Using input_output_response(...), Simple System Gives Erroneous Output #890

import matplotlib.pyplot as plt
import numpy as np
import control as ctrl

R = 22e3
C = 470e-6

circuit = ctrl.ss(-1/(R*C), 1/(R*C), 1, 0)
t, resp = ctrl.step_response(circuit)
plt.plot(t, resp)
plt.title('Step Response of the RC Circuit')
plt.grid()
print("The eigenvalue is: ",-1/(R*C))
print("numpy gives the eigenvalue, and eigen vector respectively as: ")
np.linalg.eig(circuit.A)
t = np.arange(0, 120, 0.01)
u = 3.3*148/256-3.3*40/256*np.heaviside(t-60,1)
plt.plot(t,u)
x0 = 3.3*128/256
t, vc = ctrl.input_output_response(circuit, t, u, x0)
plt.plot(t,vc)
plt.grid()
plt.title("Response of RC Circuit")
plt.legend(["u","$v_c$"])
plt.xlabel("time (seconds)")
plt.ylabel("Voltage (Volts)")
plt.show()