Source code for scenarioAttitudeGG

#
#  ISC License
#
#  Copyright (c) 2020, Autonomous Vehicle Systems Lab, University of Colorado at Boulder
#
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r"""
Overview
--------

Illustrates how to add a :ref:`GravityGradientEffector` to a 6U cube-sat spacecraft while a Hill-frame pointing
control solution is active.  This script expands on :ref:`scenarioAttitudeGuidance` sets
up a 6-DOF spacecraft which is orbiting the Earth.  More illustrations on using the gravity gradient
torque effector can be found in the modules :ref:`UnitTestGravityGradientEffector` folder.

The script is found in the folder ``basilisk/examples`` and executed by using::

    python3 scenarioAttitudeGG.py

The simulation layout is shown in the following illustration.  The :ref:`GravityGradientEffector` is added
to the spacecraft to create a position depended external torque.  This

.. image:: /_images/static/test_scenarioAttitudeGG.svg
   :align: center

Illustration of Simulation Results
----------------------------------
In this simulation the reference frame is not aligned with the Hill frame, but rather it has a fixed angular
offset along the 2nd body axis.  As the Body frame inertia tensor is diagonal, this reference orientation
represents a non-equilibrium gravity gradient torque orientation.  Thie simulation results are shown in the
following figures:

.. image:: /_images/Scenarios/scenarioAttitudeGG1.svg
   :align: center

.. image:: /_images/Scenarios/scenarioAttitudeGG2.svg
   :align: center

.. image:: /_images/Scenarios/scenarioAttitudeGG3.svg
   :align: center

Where in :ref:`scenarioAttitudeGuidance` the attitude error asymptotically converged to zero, with the
gravity gradient torque the closed loop dynamics is now only Lagrange stable or bounded.

"""

#
# Basilisk Scenario Script and Integrated Test
#
# Purpose:  Integrated test of the spacecraft(), extForceTorque, simpleNav(),
#           mrpFeedback() with attitude navigation modules.  Illustrates how
#           attitude guidance behavior can be changed in a very modular manner.
# Author:   Hanspeter Schaub
# Creation Date:  Dec. 2, 2016
#

import os

import matplotlib.pyplot as plt
import numpy as np
# The path to the location of Basilisk
# Used to get the location of supporting data.
from Basilisk import __path__
# import message declarations
from Basilisk.architecture import messaging
from Basilisk.fswAlgorithms import attTrackingError
from Basilisk.fswAlgorithms import hillPoint
# import FSW Algorithm related support
from Basilisk.fswAlgorithms import mrpFeedback
from Basilisk.simulation import GravityGradientEffector
from Basilisk.simulation import extForceTorque
from Basilisk.simulation import simpleNav
# import simulation related support
from Basilisk.simulation import spacecraft
# import general simulation support files
from Basilisk.utilities import SimulationBaseClass
from Basilisk.utilities import macros
from Basilisk.utilities import orbitalMotion
from Basilisk.utilities import simIncludeGravBody
from Basilisk.utilities import unitTestSupport  # general support file with common unit test functions
# attempt to import vizard
from Basilisk.utilities import vizSupport

bskPath = __path__[0]
fileName = os.path.basename(os.path.splitext(__file__)[0])


[docs] def run(show_plots): """ The scenarios can be run with the followings setups parameters: Args: show_plots (bool): Determines if the script should display plots """ # Create simulation variable names simTaskName = "simTask" simProcessName = "simProcess" # Create a sim module as an empty container scSim = SimulationBaseClass.SimBaseClass() # set the simulation time variable used later on simulationTime = macros.min2nano(10.) # # create the simulation process # dynProcess = scSim.CreateNewProcess(simProcessName) # create the dynamics task and specify the integration update time simulationTimeStep = macros.sec2nano(0.1) dynProcess.addTask(scSim.CreateNewTask(simTaskName, simulationTimeStep)) # # setup the simulation tasks/objects # # initialize spacecraft object and set properties scObject = spacecraft.Spacecraft() scObject.ModelTag = "spacecraftBody" # define the simulation inertia I = [900., 0., 0., 0., 800., 0., 0., 0., 600.] scObject.hub.mHub = 750.0 # kg - spacecraft mass scObject.hub.r_BcB_B = [[0.0], [0.0], [0.0]] # m - position vector of body-fixed point B relative to CM scObject.hub.IHubPntBc_B = unitTestSupport.np2EigenMatrix3d(I) # add spacecraft object to the simulation process scSim.AddModelToTask(simTaskName, scObject) # clear prior gravitational body and SPICE setup definitions gravFactory = simIncludeGravBody.gravBodyFactory() # setup Earth Gravity Body earth = gravFactory.createEarth() earth.isCentralBody = True # ensure this is the central gravitational body mu = earth.mu # attach gravity model to spacecraft gravFactory.addBodiesTo(scObject) # # initialize Spacecraft States with initialization variables # # setup the orbit using classical orbit elements oe = orbitalMotion.ClassicElements() oe.a = 10000000.0 # meters oe.e = 0.1 oe.i = 33.3 * macros.D2R oe.Omega = 48.2 * macros.D2R oe.omega = 347.8 * macros.D2R oe.f = 85.3 * macros.D2R rN, vN = orbitalMotion.elem2rv(mu, oe) scObject.hub.r_CN_NInit = rN # m - r_CN_N scObject.hub.v_CN_NInit = vN # m/s - v_CN_N scObject.hub.sigma_BNInit = [[0.1], [0.2], [-0.3]] # sigma_BN_B scObject.hub.omega_BN_BInit = [[0.001], [-0.01], [0.03]] # rad/s - omega_BN_B # add gravity gradient effector ggEff = GravityGradientEffector.GravityGradientEffector() ggEff.ModelTag = scObject.ModelTag ggEff.addPlanetName(earth.planetName) scObject.addDynamicEffector(ggEff) scSim.AddModelToTask(simTaskName, ggEff) # setup extForceTorque module # the control torque is read in through the messaging system extFTObject = extForceTorque.ExtForceTorque() extFTObject.ModelTag = "externalDisturbance" # use the input flag to determine which external torque should be applied # Note that all variables are initialized to zero. Thus, not setting this # vector would leave it's components all zero for the simulation. scObject.addDynamicEffector(extFTObject) scSim.AddModelToTask(simTaskName, extFTObject) # add the simple Navigation sensor module. This sets the SC attitude, rate, position # velocity navigation message sNavObject = simpleNav.SimpleNav() sNavObject.ModelTag = "SimpleNavigation" scSim.AddModelToTask(simTaskName, sNavObject) # # setup the FSW algorithm tasks # # setup hillPoint guidance module attGuidance = hillPoint.hillPoint() attGuidance.ModelTag = "hillPoint" scSim.AddModelToTask(simTaskName, attGuidance) # setup the attitude tracking error evaluation module attError = attTrackingError.attTrackingError() attError.ModelTag = "attErrorInertial3D" scSim.AddModelToTask(simTaskName, attError) attError.sigma_R0R = [0, 0.2, 0] # setup the MRP Feedback control module mrpControl = mrpFeedback.mrpFeedback() mrpControl.ModelTag = "mrpFeedback" scSim.AddModelToTask(simTaskName, mrpControl) mrpControl.K = 3.5 mrpControl.Ki = -1.0 # make value negative to turn off integral feedback mrpControl.P = 30.0 mrpControl.integralLimit = 2. / mrpControl.Ki * 0.1 # # Setup data logging before the simulation is initialized # numDataPoints = 100 samplingTime = unitTestSupport.samplingTime(simulationTime, simulationTimeStep, numDataPoints) mrpLog = mrpControl.cmdTorqueOutMsg.recorder(samplingTime) attErrLog = attError.attGuidOutMsg.recorder(samplingTime) ggLog = ggEff.gravityGradientOutMsg.recorder(samplingTime) scSim.AddModelToTask(simTaskName, mrpLog) scSim.AddModelToTask(simTaskName, attErrLog) scSim.AddModelToTask(simTaskName, ggLog) # # create simulation messages # # create the FSW vehicle configuration message vehicleConfigOut = messaging.VehicleConfigMsgPayload() vehicleConfigOut.ISCPntB_B = I # use the same inertia in the FSW algorithm as in the simulation vcMsg = messaging.VehicleConfigMsg().write(vehicleConfigOut) # connect messages sNavObject.scStateInMsg.subscribeTo(scObject.scStateOutMsg) attGuidance.transNavInMsg.subscribeTo(sNavObject.transOutMsg) attError.attNavInMsg.subscribeTo(sNavObject.attOutMsg) attError.attRefInMsg.subscribeTo(attGuidance.attRefOutMsg) mrpControl.guidInMsg.subscribeTo(attError.attGuidOutMsg) mrpControl.guidInMsg.subscribeTo(attError.attGuidOutMsg) mrpControl.vehConfigInMsg.subscribeTo(vcMsg) extFTObject.cmdTorqueInMsg.subscribeTo(mrpControl.cmdTorqueOutMsg) # if this scenario is to interface with the BSK Viz, uncomment the following lines vizSupport.enableUnityVisualization(scSim, simTaskName, scObject , modelDictionaryKeyList="6USat" # , saveFile=fileName ) # # initialize Simulation # scSim.InitializeSimulation() # # configure a simulation stop time and execute the simulation run # scSim.ConfigureStopTime(simulationTime) scSim.ExecuteSimulation() # # retrieve the logged data # dataLr = mrpLog.torqueRequestBody dataSigmaBR = attErrLog.sigma_BR ggData = ggLog.gravityGradientTorque_B np.set_printoptions(precision=16) # # plot the results # timeLineSet = mrpLog.times() * macros.NANO2MIN plt.close("all") # clears out plots from earlier test runs plt.figure(1) fig = plt.gcf() ax = fig.gca() vectorData = dataSigmaBR sNorm = np.array([np.linalg.norm(v) for v in vectorData]) plt.plot(timeLineSet, sNorm, color=unitTestSupport.getLineColor(1, 3), ) plt.xlabel('Time [min]') plt.ylabel(r'Attitude Error Norm $|\sigma_{B/R}|$') ax.set_yscale('log') figureList = {} pltName = fileName + "1" figureList[pltName] = plt.figure(1) plt.figure(2) fig = plt.gcf() ax = fig.gca() vectorData = dataLr sNorm = np.array([np.linalg.norm(v) for v in vectorData]) plt.plot(timeLineSet, sNorm, color=unitTestSupport.getLineColor(1, 3), ) plt.xlabel('Time [min]') plt.ylabel(r'Control Torque $L_r$ [Nm]') ax.set_yscale('log') pltName = fileName + "2" figureList[pltName] = plt.figure(2) plt.figure(3) for idx in range(3): plt.plot(timeLineSet, ggData[:, idx], color=unitTestSupport.getLineColor(idx, 3), label=r'$r_' + str(idx) + '$') plt.legend(loc='lower right') plt.xlabel('Time [min]') plt.ylabel(r'GG Torque [Nm]') pltName = fileName + "3" figureList[pltName] = plt.figure(3) if show_plots: plt.show() # close the plots being saved off to avoid over-writing old and new figures plt.close("all") return figureList
# # This statement below ensures that the unit test scrip can be run as a # stand-along python script # if __name__ == "__main__": run( True # show_plots )