New vehicle type: Airship #490

dan-leo · 2020-05-07T21:57:05Z

As mentioned in PX4/PX4-Autopilot#14792 and https://discuss.px4.io/t/new-vehicle-type-airship/16514, our team has developed a new vehicle type for the PX4 developer community, and we would like to submit a pull request for review.

added cloudship model

- aerodynamics - bouyancy - gazebo freezes upon entering

- direct use of -gen.sdf from sdf.jinja

TSC21 · 2020-05-07T22:08:14Z

@dan-leo can you put here a screenshot of how it looks?

dan-leo · 2020-05-07T22:11:42Z

Absolutely!

Jaeyoung-Lim

Thanks for the great contribution!

Small comments

It seems like there is some changes regarding the motor_model that is not compatible with multirotors. This seems to be coming from the fact that you want to support bidirectional thrust. Could we maybe make this compatible for also multirotors?
It is not clear why you need a buoyancy plugin and aerodynamics plugin separately unless it is expected other systems use the plugin as a module. Otherwise I think it should be a single plugin that simulates airship dynamics.
Maybe not for this PR, but to note: the airship doesn't have any effect with wind currently.
the .world. file is not used unless you want to have vehicle specific physics.

include/gazebo_lta_aerodynamics_plugin.h

models/cloudship/cloudship.sdf

models/cloudship/model.config

src/gazebo_buoyancy_plugin.cpp

src/gazebo_motor_model.cpp

worlds/cloudship.world

CMakeLists.txt

antonerasm · 2020-05-11T11:46:40Z

@Jaeyoung-Lim thank you for the informative review, your feedback is much appreciated.

On your comments:

Yes, we would like to incorporate bidirectional thrust. I was thinking of having a third option for the motor directions 'cw', 'ccw' to support it. Can I open another PR for this feature?
It does make a lot more sense to include everything in a single plugin for the airship. We will make the necessary changes and update it.
We will add descriptive comments, the jinja file instead of the sdf, remove the world file, and fix the things you pointed out.
We would also like to add support for simulating wind, we are looking into that.

…date airship model with the addition of wind

antonerasm · 2020-05-17T15:46:55Z

@Jaeyoung-Lim I made the necessary changes as you suggested.
I look forward to your feedback.

antonerasm · 2020-05-17T15:47:05Z

The following command does not work to start the simulation:
make px4_sitl gazebo_cloudship

This is because of the recent changes to split the models and worlds for sitl_gazebo. The models that are auto-generated with jinja have the suffix -gen.sdf to exclude them from git pushes.
However, in the PX4/Firmware file Tools/sitl_run.sh there is a clear reference to the SDF file Tools/sitl_gazebo/models/${model}/${model}.sdf. This fails for the auto-generated models as it does not include the -gen.sdf suffix.

Any ideas how to fix this?
My suggestion would be to extract the SDF file name in the model.config file. Do you agree? Can I submit a PR in PX4/Firmware to fix this?

Jaeyoung-Lim · 2020-05-17T17:46:07Z

include/gazebo_lta_dynamics_plugin.h

+
+  double param_hull_volume_;
+  double param_air_density_;
+  double param_m11_;


Could you document what each parameter stands for?

On lines 56-83 I documented what each of the gazebo plugin parameters are. I thought that would be sufficient. Would you rather that I restate that here for each variable as well? Let me know what you think and I'll make the necessary changes

…odynamic forces

antonerasm · 2020-06-08T18:38:13Z

@Jaeyoung-Lim please let me know if there is anything else you would recommend/suggest for the PR?

There is one CI check that is failing. It is related to the macOS build, any advice on this?

dan-leo · 2020-06-09T12:10:06Z

I see the same macOS build error showing in latest commit: Fix typhoon h480 internals (#512) ... e2bf962

Jaeyoung-Lim

This is really cool and thanks for the contribution. The macOS failure is most likely unrelated to this PR

I believe the optical fow submodule was unintentionally updated
I am a bit concerned on how the reversible thrust is handled. I would prefer if we have a turning direction and a separate reversible(true/false) parameter which makes it more explicit. This is actually more inline on what the px4 mixer is doing.
I also think that you need to explicitly specify MAV_TYPE to airship as commented in New vehicle type: Airship PX4-Autopilot#14862 (comment) so that we are sure that the rotor velocity setpoints actually range from -1 ~ + 1 rather than 0 ~ 1
Since the MAV_TYPE is called airship in the mavlink standard, wouldn't it be more straight forward to call the dynamics plugin airship_dynamics_plugin rather than lta_dynamics plugin? LTA doesn't seem to be a term that is used in any of the mavlink standard or the px4 ecosystem.
Regarding New vehicle type: Airship #490 (comment) please do!

src/gazebo_wind_plugin.cpp

Jaeyoung-Lim · 2020-06-09T21:17:12Z

src/gazebo_motor_model.cpp

+    force = std::abs(force);
+  }
+
+  int turning_dir = turning_direction_type_ / std::abs(turning_direction_type_);


Could we maybe not mix turning_direction_type_ and the turning_direction? maybe add another boolean sdf element for "reversible"? I think this matches the mixer definitions better and makes it more explicit.

Jaeyoung-Lim · 2020-06-09T21:20:28Z

src/gazebo_motor_model.cpp

@@ -233,7 +243,7 @@ void GazeboMotorModel::UpdateForcesAndMoments() {
 #else
  ignition::math::Pose3d pose_difference = ignitionFromGazeboMath(link_->GetWorldCoGPose() - parent_links.at(0)->GetWorldCoGPose());
 #endif
-  ignition::math::Vector3d drag_torque(0, 0, -turning_direction_ * force * moment_constant_);
+  ignition::math::Vector3d drag_torque(0, 0, -turning_dir * force * moment_constant_);


My main concern with making the reversible parameter part of the turning direction, is that the reference rotor velocity range are not explicitly defined. (It can range from 0~~1 or -1~~+1 depending on the MAV_TYPE( https://github.com/PX4/Firmware/blob/master/src/modules/simulator/simulator_mavlink.cpp#L133 ). This will add an additional layer of confusion when something is not working as intended.

I've set MAV_TYPE to 7 (Airship, controlled) only and by sticking to -1..1, that should certainly help.

Jaeyoung-Lim · 2020-06-09T21:22:39Z

include/gazebo_motor_model.h

@@ -42,6 +42,8 @@
 namespace turning_direction {
 const static int CCW = 1;
 const static int CW = -1;
+const static int CCW_REVERSABLE = 2;
+const static int CW_REVERSABLE = -2;


As I commented in the other part of the code, I think reversible should be a separate state (possibly a boolean)

src/gazebo_lta_dynamics_plugin.cpp

Jaeyoung-Lim · 2020-06-21T08:44:52Z

@dan-leo @antonerasm Could we maybe try to conclude this and try to get it in?

antonerasm · 2020-06-21T14:31:46Z

@Jaeyoung-Lim Certainly! My apologies for the delay. I will add the latest requests to get this done.

antonerasm · 2020-06-28T16:29:38Z

@Jaeyoung-Lim I think I have covered everything. I also updated the PR in the Firmware branch to change the MAV_TYPE and the actuator command ranges. Please, let me know if there is anything else.

Jaeyoung-Lim

This looks good to me,

Could you maybe resolve the conflict so that we can merge? Thanks!

* added cloudship model * detail edit * added cloudship model from v1.10.1 - aerodynamics - bouyancy - gazebo freezes upon entering * working cloudship in gazebo - direct use of -gen.sdf from sdf.jinja * Update airship hull profile * Update airship dynamics, add reversable thrust to motor_model, and update airship model with the addition of wind * Add parameter descriptions, fix Gazebo7 implementation and update aerodynamic forces * reset pwm input offset * Update reversible motor model * Revert accidental submodule OpticalFlow updates * Update GPS sensor * Update airship model Co-authored-by: Anton Erasmus <anton@flycloudline.com> Co-authored-by: antonerasm <57213348+antonerasm@users.noreply.github.com>

This adds the dynamics to simulate a lighter-than-air vehicle such as blimps/airships. The modelling is based on [1] and [2]. Previously we added an airship-dynamics-plugin to Gazebo-Classic for [PX4 Gazebo SITL](PX4/PX4-SITL_gazebo-classic#490) , but we suffered simulation instability similar to that of the underwater-vehicles since Gazebo-Classic could not simulate the Added Mass dynamics. This PR brings that airship-dynamics-plugin to Gazebo which supports the Added Mass dynamics. Furthermore, I have extended, the Link class to provide access to the AddedMassMatrix, to allow the lighter-than-air system to easily access this matrix. The code is somewhat based of the Hydrodynamics system. I have an STL file which I can contribute, which is an envelope from [Wind Reiter](https://www.windreiter.com/shop/sb-324-300/), and the coefficients in the integrations test is for this envelope model. ### Citations [1] Li, Y., & Nahon, M. (2007). Modeling and simulation of airship dynamics. Journal of Guidance, Control, and Dynamics, 30(6), 1691–1700. [2] Li, Y., Nahon, M., & Sharf, I. (2011). Airship dynamics modeling: A literature review. Progress in Aerospace Sciences, 47(3), 217–239. Signed-off-by: henrykotze <henry@flycloudline.com>

antonerasm and others added 5 commits April 22, 2020 17:45

added cloudship model

7d48768

detail edit

ccaf16f

Merge pull request #1 from flycloudline/cloudline_airship_model

8b2a3c0

added cloudship model

added cloudship model from v1.10.1

4deba1b

- aerodynamics - bouyancy - gazebo freezes upon entering

working cloudship in gazebo

eb3552f

- direct use of -gen.sdf from sdf.jinja

dan-leo mentioned this pull request May 7, 2020

Port new airship vehicle type from v1.10 to master PX4/PX4-Autopilot#14792

Closed

TSC21 requested a review from Jaeyoung-Lim May 7, 2020 22:08

TSC21 added enhancement models labels May 7, 2020

Jaeyoung-Lim requested changes May 8, 2020

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antonerasm added 3 commits May 12, 2020 16:19

Update airship hull profile

4848665

Merge cloudline branch

96155a0

Update airship dynamics, add reversable thrust to motor_model, and up…

f046038

…date airship model with the addition of wind

Jaeyoung-Lim reviewed May 17, 2020

View reviewed changes

antonerasm added 2 commits June 7, 2020 11:16

Add parameter descriptions, fix Gazebo7 implementation and update aer…

a01b3f5

…odynamic forces

Merge remote-tracking branch 'upstream/master'

982e62b

Jaeyoung-Lim requested changes Jun 9, 2020

View reviewed changes

Jaeyoung-Lim reviewed Jun 11, 2020

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src/gazebo_lta_dynamics_plugin.cpp Outdated Show resolved Hide resolved

reset pwm input offset

f6e68a0

antonerasm added 2 commits June 28, 2020 07:24

Update reversible motor model

3ad6b7c

Merge remote-tracking branch 'upstream/master'

667a1d7

antonerasm added 2 commits June 28, 2020 11:28

Revert accidental submodule OpticalFlow updates

acc3948

Update GPS sensor

cfc5831

Jaeyoung-Lim approved these changes Jul 7, 2020

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antonerasm added 2 commits July 7, 2020 22:21

Update airship model

eb5a9e0

Merge upstream master

66dc928

Jaeyoung-Lim merged commit ce1eca2 into PX4:master Jul 19, 2020

Jaeyoung-Lim mentioned this pull request Jul 23, 2020

Fix wind topic names for vtols #552

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henrykotze mentioned this pull request Nov 11, 2023

Lighter Than Air Dynamics Systems gazebosim/gz-sim#2241

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New vehicle type: Airship #490

New vehicle type: Airship #490

dan-leo commented May 7, 2020

TSC21 commented May 7, 2020

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New vehicle type: Airship #490

New vehicle type: Airship #490

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