Configuration

The simulator’s per-drone parameters live in YAML files under config/. Two are shipped:

Pass a config file at simulator launch time:

python3 isaac_run/scene_mavlink_sim.py --config config/px4_iris.yaml

Any key you omit falls back to the dataclass default. The schema is split into four top-level sections, all optional:

quadrotor:    {...}    # physical body + rotors
sensor:       {...}    # IMU / baro / mag / GPS / VO noise
mavlink:      {...}    # connection metadata (rarely overridden)
gps_origin:   {...}    # WGS84 reference for the local frame

Below is the full reference. The dataclass source of truth is rs_isaac_uav_sim/sim/config.py.

quadrotor:

key type default meaning
mass float 1.0 Total vehicle mass in kg
inertia [Ixx, Iyy, Izz] [0.0052, 0.0052, 0.0082] Diagonal inertia tensor in kg·m²
rotor_positions list of [x, y, z] 4 × cardinal arms Rotor positions in FLU body frame, meters
ct float 1.1e-05 Thrust coefficient: T = ct * ω² (N per (rad/s)²)
cq float 1.56e-07 Torque coefficient: Q = cq * ω²
rot_dirs list of ±1 [-1, 1, -1, 1] Spin direction per rotor (-1=CCW, +1=CW from above in FLU)
omega_min float 0.0 Minimum rotor angular velocity (rad/s)
omega_max float 1000.0 Maximum rotor angular velocity (rad/s)
drag [dx, dy, dz] [0, 0, 0] Linear drag coefficients (kg/s); F_drag = -diag(drag) * v_body
thr_mdl_fac float 0.0 PX4 THR_MDL_FAC: 0.0 = linear thrust curve, 1.0 = quadratic
usd_asset string '' (basic_quadrotor) Path to a USD asset relative to the package’s assets/ directory

The number of rotors is inferred from the length of rotor_positions — to add or remove motors, just adjust this list and the matching rot_dirs.

sensor:

Sensor noise models follow PX4 conventions. The defaults match the iris PX4 airframe.

Gyro

key unit default
gyro_noise_density rad/s/√Hz 3.39e-04
gyro_random_walk rad/s·√Hz 3.88e-05
gyro_bias_correlation_time s 1000.0
gyro_turn_on_bias_sigma rad/s 8.73e-03

Accelerometer

key unit default
accel_noise_density m/s²/√Hz 4.0e-03
accel_random_walk m/s²·√Hz 6.0e-03
accel_bias_correlation_time s 300.0
accel_turn_on_bias_sigma m/s² 0.196

GPS

key unit default
gps_xy_random_walk (m/s)/√Hz 2.0
gps_z_random_walk (m/s)/√Hz 4.0
gps_xy_noise_density m/√Hz 2.0e-04
gps_z_noise_density m/√Hz 4.0e-04
gps_vxy_noise_density (m/s)/√Hz 0.2
gps_vz_noise_density (m/s)/√Hz 0.4
gps_correlation_time s 60.0

Barometer

key unit default
baro_drift_pa_per_sec Pa/s 0.0

Magnetometer

key unit default
mag_noise_density gauss/√Hz 4.0e-04
mag_random_walk gauss·√Hz 6.4e-06
mag_bias_correlation_time s 600.0

Localization mode

key type default meaning
localization_mode str gps gps or mocap (mutually exclusive)

gps_origin:

WGS84 reference frame for the simulator’s local-tangent ENU coordinates. All HIL_GPS lat/lon are computed by reprojecting the drone’s local position relative to this origin.

key unit default
lat deg 47.24926 (Nantes, France)
lon deg -1.54844
alt m AMSL 0.0

Rarely overridden — the CLI flags --base_port, --connection_ip, and --num_drones on scene_mavlink_sim.py set these at launch time.

key default notes
base_port 4560 Drone i uses TCP port base_port + i + 1
connection_ip 'localhost' Where PX4 SITL expects to find the sim
num_rotors derived from quadrotor.rotor_positions not user-set

Adding a new airframe

The minimum set of changes for a new quadrotor:

  1. Drop a USD asset under assets/<your_drone>/ and reference it via quadrotor.usd_asset in your YAML.
  2. Set mass, inertia, rotor_positions, ct, cq, rot_dirs, omega_max to match the physical drone.
  3. If you’re targeting a PX4 airframe, double-check that the rotor index order in rotor_positions matches the PX4 CA_ROTOR*_PX/PY convention for that airframe.
  4. Update gps_origin if you want to fly somewhere other than Nantes.

Then point the simulator at your new YAML:

python3 isaac_run/scene_mavlink_sim.py --config config/your_drone.yaml