Airframe presets

from uav_sim.vehicles.fixed_wing import create_fixed_wing, FixedWingPreset

aircraft = create_fixed_wing(FixedWingPreset.SKYWALKER_X8)
aircraft = create_fixed_wing(FixedWingPreset.SKYWALKER_X8, mass=4.0)   # override

The four aircraft

Preset	Mass	Span	AR	Wing loading	V stall	V cruise
MINI_TRAINER	0.60 kg	1.00 m	5.56	32.7 N/m²	6.3 m/s	12 m/s
SKYWALKER_X8	3.36 kg	2.10 m	5.88	44.0 N/m²	8.4 m/s	18 m/s
AEROSONDE	13.5 kg	2.90 m	15.24	240.8 N/m²	12.5 m/s	35 m/s
CARGO_UAV	25.0 kg	4.00 m	13.33	204.4 N/m²	11.7 m/s	32 m/s

Stall speeds are derived from each model's own lift curve, not entered by hand, so they cannot drift out of sync with the coefficients.

Provenance

Only one of these is a published coefficient set

AEROSONDE uses the coefficients tabulated in Beard & McLain, Appendix E, and is the reference airframe for this module.

The other three are representative, not measured. Their geometry and mass come from the real aircraft; their aerodynamic coefficients are scaled from the Aerosonde set with configuration-appropriate adjustments — a flying wing gets reduced yaw stiffness and pitch damping because it has no tail boom, a small foam model gets higher parasitic drag and an earlier, softer stall.

They are good enough to fly, to tune controllers against, and to teach with. They are not a substitute for wind-tunnel data on a specific airframe, and you should not use them to predict how a real X8 behaves.

Choosing one

MINI_TRAINER — 0.6 kg foam model. Slow and docile, and the only preset that fits comfortably in a world smaller than a few hundred metres. Start here if you are building small demos.

SKYWALKER_X8 — flying wing, no rudder. Cndr is zero, so the autopilot's sideslip loop disables itself automatically. That makes it the most interesting preset for control work: it cannot coordinate its own turns, which is exactly the case that exposes a course loop closed on heading instead of on course.

AEROSONDE — the textbook reference. Use it when you want numbers you can check against Beard & McLain. Note the high aspect ratio and wing loading: it is a long-endurance aircraft and needs room.

CARGO_UAV — 25 kg twin-boom. Heavy, high wing loading, sluggish. Good for checking that a controller does not secretly depend on high control authority.

Custom airframes

from dataclasses import replace
from uav_sim.vehicles.fixed_wing import (
    AeroCoefficients, FixedWing, FixedWingParams, PropulsionParams,
)
import numpy as np

aircraft = FixedWing(FixedWingParams(
    mass=2.0,
    wing_area=0.35,
    wing_span=1.6,
    chord=0.22,
    inertia=np.diag([0.06, 0.08, 0.12]),
    coeffs=replace(AeroCoefficients(), CLa=4.8, Cma=-1.5, Cmq=-18.0),
    propulsion=PropulsionParams(prop_area=0.02, k_motor=30.0),
    cruise_airspeed=16.0,
))

Or via the CUSTOM preset:

aircraft = create_fixed_wing(FixedWingPreset.CUSTOM, mass=2.0, wing_area=0.35)

Check it trims before trusting it:

from uav_sim.vehicles.fixed_wing import compute_trim
print(compute_trim(aircraft.fw_params, airspeed=16.0).residual)   # want < 1e-3

Multirotor and VTOL presets

Multirotors have their own catalogue in VehiclePreset: four quadrotors from a 27 g Crazyflie to a 3.6 kg Matrice, plus a HEX_S550 hexacopter and a coaxial OCTO_X8. See Quadrotor for the four-rotor platforms and Multirotor for the rest.

from uav_sim.vehicles import VehiclePreset, create_multirotor

craft = create_multirotor(VehiclePreset.HEX_S550)
craft = create_multirotor(VehiclePreset.OCTO_X8, mass=5.2)   # override

The tilt-rotor currently ships a single default configuration; construct TiltrotorParams directly to vary it.

See also

• Fixed-wing model
• Multirotor model
• Trim and equilibrium