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Summary
| Description |
English: Step responses for a second order system defined by the transfer function:
where is the damping ratio and is the undamped natural frequency. The equations were obtained from here, plotted using maxima and edited in a text editor to insert the Greek alphabets in the plot. The equations are: |
| Date | |
| Source | Own work |
| Author | Krishnavedala |
Source code using w:python (programming language) with numpy and matplotlib toolboxes
|
|---|
from matplotlib.pyplot import *
from numpy import *
wt = linspace(0,15,100)
b = lambda z: sqrt(1. - z**2)
t = lambda z: arctan(b(z)/z)
h1 = lambda wt,z: 1. - exp(-z*wt)*sin(b(z)*wt+t(z))/b(z)
h2 = lambda wt: 1. - cos(wt)
h3 = lambda wt: 1. - exp(-wt)*(1.+wt)
s1 = lambda z: (z + sqrt(z**2-1.))
s2 = lambda z: (z - sqrt(z**2-1.))
h4 = lambda wt,z: 1. + ( (exp(-s1(z)*wt)/s1(z)) - \
(exp(-s2(z)*wt)/s2(z)) ) / (2.*sqrt(z**2-1.))
fig = figure(figsize=(8,4))
ax = fig.add_subplot(111)
ax.grid(True)
ax.plot(wt,h2(wt),'g',label=r"undamped $(\zeta=0)$")
ax.plot(wt,h1(wt,.5),'b',label=r"under $(\zeta=0.5)$")
ax.plot(wt,h3(wt),'r',label=r"critical $(\zeta=1.0)$")
ax.plot(wt,h4(wt,1.5),'m',label=r"over $(\zeta=1.5)$")
ax.set_ylim(0,2)
ax.minorticks_on()
leg = ax.legend(frameon=False,handletextpad=.05)
setp(leg.get_texts(),fontsize=10)
ax.set_xlim(0,15)
ax.set_xlabel(r"$\omega t$",fontsize=15)
ax.set_ylabel("Step response",fontsize=12)
fig.savefig("Second_order_transfer_function.svg",bbox_inches="tight",\
pad_inches=.15)
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The maxima source code
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beta(zeta) := sqrt(1-zeta^2);
theta(zeta) := atan(beta(zeta)/zeta);
h_under(wt) := 1 - beta(0.5)^-1*exp(-0.5*wt)*sin(wt*beta(.5)+theta(0.5));
h_un(wt) := 1 - cos(wt);
h_crit(wt) := 1 - exp(-wt) * (1+wt);
s1(zeta) := zeta+sqrt(zeta^2-1);
s2(zeta) := zeta-sqrt(zeta^2-1);
h_over(wt) := 1 + ((exp(-s1(1.5)*wt)/s1(1.5))-(exp(-s2(1.5)*wt)/s2(1.5)))/(2*sqrt(1.5^2-1));
load(draw);
draw2d(dimensions=[800,400],terminal=svg,
user_preamble="set mxtics; set mytics;",
grid=true, yrange=[0,2], xlabel="omega t",
line_width=1.5, ylabel="Step response",
key="under (zeta=0.5)",color=blue,explicit(h_under(wt),wt,0,15),
key="critical (zeta=1)",color=red,explicit(h_crit(wt),wt,0,15),
key="over (zeta=1.5)",color=magenta,explicit(h_over(wt),wt,0,15),
key="undamped (zeta=0)",color=green,explicit(h_un(wt),wt,0,15)
);
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Licensing
I, the copyright holder of this work, hereby publish it under the following license:
This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
- You are free:
- to share – to copy, distribute and transmit the work
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- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
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File history
Click on a date/time to view the file as it appeared at that time.
| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 15:57, 7 June 2011 | | 631 × 356 (80 KB) | Krishnavedala | figure correction after correcting the equations |
| 19:25, 26 May 2011 |  | 800 × 400 (36 KB) | Krishnavedala | erroneous under-damped curve corrected. | |
| 18:28, 26 May 2011 |  | 800 × 400 (36 KB) | Krishnavedala |
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