PID Matlab scripts is not running

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germanbrain common
germanbrain common on 31 Dec 2020
Commented: Walter Roberson on 31 Dec 2020
%Closed loop Algorthim
%Error=Setpoint -Feedback
%Setpoint:5
%Feedback:0,1,2,3,4,5(my assumption)
previous_error=0;
integral=0;
kp=1;
ki=1;
kd=1;
sp=[5,5,5,5,5,5];
fb=[0,1,2,3,4,5];
error=[5,4,3,2,1,0];
dt=[0,1,2,3,4,5]
error=sp-fb
integral=(integral + error) * dt
derivative= (error - previous_error) / dt
output=(er*kp)+(ki*integral)+(kd*derivative)
previous_error= error
plot(output,dt)

Answers (1)

Walter Roberson
Walter Roberson on 31 Dec 2020
Change all * to .* and all / to ./
  1 Comment
Walter Roberson
Walter Roberson on 31 Dec 2020
format long g
%Closed loop Algorthim
%Error=Setpoint -Feedback
%Setpoint:5
%Feedback:0,1,2,3,4,5(my assumption)
previous_error=0;
integral=0;
kp=1;
ki=1;
kd=1;
sp=[5,5,5,5,5,5];
fb=[0,1,2,3,4,5];
error=[5,4,3,2,1,0];
dt=[0,1,2,3,4,5]
dt = 1×6
0 1 2 3 4 5
error=sp-fb
error = 1×6
5 4 3 2 1 0
integral=(integral + error) .* dt
integral = 1×6
0 4 6 6 4 0
derivative= (error - previous_error) ./ (dt+(dt==0)/5)
derivative = 1×6
25 4 1.5 0.666666666666667 0.25 0
output=(error.*kp)+(ki.*integral)+(kd.*derivative)
output = 1×6
30 12 10.5 8.66666666666667 5.25 0
previous_error= error
previous_error = 1×6
5 4 3 2 1 0
plot(dt,output)
The (dt+(dt==0)/5) clause is effectively: dt if dt is non-zero, 1/5 if dt is zero. It is there to prevent division by 0, which would give infinity. The 1/5 was chosen arbitrarily to not skew the plot too high but stil emphasize that the value is much higher than the others.

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