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Fix gyroscopic precession sign: pitch term opposite roll #1

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Fix gyroscopic precession sign: pitch term opposite roll #1

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9 changes: 7 additions & 2 deletions crazyflow/dynamics/first_principles/dynamics.py
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Original file line number Diff line number Diff line change
Expand Up @@ -139,10 +139,13 @@ def dynamics(
rotor_vel_dot_rads = (
rotor_vel_dot * rpm_to_rad if rotor_vel_dot is not None else xp.zeros_like(rotor_vel)
)
# Gyroscopic reaction torque -ω × h, with rotor angular momentum h = h_z·ẑ.
# -ω × (0,0,h_z) = (-q·h_z, +p·h_z, 0): the roll and pitch components have
# OPPOSITE signs. The z row is the spin-up/down reaction torque.
torque_inertia = prop_inertia * xp.stack(
[
-ang_vel[..., 1] * xp.sum(mixing_matrix[..., -1, :] * rotor_vel_rads, axis=-1),
-ang_vel[..., 0] * xp.sum(mixing_matrix[..., -1, :] * rotor_vel_rads, axis=-1),
ang_vel[..., 0] * xp.sum(mixing_matrix[..., -1, :] * rotor_vel_rads, axis=-1),
xp.sum(mixing_matrix[..., -1, :] * rotor_vel_dot_rads, axis=-1),
],
axis=-1,
Expand Down Expand Up @@ -260,9 +263,11 @@ def symbolic_dynamics(
rpm_to_rad = 2 * cs.pi / 60
rotor_vel_rads = symbols.rotor_vel * rpm_to_rad
rotor_vel_dot_rads = rotor_vel_dot * rpm_to_rad if model_rotor_vel else symbols.rotor_vel * 0.0
# Gyroscopic reaction torque -ω × h (see dynamics()): roll and pitch
# components have OPPOSITE signs.
torque_inertia = prop_inertia * cs.vertcat(
-symbols.ang_vel[1] * cs.sum(mixing_matrix[-1, :] * rotor_vel_rads),
-symbols.ang_vel[0] * cs.sum(mixing_matrix[-1, :] * rotor_vel_rads),
symbols.ang_vel[0] * cs.sum(mixing_matrix[-1, :] * rotor_vel_rads),
cs.sum(mixing_matrix[-1, :] * rotor_vel_dot_rads),
)
torques_motor_vec = torques_thrust + torques_drag + torque_inertia
Expand Down