jMAVSim Simulation
jMAVSim is a simple multirotor/Quad simulator that allows you to fly copter type vehicles running PX4 around a simulated world. It is easy to set up and can be used to test that your vehicle can take off, fly, land, and responds appropriately to various fail conditions (e.g. GPS failure).
Supported Vehicles:
Quad
This topic shows how to set up jMAVSim to connect with a SITL version of PX4.
jMAVSim can also be used for HITL Simulation (as shown here).
Installation
jMAVSim setup is included in our standard build instructions (for macOS, Ubuntu Linux, Windows).
Simulation Environment
Software in the Loop Simulation runs the complete system on the host machine and simulates the autopilot. It connects via local network to the simulator. The setup looks like this:
Running SITL
After ensuring that the simulation prerequisites are installed on the system, just launch: The convenience make target will compile the POSIX host build and run the simulation.
This will bring up the PX4 shell:
It will also bring up a window showing a 3D view of the jMAVSim simulator:
Taking it to the Sky
The system will start printing status information. You will be able to start flying once you have a position lock (shortly after the console displays the message: EKF commencing GPS fusion).
To takeoff enter the following into the console:
You can use QGroundControl to fly a mission or to connect to a joystick.
Usage/Configuration Options
Options that apply to all simulators are covered in the top level Simulation topic (some of these may be duplicated below).
Simulating Sensor/Hardware Failure
Simulate Failsafes explains how to trigger safety failsafes like GPS failure and battery drain.
Set Custom Takeoff Location
The default takeoff location in can be overridden using the environment variables: PX4_HOME_LAT
, PX4_HOME_LON
, and PX4_HOME_ALT
.
For example, to set the latitude, longitude and altitude:
Change Simulation Speed
The simulation speed can be increased or decreased with respect to realtime using the environment variable PX4_SIM_SPEED_FACTOR
.
For more information see: Simulation > Run Simulation Faster than Realtime.
Using a Joystick
Joystick and thumb-joystick support are supported through QGroundControl (setup instructions here).
Simulating a Wifi Drone
There is a special target to simulate a drone connected via Wifi on the local network:
The simulator broadcasts its address on the local network as a real drone would do.
Start JMAVSim and PX4 Separately
You can start JMAVSim and PX4 separately:
This allows a faster testing cycle (restarting jMAVSim takes significantly more time).
Headless Mode
To start jMAVSim without the GUI, set the env variable HEADLESS=1
as shown:
Multi-Vehicle Simulation
JMAVSim can be used for multi-vehicle simulation: Multi-Vehicle Sim with JMAVSim.
Extending and Customizing
To extend or customize the simulation interface, edit the files in the Tools/jMAVSim folder. The code can be accessed through thejMAVSim repository on Github.
The build system enforces the correct submodule to be checked out for all dependencies, including the simulator. It will not overwrite changes in files in the directory, however, when these changes are committed the submodule needs to be registered in the Firmware repo with the new commit hash. To do so, git add Tools/jMAVSim
and commit the change. This will update the GIT hash of the simulator.
Interfacing to ROS
The simulation can be interfaced to ROS the same way as onboard a real vehicle.
Important Files
The startup scripts are discussed in System Startup.
The simulated root file system ("
/
" directory) is created inside the build directory here:build/px4_sitl_default/tmp/rootfs
.
Troubleshooting
java.long.NoClassDefFoundError
This error should no longer occur once the jMAVSim submodule is updated to newer jar libs and Java 11 or Java 14 should work fine.
An illegal reflective access operation has occured
This warning can be ignored (it will probably be displayed but the simulation will still work correctly).
java.awt.AWTError: Assistive Technology not found: org.GNOME.Accessibility.AtkWrapper
If you see this error, try this workaround:
Edit the accessibility.properties file:
and comment out the line indicated below:
For more info, check this GitHub issue. A contributor found the fix in askubuntu.com.
Exception in thread "main" java.lang.UnsupportedClassVersionError:
When compiling jMAVsim, you might encounter the following error:
This error is telling you, you need a more recent version of Java in your environment. Class file version 58 corresponds to jdk14, version 59 to jdk15, version 60 to jdk 16 etc.
To fix it under macOS, we recommend installing OpenJDK through homebrew
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