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BUG: Fix the missing x y forces from TVC #28

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Merged
zuorenchen merged 2 commits into from
Aug 27, 2026
Merged

BUG: Fix the missing x y forces from TVC #28

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1c3a672
Fix the missing x y forces from TVC
zuorenchen Aug 24, 2026
461ce43
Fix the cases where thrust1/2 are not calculated
zuorenchen Aug 24, 2026
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91 changes: 38 additions & 53 deletions rocketpy/simulation/flight.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2154,39 +2154,28 @@ def u_dot(self, t, u, post_processing=False): # pylint: disable=too-many-locals

# Thrust Vector Control (TVC)
if hasattr(self.rocket, "thrust_vector_control"):
# TVC Fz thrust: F = T * sqrt(1 - sin(gimbal_angle_x)**2 - sin(gimbal_angle_y)**2)
thrust3 = effective_thrust * np.sqrt(
1
- np.sin(
self.rocket.thrust_vector_control.gimbal_angle_x * (np.pi / 180)
)
** 2
- np.sin(
self.rocket.thrust_vector_control.gimbal_angle_y * (np.pi / 180)
)
** 2
)
tvc_lever = self.rocket.nozzle_to_cdm
# TVC Mx My moments: M = T * sin(x) * r
M1 += (
np.sin(
self.rocket.thrust_vector_control.gimbal_angle_x * (np.pi / 180)
)
* effective_thrust
* tvc_lever
# thrust{1/2/3}: thrust force vector on nozzle among body axes.
# positive gimbal_angle results in positive moment.
thrust1 = -np.sin(
self.rocket.thrust_vector_control.gimbal_angle_y * (np.pi / 180)
)
M2 += (
np.sin(
self.rocket.thrust_vector_control.gimbal_angle_y * (np.pi / 180)
)
* effective_thrust
* tvc_lever
thrust2 = np.sin(
self.rocket.thrust_vector_control.gimbal_angle_x * (np.pi / 180)
)
# thrust3 is the remaining force on body3 direction
thrust3 = effective_thrust * np.sqrt(1 - thrust1**2 - thrust2**2)
tvc_lever = self.rocket.nozzle_to_cdm
M1 += thrust2 * effective_thrust * tvc_lever
M2 += -thrust1 * effective_thrust * tvc_lever
else:
thrust3 = effective_thrust
thrust1, thrust2, thrust3 = 0, 0, effective_thrust
# Off center moment
M1 += self.rocket.thrust_eccentricity_y * thrust3
M2 -= self.rocket.thrust_eccentricity_x * thrust3
M3 += (
self.rocket.thrust_eccentricity_x * thrust2
- self.rocket.thrust_eccentricity_y * thrust1
)

else:
# Motor stopped
Expand All @@ -2200,7 +2189,7 @@ def u_dot(self, t, u, post_processing=False): # pylint: disable=too-many-locals
# Mass
mass_flow_rate_at_t, propellant_mass_at_t = 0, 0
# thrust
thrust3 = 0
thrust1, thrust2, thrust3 = 0, 0, 0
net_thrust = 0

# Retrieve important quantities
Expand Down Expand Up @@ -2425,12 +2414,14 @@ def u_dot(self, t, u, post_processing=False): # pylint: disable=too-many-locals
R1
- b * propellant_mass_at_t * (omega2**2 + omega3**2)
- 2 * c * mass_flow_rate_at_t * omega2
+ thrust1
)
/ total_mass_at_t,
(
R2
+ b * propellant_mass_at_t * (alpha3 + omega1 * omega2)
+ 2 * c * mass_flow_rate_at_t * omega1
+ thrust2
)
/ total_mass_at_t,
(R3 - b * propellant_mass_at_t * (alpha2 - omega1 * omega3) + thrust3)
Expand Down Expand Up @@ -2885,32 +2876,21 @@ def u_dot_generalized(self, t, u, post_processing=False): # pylint: disable=too

# Thrust Vector Control (TVC)
if hasattr(self.rocket, "thrust_vector_control"):
tvc_lever = self.rocket.nozzle_to_cdm
# TVC Mx My moments: M = T * sin(x) * r
M1 += (
np.sin(self.rocket.thrust_vector_control.gimbal_angle_x * (np.pi / 180))
* effective_thrust
* tvc_lever
# thrust{1/2/3}: thrust force vector on nozzle among body axes.
# positive gimbal_angle results in positive moment.
thrust1 = -np.sin(
self.rocket.thrust_vector_control.gimbal_angle_y * (np.pi / 180)
)
M2 += (
np.sin(self.rocket.thrust_vector_control.gimbal_angle_y * (np.pi / 180))
* effective_thrust
* tvc_lever
)
# TVC Fz thrust: F = T * sqrt(1 - sin^2(x) - sin^2(y))
thrust3 = effective_thrust * np.sqrt(
1
- np.sin(
self.rocket.thrust_vector_control.gimbal_angle_x * (np.pi / 180)
)
** 2
- np.sin(
self.rocket.thrust_vector_control.gimbal_angle_y * (np.pi / 180)
)
** 2
thrust2 = np.sin(
self.rocket.thrust_vector_control.gimbal_angle_x * (np.pi / 180)
)
# thrust3 is the remaining force on body3 direction
thrust3 = effective_thrust * np.sqrt(1 - thrust1**2 - thrust2**2)
tvc_lever = self.rocket.nozzle_to_cdm
M1 += thrust2 * effective_thrust * tvc_lever
M2 += -thrust1 * effective_thrust * tvc_lever
else:
thrust3 = effective_thrust
thrust1, thrust2, thrust3 = 0, 0, effective_thrust

# Off center moment
M1 += (
Expand All @@ -2921,7 +2901,12 @@ def u_dot_generalized(self, t, u, post_processing=False): # pylint: disable=too
self.rocket.cp_eccentricity_x * R3
+ self.rocket.thrust_eccentricity_x * thrust3
)
M3 += self.rocket.cp_eccentricity_x * R2 - self.rocket.cp_eccentricity_y * R1
M3 += (
self.rocket.cp_eccentricity_x * R2
- self.rocket.cp_eccentricity_y * R1
+ self.rocket.thrust_eccentricity_x * thrust2
- self.rocket.thrust_eccentricity_y * thrust1
)

# Roll control moment
if hasattr(self.rocket, "roll_control"):
Expand All @@ -2937,7 +2922,7 @@ def u_dot_generalized(self, t, u, post_processing=False): # pylint: disable=too
T00 = total_mass * r_CM
T03 = 2 * total_mass_dot * (r_NOZ - r_CM) - 2 * total_mass * r_CM_dot
T04 = (
Vector([0, 0, thrust3])
Vector([thrust1, thrust2, thrust3])
- total_mass * r_CM_ddot
- 2 * total_mass_dot * r_CM_dot
+ total_mass_ddot * (r_NOZ - r_CM)
Expand Down
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