ROS for Object Avoidance

../_images/ros-object-avoidance.png

This page describes how to setup ROS’s base local planner to provide velocity commands to ArduPilot to steer a rover around obstacles. This assumes all the previous setup including Cartographer and rviz have already been completed.

These instructions were tested on a Nvidia TX2 running an APSync image with ROS installed as described here.

Some of the information on this page was found on these wiki pages:

Note

these pages are a work-in-progress

Companion Computer Setup

  • ssh onto the companion computer. If using APsync the following should work (password is “apsync”)
ssh apsync@apsync.local
  • Configure mavros to send velocity targets to ArduPilot by modifying mavros’s node.launch file with your favourite editor (like gedit shown below)
roscd mavros   <-- this assumes mavros has been installed with rosdep
cd launch
sudo gedit node.launch
  • After <rosparam command="load" file="$(arg config_yaml)" /> add a line like below
<remap from="/mavros/setpoint_velocity/cmd_vel_unstamped" to="/cmd_vel" />
  • Install ros-kinetic-navigation package
sudo apt-get install ros-kinetic-navigation
cd ~/catkin/src
wget https://github.com/ArduPilot/companion/raw/master/Common/ROS/ap_navigation.zip
unzip ap_navigation.zip
  • Rebuild all packages including ap_navigation
cd ~/catkin
source devel
cakin build

Start ap_navigation

  • restart all packages (roscore, rplidar, mavros and cartographer) and then start ap_navigation package
cd ~/catkin
source devel
roslaunch ap_navigation ap_nav.launch

Sending Position Targets

  • Arm the vehicle and switch to Guided mode
  • Use rviz’s “2D Nav Goal” button to set a position target. If all goes well a green line will appearing showing the route the vehicle will take to the target (see top image)