Hi @Rubayet
The liquid level system can be represented as a first-order transfer function. Consequently, it will display an exponential response. Given that the system's time constant (τ) is 1758 seconds, it will take approximately 5 times τ for the system to converge to a steady-state value. By the way, have you ensured that the system has been linearized and modeled accurately?
im1 = imread("image1.png");
im2 = imcrop(im1, [150 200 1500 175]);
imshow(im2)
% time constant of 1st-order system
tau = 1758; % it will settle around 5*tau = 8790 sec
% Gains
G1 = 0.0034;
G2 = 5.34;
% liquid level process
Gp = tf(140, [tau, 1])
% open-loop system
Gol = G1*Gp*G2;
% plot response
figure
step(Gol, 10*tau), grid on
xl = xline(5*tau, '--r', {'Settling Time'});
xl.LabelVerticalAlignment = 'middle';
xl.LabelHorizontalAlignment = 'center';
