[#144] Add Hill-frame impulsive thrust

Author: Mark2000

docs/source/release_notes.rst

@@ -33,7 +33,7 @@ Development - |version|
 * Add a maximum range checking dynamics model in :class:`MaxRangeDynModel`. Useful for keeping an agent
   in the vicinity of a target early in training.
 * Add properties in spacecraft dynamics for orbital element observations.
-
+* Add :class:`ImpulsiveThrustHill` for impulsive thrust the Hill frame.
 
 Version 1.1.0
 -------------

src/bsk_rl/act/__init__.py

@@ -45,18 +45,24 @@ class MyActionSatellite(Satellite):
 Use :class:`ContinuousAction` for actions with a continuous action space. Currently, satellites
 can only have a single continuous action in their ``action_spec``.
 
-+----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
-| **Action**                 |**Dimension**| **Description**                                                                                       |
-+----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
-| :class:`ImpulsiveThrust`   | 4           | Instantaneously change the satellite's velocity, and drift for some duration.                         |
-+----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
++-----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
+| **Action**                  |**Dimension**| **Description**                                                                                       |
++-----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
+| :class:`ImpulsiveThrust`    | 4           | Instantaneously change the satellite's velocity, and drift for some duration.                         |
++-----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
+| :class:`ImpulsiveThrustHill`| 4           | Like :class:`ImpulsiveThrust`, but specified in the Hill frame of another satellite.                  |
++-----------------------------+-------------+-------------------------------------------------------------------------------------------------------+
 
 
 
 """
 
 from bsk_rl.act.actions import Action
-from bsk_rl.act.continuous_actions import ContinuousAction, ImpulsiveThrust
+from bsk_rl.act.continuous_actions import (
+    ContinuousAction,
+    ImpulsiveThrust,
+    ImpulsiveThrustHill,
+)
 from bsk_rl.act.discrete_actions import (
     Charge,
     Desat,
@@ -81,4 +87,5 @@ class MyActionSatellite(Satellite):
     "Scan",
     "ContinuousAction",
     "ImpulsiveThrust",
+    "ImpulsiveThrustHill",
 ]

src/bsk_rl/act/continuous_actions.py

@@ -154,3 +154,33 @@ def set_action(self, action: np.ndarray) -> None:
         if self.fsw_action is not None:
             getattr(self.satellite.fsw, self.fsw_action)()
             self.satellite.log_info(f"FSW action {self.fsw_action} activated.")
+
+
+class ImpulsiveThrustHill(ImpulsiveThrust):
+    def __init__(self, chief_name, *args, **kwargs):
+        """Impulsive thrusts in the Hill frame.
+
+        Args:
+            chief_name: Chief to use for Hill frame.
+            *args: Passed to ``ImpulsiveThrust``.
+            **kwargs: Passed to ``ImpulsiveThrust``.
+        """
+        self.chief_name = chief_name
+        super().__init__(*args, **kwargs)
+
+    def reset_post_sim_init(self) -> None:
+        """Connect to the chief satellite.
+
+        :meta private:
+        """
+        self.chief = self.satellite.simulator.get_satellite(self.chief_name)
+
+    def set_action(self, action: np.ndarray) -> None:
+        """Activate the action by setting the continuous value."""
+        dv_H = action[0:3]
+        dt = action[3]
+
+        NH = self.chief.dynamics.HN.T
+        dv_N = NH @ dv_H
+
+        super().set_action(np.concatenate((dv_N, [dt])))

tests/integration/act/test_int_actions_continuous.py

@@ -4,6 +4,7 @@
 
 from bsk_rl import act, obs, sats
 from bsk_rl.sim import dyn, fsw
+from bsk_rl.utils.orbital import random_orbit
 
 
 class TestImpulsiveThrust:
@@ -34,3 +35,36 @@ def test_thrust(self):
         self.env.step([0.0, 0.0, 0.0, 5.0])
         time_after = self.env.unwrapped.simulator.sim_time
         assert time_after - time_before == approx(5.0)
+
+
+class TestHillImpulsiveThrust:
+    class ThrustSat(sats.Satellite):
+        dyn_type = dyn.BasicDynamicsModel
+        fsw_type = fsw.MagicOrbitalManeuverFSWModel
+        observation_spec = [obs.SatProperties(dict(prop="v_BN_N"))]
+        action_spec = [act.ImpulsiveThrustHill(chief_name="ThrusterSat")]
+
+    env = gym.make(
+        "SatelliteTasking-v1",
+        satellite=ThrustSat(
+            "ThrusterSat",
+            sat_args=dict(
+                dv_available_init=1000.0,
+                oe=random_orbit(i=0.0, e=0.0, Omega=0.0, omega=0.0, f=90.0),
+            ),
+        ),
+        sim_rate=0.01,
+        time_limit=10000.0,
+        disable_env_checker=True,
+    )
+
+    def test_thrust(self):
+        observation_before, _ = self.env.reset()
+        observation_after, _, _, _, _ = self.env.step([100.0, 0.0, 0.0, 0.02])
+        diff = observation_after - observation_before
+        assert np.allclose(diff, np.array([0.0, 100.0, 0.0]), atol=0.5)
+
+        time_before = self.env.unwrapped.simulator.sim_time
+        self.env.step([0.0, 0.0, 0.0, 5.0])
+        time_after = self.env.unwrapped.simulator.sim_time
+        assert time_after - time_before == approx(5.0)