This package provides basic state (i.e. linear and angular position, velocity, acceleration) estimation functionality using optical flow data from a camera rigidly mounted to the chassis of the robot. The camera data is fused with IMU data using an Extended Kalman Filter to improve accuracy. Keep reading for specifics.
Make sure you have ROS indigo and OpenCV 2.4 installed and working on the host computer and robot. Then, to install this package:
- Clone this repo into a workspace and build†
- SSH into Jackal and repeat the process
†I highly recommend using [catkin_tools][11], which has a modernized version of the catkin_make command and other useful command line tools for working with ROS/catkin packages
Navigate to your workspace and source your setup file: source devel/setup.bash. Then run roslaunch eecs432_project <launch file name> for any of the launch files below.
project.launch
Launches both ekf_robot_localization.launch and ekf_robot_localization_imu.launch. Publishes nav_msgs/Odometry messages to /odometry/visual and /odometry/imu topics.
ekf_robot_localization.launch
Launches nodes necessary to extract motion from a camera feed (flow.cpp), converts that output to usable data (twist_data.py), and fuses visual and IMU data to create visual-inertial odometry (robot_localization). Publishes a nav_msgs/Odometry message to /odometry/visual.
ekf_robot_localization_imu.launch
Launches only the robot_localization node to convert IMU data to odometry data to be consistent in format with the other odometry outputs (position and velocity in x, y, z, roll, pitch, yaw). Publishes a nav_msgs/Odometry message on topic /odometry/imu.
flow.cpp
Extracts features, calculates optical flow, and performs perspective transform on a live camera feed. Publishes a geometry_msgs/Twist message to /optical_flow/twist which contains twist data in the form of velocity in x, y, z, roll, pitch, and yaw.
twist_data.py
Converts output of flow.cpp from a geometry_msgs/Twist message to a nav_msgs/Odometry message which contains measurement covariances in addition to the original Twist data. This message is published to the /optical_flow topic.
robot_localization
ROS package used to perform fusion of multiple streams of sensor data. Converts the output to position and velocity in x, y, z, roll, pitch, and yaw. Publishes to /odometry/filtered by default. The documentation can be found here.
