OpenFlightAnalysis/Tests/TestChirp.py at master · UASLab/OpenFlightAnalysis · GitHub

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"""
University of Minnesota
Aerospace Engineering and Mechanics - UAV Lab
Copyright 2019 Regents of the University of Minnesota
See: LICENSE.md for complete license details

Author: Chris Regan

Exampe script for generating sin sweep type excitations.
"""

import numpy as np
import matplotlib.pyplot as plt

# Hack to allow loading the Core package
if __name__ == "__main__" and __package__ is None:
    from sys import path, argv
    from os.path import dirname, abspath, join

    path.insert(0, abspath(join(dirname(argv[0]), "..")))
    path.insert(0, abspath(join(dirname(argv[0]), "..", 'Core')))

    del path, argv, dirname, abspath, join

from Core import GenExcite
from Core import FreqTrans


# Constants
hz2rps = 2*np.pi
rps2hz = 1/hz2rps

#%% Define the frequency selection and distribution of the frequencies into the signals
freqRate_hz = 50;
freqInit_rps = 0.1 * hz2rps
freqFinal_rps = 10 * hz2rps
timeDur_s = 10.0
ampInit = 1.0
ampFinal = 1.0

time_s = np.linspace(0, timeDur_s, int(timeDur_s * freqRate_hz) + 1)
sig, ampChirp, freqChirp_rps = GenExcite.Chirp(freqInit_rps, freqFinal_rps, time_s, ampInit, ampFinal, freqType = 'linear', ampType = 'linear', initZero = 1)

## Results
plt.figure()
plt.subplot(3,1,1)
plt.plot(time_s, sig); plt.grid()
plt.ylabel('Signal (nd)');
plt.subplot(3,1,2)
plt.plot(time_s, ampChirp); plt.grid()
plt.ylabel('ampitude (nd)');
plt.subplot(3,1,3)
plt.plot(time_s, freqChirp_rps * rps2hz); plt.grid()
plt.xlabel('Time (s)'); plt.ylabel('Frequency (Hz)')
plt.show()


#%% Plot the Excitation Spectrum
## Compute Spectrum of each channel
optSpect = FreqTrans.OptSpect(freqRate_rps = freqRate_hz * hz2rps)

freq_hz, sigDft, Psd_mag = FreqTrans.Spectrum(sig, optSpect)
Psd_dB = 20*np.log10(Psd_mag)

## Plot Spectrum
plt.figure()
plt.plot(freq_hz[0], Psd_dB[0])
plt.xlabel('frequency (Hz)');
plt.ylabel('Spectrum (dB)');
plt.grid()
plt.show()


#%% Create the output for JSON config
timeFinal_s = time_s[-1]
timeStart_s = time_s[0]

jsonChirp = {}
jsonChirp['Type'] = 'LinearChirp'
jsonChirp['Duration'] = timeDur_s
jsonChirp['ampitude'] = [ampInit, ampFinal]
jsonChirp['Frequency'] = [freqInit_rps, freqFinal_rps]

import json
print(json.dumps(['Chirp', jsonChirp], separators=(', ', ': ')))