Gary Mortimer and I are leaning towards a simulation round for the next T3 contest, but I need some feedback about what would work best.

There are two kinds of simulations: "open loop" and "closed loop".

Open loop means that you connect the output of the simulator to the input of the autopilot. The simulation drives the autopilot with synthetic GPS coordinates and sometimes synthetic attitude data, essentially replacing the autopilot's sensors. This basically fools the autopilot into thinking that it is flying, and you can watch how it responds. This is typically done by having the simulator output data via the serial port and feed that into the autopilot.

Closed loop means that you also connect the output of the autopilot to the input of the simulator, so that the autopilot is "flying" the aircraft on screen. This usually requires a relatively complicated bit of hardware that converts the PWM servo output of the autopilot into what amount to joystick commands via USB or serial that steer the plane in the simulator. It can also be done entirely in software on the host PC, as in the case of Matlab simulations being driven by a flight simulator.

Here are some blog posts that show examples:

--Curt Olson's FlightGear demo

--Faisal Shah closes the loop, Part 1

--Faisal Shah closes the loop, Part 2

Here's a proposed contest structure:

Two sets of winners:

Both must write "DIY" (in cursive) over a place of their choosing.

--Group One: Open loop (video showing you mirroring the airplanes control surfaces with the arrow keys): First six to complete this win a $25 gift certificate to the DIY Drones store.

--Group Two: Closed loop (aircraft controls the flight simulator): First three to complete this win a $50 gift certificate.

What do you think? Is this doable?

Views: 749

Comment by Jason Short on March 26, 2010 at 10:32pm
You won't need to convert the servo output for Ardupilot. You can just print ch1_out, ch2_out, ch3_out for every loop and parse that.
Comment by Ryan on March 27, 2010 at 6:59am
I like this idea chris.

Having never used flight gear before I have just went to the website to download it and there is mirror 1, mirror 2, and mirror 3. Do I have to download all three?
Comment by Joel Ryan on March 27, 2010 at 7:49am
no, you only have to download from one mirror. They are all the same file, but hosted at different places.
Comment by Joel Ryan on March 27, 2010 at 7:53am
Can planes be made through a modeling software to use in the game? If so I think someone needs to make an easystar :P
Comment by Ryan on March 27, 2010 at 7:57am
cheers joel

3D Robotics
Comment by Chris Anderson on March 27, 2010 at 7:58am
Joel, you can make planes for FlightGear, but it's not easy. Most people use the Sig Cadet model that's already in it.
Comment by David Ankers on March 27, 2010 at 8:57am
I think this sounds brilliant and also a load of fun! Great idea.

Comment by Gary Mortimer on March 27, 2010 at 10:51am
Well nobody can pull the weather card ;-)
Comment by Curt Olson on March 27, 2010 at 1:14pm
A couple quick comments.

1. I love this idea. :-)

2. The Sig Rascal 110 is the aircraft that we have pretty well modeled in FlightGear. Take offs and gear dynamics are not quite right, but in the air it's pretty reasonable. My reference bird had an OS-1.60FX motor with an 18x10 prop and it could exceed 100mph in level flight. I dropped down to a lower pitch prop after the first few flights which also helped tame the landings down a bit (the prop could act as a bit of an air brake at idle rpm with a lower pitch prop.)

3. In my podcast interview I had promised my changes to the ardupilot to transform it into a servo management sub system (which would also allow it to read the pwm outputs of some other device and report them to FlightGear.) I'm still trying to refine and test my code changes here and push that over the finish line.

4, For a competition do we want to propose something slightly challenging that no one has every quite done before and then see what happens, or do we want to propose a task that we know for sure is doable, and just see who does it best?

5. FlightGear can load real time weather from the internet, so the weather card is still an option for those that want to play it. :-)

6. If anyone in the DIYdrones community wants to create a 3d model for an easystar (using sketchup, or blender, or ac3d, or creator, or 3d studio, or whatever, we could probably then try to find an aerodynamics person to rough out an initial flight dynamics model.)

7. I spoke with some of the FlightGear aero engineer guys and they were open to the idea of adding UAV class aircraft and power systems to the aeromatic tool (aeromatic is a rapid flight dynamics generator based on answering a series of questions about your aircraft. It's not perfect but it gives you a model that is in the ball park to start out with and then you can tune from there.)
Comment by David Ankers on March 27, 2010 at 5:06pm
Here's an FMS model converted into ac3d format already done by Ken Northup for the clearview sim. Should save some time.


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