Gazebo Simulation Configuration

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Overview

This package contains the necessary config files to get any rover in our X-Series Interbotix LoCoBot Family simulated in Gazebo. Specifically, it contains the locobot_configs.gazebo file which allows the black texture of the robot to display properly (following this method) and starts various plugins. It also contains YAML files with tuned PID gains for the arm, gripper, and pan/tilt joints so that ros_control can control the robot effectively. This package can either be used in conjunction with MoveIt via the FollowJointTrajectory interface or by itself via the JointPositionController interface.

Structure

../_images/xslocobot_gazebo_flowchart.png

As shown above, the interbotix_xslocobot_gazebo package builds on top of the interbotix_xslocobot_descriptions and gazebo_ros packages. To get familiar with the nodes in the interbotix_xslocobot_descriptions package, please look at its README. The other nodes are described below:

  • gzserver - responsible for running the physics update-loop and sensor data generation
  • gzclient - provides a nice GUI to visualize the robot simulation
  • controller_manager - responsible for loading and starting a set of controllers at once, as well as automatically stopping and unloading those same controllers
  • spawn_model - adds the robot model as defined in the ‘robot_description’ parameter into the Gazebo world

Note that the arm joints can be sent trajectories from MoveIt as they use the JointTrajectoryController ros_control interface or positions using the JointPositionController interface. However, the pan/tilt joints operate via the JointPositionController interface only. To control them, publish position commands directly to the appropriate topics (ex. /<robot_name>/pan_controller/command for the ‘pan’ joint).

Usage

To run this package, type the line below in a terminal (assuming the locobot_wx250s is being launched with the lidar attached and using trajectory controllers for the arm).

$ roslaunch interbotix_xslocobot_gazebo xslocobot_gazebo.launch robot_model:=locobot_wx250s show_lidar:=true use_trajectory_controllers:=true

Since by default, Gazebo is started in a ‘paused’ state (this is done to give time for the controllers to kick in), unpause the physics once it is fully loaded by typing:

$ rosservice call /gazebo/unpause_physics

This is the bare minimum needed to get up and running. Take a look at the table below to see how to further customize with other launch file arguments.

Argument Description Default Value
robot_model model type of the Interbotix Locobot such as ‘locobot_base’ or ‘locobot_wx250s’ “”
robot_name name of the robot (could be anything but defaults to ‘locobot’) “locobot”
arm_model the Interbotix Arm model on the locobot; this should never be set manually but rather left to its default value refer to xslocobot_description.launch
show_lidar if true, the lidar is included in the ‘robot_description’ parameter; only set to true if you purchased a lidar with your locobot false
show_gripper_bar if true, the gripper_bar link is included in the ‘robot_description’ parameter; if false, the gripper_bar and finger links are not loaded to the parameter server. Set to false if you have a custom gripper attachment true
show_gripper_fingers if true, the gripper fingers are included in the ‘robot_description’ parameter; if false, the gripper finger links are not loaded to the parameter server. Set to false if you have custom gripper fingers true
external_urdf_loc the file path to the custom urdf.xacro file that you would like to include in the Interbotix robot’s urdf.xacro file “”
use_rviz launches RViz; set to false if SSH’d into the physical robot true
rviz_frame fixed frame in RViz; this should be changed to map or <robot_name>/odom if mapping or using local odometry respectively $(arg robot_name)/base_footprint
world_name the file path to the Gazebo ‘world’ file to load refer to xslocobot_gazebo.launch
gui launch the Gazebo GUI; set to false if SSH’d into the physical robot true
debug Start gzserver in debug mode using gdb false
paused start Gazebo in a paused state true
recording enable Gazebo state log recording false
use_sim_time tells ROS nodes asking for time to get the Gazebo-published simulation time, published over the ROS topic /clock true
use_position_controllers set to true to have the ability to command arbitrary positions to the arm joints in Gazebo false
use_trajectory_controllers set to true to have the ability to command joint trajectories to the arm joints in Gazebo false
dof degrees of freedom of the specified arm (only necessary if use_position_controllers is set to true) 5