Simulating NaviGator

If we had to test all of our new code on the physical build of NaviGator each time we made a change, we’d never be able to make changes quickly! Therefore, when making changes, it’s recommended to simulate them before deploying NaviGator in a physical testing environment. Luckily, we have a great simulation environment, powered by VRX.

VRX

VRX is a simulation environment for aquatic unmanned vehicles, developed by the Open Source Robotics Foundation. It was originally developed for the RobotX competition, and it has continued development in strong collaboration with RoboNation, the organization running RobotX. Eventually, the VRX competition was launched, which was an exclusively-virtual robotics competition that used the VRX platform as a simulator.

VRX is a powerful simulator built on top of Gazebo, a standard simulator for ROS environments. In VRX, you can customize the vehicle used in the simulator, as well as the surrounding environmental conditions (such as the wind, waves, fog, and ambient light). Also, the VRX platform typically provides world files and object models that are similar to actual task elements used in the biannual international RobotX competition, which MIL competes in.

Launching the NaviGator simulation

To launch the simulation for NaviGator, run the following command in your terminal:

roslaunch navigator_launch simulation.launch --screen

There are some variables you can provide to this launch file to customize the simulation environment. These include:

• use_mil_world: If true, use world files from navigator_gazebo (our own ROS package built for NaviGator). Otherwise, use world files from vrx_gazebo (aka, world files provided to everyone in VRX). Default: false.

• world: Which world file to launch. Typically, there are several world files, each of which will focus on one part of the competition.

Viewing and inspecting the environment

Now, you’ve launched the simulation environment, but you’re not actually able to see NaviGator – what gives? At this point, you can run one of two commands.

gazebogui

gazebogui will launch Gazebo, which will provide a beautiful, high-level view of the simulation.

nviz

nviz will launch Rviz, which will give you a much more granular view of NaviGator. Here, you can inspect the frames and joints that make up NaviGator, the inputs of its sensors, etc.

Doing things

At this point, it should be just like NaviGator is in the lake – you can run missions, move NaviGator around using nmove, or take a peek at the cameras/sensors.