can anyone explain what this piece of code do?

[KSSV]

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Answer 1

[Abderrahim. B]

Hi!

Your code does the basic Model Interconnection and some LTI system analysis (poles zeros plot).

Try to learn from the documentation:

doc tf
doc series
doc parallel
doc feedback
doc pzmap

Transfer function g1:

num = 10 ; % numerator
den = [1 5 0] ; % denominator
g1 = tf(num, den)% tf: transfer function 

g1 =
 
     10
  ---------
  s^2 + 5 s
 
Continuous-time transfer function.

Transfer function g2:

num1 = [1 1] ; % numerator
den1 = [1 0] ; % denominator
g2 = tf(num1, den1)% tf: transfer function 

g2 =
 
  s + 1
  -----
    s
 
Continuous-time transfer function.

Transfer function sal, pal:

g1 and g2 are cascade, which means sal = g1 x g2 (multiplication). using series function you can compute this.

sal = series(g1, g2)

sal =
 
   10 s + 10
  -----------
  s^3 + 5 s^2
 
Continuous-time transfer function.

g1 and g2 are parallel, which means pal = g1 + g2 (addition). using parallel function you can compute this.

pal = parallel(g1, g2)

pal =
 
  s^3 + 6 s^2 + 15 s
  ------------------
     s^3 + 5 s^2
 
Continuous-time transfer function.

Closed loop transfer functions:

feedback function allows connecting models to calculate closed loop tf. Learn more about closed loop transfer function.

• feedback transfer function has a gain of 1.

pfeb = feedback(g1, g2, 1)

pfeb =
 
           10 s
  -----------------------
  s^3 + 5 s^2 - 10 s - 10
 
Continuous-time transfer function.

• feedback transfer function has a gain of -1.

nfeb = feedback(g1, g2, -1)

nfeb =
 
           10 s
  -----------------------
  s^3 + 5 s^2 + 10 s + 10
 
Continuous-time transfer function.

• Closed loop tf from g1 and 1 .

ufb = feedback(g1, g2, -1)

ufb =
 
           10 s
  -----------------------
  s^3 + 5 s^2 + 10 s + 10
 
Continuous-time transfer function.

Pole Zero Plots:

I assume you know about this plot.

pzmap(g1)

figure % new figure
pzmap(g2)

Hope this helps