bug: delayed dirac input not considered in forced_response #1152
Description
Hi,
I have encountered a strange issue using the function forced_response with a NonlinearIOSystem object:
When applying a dirac as input, if the dirac is applied after too much time after the beginning of the simulation, the response of the system does not include its impact.
Here is a small piece of code to reproduce the issue:
import numpy as np
import matplotlib.pyplot as plt
import control
def dynamic_function(t, x, u, param=None):
"""
Dynamic function for the system.
"""
A = np.array([[0, 1], [-1, -1]])
B = np.array([[0], [1]])
return A @ x + B @ u
def output_function(t, x, u, param=None):
"""
Output function for the system.
"""
C = np.array([[1, 0]])
return C @ x
sys = control.NonlinearIOSystem(
dynamic_function, output_function,
inputs=1,
outputs=1,
states=2
)
t = np.linspace(0, 10, 100)
u = np.zeros_like(t)
dirac_index = 6
u[dirac_index] = 1 # Dirac input at t=0
results = control.forced_response(sys, T=t, U=u)
plt.figure()
plt.plot(t, results.y[0], label='Output')
plt.title('Response of Nonlinear System to Dirac Input')
plt.xlabel('Time (s)')
plt.ylabel('Output')
plt.grid()
plt.legend()
plt.show()
If dirac_index is inferior or equal to 5, the normal output is obtained while if dirac_index is superior to 6, both the output and the state of the function are null for the whole simulation time.
Here are the installed package:
├── control v0.10.1
│ ├── matplotlib v3.10.3
│ ├── numpy v2.2.5
│ └── scipy v1.15.3
Using python 3.12.3.
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