Step is plotting backwards
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Andres Yie
am 25 Mär. 2017
Kommentiert: Star Strider
am 25 Mär. 2017
Im trying yo get the step response the transfunction:
244.2 s + 244.2
-------------------------------------------------
0.015 s^4 + 1.525 s^3 + 2.51 s^2 + 245.2 s + 1221
but the resulting plot is something kind of reversed:
Why is this happening? is there a way to solve it?
Also stepinfo give me wierd values:
RiseTime: NaN SettlingTime: NaN SettlingMin: NaN SettlingMax: NaN Overshoot: NaN Undershoot: NaN Peak: Inf PeakTime: Inf
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Star Strider
am 25 Mär. 2017
The step function is correct.
Your system is unstable.
s = tf('s');
sys = (244.2*s + 244.2) / (0.015*s^4 + 1.525*s^3 + 2.51*s^2 + 245.2*s + 1221);
sys_poles = pole(sys)
sys_poles =
-101.53 + 0i
2.2371 + 12.99i
2.2371 - 12.99i
-4.6143 + 0i
You have a conjugate pair of poles in the RHP.
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Les Beckham
am 25 Mär. 2017
Bearbeitet: Les Beckham
am 25 Mär. 2017
This transfer function is unstable. It has a pair of complex (oscillatory) poles that are slightly in the right half plane. Thus, any disturbance (like a step) will cause the response to 'blow up'.
>> damp(sys)|
Pole Damping Frequency Time Constant
(rad/seconds) (seconds)
-4.61e+00 1.00e+00 4.61e+00 2.17e-01
2.24e+00 + 1.30e+01i -1.70e-01 1.32e+01 -4.47e-01
2.24e+00 - 1.30e+01i -1.70e-01 1.32e+01 -4.47e-01
-1.02e+02 1.00e+00 1.02e+02 9.85e-03|
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