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Swarming Using Ardupilot

Video Tutorial at https://youtu.be/r15Tc6e2K7Y

This tutorial shows you how to model and control a swarming using ardupilot and Gazebo

Pre-rec

add the models folder in the iq_sim repo to the gazebo models path

echo "export GAZEBO_MODEL_PATH=${GAZEBO_MODEL_PATH}:$HOME/catkin_ws/src/iq_sim/models" >> ~/.bashrc

Connecting Multiple Vehicles SITL to Gazebo

You should think about ardupilot as purely a control system. It takes sensor inputs and outputs commands to actuators. Gazebo is playing the role of a Flight Dynamics Model (FDM). The FDM encompasses all of the following, sensor models, actuator models and the dynamics of the vehicle. In real life ardupilot would communicate with your sensors via serial connections, but when you run SITL with gazebo ardupilot talks to the sensors and actuators via UDP connections (an IP protocol). Because of this we will need to specify different UDP ports in our robot models such that these streams do not conflict.

Lets start by copying the drone1 folder in iq_sim/models and paste it as a copy. rename the folder to drone2.

then navigate to the drone2 folder open model.config and change the <name> tag to

<name>drone2</name>

open the model.sdf and change the model name to drone2 as well

scroll down to the ardupilot plugin and change

      <fdm_port_in>9002</fdm_port_in>
      <fdm_port_out>9003</fdm_port_out>

to

      <fdm_port_in>9012</fdm_port_in>
      <fdm_port_out>9013</fdm_port_out>

Each successive drone fdm port should be incremented by 10 ie.

drone3

      <fdm_port_in>9022</fdm_port_in>
      <fdm_port_out>9023</fdm_port_out>

drone4

      <fdm_port_in>9032</fdm_port_in>
      <fdm_port_out>9033</fdm_port_out>

ect...

add the drone to runway.world

    <model name="drone2">
    <pose>10 0 0 0 0 0</pose>
     <include>
        <uri>model://drone2</uri>
      </include>
    </model>

launch the world

roslaunch iq_sim runway.launch

launch ardupilot terminals

to tell the ardupilot instance to incrament it's UPD connection use

-I0 for drone1
-I1 for drone2
-I2 for drone3
ect ...

launch with

sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I0

sim_vehicle.py -v ArduCopter -f gazebo-iris --console -I1

Connecting Multiple Drones to a Ground Station

Each Drone in your swarm will be producing mavlink messages. In order to discern what message is from which drone, we will need to assign each drone a unique system ID. This is controlled by the parameter SYSID_THISMAV.

Launching Ardupilot SITL Instances with Unique Parameters

Usually when we launch the ardupilot sitl simulation we launch the instance using the below command

sim_vehicle.py -v ArduCopter -f gazebo-iris --console

-f is used to specify the frame which Ardupilot will launch the simulation for. The frame type also specifies the location of the parameter files associated with the frame type. In order to simulate drones with different parameters we will need to create our own custom frames and parameter files.

First, we will want to edit the file ardupilot/Tools/autotest/pysim/vehicleinfo.py add the following lines in the SIM section.

            "gazebo-drone1": {
                "waf_target": "bin/arducopter",
                "default_params_filename": ["default_params/copter.parm",
                                            "default_params/gazebo-drone1.parm"],
            },
            "gazebo-drone2": {
                "waf_target": "bin/arducopter",
                "default_params_filename": ["default_params/copter.parm",
                                            "default_params/gazebo-drone2.parm"],
            },
            "gazebo-drone3": {
                "waf_target": "bin/arducopter",
                "default_params_filename": ["default_params/copter.parm",
                                            "default_params/gazebo-drone3.parm"],
            },

We will then need to create the following files

  • default_params/gazebo-drone1.parm
  • default_params/gazebo-drone2.parm
  • default_params/gazebo-drone3.parm

each with their corresponding SYSID_THISMAV parameter value ie

  • default_params/gazebo-drone1.parm should contain SYSID_THISMAV 1
  • default_params/gazebo-drone2.parm should contain SYSID_THISMAV 2
  • default_params/gazebo-drone3.parm should contain SYSID_THISMAV 3

Example gazebo-drone1.parm File

# Iris is X frame
FRAME_CLASS 1
FRAME_TYPE  1
# IRLOCK FEATURE
RC8_OPTION 39
PLND_ENABLED    1
PLND_TYPE       3
# SONAR FOR IRLOCK
SIM_SONAR_SCALE 10
RNGFND1_TYPE 1
RNGFND1_SCALING 10
RNGFND1_PIN 0
RNGFND1_MAX_CM 5000
SYSID_THISMAV 1

Connecting Multiple Drones to qgroundcontrol

In order to connect multiple unique vehicles to a ground station, you will need to make sure that the TCP or UDP connection ports do not conflict. For this example we will be using a TCP connection. The first thing we need to do is relaunch our SITL ardupilot instances with a unique in/out TCP port for our GCS.

sim_vehicle.py -v ArduCopter -f gazebo-drone1 --console -I0 --out=tcpin:0.0.0.0:8100 

sim_vehicle.py -v ArduCopter -f gazebo-drone2 --console -I1 --out=tcpin:0.0.0.0:8200
  • note 0.0.0.0 allows any device on out local network to connect to the ardupilot instance

setup qgroundcontrol to accept multiple vehicles

navigate to the settings tab and click on Comm Links. then find the

fill in each as bellow for the vehicle's unique TCP ports

qg

  • note you can connect from a different device on the same network, by entering the ip address of the host computer in the host address box