Unable to simulate a problem in simulink that runs effortlessly in Python.

Hi! I wish to simulate a problem in simulink that I simulated in Python last year. This problem is throwing a lot of problems in simulink from singularity issues to algebraic loop. The python code is as follows-

import numpy as np
import matplotlib.pyplot as plt
from scipy.integrate import odeint
from numpy import tanh,sin,cos

t=np.linspace(0,100,10000)
y0=[0.3,-.4,0.1,0.3,0.5]
b,a1,a2,gamma,gamma1,gamma2,c,eta,k=2,1,3,7,5,6,3,1.5,15
def f(Y,t):
    thetadot,psi,psidot,h1,h2=Y[0],Y[1],Y[2],Y[3],Y[4]
    psiddot=a1*thetadot
    e=psi-np.sin(t)
    edot=psidot-np.cos(t)
    eddot=psiddot+sin(t)
    s=eddot+c**2*e+2*c*edot
    u=h2*psidot+h1*(-cos(t))-h1*c**2*edot-2*h1*c*eddot-eta*tanh(s)-k*s
    thetaddot=-a2*psidot+b*u
    #hdot=gamma*(c*edot*s+np.sin(t)*s+.1*tanh(s)+2*s)
    h1dot=-gamma1*(-cos(t)-c**2*edot-2*c*eddot)*s
    h2dot=-gamma2*s*psidot
    return[thetaddot,psidot,psiddot,h1dot,h2dot]

sol=odeint(f,y0,t)
thetadot=sol[:,0]
psi=sol[:,1]
psidot=sol[:,2]
h1=sol[:,3]
h2=sol[:,4]
plt.figure(1)
plt.plot(t,psi,t,psi-sin(t),'r--')
plt.figure(2)
plt.plot(t,thetadot,'r-',t,psidot,'g-')
plt.figure(3)
plt.plot(t,h1,t,h2)
plt.show()

I have also attached the simulink file- Right Now it is throwing algebraic loop error.

[Birdman]

Model can not be opened. Can you reshare it?

[Amardeep Mishra]

I have reshared it. Kindly have a look.

[Birdman]

It ran without any error for me. What was the error statement? Can you share it? Where is the algebraic loop found?

[Amardeep Mishra]

I have shared the graph with you. Can you check, are you getting similar results in matlab?

[Birdman]

Yes, they are similar.

[Amardeep Mishra]

It is constantly throwing error in my case. Here is the screenshot of algebraic loop error.

Answer 1

[Birdman]

For algebraic loop errors, simply add a Delay block to where the feedback occurs. This should solve it.

[Amardeep Mishra]

I dont know how to add delays to the loop can you help? Also it is repeatedly throwing the same error again. I wonder how come it is running in yours? What version is yours? Mine is 2015a and 2016 and I am running it on linux.

[Birdman]

Can you share the model which this error occurs?

[Amardeep Mishra]

I have already shared the model-- "gyro_model1.mdl". It is available in my original post. I have tried my problem in various versions of matlab from 2015 all the way to 2017. But the problem still persists. I dont know how you were getting correct answers in your simulink.

[Amardeep Mishra]

Ok, it started working in 2017 matlab. Weird!

[Birdman]

Anyway, keep in mind to add a Delay block if algebraic loop occurs. There are other solutions, but this is the basic one.