Simulink Control Design

Trimming and Linearization of Simulink Models

Trimming the Model

Linear control design typically requires you to consider multiple operating points to account for the various setpoints of a nonlinear model. Simulink Control Design provides a graphical interface to determine model operating points. You can:

You can use these operating points to initialize a simulation at steady state or as a basis for linearization and control design.

Trim, Linearization, and Control Design for an Aircraft 7:17
Trim and linearize a nonlinear aircraft model and use the resulting linear model to design a pitch rate damper controller.

Linearizing the Model

With Simulink Control Design you can linearize continuous, discrete, and multirate Simulink models. Using graphical signal annotations to specify loop opening and linearization inputs and outputs, you can linearize the whole model, a portion of the model, or a single block or subsystem. The signal annotations can be used for open-loop and closed-loop analysis. The annotations and analysis are nonintrusive and do not affect your model's simulation behavior.

Simulink Control Design automatically computes the linearized model and lets you visualize the results in a step response plot or Bode diagram. A Linearization Inspector is provided to visualize the impact of each block in your Simulink model on the linearization. You can fine-tune your results by specifying the linear behavior of any number of blocks in your model. The linear behavior can be specified as a matrix gain or LTI model, giving you flexibility to linearize Simulink models containing discontinuities or event-based components, such as Stateflow® charts or pulse-width modulation signal-based systems.

When working with Robust Control Toolbox™, you can compute an uncertain linear model by specifying uncertain values for transfer functions and gains directly in the model. The resulting uncertain linear model can be used to study the impact of uncertainty on the stability and performance of your control system.

All of these tools have a command-line API to write scripts for batch mode trimming and linearization. You can write these scripts yourself or automatically create MATLAB code from the graphical interface.

Batch Mode Trimming and Linearization 5:20
Create a script to do batch mode trimming and linearization of Simulink® models.

Computing the Frequency Response of the Model

Simulink Control Design provides tools for the simulation-based computation of a model’s frequency response. You can use these tools to:

  • Verify the results of a linearization
  • Compute the model’s frequency response when linearization techniques are not appropriate, such as with models described by strong discontinuities or event-based dynamics
  • Study the effects of excitation signal amplitude on a nonlinear system’s gain and phase characteristics

Simulink Control Design helps you construct the excitation signals, such as sine sweeps or chirp signals; run the simulations; collect the data; and calculate and plot the model’s frequency response. The algorithms used to compute the frequency response are designed to minimize the simulation time and support the Accelerator and Rapid Accelerator modes in Simulink to speed up the overall computation.

Frequency Response Estimation 6:15
Estimate the frequency response of a Simulink® model using simulation.

Next: Control System Design and Analysis in Simulink

Try Simulink Control Design

Get trial software

Automatic Tuning of Gain-Scheduled Controllers

View webinar

Learn Control System Design and Analysis in MATLAB and Simulink

View course