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Description
I been scratching my head about whats going on with a very simple system.
Defining the system using tf yields results as expected. But defining the system through zpk does not.
Description
I intend to define the next system:
G(s) = K --------------- (s+2)*(s+2/3)With K adjusted for a ts=1 second. Very straight forward.
Reproduction
This is my code for zpk:
import control as ctimport numpy as npimport matplotlib.pyplot as pltK = 10.314G = ct.zpk([], [-2, -2/3], K)T = ct.feedback(G)ct.step_response(T).plot()
ct.step_info(T)
{'RiseTime': np.float64(0.0), 'SettlingTime': nan, 'SettlingMin': np.float64(-4.959514534383556e+52), 'SettlingMax': np.float64(8.010508330340013e+51), 'Overshoot': np.float64(9.04605979182796e+53), 'Undershoot': np.float64(5.600651440127666e+54), 'Peak': np.float64(4.959514534383556e+52), 'PeakTime': np.float64(5.180816459236604), 'SteadyStateValue': np.float64(0.8855245835956728)}The result is not as expected. While defining the system through tf:
I = ct.tf([K], [1, 8/3, 4/3])V = ct.feedback(I)ct.step_response(V).plot()
ct.step_info(V)
{'RiseTime': np.float64(0.4186518350898263), 'SettlingTime': np.float64(2.5119110105389577), 'SettlingMin': np.float64(0.8127467853231765), 'SettlingMax': np.float64(1.118911703975943), 'Overshoot': np.float64(26.35435717033743), 'Undershoot': 0, 'Peak': np.float64(1.118911703975943), 'PeakTime': np.float64(0.9942981083383374), 'SteadyStateValue': np.float64(0.8855347207912633)}Outputting both system definitions reveals they're the same. The transfer function is exactly the same. But I don't know what may be going on with the transfer object defined with zpk.
System info
I've installed the control package in a clean conda enviroment and using a jupyter notebook through VSCode.
Conda:
conda version : 23.1.0conda-build version : 3.22.0python version : 3.9.13.final.0virtual packages : __archspec=1=x86_64__win=0=0platform : win-64