G = tf(10,[1 3 10]);
C = pid(0.2,1.5);
T = feedback(G*C,1);
With this model, you can obtain the closed-loop response from r to y. However, you
cannot analyze the open-loop response at the plant input or simulate the rejection of a
step disturbance at the plant input. To enable such analysis, mark the signal u as an
analysis point by inserting an AnalysisPoint block between the plant and controller.
AP = AnalysisPoint('u');
T = feedback(GAPC,1);
T.OutputName = 'y';
The plant input, u, is now available for analysis.
In creating the model T, you manually created the analysis point block AP and explicitly
included it in the feedback loop. When you combine models using the connect command,
you can instruct the software to insert analysis points automatically at the locations you
specify. For more information, see connect.
Specify Analysis Points for Simulink Models
In Simulink, you can mark analysis points either explicitly in the block diagram, or
programmatically using the addPoint command for slLinearizer or slTuner
interfaces.
To mark an analysis point explicitly in the model, right-click a signal and, under Linear
Analysis Points, select an analysis point type.
Mark Signals of Interest for Control System Analysis and Design