Simulink Control Design™ - MathWorks

Controller Tuning with LOOPTUNE

You can also use looptune to tune control systems modeled in Simulink. The looptune

workflow is very similar to the systune workflow. One difference is that looptune needs

to know the boundary between the plant and controller, which is specified in terms of

controls and measurements signals. For a single loop the performance is essentially

captured by the response time, or equivalently by the open-loop crossover frequency.

Based on first-order characteristics the crossover frequency should exceed 1 rad/s for the

closed-loop response to settle in less than 5 seconds. You can therefore tune the PID loop

using 1 rad/s as target 0-dB crossover frequency.

% Mark the signal "u" as a point of interest

addPoint(ST0,'u')

% Tune the controller parameters

Control = 'u';

Measurement = 'Speed';

wc = 1;

ST1 = looptune(ST0,Control,Measurement,wc);

Final: Peak gain = 0.979, Iterations = 4

Achieved target gain value TargetGain=1.

Again the final value is close to 1, indicating that the target control bandwidth was

achieved. As with systune, use getIOTransfer to compute and plot the closed-loop

response from speed command to actual speed. The result is very similar to that obtained

with systune.

T0 = getIOTransfer(ST0,'Ref','Speed');

T1 = getIOTransfer(ST1,'Ref','Speed');

step(T0,T1)

legend('Initial','Tuned')

13 Control System Tuning Examples