Simulink Control Design™ - MathWorks

Design Two-Degree-of-Freedom PID Controllers

Use PID Tuner to tune two-degree-of-freedom PID Controller (2DOF) and Discrete PID

Controller (2DOF) blocks to achieve both good setpoint tracking and good disturbance

rejection.

About Two-Degree-of-Freedom PID Controllers

A two-degree-of-freedom PID compensator, commonly known as an ISA-PID compensator,

is equivalent to a feedforward compensator and a feedback compensator, as shown in the

following figure.

The feedforward compensator is PD and the feedback compensator is PID. In the PID

Controller (2DOF) and Discrete PID Controller (2DOF) blocks, the setpoint weights b and

c determine the strength of the proportional and derivative action in the feedforward

compensator. See the PID Controller (2DOF) and Discrete PID Controller (2DOF) block

reference pages for more information.

Tuning Two-Degree-of-Freedom PID Controllers

PID Tuner tunes the PID gains P, I, D, and N. For the PID Controller (2DOF) blocks, the

tuner also automatically tunes the setpoint weights b and c. You can use the same

techniques to refine and analyze the design that you use for tuning one-degree-of-freedom

PID controllers.

To tune a 2-DOF PID controller block in a Simulink model:

(^1) Double-click the block. In the block parameters dialog box, click Tune.
7 PID Controller Tuning