Specify Steady-State Operating Point for Response Optimization

稳态操作点是什么?

Anoperating pointof a dynamic system defines the states and root-level input signals of the model at a specific time. For example, in a car engine model, variables such as engine speed, throttle angle, engine temperature, and surrounding atmospheric conditions typically describe the operating point.

Asteady-state operating pointof a model, also called an equilibrium ortrimcondition, includes state variables that do not change with time.

A model can have several steady-state operating points. For example, a hanging damped pendulum has two steady-state operating points at which the pendulum position does not change with time. Astable steady-state operating pointoccurs when a pendulum hangs straight down. When the pendulum position deviates slightly, the pendulum always returns to equilibrium. In other words, small changes in the operating point do not cause the system to leave the region of good approximation around the equilibrium value.

When using optimization search to compute operating points for nonlinear systems, your initial guesses for the states and input levels must be near the desired operating point to ensure convergence.

When linearizing a model with multiple steady-state operating points, it is important to have the right operating point. For example, linearizing a pendulum model around the stable steady-state operating point produces a stable linear model, whereas linearizing around the unstable steady-state operating point produces an unstable linear model.

For more information on operating points, seeWhat Is an Operating Point?(Simulink Control Design)andWhat Is a Steady-State Operating Point?(Simulink Control Design).

Setting up a Steady-State Operating Point

This topic shows how to setup a steady-state operating point inResponse Optimizer. To improve the fit between the model and measured data, the model must be set to steady-state before optimization.

Open theResponse Optimizerand specify your requirements using the steps outlined inDesign Optimization to Meet Frequency-Domain Requirements (GUI).
In the toolstrip, clickOptionsand selectOperating Point Optionsfrom the drop down menu.
The followingOperating Pointdialog box opens.

TheOptimize at steady-state选择是checked by default when you open the operating point dialog. Use theStates,InputsandOutputstabs to specify the known parameters, bounds and deviations. For instance, there is one state in the above figure. Use the operating point dialog to specify that this state should be treated as an unknown, and it should be set to steady state. During response optimization, the operating point computation will vary this state to set it at steady-state.

You can also sync operating point specifications from your Simulink^®model using thebutton.
TheSimulink Design Optimization™software uses optimization methods to search for operating points in a model. Use theOptionstab of the dialog to specify these optimization methods. These options specify the optimization algorithm, tolerances, and stopping conditions. For instance, the optionGradient descent with projectionis often used to find the operating point for systems that use physical modeling. For more information, click on thebutton.
Having specified the operating point parameters, continue with the optimization workflow as described inDesign Optimization to Meet Frequency-Domain Requirements (GUI).