130 lines
4.7 KiB
Python
130 lines
4.7 KiB
Python
"""
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A script validating the Preintegration of IMU measurements
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"""
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import math
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import matplotlib.pyplot as plt
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import numpy as np
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from mpl_toolkits.mplot3d import Axes3D
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import gtsam
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from gtsam_utils import plotPose3
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IMU_FIG = 1
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POSES_FIG = 2
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class PreintegrationExample(object):
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@staticmethod
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def defaultParams(g):
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"""Create default parameters with Z *up* and realistic noise parameters"""
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params = gtsam.PreintegrationParams.MakeSharedU(g)
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kGyroSigma = math.radians(0.5) / 60 # 0.5 degree ARW
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kAccelSigma = 0.1 / 60 # 10 cm VRW
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params.gyroscopeCovariance = kGyroSigma ** 2 * np.identity(3, np.float)
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params.accelerometerCovariance = kAccelSigma ** 2 * np.identity(3, np.float)
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params.integrationCovariance = 0.0000001 ** 2 * np.identity(3, np.float)
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return params
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def __init__(self, twist=None, bias=None, dt=1e-2):
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"""Initialize with given twist, a pair(angularVelocityVector, velocityVector)."""
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# setup interactive plotting
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plt.ion()
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# Setup loop as default scenario
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if twist is not None:
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(W, V) = twist
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else:
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# default = loop with forward velocity 2m/s, while pitching up
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# with angular velocity 30 degree/sec (negative in FLU)
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W = np.array([0, -math.radians(30), 0])
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V = np.array([2, 0, 0])
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self.scenario = gtsam.ConstantTwistScenario(W, V)
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self.dt = dt
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self.maxDim = 5
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self.labels = list('xyz')
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self.colors = list('rgb')
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# Create runner
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self.g = 10 # simple gravity constant
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self.params = self.defaultParams(self.g)
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ptr = gtsam.ScenarioPointer(self.scenario)
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if bias is not None:
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self.actualBias = bias
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else:
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accBias = np.array([0, 0.1, 0])
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gyroBias = np.array([0, 0, 0])
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self.actualBias = gtsam.ConstantBias(accBias, gyroBias)
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self.runner = gtsam.ScenarioRunner(ptr, self.params, self.dt, self.actualBias)
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def plotImu(self, t, measuredOmega, measuredAcc):
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plt.figure(IMU_FIG)
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# plot angular velocity
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omega_b = self.scenario.omega_b(t)
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for i, (label, color) in enumerate(zip(self.labels, self.colors)):
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plt.subplot(4, 3, i + 1)
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plt.scatter(t, omega_b[i], color='k', marker='.')
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plt.scatter(t, measuredOmega[i], color=color, marker='.')
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plt.xlabel('angular velocity ' + label)
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# plot acceleration in nav
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acceleration_n = self.scenario.acceleration_n(t)
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for i, (label, color) in enumerate(zip(self.labels, self.colors)):
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plt.subplot(4, 3, i + 4)
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plt.scatter(t, acceleration_n[i], color=color, marker='.')
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plt.xlabel('acceleration in nav ' + label)
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# plot acceleration in body
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acceleration_b = self.scenario.acceleration_b(t)
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for i, (label, color) in enumerate(zip(self.labels, self.colors)):
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plt.subplot(4, 3, i + 7)
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plt.scatter(t, acceleration_b[i], color=color, marker='.')
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plt.xlabel('acceleration in body ' + label)
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# plot actual specific force, as well as corrupted
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actual = self.runner.actualSpecificForce(t)
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for i, (label, color) in enumerate(zip(self.labels, self.colors)):
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plt.subplot(4, 3, i + 10)
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plt.scatter(t, actual[i], color='k', marker='.')
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plt.scatter(t, measuredAcc[i], color=color, marker='.')
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plt.xlabel('specific force ' + label)
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def plotGroundTruthPose(self, t):
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# plot ground truth pose, as well as prediction from integrated IMU measurements
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actualPose = self.scenario.pose(t)
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plotPose3(POSES_FIG, actualPose, 0.3)
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t = actualPose.translation()
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self.maxDim = max([abs(t.x()), abs(t.y()), abs(t.z()), self.maxDim])
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ax = plt.gca()
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ax.set_xlim3d(-self.maxDim, self.maxDim)
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ax.set_ylim3d(-self.maxDim, self.maxDim)
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ax.set_zlim3d(-self.maxDim, self.maxDim)
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plt.pause(0.01)
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def run(self):
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# simulate the loop
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T = 12
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for i, t in enumerate(np.arange(0, T, self.dt)):
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measuredOmega = self.runner.measuredAngularVelocity(t)
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measuredAcc = self.runner.measuredSpecificForce(t)
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if i % 25 == 0:
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self.plotImu(t, measuredOmega, measuredAcc)
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self.plotGroundTruthPose(t)
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pim = self.runner.integrate(t, self.actualBias, True)
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predictedNavState = self.runner.predict(pim, self.actualBias)
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plotPose3(POSES_FIG, predictedNavState.pose(), 0.1)
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plt.ioff()
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plt.show()
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if __name__ == '__main__':
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PreintegrationExample().run()
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