ENH: Add Eccentricity to Stochastic Simulations

rocketpy/rocket/rocket.py

@@ -1744,8 +1744,8 @@ def set_rail_buttons(
     def add_cm_eccentricity(self, x, y):
         """Moves line of action of aerodynamic and thrust forces by
         equal translation amount to simulate an eccentricity in the
-        position of the center of mass of the rocket relative to its
-        geometrical center line.
+        position of the center of dry mass of the rocket relative to
+        its geometrical center line.
 
         Parameters
         ----------
@@ -1781,20 +1781,18 @@ def add_cm_eccentricity(self, x, y):
     def add_cp_eccentricity(self, x, y):
         """Moves line of action of aerodynamic forces to simulate an
         eccentricity in the position of the center of pressure relative
-        to the center of mass of the rocket.
+        to the center of dry mass of the rocket.
 
         Parameters
         ----------
         x : float
             Distance in meters by which the CP is to be translated in
-            the x direction relative to the center of mass axial line.
-            The x axis is defined according to the body axes coordinate
-            system.
+            the x direction relative to the center of dry mass axial line.
+            The x axis is defined according to the body axes coordinate system.
         y : float
             Distance in meters by which the CP is to be translated in
-            the y direction relative to the center of mass axial line.
-            The y axis is defined according to the body axes coordinate
-            system.
+            the y direction relative to the center of dry mass axial line.
+            The y axis is defined according to the body axes coordinate system.
 
         Returns
         -------
@@ -1811,19 +1809,19 @@ def add_cp_eccentricity(self, x, y):
 
     def add_thrust_eccentricity(self, x, y):
         """Moves line of action of thrust forces to simulate a
-        misalignment of the thrust vector and the center of mass.
+        misalignment of the thrust vector and the center of dry mass.
 
         Parameters
         ----------
         x : float
             Distance in meters by which the line of action of the
             thrust force is to be translated in the x direction
-            relative to the center of mass axial line. The x axis
+            relative to the center of dry mass axial line. The x axis
             is defined according to the body axes coordinate system.
         y : float
             Distance in meters by which the line of action of the
-            thrust force is to be translated in the x direction
-            relative to the center of mass axial line. The y axis
+            thrust force is to be translated in the y direction
+            relative to the center of dry mass axial line. The y axis
             is defined according to the body axes coordinate system.
 
         Returns
@@ -1835,8 +1833,8 @@ def add_thrust_eccentricity(self, x, y):
         --------
         :ref:`rocket_axes`
         """
-        self.thrust_eccentricity_y = x
-        self.thrust_eccentricity_x = y
+        self.thrust_eccentricity_x = x
+        self.thrust_eccentricity_y = y
         return self
 
     def draw(self, vis_args=None, plane="xz", *, filename=None):

rocketpy/simulation/flight.py

@@ -1469,8 +1469,8 @@ def u_dot(self, t, u, post_processing=False):  # pylint: disable=too-many-locals
             # Thrust
             thrust = self.rocket.motor.thrust.get_value_opt(t)
             # Off center moment
-            M1 += self.rocket.thrust_eccentricity_x * thrust
-            M2 -= self.rocket.thrust_eccentricity_y * thrust
+            M1 += self.rocket.thrust_eccentricity_y * thrust
+            M2 -= self.rocket.thrust_eccentricity_x * thrust
         else:
             # Motor stopped
             # Inertias
@@ -1856,11 +1856,11 @@ def u_dot_generalized(self, t, u, post_processing=False):  # pylint: disable=too
         thrust = self.rocket.motor.thrust.get_value_opt(t)
         M1 += (
             self.rocket.cp_eccentricity_y * R3
-            + self.rocket.thrust_eccentricity_x * thrust
+            + self.rocket.thrust_eccentricity_y * thrust
         )
         M2 -= (
             self.rocket.cp_eccentricity_x * R3
-            - self.rocket.thrust_eccentricity_y * thrust
+            + self.rocket.thrust_eccentricity_x * thrust
         )
         M3 += self.rocket.cp_eccentricity_x * R2 - self.rocket.cp_eccentricity_y * R1
 

rocketpy/stochastic/stochastic_rocket.py

@@ -389,6 +389,105 @@ def set_rail_buttons(
             rail_buttons, self._validate_position(rail_buttons, lower_button_position)
         )
 
+    def add_cp_eccentricity(self, x=None, y=None):
+        """Moves line of action of aerodynamic forces to simulate an
+        eccentricity in the position of the center of pressure relative
+        to the center of dry mass of the rocket.
+
+        Parameters
+        ----------
+        x : tuple, list, int, float, optional
+            Distance in meters by which the CP is to be translated in
+            the x direction relative to the center of dry mass axial line.
+            The x axis is defined according to the body axes coordinate system.
+        y : tuple, list, int, float, optional
+            Distance in meters by which the CP is to be translated in
+            the y direction relative to the center of dry mass axial line.
+            The y axis is defined according to the body axes coordinate system.
+
+        Returns
+        -------
+        self : StochasticRocket
+            Object of the StochasticRocket class.
+        """
+        self.cp_eccentricity_x = self._validate_eccentricity("cp_eccentricity_x", x)
+        self.cp_eccentricity_y = self._validate_eccentricity("cp_eccentricity_y", y)
+        return self
+
+    def add_thrust_eccentricity(self, x=None, y=None):
+        """Moves line of action of thrust forces to simulate a
+        misalignment of the thrust vector and the center of dry mass.
+
+        Parameters
+        ----------
+        x : tuple, list, int, float, optional
+            Distance in meters by which the line of action of the
+            thrust force is to be translated in the x direction
+            relative to the center of dry mass axial line. The x axis
+            is defined according to the body axes coordinate system.
+        y : tuple, list, int, float, optional
+            Distance in meters by which the line of action of the
+            thrust force is to be translated in the y direction
+            relative to the center of dry mass axial line. The y axis
+            is defined according to the body axes coordinate system.
+
+        Returns
+        -------
+        self : StochasticRocket
+            Object of the StochasticRocket class.
+        """
+        self.thrust_eccentricity_x = self._validate_eccentricity(
+            "thrust_eccentricity_x", x
+        )
+        self.thrust_eccentricity_y = self._validate_eccentricity(
+            "thrust_eccentricity_y", y
+        )
+        return self
+
+    def _validate_eccentricity(self, eccentricity, position):
+        """Validate the eccentricity argument.
+
+        Parameters
+        ----------
+        eccentricity : str
+            The eccentricity to which the position argument refers to.
+        position : tuple, list, int, float
+            The position argument to be validated.
+
+        Returns
+        -------
+        tuple or list
+            Validated position argument.
+
+        Raises
+        ------
+        ValueError
+            If the position argument does not conform to the specified formats.
+        """
+        if isinstance(position, tuple):
+            return self._validate_tuple(
+                eccentricity,
+                position,
+            )
+        elif isinstance(position, (int, float)):
+            return self._validate_scalar(
+                eccentricity,
+                position,
+            )
+        elif isinstance(position, list):
+            return self._validate_list(
+                eccentricity,
+                position,
+            )
+        elif position is None:
+            position = []
+            return self._validate_list(
+                eccentricity,
+                position,
+            )
+        else:
+            raise AssertionError("`position` must be a tuple, list, int, or float")
+
     def _validate_position(self, validated_object, position):
         """Validate the position argument.
 
@@ -578,6 +677,13 @@ def _create_parachute(self, stochastic_parachute):
         self.last_rnd_dict["parachutes"].append(stochastic_parachute.last_rnd_dict)
         return parachute
 
+    def _create_eccentricities(self, stochastic_x, stochastic_y, eccentricity):
+        x_rnd = self._randomize_position(stochastic_x)
+        self.last_rnd_dict[eccentricity + "_x"] = x_rnd
+        y_rnd = self._randomize_position(stochastic_y)
+        self.last_rnd_dict[eccentricity + "_y"] = y_rnd
+        return x_rnd, y_rnd
+
     def create_object(self):
         """Creates and returns a Rocket object from the randomly generated input
         arguments.
@@ -609,6 +715,23 @@ def create_object(self):
         rocket.power_off_drag *= generated_dict["power_off_drag_factor"]
         rocket.power_on_drag *= generated_dict["power_on_drag_factor"]
 
+        if hasattr(self, "cp_eccentricity_x") and hasattr(self, "cp_eccentricity_y"):
+            cp_ecc_x, cp_ecc_y = self._create_eccentricities(
+                self.cp_eccentricity_x,
+                self.cp_eccentricity_y,
+                "cp_eccentricity",
+            )
+            rocket.add_cp_eccentricity(cp_ecc_x, cp_ecc_y)
+        if hasattr(self, "thrust_eccentricity_x") and hasattr(
+            self, "thrust_eccentricity_y"
+        ):
+            thrust_ecc_x, thrust_ecc_y = self._create_eccentricities(
+                self.thrust_eccentricity_x,
+                self.thrust_eccentricity_y,
+                "thrust_eccentricity",
+            )
+            rocket.add_thrust_eccentricity(thrust_ecc_x, thrust_ecc_y)
+
         for component_motor in self.motors:
             motor, position_rnd = self._create_motor(component_motor)
             rocket.add_motor(motor, position_rnd)

tests/unit/test_rocket.py

@@ -331,15 +331,15 @@ def test_add_cm_eccentricity_assert_properties_set(calisto):
     assert calisto.cp_eccentricity_x == -4
     assert calisto.cp_eccentricity_y == -5
 
-    assert calisto.thrust_eccentricity_y == -4
-    assert calisto.thrust_eccentricity_x == -5
+    assert calisto.thrust_eccentricity_x == -4
+    assert calisto.thrust_eccentricity_y == -5
 
 
 def test_add_thrust_eccentricity_assert_properties_set(calisto):
     calisto.add_thrust_eccentricity(x=4, y=5)
 
-    assert calisto.thrust_eccentricity_y == 4
-    assert calisto.thrust_eccentricity_x == 5
+    assert calisto.thrust_eccentricity_x == 4
+    assert calisto.thrust_eccentricity_y == 5
 
 
 def test_add_cp_eccentricity_assert_properties_set(calisto):