#
# ISC License
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# Copyright (c) 2021, Autonomous Vehicle Systems Lab, University of Colorado Boulder
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# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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import numpy as np
from Basilisk.architecture import messaging
from Basilisk.fswAlgorithms import smallBodyNavUKF
from Basilisk.utilities import SimulationBaseClass
from Basilisk.utilities import macros, orbitalMotion
from Basilisk.utilities import unitTestSupport
from matplotlib import pyplot as plt
[docs]def test_smallBodyNavUKF(show_plots):
r"""
**Validation Test Description**
This unit test checks that the filter converges to a constant position and null velocity estimates under the presence of static measurements.
Then, the non-Keplerian gravity estimation should match the Keplerian gravity with opposite sign.
**Test Parameters**
Args:
:param show_plots: flag if plots should be shown.
"""
[testResults, testMessage] = smallBodyNavUKFTestFunction(show_plots)
assert testResults < 1, testMessage
[docs]def smallBodyNavUKFTestFunction(show_plots):
"""Test method"""
testFailCount = 0
testMessages = []
unitTaskName = "unitTask"
unitProcessName = "TestProcess"
unitTestSim = SimulationBaseClass.SimBaseClass()
testProcessRate = macros.sec2nano(15)
testProc = unitTestSim.CreateNewProcess(unitProcessName)
testProc.addTask(unitTestSim.CreateNewTask(unitTaskName, testProcessRate))
# setup module to be tested
module = smallBodyNavUKF.SmallBodyNavUKF()
module.ModelTag = "smallBodyNavUKFTag"
unitTestSim.AddModelToTask(unitTaskName, module)
# Set the filter parameters (hyperparameters, small body gravitational constant, noise matrices)
module.alpha = 0 # Filter hyperparameter
module.beta = 2 # Filter hyperparameter
module.kappa = 1e-3 # Filter hyperparameter
module.mu_ast = 17.2882449693*1e9 # Gravitational constant of the asteroid m^3/s^2
module.P_proc = (0.1*np.identity(9)).tolist() # Process Noise
module.R_meas = (0.1*np.identity(3)).tolist() # Measurement Noise
vesta_radius = 2.3612 * orbitalMotion.AU * 1000 # meters
vesta_velocity = np.sqrt(orbitalMotion.MU_SUN*(1000.**3)/vesta_radius) # m/s, assumes circular orbit
x_0 = [2010., 1510., 1010., 0., 2., 0., 0.14, 0., 0.]
module.x_hat_k = x_0
module.P_k = [[1000., 0., 0., 0., 0., 0., 0., 0., 0.],
[0., 1000., 0., 0., 0., 0., 0., 0., 0.],
[0., 0., 1000., 0., 0., 0., 0., 0., 0.],
[0., 0., 0., 1, 0., 0., 0., 0., 0.],
[0., 0., 0., 0., 1, 0., 0., 0., 0.],
[0., 0., 0., 0., 0., 1, 0., 0., 0.],
[0., 0., 0., 0., 0., 0., 1e-3, 0., 0.],
[0., 0., 0., 0., 0., 0., 0., 1e-3, 0.],
[0., 0., 0., 0., 0., 0., 0., 0., 1e-3]]
#module.P_k = P_k.tolist()
# Configure blank module input messages
navTransInMsgData = messaging.NavTransMsgPayload()
navTransInMsgData.r_BN_N = [vesta_radius + 600. * 1000., -400. * 1000, 200. * 1000]
navTransInMsgData.v_BN_N = [0., vesta_velocity, 0.]
navTransInMsg = messaging.NavTransMsg().write(navTransInMsgData)
asteroidEphemerisInMsgData = messaging.EphemerisMsgPayload()
asteroidEphemerisInMsgData.r_BdyZero_N = [vesta_radius, 0., 0.]
asteroidEphemerisInMsgData.v_BdyZero_N = [0., vesta_velocity, 0.]
asteroidEphemerisInMsgData.sigma_BN = [0.0, 0.0, 0.0]
asteroidEphemerisInMsgData.omega_BN_B = [0.0, 0.0, 0.0]
asteroidEphemerisInMsg = messaging.EphemerisMsg().write(asteroidEphemerisInMsgData)
# subscribe input messages to module
module.navTransInMsg.subscribeTo(navTransInMsg)
module.asteroidEphemerisInMsg.subscribeTo(asteroidEphemerisInMsg)
# setup output message recorder objects
smallBodyNavUKFOutMsgRec = module.smallBodyNavUKFOutMsg.recorder()
unitTestSim.AddModelToTask(unitTaskName, smallBodyNavUKFOutMsgRec)
smallBodyNavUKFOutMsgRecC = module.smallBodyNavUKFOutMsgC.recorder()
unitTestSim.AddModelToTask(unitTaskName, smallBodyNavUKFOutMsgRecC)
unitTestSim.InitializeSimulation()
unitTestSim.ConfigureStopTime(macros.sec2nano(600))
unitTestSim.ExecuteSimulation()
x_hat = smallBodyNavUKFOutMsgRec.state
x_hat_c_wrapped = smallBodyNavUKFOutMsgRecC.state
covar = smallBodyNavUKFOutMsgRec.covar
# Since the small body does not rotate, no inhomogeneous gravity has
# been considered and the spacecraft velocity in the small body
# fixed frame is null, then the measured acceleration should correspond
# to the Keplerian gravity with opposite sign
true_r = np.array([[600. * 1000, -400. * 1000, 200. * 1000]])
true_v = np.array([[0., 0., 0.]])
true_a = module.mu_ast * true_r / (np.linalg.norm(true_r))**3
true_x_hat = np.zeros(9)
true_x_hat[0:3] = true_r
true_x_hat[3:6] = true_v
true_x_hat[6:9] = true_a
testFailCount, testMessages = unitTestSupport.compareArrayRelative(
[true_x_hat], np.array([x_hat[-1,:]]), 0.01, "x_hat",
testFailCount, testMessages)
testFailCount, testMessages = unitTestSupport.compareArrayRelative(
[true_x_hat], np.array([x_hat_c_wrapped[-1,:]]), 0.01, "x_hat_c_wrapped",
testFailCount, testMessages)
plt.figure(1)
plt.clf()
plt.figure(1, figsize=(7, 5), dpi=80, facecolor='w', edgecolor='k')
plt.ticklabel_format(useOffset=False)
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,0] / 1000, label='x-pos')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,1] / 1000, label='y-pos')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,2] / 1000, label='z-pos')
plt.legend(loc='lower left')
plt.xlabel('Time (min)')
plt.ylabel('${}^{A}r_{BA}$ (km)')
plt.title('Estimated Relative Spacecraft Position')
plt.figure(2)
plt.clf()
plt.figure(2, figsize=(7, 5), dpi=80, facecolor='w', edgecolor='k')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,3], label='x-vel')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,4], label='y-vel')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,5], label='z-vel')
plt.legend(loc='upper right')
plt.xlabel('Time (min)')
plt.ylabel('${}^{A}v_{BA}$ (m/s)')
plt.title('Estimated Spacecraft Velocity')
plt.figure(3)
plt.clf()
plt.figure(3, figsize=(7, 5), dpi=80, facecolor='w', edgecolor='k')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,6], label='x-acc')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,7], label='y-acc')
plt.plot(smallBodyNavUKFOutMsgRec.times() * 1.0E-9 / 60, x_hat[:,8], label='z-acc')
plt.legend(loc='lower right')
plt.xlabel('Time (min)')
plt.ylabel('${}^{A}a_{BA}$ (m/s^2)')
plt.title('Estimated Non-Keplerian Acceleration')
if show_plots:
plt.show()
if testFailCount == 0:
print("PASSED: " + module.ModelTag)
else:
print(testMessages)
return [testFailCount, "".join(testMessages)]
if __name__ == "__main__":
test_smallBodyNavUKF(True)