vehicles: add px4 sih quadx

[mrpollo]

Basic implementation of PX4 SITL SIH QUADX, using the defaults from the 10040_sihsim_quadx airframe in PX4.

$ python examples/basic_usage_px4.py
-------------------RESULTS-----------------------
SIM TIME -- 30.00 seconds | WALL TIME -- 2.50 seconds
EXIT STATUS -- Timeout: Simulation end time reached.
Done—PX4 SITL ran for 3001 steps

[mrpollo]

@spencerfolk it's a very primitive interface, still needs more love, but can be extended over time. I would appreciate your help with a thorough review. I'm not much of a sim person.

[spencerfolk]

This is amazing @mrpollo !!

It looks like we still need to translate the RotorPy sensor data into a format that PX4 likes. A similar method was implemented for the Arudpilot SITL interface

RotorPy has a 6 axis IMU sensor for computing noisy accelerations and body rates.

One minor thing: for consistency can you move the vehicle params dict sihsim_quadx to a separate file and import it in the basic usage script? For example: CF, CFBL, and Hummingbird.

Happy to help if needed. I'm also wondering if there is any desire to model more complex aero like rotor drag or blade flapping for the PX4 SIH quad. But for that we'd need some data.

[Tuxliri]

@mrpollo when using the PX4 SITL SIH QUADX is the physics being simulated inside the PX4 firmware? If so then wouldn't this clash with the simulation in rotorpy itself when updating the state and sensors?

[mrpollo]

@Tuxliri, I don't think we are simulating the physics, but I haven't looked into this. Maybe @MaEtUgR can chime in?

[Tuxliri]

@Tuxliri, I don't think we are simulating the physics, but I haven't looked into this. Maybe @MaEtUgR can chime in?

I delved a bit more into it, it is being simulated when running the SIH module. I ended up reusing rotorpy's own physics engine in PR #26.