wind_params_tutorial

Adjusting the Wind

• The wind can be characterized by a direction and mean velocity.
• In the current implementation of VRX, the wind only affects the WAM-V.
• The windage coefficients used for the WAM-V are based on the FAU report(Station-keeping control of an unmanned surface vehicle exposed to current and wind disturbances)[https://doi.org/10.1016/j.oceaneng.2016.09.037].

Steps

Step 1: Modify parameters

Open vrx/vrx_gz/worlds/sydney_regatta.sdf and edit the values given in the wind plugin element:

<!-- Load the plugin for the wind --> 
<plugin
  filename="libUSVWind.so"
  name="vrx::USVWind">
  <wind_obj>
    <name>wamv</name>
    <link_name>wamv/base_link</link_name>
    <coeff_vector>.5 .5 .33</coeff_vector>
  </wind_obj>
  <!-- Wind -->
  <wind_direction>240</wind_direction>
  <!-- in degrees -->
  <wind_mean_velocity>0.0</wind_mean_velocity>
  <var_wind_gain_constants>0</var_wind_gain_constants>
  <var_wind_time_constants>2</var_wind_time_constants>
  <random_seed>10</random_seed>
  <!-- set to zero/empty to randomize -->
  <update_rate>10</update_rate>
  <topic_wind_speed>/vrx/debug/wind/speed</topic_wind_speed>
  <topic_wind_direction>/vrx/debug/wind/direction</topic_wind_direction>
 </plugin>

For example, try changing wind_mean_velocity to 5 (m/s) and wind_direction to 180 (degrees).

Step 2: Rebuild

Recompile your workspace:

cd <VRX_WS>
GZ_VERSION=harmonic colcon build --merge-install

Step 3: Test

Launch the simulation:

ros2 launch vrx_gz competition.launch.py world:=sydney_regatta

In a separate terminal, source the workspace and echo the wind direction topic to confirm the change:

. install/setup.bash
ros2 topic echo /vrx/debug/wind/direction

To see the effect on wind speed, press CTRL+C to terminate the echo command and run:

ros2 topic echo /vrx/debug/wind/speed

You should see a series of wind velocity values varying around a mean of 5 m/s.

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