

    publish_rate: 50.0

    base_frame_id: base_link

    left_wheel_names: ['front_left_wheel_joint', 'back_left_wheel_joint']
    right_wheel_names: ['front_right_wheel_joint', 'back_right_wheel_joint']
    wheel_separation: 0.229
    wheel_radius: 0.06

    use_stamped_vel: false

    open_loop: true

    # wheels_per_side: 2
    # wheel_separation_multiplier: 0.08
    # left_wheel_radius_multiplier: x
    # right_wheel_radius_multiplier: x

    # odom_frame_id: odom
    pose_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.01]
    twist_covariance_diagonal: [0.001, 0.001, 0.001, 0.001, 0.001, 0.01]
    # open_loop: x
    # enable_odom_tf: x

    # cmd_vel_timeout: x
    # publis_limited_velocity: x
    # velocity_roling_window_size: x

    # linear.x.has_velocity_limits: true
    # linear.x.has_acceleration_limits: true
    # linear.x.has_jerk_limits: false
    # linear.x.max_velocity: 1
    # linear.x.min_velocity: NAN
    # linear.x.max_acceleration: 3
    # linear.x.min_acceleration: NAN
    # linear.x.max_jerk: NAN
    # linear.x.min_jerk: NAN

    # angular.z.has_velocity_limits: true
    # angular.z.has_acceleration_limits: true
    # angular.z.has_jerk_limits: false
    # angular.z.max_velocity: 1
    # angular.z.min_velocity: NAN
    # angular.z.max_acceleration: 3
    # angular.z.min_acceleration: NAN
    # angular.z.max_jerk: NAN
    # angular.z.min_jerk: NAN

# joint_broad:
#   ros_parameters:

And this is my launch file:

import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
from launch_ros.actions import Node

def generate_launch_description():
    package_name = "vox"
    rsp = IncludeLaunchDescription(
        PythonLaunchDescriptionSource([
            os.path.join(get_package_share_directory(package_name), "launch", "rsp.launch.py")
        ]),
        launch_arguments={"use_sim_time": "true", "use_ros2_control": "true"}.items()
    )

    gazebo_params_file = os.path.join(get_package_share_directory(package_name), "config", "gazebo_params.yaml")
    gazebo = IncludeLaunchDescription(
        PythonLaunchDescriptionSource([
            os.path.join(get_package_share_directory("gazebo_ros"), "launch", "gazebo.launch.py")
        ]),
        launch_arguments={'extra_gazebo_args': '--ros-args --param-files' + gazebo_params_file}.items()
    )
    spawn_entity = Node(
        package="gazebo_ros", executable="spawn_entity.py",
        arguments=["-topic", "robot_description", "-entity", "vox"],
        output="screen"
    )

    diff_drive_spawner = Node(
        package="controller_manager",
        executable="spawner",
        arguments=["diff_cont"],
    )
    
    joint_broad_spawner = Node(
        package="controller_manager",
        executable="spawner",
        arguments=["joint_broad"],
    )

    return LaunchDescription([
        rsp, 
        gazebo, 
        spawn_entity,
        diff_drive_spawner,
        joint_broad_spawner
    ])

The way I start everything up is by running the following commands: Terminal 1:

source install/setup.bash
ros2 launch vox launch_sim.launch.py

Terminal 2:

ros2 run teleop_twist_keyboard teleop_twist_keyboard --ros-args -r /cmd_vel:=/diff_cont/cmd_vel_unstamped

Terminal 3:

rviz2

After pressing "l" once, which is "turn right", the RViz2 representation turned a lot more then the Gazebo one.

I haven't noticed this very much until I started implementing SLAM into the project. This difference in turn messes up mapping a lot.

I would appreciate any and all suggestions to fix this drift between RViz2 and Gazebo. If you need anything else from my side, I'll post them ASAP.