is damp function got any limitation?
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Hi,
fs =
3
-------------
s^2 + 3 s + 2
Continuous-time transfer function.
Pole Damping Frequency Time Constant
(rad/seconds) (seconds)
-1.00e+00 1.00e+00 1.00e+00 1.00e+00
-2.00e+00 1.00e+00 2.00e+00 5.00e-01
above are the result of my damp line, why my wn not √2 and damping not (3√2)/2 ? is there any limitation for damp function?
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Birdman
2018-4-8
I don't understand clearly your question, but the damping ratio and natural frequency can be found mathematically as follows:
It is known that an ideal second order transfer function is as follows:
K*Wn^2
------------------------
s^2 + 2*zeta*Wn*s + Wn^2
If we extract the coefficients of both transfer functions' denominator and solve for zeta and Wn,
2*zeta*wn=3
Wn^2=2;
From this, Wn is found as sqrt(2) and zeta(damping ratio) is found as 3/(2*sqrt(2)). This means zeta is greater than 1, which is normal since both poles are real, which will result in an overdamped step response. Hope this helps.
3 个评论
llca llasd
2018-4-9
Birdman
2018-4-9
Oh, that is because damp function finds the damping ratio and frequency of the poles, not the system. What you want to find and what I showed you above is the damping ratio and natural frequency of the second order system. Please note the difference.
llca llasd
2018-4-9
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