robile_gazebo

Gazebo simulations for KELO ROBILE robots

Installation

In addition to a few ROS dependencies, this package also depends on the following packages provided by KELO-robotics:

1. kelo_tulip [Optional: only if you want smart wheel emulated]
2. robile_description

Assuming you have a catkin workspace at ~/ros2_ws, execute the below commands to install the simulator and its dependencies

cd ~/catkin_ws/src
git clone https://github.com/kelo-robotics/kelo_tulip.git
git clone https://github.com/kelo-robotics/robile_description.git
git clone https://github.com/kelo-robotics/robile_gazebo.git

cd ~/catkin_ws
rosdep install --from-paths src --ignore-src -r -y

catkin build kelo_tulip # you will need to enter your password for the kelo_tulip build to complete

colcon build --packages-select robile_gazebo robile_description 
source ~/catkin_ws/devel/setup.bash

Usage

To start the gazebo simulator, use one of the launch files defined in the launch/ directory as follows:

ros2 launch robile_gazebo gazebo_4_wheel.launch.py

You can then publish command velocities on the ros topic /cmd_vel to move the robot around. For example, to move the robot forward with 0.5 m/s velocity, execute the below command in a new terminal:

rostopic pub /cmd_vel geometry_msgs/Twist "linear:
  x: 0.5
  y: 0.0
  z: 0.0
angular:
  x: 0.0
  y: 0.0
  z: 0.0" -r 10

Disabling kelo_tulip platform controller

The kelo_tulip platform controller requires information about every continuous (or movable) joint in all the connected KELO Drives. Moreover, it sends control data for every hub wheel. This can potentially increase the simulation load on weaker computers. If the goal of simulation is to move the robot around without worrying about the platform controller used, then kelo_tulip can be switched off and the more simpler gazebo_ros_planar_move platform controller can be used. To start the simulation with the gazebo_ros_planar_move instead of kelo_tulip use the below command:

ros2 launch robile_gazebo gazebo_4_wheel.launch.py

Adding laser scanner to URDF

You can add a laser scanner to the root by editing the robile description and addting the following lines, for example in the robile_gaebo.xacro file

    <!-- sensors -->
    <xacro:include filename="$(find robile_description)/urdf/sensors/hokuyo_urg04_laser.urdf.xacro"/>

    <!-- base laser front -->
    <xacro:hokuyo_urg04_laser name="base_laser_front" parent="base" ros_topic="scan_front" update_rate="10" min_angle="-1.57" max_angle="1.57">
    <origin xyz="0.3 0 0.3" rpy="0 0 0"/>
    </xacro:hokuyo_urg04_laser>

You also need to install the gazebo package to simulate the laser scanner

sudo apt install ros-$ROS_DISTRO-gazebo-ros-pkgs

Now if you launch you will have an additional topic /scan_front in rostopic list.

Moving the robot using a keyboard

The teleop_twist_keyboard ROS package can be used to simplify controlling the motion of the robot. This requires a one time installation of the teleop_twist_keyboard package using the below command:

sudo apt install ros-$ROS_DISTRO-teleop-twist-keyboard
source /opt/ros/$ROS_DISTRO/setup.bash

Then start the teleop_twist_keyboard.py node using the command rosrun teleop_twist_keyboard teleop_twist_keyboard.py and move the robot as per the instructions displayed on the terminal. Below is an example of the output after running the node:

rosrun teleop_twist_keyboard teleop_twist_keyboard.py 

Reading from the keyboard  and Publishing to Twist!
---------------------------
Moving around:
   u    i    o
   j    k    l
   m    ,    .

For Holonomic mode (strafing), hold down the shift key:
---------------------------
   U    I    O
   J    K    L
   M    <    >

t : up (+z)
b : down (-z)

anything else : stop

q/z : increase/decrease max speeds by 10%
w/x : increase/decrease only linear speed by 10%
e/c : increase/decrease only angular speed by 10%

CTRL-C to quit

currently:	speed 0.5	turn 1.0 

Additional launch file arguments

Several arguments can be passed when launching the simulator. A complete list of supported roslaunch arguments can be found in the launch/platform_independent/robile_gazebo.launch file. We list a few most important ones here.

Argument name	Type	Default	Description
platform_max_lin_vel	float	1.0	Maximum linear velocity the platform can achieve in the XY plane (in m/s)
platform_max_ang_vel	float	1.0	Maximum angular velocity the platform can achieve along the Z axis (in rad/s)
init_pos_x	float	0.0	Spawn position of robot along the world X-axis
init_pos_y	float	0.0	Spawn position of robot along the world Y-axis
init_yaw	float	0.0	Spawn orientation of robot along the world Z-axis
gazebo_gui	boolean	true	Start the Gazebo simulation GUI
start_rviz	boolean	true	Start RViz with a predefined RViz configuration file

For example to change the spawn position of the robot to (2.0, 3.0), and disable the Gazebo GUI, use the below command:

roslaunch robile_gazebo 4_wheel_platform.launch init_pos_x:=2.0 init_pos_y:=3.0 gazebo_gui:=false

TUTORIAL: Adding a custom ROBILE platform

In this section we describe the procedure to simulate custom ROBILE platform configurations.

Step-1: Add a new ROBILE platform definition

Simulating a custom platform, requires defining the robot configuration in a URDF file. This must be done in the robile_description package and detailed instructions for the same are available here.

Step-2: Define ros-control configuration file for the custom platform

Lets assume our custom platform config is called simple_config (continuing from the robile_description tutorial). Follow the below steps to add ros-controllers for the custom platform.

1. Add a new file called simple_config.yaml in the directory config/ros_controller/. This file name must match the name of the platform defined in the robile_description package.
2. Add the following block of code to the file to create a joint_state_controller.

   # Publish all joint states -----------------------------------
   joint_state_controller:
       type: joint_state_controller/JointStateController
       publish_rate: 50
   
   # Velocity Controllers -----------------------------------------

3. For every robile_active_wheel module defined in the platform configuration file robile_description/robots/simple_config.urdf.xacro, include the below block of code in the YAML file. Replace the <ROBILE_MODULE_NAME> with the actual name defined for the ROBILE module in the URDF file.

   <ROBILE_MODULE_NAME>_left_hub_wheel_controller:
       type: effort_controllers/JointVelocityController
       joint: <ROBILE_MODULE_NAME>_drive_left_hub_wheel_joint
       pid: {p: 100.0, i: 10.0, d: 0.01}
   <ROBILE_MODULE_NAME>_right_hub_wheel_controller:
       type: effort_controllers/JointVelocityController
       joint: <ROBILE_MODULE_NAME>_drive_right_hub_wheel_joint
       pid: {p: 100.0, i: 10.0, d: 0.01}

4. A complete config/ros_controller/simple_config.yaml should look something like the one shown below:

   # Publish all joint states -----------------------------------
   joint_state_controller:
       type: joint_state_controller/JointStateController
       publish_rate: 50
   
   # Velocity Controllers -----------------------------------------
   robile_3_left_hub_wheel_controller:
       type: effort_controllers/JointVelocityController
       joint: robile_3_drive_left_hub_wheel_joint
       pid: {p: 100.0, i: 10.0, d: 0.01}
   robile_3_right_hub_wheel_controller:
       type: effort_controllers/JointVelocityController
       joint: robile_3_drive_right_hub_wheel_joint
       pid: {p: 100.0, i: 10.0, d: 0.01}
   
   
   robile_4_left_hub_wheel_controller:
       type: effort_controllers/JointVelocityController
       joint: robile_4_drive_left_hub_wheel_joint
       pid: {p: 100.0, i: 10.0, d: 0.01}
   robile_4_right_hub_wheel_controller:
       type: effort_controllers/JointVelocityController
       joint: robile_4_drive_right_hub_wheel_joint
       pid: {p: 100.0, i: 10.0, d: 0.01}

Step-3: Define a ros launch file for the custom platform

A platform specific launch file can be defined as follows:

1. Add a new launch file called simple_config.launch in the launch/ directory.
2. Add the following code block to the launch file:

   <?xml version="1.0"?>
   <launch>
       <!--
           Platform specific arguments must be defined here
       -->
       
       <include file="$(find robile_gazebo)/launch/platform_independent/robile_gazebo.launch" pass_all_args="true"/>
   </launch>
   

3. Add an argument to specify the name of the platform configuration file. The name must exactly match the platform config URDF file name which is defined in the robile_description/robots/ directory. In our example this would be simple_config.

   <arg name="platform_config" value="simple_config"/>

4. Add an argument to specify if kelo_tulip must be used as the platform controller by default. If this is set to false, all the wheel and pivot joints will be treated as fixed and the gazebo_ros_planar_move plugin will be used as the platform controller.

   <arg name="use_kelo_tulip" default="true"/>

5. Finally list all the hub wheel controller names defined in the config/ros_controller/simple_config.yaml file as follows:

   <arg name="hub_wheel_controller_list" 
        value="robile_3_left_hub_wheel_controller
               robile_3_right_hub_wheel_controller
               robile_4_left_hub_wheel_controller
               robile_4_right_hub_wheel_controller" />

6. The complete ros launch file should look something like the one shown below:

   <?xml version="1.0"?>
   <launch>
       <!--
           Platform specific arguments must be defined here
       -->
       <arg name="platform_config" value="simple_config"/>
       <arg name="use_kelo_tulip" default="true"/>
       <arg name="hub_wheel_controller_list" 
            value="robile_3_left_hub_wheel_controller
                   robile_3_right_hub_wheel_controller
                   robile_4_left_hub_wheel_controller
                   robile_4_right_hub_wheel_controller" />
   
       <include file="$(find robile_gazebo)/launch/platform_independent/robile_gazebo.launch" pass_all_args="true"/>
   </launch>