Merge pull request #195 from aidotse/geometric_model

Creating Geometric Model

environment.yml

@@ -18,3 +18,4 @@ dependencies:
   - sphinx_rtd_theme # for docs
   - toml>=0.10.2 # core non-optional dependency
   - tqdm>=4.64.1 # core non-optional dependency
+  - trimesh>=4.0.7  # for geometric model

paseos/actors/actor_builder.py

@@ -13,6 +13,7 @@
 from ..thermal.thermal_model import ThermalModel
 from ..power.power_device_type import PowerDeviceType
 from ..radiation.radiation_model import RadiationModel
+from paseos.geometric_model.geometric_model import GeometricModel
 
 
 class ActorBuilder:
@@ -305,6 +306,34 @@ def set_position(actor: BaseActor, position: list):
         actor._position = position
         logger.debug(f"Setting position {position} on actor {actor}")
 
+    @staticmethod
+    def set_geometric_model(
+        actor: SpacecraftActor, mass: float, vertices=None, faces=None, scale: float = 1
+    ):
+        """Define geometry of the spacecraft actor. This is done in the spacecraft body reference frame, and can be
+        transformed to the inertial/PASEOS reference frame using the reference frane transformations in the attitude
+        model. When used in the attitude model, the geometric model is in the body reference frame.
+
+        Args:
+            actor (SpacecraftActor): Actor to update.
+            mass (float): Mass of the spacecraft in kg.
+            vertices (list): List of all vertices of the mesh in terms of distance (in m) from origin of body frame.
+                Coordinates of the corners of the object. If not selected, it will default to a cube that can be scaled.
+                by the scale. Uses Trimesh to create the mesh from this and the list of faces.
+            faces (list): List of the indexes of the vertices of a face. This builds the faces of the satellite by
+                defining the three vertices to form a triangular face. For a cuboid each face is split into two
+                triangles. Uses Trimesh to create the mesh from this and the list of vertices.
+            scale (float): Parameter to scale the cuboid by, defaults to 1.
+        """
+        assert mass > 0, "Mass is > 0"
+
+        actor._mass = mass
+        geometric_model = GeometricModel(
+            local_actor=actor, actor_mass=mass, vertices=vertices, faces=faces, scale=scale
+        )
+        actor._mesh = geometric_model.set_mesh()
+        actor._moment_of_inertia = geometric_model.find_moment_of_inertia
+
     @staticmethod
     def set_power_devices(
         actor: SpacecraftActor,

paseos/geometric_model/geometric_model.py

@@ -0,0 +1,102 @@
+from loguru import logger
+import trimesh
+
+
+class GeometricModel:
+    """This model describes the geometry of the spacecraft
+    Currently it assumes the spacecraft to be a cuboid shape, with width, length and height
+    """
+
+    _actor = None
+    _actor_mesh = None
+    _actor_center_of_gravity = None
+    _actor_moment_of_inertia = None
+
+    def __init__(self, local_actor, actor_mass, vertices=None, faces=None, scale=1) -> None:
+        """Describes the geometry of the spacecraft and outputs relevant parameters related to the spacecraft body.
+        If no vertices or faces are provided, defaults to a cube with unit length sides. This is in the spacecraft body
+        reference frame and can be transformed to the inertial/PASEOS reference frame by using the transformations in the
+        attitude model.
+
+        Args:
+            local_actor (SpacecraftActor): Actor to model.
+            actor_mass (float): Actor's mass in kg.
+            vertices (list): List of all vertices of the mesh in terms of distance (in m) from origin of body frame.
+                Coordinates of the corners of the object. If not selected, it will default to a cube that can be scaled
+                by the scale. Uses Trimesh to create the mesh from this and the list of faces.
+            faces (list): List of the indexes of the vertices of a face. This builds the faces of the satellite by
+                defining the three vertices to form a triangular face. For a cuboid each face is split into two
+                triangles. Uses Trimesh to create the mesh from this and the list of vertices.
+            scale (float): Parameter to scale the cuboid by, defaults to 1.
+        """
+        logger.trace("Initializing cuboid geometrical model.")
+
+        self._actor = local_actor
+        self._actor_mass = actor_mass
+        self.vertices = vertices
+        self.faces = faces
+        self.scale = scale
+
+    def set_mesh(self):
+        """Creates the mesh of the satellite. If no vertices input is given, it defaults to a cuboid scaled by the
+        scale value. The default without scale values is a cube with 1m sides. This uses the python module Trimesh.
+
+        Returns:
+            mesh: Trimesh mesh of the satellite
+        """
+        if self.vertices is None:
+            # Defines the corners of the mesh, values are in meters, from the origin of the body frame.
+            self.vertices = [
+                [-0.5, -0.5, -0.5],
+                [-0.5, -0.5, 0.5],
+                [-0.5, 0.5, -0.5],
+                [-0.5, 0.5, 0.5],
+                [0.5, -0.5, -0.5],
+                [0.5, -0.5, 0.5],
+                [0.5, 0.5, -0.5],
+                [0.5, 0.5, 0.5],
+            ]
+            # List of three vertices to form a triangular face of the satellite.
+            # Two triangular faces are used per side of the cuboid.
+            self.faces = [
+                [0, 1, 3],
+                [0, 3, 2],
+                [0, 2, 6],
+                [0, 6, 4],
+                [1, 5, 3],
+                [3, 5, 7],
+                [2, 3, 7],
+                [2, 7, 6],
+                [4, 6, 7],
+                [4, 7, 5],
+                [0, 4, 1],
+                [1, 4, 5],
+            ]
+
+        mesh = trimesh.Trimesh(self.vertices, self.faces)
+        # Scales the mesh by the scale factor.
+        self._actor_mesh = mesh.apply_scale(self.scale)
+        return self._actor_mesh
+
+    @property
+    def find_moment_of_inertia(self):
+        """Gives the moment of inertia of the actor, assuming constant density.
+
+        Returns:
+            np.array: Mass moments of inertia for the actor
+
+        I is the moment of inertia, in the form of [[Ixx Ixy Ixz]
+                                                    [Iyx Iyy Iyx]
+                                                    [Izx Izy Izz]]
+        """
+        self._actor_moment_of_inertia = self._actor_mesh.moment_inertia
+        return self._actor_moment_of_inertia
+
+    def find_center_of_gravity(self):
+        """Gives the volumetric center of mass of the actor.
+
+        Returns:
+            np.array: Coordinates of the center of gravity of the mesh.
+        """
+        self._actor_center_of_gravity = self._actor_mesh.center_mass
+        return self._actor_center_of_gravity

requirements.txt

@@ -7,4 +7,5 @@ pyquaternion>=0.9.9
 scikit-spatial>=6.5.0
 skyfield>=1.45
 toml>=0.10.2
-tqdm>=4.64.1
+tqdm>=4.64.1
+trimesh>=4.0.7

setup.py

@@ -22,6 +22,7 @@
         "skyfield>=1.45",
         "toml>=0.10.2",
         "tqdm>=4.64.1",
+        "trimesh>=4.0.7",
     ],
     classifiers=[
         "Development Status :: 3 - Alpha",