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Automated Tuning Design

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Supported Automated Tuning Methods Loading and Displaying the DC Motor Example for Automated Tuning Applying Automated PID Tuning

Supported Automated Tuning Methods

The SISO Design Tool simplifies the task of designing and tuning compensators. There are five automated tuning methods in the SISO Design Tool to help you design an initial stabilizing compensator for a SISO loop on-the-fly or refine existing compensator design so that it satisfies a certain user-defined design specification.

The available tuning methods are:

• Optimization-based tuning

• PID tuning

• Internal Model Control (IMC) tuning

• LQG synthesis

• Loop shaping

For a detailed discussion of these, see Automated Tuning in the Control System ToolboxUser's Guide.

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Loading and Displaying the DC Motor Example for Automated Tuning

Follow these steps to load and display the DC Motor example for automated tuning:

1. If you have not yet built the DC Motor example, type

   load ltiexamples
   

2. To open the SISO Design Tool and import the DC motor, type

   sisotool(sys_dc)
   

   at the MATLAB prompt. This opens both the SISO Design Task node on the Control and Estimation Tools Manager and the Graphical Tuning window with sys_dc loaded.

3. Click the Analysis Plots tab to set the analysis plots. Select the plot type as Step for Plot 1. Then, check the box for plot 1 to the left of Closed-Loop r to y, as shown in the following figure, to open a linked LTI Viewer with the closed-loop step response from reference signal r to output signal y.

   

4. In the LTI Viewer that appears, use the right-click menu to add rise time and steady state values to your plot.

Step Response When Compensator = 1

Note that by default, the compensator is 1 and unit negative feedback is used (see Architecture in the Control System Toolbox User's Guide). When a unit step is applied to the setpoint change, the steady state value of the system output is 0.0361, which is far from the setpoint, and its rise time is 0.589.

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Applying Automated PID Tuning

1. Click the Automated Tuning tab.

2. Select PID tuning from the Design method list.

3. Leave C as the default compensator.

   

You can choose from the following controller types:

• P

• PI

• PID

• PID with derivative filter

Designing a Proportional-Only Controller

1. For the controller type, click the P option button for proportional-only control ( ).

2. Select the Ziegler-Nichols open loop tuning algorithm from the Tuning algorithm list.

3. Click the Set-Point Tracking option button.

4. Click Update Compensator. The LTI Viewer is updated with the application of PID automated tuning with P and the compensator value is now 205.49.

Note that the rise time is arrived at in just 0.0774 seconds, compared with 0.589 when C=1. However, the steady state value of 0.885 can still be improved by setting the automated tuning controller type to PI, as described in Designing a Proportional-Integral Controller.

Designing a Proportional-Integral Controller

1. For the controller type, click the PI option button for proportional-integral control ( ).

2. Select the Ziegler-Nichols open loop tuning algorithm from the Tuning algorithm list.

3. Click the Set-Point Tracking option button.

4. Click Update Compensator. The LTI Viewer is updated with the application of PID automated tuning with PI and the compensator value is now .

Although the rise time has increased slightly (0.0876), the steady state value is 1. Applying automated tuning using PID tuning set to PI will guarantee zero offset.

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Nichols Plot Design

Multi-Loop Compensator Design

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