Simulink Design Optimization

Optimizing Simulink Model Responses

With Simulink Design Optimization, you can tune Simulink model parameters to meet time-domain requirements, frequency-domain requirements, or both simultaneously. Using the Design Optimization tool in Simulink Design Optimization, you can add and edit design requirements graphically or by entering tabular data, and then run the optimization. The graphical tool also lets you monitor optimization progress. It shows plots for each requirement as well as the optimization status in a single view.

As with parameter estimation, you can simultaneously optimize multiple model parameters, including scalars, vectors, matrices, or fields of structured variables defined in the MATLAB or Simulink model workspace. You can also specify minimum and maximum values for each parameter.

You can choose from a variety of optimization algorithms, such as gradient descent, nonlinear least squares, simplex search, and, with Global Optimization Toolbox, pattern search. You can adjust optimization algorithm settings, such as convergence tolerances and number of iterations, to improve optimization performance. To accelerate the process by performing the optimization on multiple cores or processors, you can use Parallel Computing Toolbox with Simulink Design Optimization.

Tuning Simulink Model Parameters to Meet Time-Domain Requirements

You can add a new time-domain design requirement by selecting a requirement type and specifying the model signals to use for evaluating the requirement. Simulink Design Optimization lets you specify time-domain design requirements on a signal by:

  • Enforcing upper and lower amplitude bounds
  • Specifying step response characteristics
  • Tracking a reference signal
  • Specifying a custom signal requirement

You can edit requirements graphically or by entering numeric values. For example, to edit a step response envelope requirement, you can graphically adjust the bounds or enter values for rise time, overshoot, settling time, and other parameters that define step response characteristics.

You can set up the optimization to meet time-domain design requirements directly from the graphical tool, without adding any blocks to the model. You can also use several design requirements simultaneously to optimize multiple design criteria.

During the optimization, the product updates the plots for each design requirement so you can visually monitor optimization progress in one window.

Nonlinear model for which parameters are optimized using the Design Optimization tool to meet several time domain requirements simultaneously.
Nonlinear model (top) for which parameters are optimized using the Design Optimization tool (bottom) to meet several time-domain objectives (orange box) simultaneously. Optimization minimizes the cross-sectional area (design variable AC), while satisfying constraints on pressure and piston position.

Tuning Simulink Model Parameters to Meet Frequency-Domain Requirements

For frequency-domain optimization, you can use Simulink Design Optimization with Simulink Control Design to linearize a Simulink model and use the resulting linear model to evaluate the following requirements:

  • Frequency-dependent upper and lower magnitude bounds
  • Gain and phase margin bounds
  • Natural frequency and damping ratio bounds
  • Bounds on the magnitude of the system’s singular values

You can optimize not only the frequency-domain characteristics of the control system, but also the frequency response of the plant model.

Simulink model with a rectifier filter, for which parameters R (resistance), L (inductance), and C (capacitance) are optimized using the graphical tool to meet frequency-domain requirements.
Simulink model with a rectifier filter (top, red block), for which parameters R (resistance), L (inductance), and C (capacitance) are optimized using the graphical tool (bottom) to meet frequency-domain requirements.

Optimizing Time-Domain and Frequency-Domain Responses Simultaneously

Simulink Design Optimization lets you manage tradeoffs among requirements, such as stability, robustness, and performance, as you fine-tune your design.

Optimizing a Flight Control System 4:53
Optimize the parameters of a flight control system to simultaneously meet time-domain and frequency-domain design requirements.

You can specify a variety of time-domain and frequency-domain requirements to optimize system performance. Typical requirements include gain and phase margins, damping ratio, minimum bandwidth, high-frequency rolloff, and constraints on the step or impulse responses. You can optimize the poles, zeros, and gains of your compensators, or directly tune the parameters of the corresponding blocks in Simulink. Plots comparing the current response with your design requirements help you monitor progress while the optimization runs.

Next: Meeting Requirements Specified by Model Verification Blocks

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