Gazebo Simulation with Matlab

[Izzal]

Hello

I would like to simulate the Gazebo using my own control which i have done in Matlab simulink. I cannot find any documents on this. I used ROS toolbox in matlab, but when i publish it to Gazebo i cannot control the motors of the quadrotor. I just want to work with Gazebo for now to test, then will fly the actual hardware.

I am looking for hints/guidelines or documents.

[di55olve88]

Hi @Izzal,

I have done what you are intending to do, control of the Erlecopter in Gazebo via Matlab/Simulink. Depending on the hierarchy of your controller, you have some options. I was experimenting with a controller that generated motor velocities as outputs. What enabled me to use these so was modifying the .launch file such that the line corresponding to APM was commented out. This allows direct publishing of motor velocities to the rotors via ROS topics without conflicting with APM. This is valid in any Gazebo drone simulator built upon the ROTORS platform but I wanted to accomplish this with a model that was close to that of physical Erlecopter so chose this method.

If you need the physical constants relating the square of the motor velocities and the generated force these and other relevant information are available in the .yaml files corresponding to the model, as per ROTORS specification. These can be found in ~/simulation/rotors_simulator/ros_catkin_ws/rotors_gazebo/resource/

My current project is in developing this controller as a linux ROS2 compliant application that will be run onboard so if you have similar goals please get in touch with me!

• @di55olve88

[Krishneel]

Hi @di55olve88

I am doing a similar project whereby I am trying to control the Erlecopter in Gazebo via Matlab/SImulink. The output of my controller are also motor velocities which Iam publishing to gazebo with the ROS topic /erlecopter/command/motor_speed with message type mav_msgs/CommandMotorSpeed.

However when I publish this to gazebo, the motors of my erlecopter model in gazebo stop/freeze and I recieve the following error:

F021414 0000::484802:.200000.2188582100530 23823 gazebo_motor_model.cpp:127] Check failed: rot_velocities->motor_speed.size() > motor_number_ You tried to access index 0 of the MotorSpeed message array which is of size 0.

Also, you mentioned above that you managed to do the simulation by modifying the .launch file hence I was hoping if you could please show which lines to modify in the .launch file which would be very helpful.

Hoping if you could advise on how you managed to simulate your erlecopter in gazebo with Matlab/Simulink

Thanks in advance
@Krishneel

[di55olve88]

Hi @Krishneel,

Did you make sure that you added custom message support for mav_msgs/CommandMotorSpeed in Matlab? That error seems to be related that you are using the CommandMotorSpeed message in an incorrect way. I haven't run the simulation for a few weeks so I'll need to check the way that I am using the messages and get back to you.

I commented line 6 of this file, which prevents apm from initializing and running, leaving it as a pure gazebo simulation (no SITL with apm).

I'd be curious to learn more about your project, as it seem like you might be heading in the same direction as I am. Please shoot me an email at aganl001@ucr.edu

@di55olve88

[Krishneel]

Hi @di55olve88

Yes, I have added custom message support for mav_msgs/CommandMotorSpeed in Matlab. However, I still obtain the error which I mentioned. Below is the full error which I receive when I run the simulation.

Hoping if you could advice on how to use the publish messages for motor speed in order to control the copter in gazebo.

Thanks in advance
@Krishneel

[Sharu]

Hi, i'm also trying to simulate the Gazebo using my own control which i have done in Matlab simulink but i don't know how to add custom message support for mav_msgs in simulink. I tryied to follow some guide online but i got many errors, can you explain how to implement this messages?

Thanks in advance.

[di55olve88]

Hi @Sharu

I had issues with it at first two but it was due to imprecise forming of the package.xml file for the packages. Most don't include dependencies for std_msgs. See here for details on that https://www.mathworks.com/matlabcentral/answers/230531-error-building-custom-ros-messages.

If adding those dependencies doesn't work then post more details on what the errors are.

@di55olve88

[di55olve88]

@Krishneel,

I have replied to your email but it seems as though your inbox is full.

[Krishneel]

Hi @di55olve88

I am not sure as to why you are unable to send emails on that account as I am able to receive others emails in it.

However, I have sent you an email with my other gmail account hoping that we are able to communicate through that.

Thanks in advance

@Krishneel

[husseinhazem]

Hi @di55olve88 @Krishneel

I am currently to stuck at the same step as @Krishneel where gazebo freezes when i send the motor speed command. Did you manage to solve it?