There is one part of PID code I don't understand

full code

The part is here

%% You can replace the follwoing five lines with your system/hardware/model

STATE1(i+1) = sum(PID); % sum PID term to calculate the first integration

state2(i+1) = (STATE1(i+1) + STATE1(i))*dt/2; % output after the first integrator

STATE2(i+1) = sum(state2); % sum output of first integrator to calculate the second integration

Output(i+1) = (STATE2(i+1) + STATE2(i))*dt/2; % output of the system after the second integrator

FeedBack(i+1) = state2(i+1)*feed1 + Output(i+1)*feed2;

I just don't understand what it means

why i have to integrate twitce to get the output and feedback?

I watch the block diagram but just simple pid controller and output input

Answer 1

[Luigi Emanuel di Grazia]

As can I see from the link you attached, the cose uses as plant a double integrator.

This is the plant to be controller, not the PID itself

[kung li lin]

Thank you very much !