For and Break Stuck

Hi everybody. I wrote a code but something is going wrong, I need at that point.

I need to stop the code at the gain of 0.5 and I need to take the values that I need as P and D. But The code does not do what I need. It always work around i = 65 and j = 65. What is the error ?

clear all; clc;

Kp = -10:0.31:10;
Kd = -10:0.31:10;

% n = [Kd Kp];
% d = [(1+Kd) (Kp+1)];
%
% [r,p,k] = residue(n,d);

A = zeros(length(Kp), length(Kd));

for i = 1:length(Kp)
    for j = 1:length(Kd)

          n = [Kd(j) Kp(i)];
          d = [(1+Kd(j)) (Kp(i)+1)];

          [r,p,k] = residue(n,d);
          S = sum(r);

          TF = tf(n,d);

          [z, gain] = zero(TF);

          if gain == 0.5
              break;
          end

          % if S<0.6 && S>0.4
          %     A(i,j) = 1;
          % else
          %     A(i,j) = 0;
          % end
      end
  end

Answer 1

[James Tursa]

It is often better to use tolerances for floating point comparisons, unless you wrote the underlying code and you know that the result must be exactly 0.5. So this test

if gain == 0.5

should probably look something like this instead

if abs(gain - 0.5) < tol  % for some appropriate value of tol

[Stephen23]

Berkcan Oz's "Answer" moved here:

What do you mean ? What should I change ?

[Stephen23]

@Berkcan Oz: your code contains exactly one instance of the operator ==. Change it as James Tursa recommended.

[Berkcan Oz]

What is tol ? How to define ?

[Stephen23]

You could start with tol=1e-5;

[Berkcan Oz]

Now, I did this but this give me a system that starts at gain almost 0.5 and goes 1. I need to make it from 0 to 0.5. Not from 0.5 to 1. What should I do ?

    clear all; clc;

Kp = -10:0.31:10;
Kd = -10:0.31:10;
tol = 1e-5;
A = zeros(length(Kp), length(Kd));

for i = 1:length(Kp)
    for j = 1:length(Kd)

n = [Kd(j) Kp(i)];
d = [(1+Kd(j)) (Kp(i)+1)];

[r,p,k] = residue(n,d);
S = sum(r);

TF = tf(n,d);

[z, gain] = zero(TF);

if gain <0.6 && gain>0.4
    break;
end
    end
end

sys = tf(n,d)
step(sys);
grid;