I want to implement a 4 wheel robot with car like steering(having 2 front steerable wheels and 2 back drive wheels) in ros2 using ros2_control. Can you suggest me which ros2 controller should I use(with example)? Is there any example I could refer to? The ros2_control documentation is not detailed enough and their example are mostly differential drive based.
Edit:
Distro: ros2-humble
Directory Structure
race_it_ws
/src
/race_it
/description
/race_car.xacro
/ros2_ack.xacro
/inertial.xacro
/config
/controller
/my_controllers.yaml
/launch
/rsp.launch.py
/hardware ## NOTE: I have just copied this folder from "ros2_control_demos/example_11" AS IT IS.
Complete source code is provided below.
Description
race_car.xacro(main urdf file)
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="simple_car">
<xacro:include filename="inertial.xacro"/>
<!-- <xacro:include filename="gazebo_control_dd.xacro"/> -->
<!-- <xacro:include filename="gazebo_control_steer.xacro"/> -->
<xacro:property name="wheel_width" value="0.04"/>
<xacro:property name="wheel_radius" value="0.1"/>
<!-- Wheel macro -->
<xacro:macro name="wheel" params="name">
<link name="${name}">
<visual>
<geometry>
<cylinder length="${wheel_width}" radius="${wheel_radius}" />
</geometry>
<material name="blue"/>
</visual>
<collision>
<geometry>
<cylinder length="${wheel_width}" radius="${wheel_radius}" />
</geometry>
</collision>
<xacro:inertial_cylinder mass="0.1" length="${wheel_width}" radius="${wheel_radius}"/>
</link>
<gazebo reference="${name}">
<material>Gazebo/Blue</material>
</gazebo>
</xacro:macro>
<!-- Base Link -->
<link name="base_link">
</link>
<!-- Chassis Link -->
<link name="chassis_link">
<visual>
<geometry>
<box size="0.5 1.0 0.2"/>
</geometry>
<origin xyz="0 0 0" rpy="0 0 0"/>
<material name="blue">
<color rgba="0 0 1 1"/>
</material>
</visual>
<xacro:inertial_box mass="0.5" x="0.5" y="1.0" z="0.15"/>
</link>
<gazebo reference="chassis_link">
<material>Gazebo/Orange</material>
</gazebo>
<!-- Base Chassis Joint -->
<joint name="base_chassis_joint" type="fixed">
<parent link="base_link"/>
<child link="chassis_link"/>
<origin xyz="0 0 0.2" rpy="0 0 0 "/>
</joint>
<!-- Front Left Wheel -->
<xacro:wheel name="front_left_link"/>
<joint name="front_left_joint" type="continuous">
<parent link="chassis_link"/>
<child link="front_left_link"/>
<origin xyz="-0.3 0.5 -0.1" rpy="0 ${pi/2} 0"/>
<axis xyz="0 0 1"/>
</joint>
<gazebo reference="front_left_link">
<material>Gazebo/Red</material>
<mu1 value="0.001"/>
<mu2 value="0.001"/>
</gazebo>
<!-- Front Right Wheel -->
<xacro:wheel name="front_right_link"/>
<joint name="front_right_joint" type="continuous">
<parent link="chassis_link"/>
<child link="front_right_link"/>
<origin xyz="0.3 0.5 -0.1" rpy="0 ${pi/2} 0"/>
<axis xyz="0 0 1"/>
</joint>
<gazebo reference="front_right_link">
<material>Gazebo/Red</material>
<mu1 value="0.001"/>
<mu2 value="0.001"/>
</gazebo>
<!-- Rear Left Wheel -->
<xacro:wheel name="rear_left_link"/>
<joint name="rear_left_joint" type="continuous">
<parent link="chassis_link"/>
<child link="rear_left_link"/>
<origin xyz="-0.3 -0.5 -0.1" rpy="0 ${pi/2} 0"/>
<axis xyz="0 0 1"/>
</joint>
<!-- Rear Right Wheel -->
<xacro:wheel name="rear_right_link" />
<joint name="rear_right_joint" type="continuous">
<parent link="chassis_link"/>
<child link="rear_right_link"/>
<origin xyz="0.3 -0.5 -0.1" rpy="0 ${pi/2} 0"/> <!-- Default value for x is "0.27" -->
<axis xyz="0 0 1"/>
</joint>
<xacro:include filename="ros2_ack.xacro"/>
</robot>
ros2_ack.xacro
<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="simple_car">
<ros2_control name="carbot" type="system">
<hardware>
<!-- <plugin>gazebo_ros2_control/GazeboSystem</plugin> -->
<plugin>ros2_control_demo_example_11/CarlikeBotSystemHardware</plugin>
<param name="example_param_hw_start_duration_sec">0</param>
<param name="example_param_hw_stop_duration_sec">3.0</param>
<param name="is_simulation">1</param>
</hardware>
<!-- Front Left Wheel -->
<joint name="front_left_joint">
<command_interface name="position"/>
<state_interface name="position" />
</joint>
<!-- Front Right Wheel -->
<joint name="front_right_joint">
<command_interface name="position"/>
<state_interface name="position" />
</joint>
<!-- Rear Left Wheel -->
<joint name="rear_left_joint">
<command_interface name="velocity"/>
<state_interface name="velocity" />
</joint>
<!-- Rear Right Wheel -->
<joint name="rear_right_joint">
<command_interface name="velocity"/>
<state_interface name="velocity" />
</joint>
</ros2_control>
<gazebo>
<plugin filename="libgazebo_ros2_control.so" name="gazebo_ros2_control">
<parameters>$(find race_it)/config/controller/my_controllers.yaml</parameters>
</plugin>
</gazebo>
</robot>
Controller Config
my_controllers.yaml
controller_manager:
ros__parameters:
update_rate: 30
use_sim_time: true
asc:
type: ackermann_steering_controller/AckermannSteeringController
jsc:
type: joint_state_broadcaster/JointStateBroadcaster
asc:
ros__parameters:
reference_timeout: 2.0
front_steering: true
open_loop: false
velocity_rolling_window_size: 10
position_feedback: false
use_stamped_vel: true
#rear_wheels_names: [rear_right_joint, rear_left_joint]
#front_wheels_names: [front_right_joint, front_left_joint]
rear_wheels_names: [rear_right_joint, rear_left_joint]
front_wheels_names: [front_right_joint, front_left_joint]
wheelbase: 1.0
front_wheel_track: 0.55
rear_wheel_track: 0.55
front_wheels_radius: 0.1
rear_wheels_radius: 0.1
#jsc:
# ros__parameters:
# type: joint_state_controller/JointStateController
Launch File
rsp.launch.py
import os
from ament_index_python.packages import get_package_share_directory
from launch import LaunchDescription
from launch.substitutions import LaunchConfiguration
from launch.actions import DeclareLaunchArgument
from launch_ros.actions import Node
import launch_ros
from launch.actions import IncludeLaunchDescription
from launch.launch_description_sources import PythonLaunchDescriptionSource
import xacro
def generate_launch_description():
# Check if we're told to use sim time
use_sim_time = LaunchConfiguration('use_sim_time')
# Process the URDF file
pkg_path = os.path.join(get_package_share_directory('race_it'))
#xacro_file = os.path.join(pkg_path,'description','robot.urdf.xacro')
xacro_file = os.path.join(pkg_path,'description', 'race_car.xacro')
robot_description_config = xacro.process_file(xacro_file)
default_rviz_config_path = os.path.join(pkg_path, 'config/rviz/urdf_config.rviz')
# Create a robot_state_publisher node
params = {'robot_description': robot_description_config.toxml(), 'use_sim_time': use_sim_time}
node_robot_state_publisher = Node(
package='robot_state_publisher',
executable='robot_state_publisher',
output='screen',
parameters=[params]
)
joint_state_publisher_node = launch_ros.actions.Node(
package='joint_state_publisher',
executable='joint_state_publisher',
name='joint_state_publisher'
)
rviz_node = launch_ros.actions.Node(
package='rviz2',
executable='rviz2',
name='rviz2',
output='screen',
arguments=['-d', default_rviz_config_path],
)
gazebo = IncludeLaunchDescription(
PythonLaunchDescriptionSource([os.path.join(
get_package_share_directory('gazebo_ros'), 'launch', 'gazebo.launch.py')])#,
# launch_arguments={'world': "my_bot/worlds/obstacles.world"}.items()
)
spawn_entity = launch_ros.actions.Node(
package='gazebo_ros',
executable='spawn_entity.py',
arguments=['-entity', '', '-topic', 'robot_description'],
output='screen'
)
# Launch!
return LaunchDescription([
DeclareLaunchArgument(
'use_sim_time',
default_value='true',
description='Use sim time if true'),
node_robot_state_publisher,
joint_state_publisher_node,
rviz_node,
gazebo,
spawn_entity
])
