simulation

Simulation assets of space-ros demos

Plugins

Custom Gazebo plugins are included in the package.

SolarPanelPlugin

The solar panel plugin allows to simulate solar panel power output depending on the panel orientation relative to the sun and LOS.

• Required elements

  • link_name (str) -- The solar panel link in the model
  • nominal_power (float) -- The maximum power supplied by the solar panel when the sun is hitting perdendicular

• Publications

  • /model/<model_name>/<link_name>/solar_panel_output (std_msgs::msg::Float) -- Publishes the current solar panel output in watt.

How to setup the plugin

The plugin needs to be attached to a model. The link specified by <link_name> is the solar panel.

<plugin filename="libSolarPanelPlugin.so" name="simulation::SolarPanelPlugin">
    <link_name>rear_solar_panel</link_name>
    <nominal_power>150.0</nominal_power>
 </plugin>

• The solar panel link needs to have a visual element. The power output is calculated by using the Z-axis of the solar panel link (Z-axis is considered the normal axis to the solar panel).

• Important: Some URDF parsers lump together links with fixed joints. To ensure the plugin is working correctly, it might be necessary for the solar panel link to be joined with a dynamic type of joint (and by setting the limits to zero if no motion is required). Example below:

  <joint name="solar_panel_joint" type="revolute">
      <parent link="body"/>
      <child link="solar_panel"/>
      <origin xyz="0.0252 0.7253 0.3829" rpy="1.4673 0 ${-PI}"/>
      <axis xyz="0 0 1"/>
      <limit lower="0.0" upper="0.0" effort="1e10" velocity="0.0"/>
  </joint>

• The plugin need a sun entity in the world. The sun needs to be a light entity of type directional with the name sun. The element <pose> and <direction> of the sun are used by the plugin and need to be set properly. Example below:

  <light type="directional" name="sun">
      <cast_shadows>true</cast_shadows>
      <pose>-2000 2000 100 0 0 0</pose>
      <diffuse>0.8 0.8 0.8 1</diffuse>
      <specular>0.2 0.2 0.2 1</specular>
      <intensity>1.5</intensity>
      <attenuation>
          <range>100000000</range>
          <constant>1.0</constant>
          <linear>0.0</linear>
          <quadratic>0.001</quadratic>
      </attenuation>
      <direction>0.9 -0.9 -0.2</direction>
  </light>

• LOS (Line-Of-Sight): If the sun is occulted, no power is supplied by the solar panel plugin. To know if the panel is occulted, the plugin checks the line of sight between the sun (by using the <pose> element) and the link visual children. The panel solar link needs to have at least one visual element for the plugin to work.

• Power computation: The plugin computes the power generated by the panel by checking the angle between the Z-axis of the solar panel link and the direction vector of the sun.

RadioisotopeThermalGeneratorPlugin

The radioisotope thermal generator plugin allows to simulate an RTG power output. It provides a constant power supply.

• Required elements

  • link_name (str) -- The RTG link in the model
  • nominal_power (float) -- The constant power in watt generated by the RTG.

• Publications

  • /model/<model_name>/<link_name>/radioisotope_thermal_generator_output (std_msgs::msg::Float) -- Publishes the current solar panel output in watt.

How to setup the plugin

The plugin needs to be attached to a model. Example below:

<plugin filename="libRadioisotopeThermalGeneratorPlugin.so" name="simulation::RadioisotopeThermalGeneratorPlugin">
    <link_name>chassis</link_name>
    <nominal_power>100.0</nominal_power>
</plugin>

RechargeableBatteryPlugin

The rechargeable battery plugin is a modified version of the stock LinearBatteryPlugin to allow recharge at variable rate. It can be charged by any plugin providing a power output in watt on a Gazebo topic.

• Required elements
  • battery_name (str) -- Unique name for the battery (required)
  • voltage (double) -- Initial voltage of the battery (required)
  • open_circuit_voltage (double) --
  • open_circuit_voltage_constant_coef (double) -- Voltage at full charge
  • open_circuit_voltage_linear_coef (double) -- Amount of voltage decrease when no charge
  • initial_charge (double) -- Initial charge of the battery in Ah
  • capacity (double) -- Total charge that the battery in Ah
  • resistance (double) -- Internal resistance in Ohm
  • smooth_current_tau (double) -- Coefficient for smoothing current [0, 1]
  • power_source (array[str]) -- List of topic of power sources.
  • power_load (double) -- Idle power load

How to setup the plugin

The plugin needs to be attached to a model. Example below:

<plugin filename="libRechargeableBatteryPlugin.so" name="simulation::RechargeableBatteryPlugin">
    <battery_name>rechargeable_battery</battery_name>
    <voltage>30.0</voltage>
    <open_circuit_voltage>30.0</open_circuit_voltage>
    <open_circuit_voltage_constant_coef>30.0</open_circuit_voltage_constant_coef>
    <open_circuit_voltage_linear_coef>-3.0</open_circuit_voltage_linear_coef>
    <initial_charge>9.0</initial_charge>
    <capacity>10.0</capacity>
    <resistance>0.1</resistance>
    <smooth_current_tau>1.0</smooth_current_tau>

    <!-- power source -->
    <power_source>left_solar_panel/solar_panel_output</power_source>
    <power_source>right_solar_panel/solar_panel_output</power_source>
    <power_source>rtg_body/radioisotope_thermal_generator_output</power_source>

    <power_load>11.0</power_load>
    <power_draining_topic>/battery/discharge</power_draining_topic>
</plugin>

• The power source topic needs to be on the format <link_name>/<plugin_power_output_name>. As of now, the following plugins can provide power to charge the battery:
  • SolarPanelPlugin: with topic <link_name>/solar_panel_output
  • RadioisotopeThermalGeneratorPlugin: with topic <link_name>/radioisotope_thermal_generator_output

Models

lunar_pole_exploration_rover

The lunar pole exploration rover is a lunar rover heavily inspired by the VIPER rover. The model can be loaded in Gazebo to fully simulate the rover. information on the rover was obtained from https://ntrs.nasa.gov/api/citations/20210015009/downloads/20210015009%20-%20Colaprete-VIPER%20PIP%20final.pdf.

Simulated power

The rover model includes a battery simulated by the RechargeableBatteryPlugin. The battery is recharged by three solar panels of 150W each. The solar panels are simulated by the SolarPanelPlugin.

Control

The model has four steerable powered wheels. Each wheels is attached to the rover body with a passive suspension. In addition, the navigation cameras are mounted on a mast and can pan and tilt.

Sensors

It features a similar sensor suit of the real VIPER rover:

• A pair of monochrome cameras for navigation, NavCam, mounted on the rover mast
• A pair of monochrome cameras for the aft blind spots, AftCam, facing back
• An IMU
• Odometry plugin

Published Topics

• /model/lunar_pole_exploration_rover/left_solar_panel/solar_panel_output (ignition_msgs::msg::Float32) -- Publishes the current output of the left solar panel in watt
• /model/lunar_pole_exploration_rover/right_solar_panel/solar_panel_output (ignition_msgs::msg::Float32) -- Publishes the current output of the right solar panel in watt
• /model/lunar_pole_exploration_rover/rear_solar_panel/solar_panel_output (ignition_msgs::msg::Float32) -- Publishes the current output of the rear solar panel in watt
• /model/lunar_pole_exploration_rover/odometry (ignition_msgs::msg::Odometry) -- Robot odometry
• /model/lunar_pole_exploration_rover/odometry_with_covariance(ignition_msgs::msg::OdometryWithCovariance) -- Robot odometry
• /model/lunar_pole_exploration_rover/pose(ignition_msgs::msg::Pose) -- Robot estimated pose from odometry
• aft_cam_left/camera_info (ignition_msgs::msg::CameraInfo) -- AftCam left camera info
• aft_cam_right/camera_info (ignition_msgs::msg::CameraInfo) -- AftCam right camera info
• nav_cam_left/camera_info (ignition_msgs::msg::CameraInfo) -- NavCam left camera info
• nav_cam_right/camera_info (ignition_msgs::msg::CameraInfo) -- NavCam right camera info
• aft_cam_left/image_raw (ignition_msgs::msg::Image) -- AftCam left camera image
• aft_cam_right/image_raw (ignition_msgs::msg::Image) -- AftCam right camera image
• nav_cam_left/image_raw (ignition_msgs::msg::Image) -- NavCam left camera image
• nav_cam_right/image_raw (ignition_msgs::msg::Image) -- NavCam right camera image

Controllable Joint Interfaces

• mast_head_pivot_joint (revolute) -- NavCam pan joint
• mast_camera_joint (revolute) -- NavCam tilt joint
• front_left_wheel_joint (revolute) -- front left wheel rotation joint
• rear_left_wheel_joint (revolute) -- rear left wheel rotation joint
• front_right_wheel_joint (revolute) -- front right wheel rotation joint
• rear_right_wheel_joint (revolute) -- rear right wheel rotation joint
• front_left_wheel_axle_joint (revolute) -- front left wheel steer joint
• rear_left_wheel_axle_joint (revolute) -- rear left wheel steer joint
• front_right_wheel_axle_joint (revolute) -- front right wheel steer joint
• rear_right_wheel_axle_joint (revolute) -- rear right wheel steer joint

moon_mons_mouton

A model for the terrain of the Mons Mouton mountain located near the lunar south pole (also formaly refered to as Liebnitz Beta). This model was generated by using DEM data (site20) from the NASA LRO mission: https://pgda.gsfc.nasa.gov/products/78 (Barker, M.K., et al. (2021), Improved LOLA Elevation Maps for South Pole Landing Sites: Error Estimates and Their Impact on Illumination Conditions, Planetary & Space Science, Volume 203, 1 September 2021, 105119, doi:10.1016/j.pss.2020.105119.).