Tune at a Different Operating Point
By default, PID Tuner linearizes your plant and designs a controller at the operating
point specified by the initial conditions in your Simulink model. Sometimes, this operating
point differs from the operating point for which you want to design a controller. For
example, you want to design a controller for your system at steady-state. However, the
Simulink model is not generally at steady-state at the initial condition. In this case,
change the operating point that PID Tuner uses for linearizing your plant and designing
a controller.To set a new operating point for PID Tuner, use one of the following methods. The
method you choose depends upon the information you have about your desired operating
point.Known State Values Yield the Desired Operating Conditions
In this case, set the state values in the model directly.(^1) Close PID Tuner.
(^2) Set the initial conditions of the components of your model to the values that yield the
desired operating conditions.
(^3) Click Tune in the PID controller dialog box to open PID Tuner. PID Tuner linearizes
the plant using the new default operating point and designs a new initial controller
for the new linear plant model.
After PID Tuner generates a new initial controller design, continue from “Analyze Design
in PID Tuner” on page 7-9.
Model Reaches Desired Operating Conditions at a Finite Time
In this case, use PID Tuner to relinearize the model at a particular simulation time.
(^1) In the PID Tuner tab, in the Plant menu, select Re-linearize Closed Loop.
2
In the Closed Loop Re-Linearization tab, click Run Simulation to simulate
the model for the time specified in the Simulation Time text box.
PID Tuner plots the error signal as a function of time. You can use this plot to
identify a time at which the model is in steady-state. Slide the vertical bar to a
snapshot time at which you want to linearize the model.
Tune at a Different Operating Point