ROS Integration

Introduction

ROS is a set of well-engineered software libraries for building robotics applications. It includes a wide variety of packages, from low level drivers to efficient implementations of state of the art algorithms. As we strive to build intelligent agents and transfer them to real-world (on a real robot), we need to take advantage of ROS packages to complete the robot application pipeline.

There are three key applications of integrating iGibson with ROS.

  • Benchmark existing algorithms in a controlled realistic simulation environment. And this allows comparing learning-based methods with traditional methods in simulation environments.

  • Comparing robot in simulation with robot in real world. In simulation, iGibson can simulate sensors of a robot and publish as messages. In the real world, a real robot publish sensor messages. So it is possible to only change the message subscribed and benchmark the performance of downstream applications. This helps locating domain gap and debugging algorithms.

  • Using ROS functions in simulation, such as many motion planning implementations.

The possibility of using iGibson with ROS is unlimited. As a starter, we provide an example of integrating iGibson with ROS for navigation. This is a ros package integrates iGibson Env with ros navigation stack. It follows the same node topology and topics as turtlebot_navigation package. As shown below, so after a policy is trained in iGibson, it requires minimal changes to deploy onto a turtlebot.

_images/node_topo.jpg

Environment Setup

Here is all the steps you need to perform to install gibson and ros. Note that here you will need to install using pip install -e . and use python2.7. If you did it differntly when installing iGibson, you will need to do it again. python3 is known to not being able to work with ros.

Preparation

  1. Install ROS: in this package, we use navigation stack from ros kinetic. Please follow the instructions.

  2. Install iGibson from source following installation guide in python2.7. However, as ROS only supports python2.7 at the moment, you need to create python2.7 virtual environment instead of python3.x.

  3. If you use annaconda for setting up python environment, some tweaks of PATH and PYTHONPATH variable are required to avoid conflict. In particular:

    1. For PATH: conda related needs to be removed from PATH

    echo $PATH | grep -oP "[^:;]+" | grep conda	## Remove these paths from $PATH

    1. For PYTHONPATH: /usr/lib/python2.7/dist-packages/, /opt/ros/kinetic/lib/python2.7/dist-packages(ros python libraries), <anaconda installation root>/anaconda2/envs/py27/lib/python2.7/site-packages(gibson dependencies) and <gibson root> need to be in PYTHONPATH.

  4. Copy (or soft link) gibson-ros folder to your catkin_ws/src and run catkin_make to index gibson-ros package.

ln -s $PWD/examples/ros/gibson-ros/ ~/catkin_ws/src/
cd ~/catkin_ws && catkin_make && cd -

  1. Install gibson2-ros dependencies:

rosdep install gibson2-ros

Sanity check

which python #should give /usr/bin/python 
python -c 'import gibson2, rospy, rospkg' #you should be able to do those without errors.

Running

In order to run gibson+ros examples, you will need to perform the following steps:

  1. Prepare ROS environment

source /opt/ros/kinetic/setup.bash
source <catkin-workspace-root>/catkin_ws/devel/setup.bash

  1. Repeat step 3 from Preparation, sanitize PATH and PYTHONPATH

  2. Here are some of the examples that you can run, including gmapping, hector mapping and navigation.

roslaunch gibson2-ros turtlebot_rgbd.launch #Bare minimal bringup example
roslaunch gibson2-ros turtlebot_gmapping.launch #Run gmapping
roslaunch gibson2-ros turtlebot_hector_mapping.launch #Run hector mapping
roslaunch gibson2-ros turtlebot_navigation.launch #Run the navigation stack, we have provided the map
roslaunch gibson2-ros turtlebot_gt_navigation.launch #Run the navigation stack with ground truth localization

The following screenshot is captured when running the bare minimal bringup example.

_images/sensing.png

The following screenshot is captured when running the gmapping example.

_images/slam.png

Topics

Here are all the topics that turtlebot_rgbd.py publishes and subscribes.

  • turtlebot_rgbd.py

Publishes:

Topic name Type Usage
/gibson_ros/camera/depth/camera_info sensor_msgs/CameraInfo Camera parameters used in iGibson, same for depth and rgb
/gibson_ros/camera/rgb/image sensor_msgs/Image RGB image captured in iGibson
/gibson_ros/camera/rgb/depth sensor_msgs/Image depth image captured in iGibson, in meters, with dtype being float32
/gibson_ros/camera/rgb/depth_raw sensor_msgs/Image depth image captured in iGibson, mimic raw depth data captured with OpenNI cameras, with dtype being uint16, see more here
/odom nav_msgs/Odometry odometry from odom frame to base_footprint, generated with groudtruth pose in iGibson

Subscribes:

Topic name Type Usage
/mobile_base/commands/velocity geometry_msgs/Twist Velocity command for turtlebot, msg.linear.x is the forward velocity, msg.angular.z is the angular velocity