The navigation speed of the robot is specified through a couple of launch files. In order to modify these launch files, you will need to create a copy of them and run those copies instead.

Make copies of the launch files

In addition to copying the main fetch_nav.launch file, we need to copy an additional file that is included by fetch_nav.launch. You can see what files are included in fetch_nav.launch by running rosed fetch_navigation fetch_nav.launch.

cd fetch_api/launch
roscp fetch_navigation fetch_nav.launch .
roscp fetch_navigation move_base.launch.xml .
ls

You should see two new files: fetch_nav.launch and move_base.launch.xml.

Make a copy of the config files

If you look at move_base.launch.xml, you will see that loads two configuration files related to the move_base node: move_base.yaml and fetch/move_base.yaml.

Create a folder named config if it doesn't exist and copy these two files:

cd fetch_api/config

Both files are named move_base.yaml, so roscp will ask you which one to copy. This command copies the main move_base.yaml (double check the numbers, which may be different for you):

> roscp fetch_navigation move_base.yaml .
You have chosen a non-unique filename, please pick one of the following:
1) /opt/ros/indigo/share/fetch_navigation/config/freight/move_base.yaml
2) /opt/ros/indigo/share/fetch_navigation/config/move_base.yaml
3) /opt/ros/indigo/share/fetch_navigation/config/fetch/move_base.yaml
#? 2
/opt/ros/indigo/share/fetch_navigation/config/move_base.yaml

This command copies the Fetch-specific configuration:

> roscp fetch_navigation move_base.yaml fetch_move_base.yaml
You have chosen a non-unique filename, please pick one of the following:
1) /opt/ros/indigo/share/fetch_navigation/config/freight/move_base.yaml
2) /opt/ros/indigo/share/fetch_navigation/config/move_base.yaml
3) /opt/ros/indigo/share/fetch_navigation/config/fetch/move_base.yaml
#? 3
/opt/ros/indigo/share/fetch_navigation/config/fetch/move_base.yaml

Edit the launch files

To run the modified versions of the launch files, you will need to start navigation using this command from now on:

roslaunch fetch_api fetch_nav.launch

Also be sure to edit any launch files you have that include fetch_nav.launch:

<include file="$(find fetch_api)/launch/fetch_nav.launch">

However, you also need to edit your copy of fetch_nav.launch to use your copy of move_base.launch.xml and the two move_base.yamls.

Edit fetch_nav.launch and replace:

<arg name="move_base_include" default="$(find fetch_navigation)/launch/include/move_base.launch.xml" />

with:

<arg name="move_base_include" default="$(find fetch_api)/launch/move_base.launch.xml" />

Edit move_base.launch.xml and replace:

<rosparam file="$(find fetch_navigation)/config/move_base.yaml" command="load" />
<rosparam file="$(find fetch_navigation)/config/$(arg name)/move_base.yaml" command="load" />

with (notice the three differences on the two lines):

<rosparam file="$(find fetch_api)/config/move_base.yaml" command="load" />
<rosparam file="$(find fetch_api)/config/fetch_move_base.yaml" command="load" />

Edit the configuration

To limit the robot's speed, edit fetch_move_base.yaml and set the max_vel_x parameter from 1.0 to something slower, like 0.3. max_vel_x is in meters/second, {min,max}_vel_theta are in radians/second.

You can also experiment with the tolerances in move_base.yaml (yaw_goal_tolerance and xy_goal_tolerance). However, we have not tested how tight of tolerances the robot can actually achieve.

You can refer to the course repository for a working example of the launch/config files and the edits we made.