# Changes

,  08:47, 6 July 2015
Line 38: Line 38:
[-0.777688831121563, -0.7776888311215626]

[-0.777688831121563, -0.7776888311215626]

[0.22911205809043574, 0.2291120580904359]

[0.22911205809043574, 0.2291120580904359]
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</source>
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* '''Demo of ODE with a step input and initial conditions.'''
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<source lang="octave">
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## This is a demo of a second order transfer function and a unit step input.
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## in laplace we would have        1                      1
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##                              _______________        *  _____
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##                            s^2 + sqrt(2)*s +1          s
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##
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## So the denominator is s^3 + sqrt(2) * s^2 + s
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# and for laplace initial conditions area
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##            t(0)=0 t'(0) =0  and the step has initial condition of  1
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## so we set  t''(0)=1
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## In the code we use diff(y,1)(0) == 0 to do t'(0)=0
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##
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## I know that all this can be done using the control pkg
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## But I used this to verify that this solution is the
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##  same as if I used the control pkg.
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## With this damping ratio we should have a 4.321% overshoot.
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##
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syms y(x)
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de =diff(y, 3 ) +sqrt(2)*diff(y,2) + diff(y) == 0;
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f = dsolve(de, y(0) == 0, diff(y,1)(0) == 0 , diff(y,2)(0) == 1)
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ff=function_handle(rhs(f))
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x1=0:.01:10;
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y=ff(x1);
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plot(x1,y)
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grid minor on

</source>

</source>
17

edits