How To Simulate Camera Flash

# Gazebo Simulation

Gazebo (opens new window) is a powerful 3D simulation environs for autonomous robots that is particularly suitable for testing object-avoidance and computer vision. This page describes its apply with SITL and a single vehicle. Gazebo can also exist used with HITL and for multi-vehicle simulation.

Supported Vehicles: Quad (Iris and Solo, Hex (Typhoon H480), Generic quad delta VTOL, Tailsitter, Plane, Rover, Submarine/UUV.

WARNING

Gazebo is often used with ROS, a toolkit/offboard API for automating vehicle control. If you plan to utilise PX4 with ROS you should follow the ROS Instructions to install both ROS and Gazebo (and thereby avoid installation conflicts).

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Note

See Simulation for full general information about simulators, the simulation environment, and simulation configuration (e.g. supported vehicles).

# Installation

Gazebo ix setup is included in our standard build instructions:

• macOS: Development Environment on Mac
• Linux: Development Environment on Ubuntu LTS / Debian Linux > Gazebo, JMAVSim and NuttX (Pixhawk) Targets
• Windows: Not supported.

Additional installation instructions can be found on gazebosim.org (opens new window) .

# Running the Simulation

Run a simulation by starting PX4 SITL and gazebo with the airframe configuration to load (multicopters, planes, VTOL, optical flow and multi-vehicle simulations are supported).

The easiest way to do this is to open a final in the root directory of the PX4 PX4-Autopilot repository and call make for the desired target. For example, to beginning a quadrotor simulation (the default):

The supported vehicles and make commands are listed below (click links to run into vehicle images).

Note

For the full listing of build targets run make px4_sitl list_vmd_make_targets (and filter on those that start with gazebo_).

Vehicle	Control
Quadrotor	make px4_sitl gazebo
Quadrotor with Optical Menstruation	make px4_sitl gazebo_iris_opt_flow
3DR Solo (Quadrotor)	make px4_sitl gazebo_solo
Typhoon H480 (Hexrotor) (supports video streaming)	make px4_sitl gazebo_typhoon_h480
Standard Plane	brand px4_sitl gazebo_plane
Standard Plane (with catapult launch)	make px4_sitl gazebo_plane_catapult
Standard VTOL	make px4_sitl gazebo_standard_vtol
Tailsitter VTOL	make px4_sitl gazebo_tailsitter
Ackerman vehicle (UGV/Rover)	make px4_sitl gazebo_rover
HippoCampus TUHH (UUV: Unmanned Underwater Vehicle)	brand px4_sitl gazebo_uuv_hippocampus
Gunkhole (USV: Unmanned Surface Vehicle)	make px4_sitl gazebo_boat
Cloudship (Airship)	make px4_sitl gazebo_cloudship

The commands above launch a single vehicle with the full UI. Other options include:

• Starting PX4 and Gazebo separately so that yous tin go along Gazebo running and just re-launch PX4 when needed (quicker than restarting both).
• Run the simulation in Headless Way, which does not start the Gazebo UI (this uses fewer resource and is much faster).

# Taking it to the Sky

The make commands above offset build PX4, and and so run it along with the Gazebo simulator.

In one case PX4 has started it will launch the PX4 trounce equally shown below.

The console will print out status as PX4 loads the airframe-specific initialisation and parameter files, waits for (and connects to) the simulator. Once in that location is an INFO print that [ecl/EKF] is commencing GPS fusion the vehicle is ready to arm.

Notation

Right-clicking the quadrotor model allows to enable follow manner from the context bill of fare, which is handy to proceed it in view.

You tin bring it into the air by typing:

# Usage/Configuration Options

Options that utilize to all simulators are covered in the peak level Simulation topic (some of these may be duplicated below).

# Simulating Sensor/Hardware Failure

Simulate Failsafes explains how to trigger safe failsafes like GPS failure and battery drain.

# Headless Fashion

Gazebo can be run in a headless mode in which the Gazebo UI is not launched. This starts upward more chop-chop and uses less organization resources (i.e. it is a more "lightweight" mode to run the simulation).

But prefix the normal brand command with HEADLESS=1 as shown:

# Set Custom Takeoff Location

The takeoff location in SITL Gazebo can be gear up using environment variables. This will override both the default takeoff location, and any value fix for the earth.

The variables to gear up are: PX4_HOME_LAT, PX4_HOME_LON, and PX4_HOME_ALT.

For example:

# Change Simulation Speed

The simulation speed tin exist increased or decreased with respect to realtime using the environment variable PX4_SIM_SPEED_FACTOR.

For more than information run across: Simulation > Run Simulation Faster than Realtime.

# Change Current of air Speed

To simulate wind speed, add together this plugin to your world file and gear up windVelocityMean in yard/s (supercede SET_YOUR_WIND_SPEED with your desired speed). If needed, arrange the windVelocityMax parameter and then that it is greater than windVelocityMean:

Wind direction is passed as a direction vector (standard ENU convention), which volition exist normalized in the gazebo plugin. Additionally you lot can country air current velocity variance in (m/s)² and direction variance based on a normal distribution to add some random factor into the simulation. Gust is internally handled in the same way as current of air, with the slight difference that you can land start time and duration with the following 2 parameters windGustStart and windGustDuration.

You tin see how this is done in PX4/PX4-SITL_gazebo/worlds/windy.world (opens new window) .

# Using a Joystick

Joystick and thumb-joystick support are supported through QGroundControl (setup instructions hither).

# Improving Distance Sensor Performance

The electric current default globe is PX4/sitl_gazebo/worlds/iris.world (opens new window) ), which uses a heightmap as ground.

This can crusade difficulty when using a distance sensor. If there are unexpected results we recommend you modify the model in iris.model from uneven_ground to asphalt_plane.

# Simulating GPS Noise

Gazebo can simulate GPS dissonance that is similar to that typically institute in existent systems (otherwise reported GPS values will be noise-free/perfect). This is useful when working on applications that might be impacted by GPS noise - east.grand. precision positioning.

GPS noise is enabled if the target vehicle'southward SDF file contains a value for the gpsNoise element (i.e. it has the line: <gpsNoise>true</gpsNoise>). It is enabled past default in many vehicle SDF files: solo.sdf, iris.sdf, standard_vtol.sdf, delta_wing.sdf, plane.sdf, typhoon_h480, tailsitter.sdf.

To enable/disable GPS racket:

1. Build whatsoever gazebo target in society to generate SDF files (for all vehicles). For example:

   TIP

   The SDF files are not overwritten on subsequent builds.

2. Open the SDF file for your target vehicle (e.g. ./Tools/sitl_gazebo/models/iris/iris.sdf).

3. Search for the gpsNoise element:

   • If information technology is nowadays, GPS is enabled. You tin disable it by deleting the line: <gpsNoise>true</gpsNoise>
   • If it is not present, GPS is disabled. You tin enable it by adding the gpsNoise element to the gps_plugin section (as shown above).

The next time you lot build/restart Gazebo it volition use the new GPS noise setting.

# Loading a Specific Earth

PX4 supports a number of Gazebo Worlds, which are stored in PX4/sitl_gazebo/worlds (opens new window) ) By default Gazebo displays a apartment characterless plane, as defined in empty.world (opens new window) .

Yous tin can load whatsoever of the worlds by specifying them as the final option in the PX4 configuration target.

For case, to load the warehouse world, you tin append information technology every bit shown:

You can too specify the full path to a world to load using the PX4_SITL_WORLD environment variable. This is useful if testing a new world that is not yet included with PX4.

TIP

If the loaded world does non align with the map, you may need to prepare the world location.

# Set World Location

The vehicle gets spawned very close to the origin of the world model at some fake GPS location.

Notation

The vehicle is not spawned exactly at the Gazebo origin (0,0,0), but using a slight offset, which can highlight a number of mutual coding issues.

If using a earth that recreates a real location (e.grand. a particular airport) this can result in a very obvious mismatch betwixt what is displayed in the simulated globe, and what is shown on the basis station map. To overcome this problem you lot can set the location of the globe origin to the GPS co-ordinates where it would be in "real life".

Note

Y'all can likewise gear up a Custom Takeoff Location that does the same affair. However adding the location to the map is easier (and can still be over-ridden by setting a custom location if needed).

The location of the world is divers in the .world file by specifying the location of the origin using the spherical_coordinates tag. The breadth, longitude, superlative must all be specified (for this to be a valid).

An example can be found in the sonoma_raceway.globe (opens new window) :

You tin examination this past spawning a rover in the Sonoma Raceway Earth using the post-obit brand command (note that spawning takes longer the outset time as the model needs to be downloaded from the model database):

The video below shows that the location of the surroundings is aligned with the gazebo globe:

# Starting Gazebo and PX4 Separately

For extended development sessions it might be more convenient to start Gazebo and PX4 separately or fifty-fifty from within an IDE.

In addition to the existing cmake targets that run sitl_run.sh with parameters for px4 to load the right model information technology creates a launcher targets named px4_<way> that is a sparse wrapper effectually original sitl px4 app. This thin wrapper just embeds app arguments like current working directories and the path to the model file.

To start Gazebo and PX4 separately:

• Run gazebo (or any other sim) server and customer viewers via the terminal specifing an _ide variant:or
• In your IDE select px4_<mode> target you want to debug (due east.yard. px4_iris)
• Start the debug session directly from IDE

This approach significantly reduces the debug bike time because simulator (due east.g. Gazebo) is always running in background and you merely re-run the px4 procedure which is very calorie-free.

# False Survey Photographic camera

The Gazebo survey camera simulates a MAVLink camera (opens new window) that captures geotagged JPEG images and sends camera capture data to a connected ground station. The photographic camera as well supports video streaming. It tin exist used to examination camera capture, in particular inside survey missions.

The photographic camera emits the CAMERA_IMAGE_CAPTURED (opens new window) message every fourth dimension an epitome is captured. The captured images are saved to: PX4-Autopilot/build/px4_sitle_default/tmp/frames/DSC_n_.jpg (where n starts as 00000 and is iterated by one on each capture).

To simulate a aeroplane with this camera:

Notation

The camera too supports/responds to the following MAVLink commands: MAV_CMD_REQUEST_CAMERA_CAPTURE_STATUS (opens new window) , MAV_CMD_REQUEST_STORAGE_INFORMATION (opens new window) , MAV_CMD_REQUEST_CAMERA_SETTINGS (opens new window) , MAV_CMD_REQUEST_CAMERA_INFORMATION (opens new window) , MAV_CMD_RESET_CAMERA_SETTINGS (opens new window) , MAV_CMD_STORAGE_FORMAT (opens new window) , MAV_CMD_SET_CAMERA_ZOOM (opens new window) , MAV_CMD_IMAGE_START_CAPTURE (opens new window) , MAV_CMD_IMAGE_STOP_CAPTURE (opens new window) , MAV_CMD_REQUEST_VIDEO_STREAM_INFORMATION (opens new window) , MAV_CMD_REQUEST_VIDEO_STREAM_STATUS (opens new window) , MAV_CMD_SET_CAMERA_MODE (opens new window) .

# Imitation Parachute/Flight Termination

Gazebo can be used to simulate deploying a parachute during Flight Termination (flying termination is triggered by the PWM command that is simulated in Gazebo).

The if750a target has a parachute attached to the vehicle. To simulate the vehicle, run the following command:

To put the vehicle into flying termination land, you can forcefulness it to neglect a prophylactic check that has flight termination set as the failsafe activity. For example, y'all could do this by forcing a Geofence violation.

For more than information come across:

• Flight Termination
• Parachute
• Safety Configuration (Failsafes)

# Video Streaming

PX4 SITL for Gazebo supports UDP video streaming from a Gazebo camera sensor attached to a vehicle model. When streaming is enabled, you tin connect to this stream from QGroundControl (on UDP port 5600) and view video of the Gazebo surroundings from the false vehicle - simply every bit you would from a existent camera. The video is streamed using a gstreamer pipeline and can be enabled/disabled using a push in the Gazebo UI.

The Gazebo camera sensor is supported/enabled on the following frames:

• Typhoon H480

# Prerequisites

Gstreamer ane.0 is required for video streaming. The required dependencies should already have been installed when yous fix Gazebo (they are included in the standard PX4 installation scripts/instructions for macOS and Ubuntu Linux).

Note

FYI only, the dependencies include: gstreamer1.0-plugins-base, gstreamer1.0-plugins-good, gstreamer1.0-plugins-bad, gstreamer1.0-plugins-ugly, libgstreamer-plugins-base1.0-dev.

# Start/Stop Video Streaming

Video streaming is automatically started when supported by the target vehicle. For example, to start streaming video on the Draft H480:

Streaming tin be paused/restarted using the Gazebo UI Video ON/OFF push..

# How to View Gazebo Video

The easiest way to view the SITL/Gazebo camera video stream is in QGroundControl. Simply open Application Settings > General and prepare Video Source to UDP h.264 Video Stream and UDP Port to 5600:

The video from Gazebo should so display in QGroundControl just as information technology would from a real photographic camera.

Note

The Typhoon world is not very interesting.

It is too possible to view the video using the Gstreamer Pipeline. Simply enter the post-obit terminal command:

# Verbose Logging

SITL fails silently when at that place is something incorrect with the gazebo model. You can enable more verbose logging using VERBOSE_SIM, as shown:

or

# Extending and Customizing

To extend or customize the simulation interface, edit the files in the Tools/sitl_gazebo folder. The code is available on the sitl_gazebo repository (opens new window) on Github.

Notation

The build system enforces the right GIT submodules, including the simulator. It will not overwrite changes in files in the directory.

# Further Information

• ROS with Gazebo Simulation
• Gazebo Octomap

Source: https://docs.px4.io/master/en/simulation/gazebo.html

Posted by: morristwounds.blogspot.com

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