- #1

tehsportsmaen

- 3

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- TL;DR Summary
- I try to simulate a two-mass oscillator for a speaker-system and i don't know if my approach makes sense because the physiscal and code-wise details are very complex for me right now.

**Idea**:

Given a system of two coupled oscillators in which 2 masses are connected to a spring in the middle. Each of the two masses is coupled to another spring on the left and right, which have fixed ends but are not connected to each other. So we have 3 springs, two masses and the springs also have their own damping parameters in addition to the spring constants. Mass m1 is driven by a constant sinusoidal force. So parameters should be: m1, m2, c1, c2, c3, k1, k2, k3, F1. I try to plot the amplitudes over the frequncies in hertz (not omega)

- Define equations and parameters
- Calculate Amplitudes of x1,x2, then for-loop with fast fourier tranformation-calculate in a frequency-range (np.logspace) from 10-1000Hz in 81 steps
- Plot the amplitudes of x1,x2 over the f-range
- Change parameters to see how the system reacts

Code::

```
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from scipy.integrate import odeint
def equations(Y, t, m1, m2, c1, c2, c3, k1, k2, k3, F1, omega):
x1, v1, x2, v2 = Y
dx1dt = v1
dv1dt = (-k1*x1 + k2*(x2 - x1) - c1*v1 + F1*np.sin(omega*t)) / m1
dx2dt = v2
dv2dt = (-k3*x2 - k2*(x2 - x1) - ((c2+c3)*v2))/ m2
return [dx1dt, dv1dt, dx2dt, dv2dt]#SYSTEM
m1, m2 = 0.001, 0.090
c1, c2, c3 = 2.85, 0.5, 1
k1, k2, k3 = 1872.5, 1777.3, 130
F1 = 1.63#TIME AND FREQUENCIES
t = np.linspace(0, 10, 1000)
frequencies = np.logspace(1, 3, 81)def integrate_system(frequency, m1, m2, c1, c2, c3, k1, k2, k3, F1, t):
omega = 2 * np.pi * frequency
Y0 = [0, 0, 0, 0] # initial conditions: [x1, v1, x2, v2]
solution = odeint(equations, Y0, t, args=(m1, m2, c1, c2, c3, k1, k2, k3, F1, omega))
return solution[:, 0], solution[:, 2] #return x1 x2amplitudes_x1 = []
amplitudes_x2 = []for frequency in frequencies:
x1, x2 = integrate_system(frequency, m1, m2, c1, c2, c3, k1, k2, k3, F1, t)
#FFT
fft_x1 = np.fft.fft(x1)
fft_x2 = np.fft.fft(x2)
#compute amplitudes
amplitude_spectrum_x1 = np.abs(fft_x1) / len(fft_x1)
amplitude_spectrum_x2 = np.abs(fft_x2) / len(fft_x2)
#index of fft frequencies
frequency_index = np.argmin(np.abs(frequency - np.fft.fftfreq(len(t), d=t[1]-t[0])))
#amplitudes of driving frequencies
amplitudes_x1.append(amplitude_spectrum_x1[frequency_index])
amplitudes_x2.append(amplitude_spectrum_x2[frequency_index])pd.set_option('display.max_rows', None)
df = pd.DataFrame({'Frequency_Hz': frequencies,'Amplitude_m1': amplitudes_x1,'Amplitude_m2': amplitudes_x2})
print(df)plt.figure(figsize=(12, 6))
plt.loglog(frequencies, amplitudes_x1, label='Amplitude of m1', color='red')
plt.loglog(frequencies, amplitudes_x2, label='Amplitude of m2', color='blue')
plt.xlabel('Frequency (Hz)')
plt.ylabel('Amplitude')
plt.title('LS FREQUENCIES')
plt.legend()
plt.grid(True)
plt.show()
```

*(timearray, integration, FFT, calculation, initial conditions, parameter interpretation)*I am happy to get advices, comments and remarks on this.

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