operpoint

Create operating point for Simulink model

Syntax

op = operpoint(mdl)

Description

op = operpoint(mdl) returns the operating point of Simulink^® model mdl. You can compute a linear model of your system at this operating point using the linearize function.

Examples

Create Operating Point for Simulink Model

Open Simulink model.

open_system('magball')

Create operating point for the model.

op = operpoint('magball')

op = 


 Operating point for the Model magball.
 (Time-Varying Components Evaluated at time t=0)

States: 
----------
   x   
_______
       
(1.) magball/Controller/PID Controller/Filter/Cont. Filter/Filter
   0   
(2.) magball/Controller/PID Controller/Integrator/Continuous/Integrator
14.0071
(3.) magball/Magnetic Ball Plant/Current
7.0036 
(4.) magball/Magnetic Ball Plant/dhdt
   0   
(5.) magball/Magnetic Ball Plant/height
 0.05  

Inputs: None 
----------

op lists each block in the model that has states. There are no root-level inports in this model, therefore op does not contain inputs.

Copy an Operating Point

You can create new operating-point variables in three ways:

• Using the operpoint function

• Using assignment with the equals (=) operator

• Using the copy function

Using the = operator results in linked variables that both point to the same underlying data. Using the copy function results in an independent operating-point object. In this example, create operating-point objects both ways, and examine their behavior.

mdl = 'watertank';
open_system(mdl)
op1 = operpoint(mdl)

op1 = 
 Operating point for the Model watertank.
 (Time-Varying Components Evaluated at time t=0)

States: 
----------
x
_
 
(1.) watertank/PID Controller/Integrator/Continuous/Integrator
0
(2.) watertank/Water-Tank System/H
1

Inputs: None 
----------

Create a new operating-point object using assignment with the = operator.

op2 = op1;

op2 is an operating-point object that points to the same underlying data as op1. Because of this link, you cannot independently change properties of the two operating-point objects. To see this, change a property of op2. For instance, change the value for the first state from 0 to 2. The change shows in the States section of the display.

op2.States(1).x = 2

op2 = 
 Operating point for the Model watertank.
 (Time-Varying Components Evaluated at time t=0)

States: 
----------
x
_
 
(1.) watertank/PID Controller/Integrator/Continuous/Integrator
2
(2.) watertank/Water-Tank System/H
1

Inputs: None 
----------

Examine the display of op1 to see that the corresponding property value of op1 also changes from 0 to 2.

op1

op1 = 
 Operating point for the Model watertank.
 (Time-Varying Components Evaluated at time t=0)

States: 
----------
x
_
 
(1.) watertank/PID Controller/Integrator/Continuous/Integrator
2
(2.) watertank/Water-Tank System/H
1

Inputs: None 
----------

To create an independent copy of an operating-point object, use the copy function.

op3 = copy(op1);

Now, when you change a property of op3, op1 does not change. For instance, change the value for the first state from 2 to 4.

op3.States(1).x = 4

op3 = 
 Operating point for the Model watertank.
 (Time-Varying Components Evaluated at time t=0)

States: 
----------
x
_
 
(1.) watertank/PID Controller/Integrator/Continuous/Integrator
4
(2.) watertank/Water-Tank System/H
1

Inputs: None 
----------

In op1, the corresponding value remains 2.

op1.States(1).x

ans = 
2

This copy behavior occurs because the operating-point object is a handle object. For more information about handle objects, see Handle Object Behavior.

Input Arguments

mdl — Simulink model name

character vector | string

Simulink model name, specified as a character vector or string. The model must be in the current working folder or on the MATLAB^® path.

Output Arguments

op — Operating point

OperatingPoint object

Operating point, returned as an OperatingPoint object with the following properties.

Property	Description
Model	Simulink model name, returned as a character vector.
States	State operating point, returned as a vector of state objects. Each entry in States represents the supported states of one Simulink block. For a list of supported states for operating point objects, see Simulink Model States Included in Operating Point Object. Note If the block has multiple named continuous states, States contains one structure for each named state. Each state object has the following fields: Field Description Nx (read only) Number of states in the block Block Block path, returned as a character vector. StateName State name x Values of all supported block states, returned as a vector of length Nx. Ts Sample time and offset of each supported block state, returned as a vector. For continuous-time systems, Ts is zero. SampleType State time rate, returned as one of the following: 'CSTATE' — Continuous-time state 'DSTATE' — Discrete-time state inReferencedModel Flag indicating whether the block is inside a reference model, returned as one of the following: 1 — Block is inside a reference model. 0 — Block is in the current model file. Description Block state description, returned as a character vector.
Inputs	Input level at the operating point, returned as a vector of input objects. Each entry in Inputs represents the input levels of one root-level inport block in the model. Each input object has the following fields: Field Description Nu (read only) Number of inport block signals Block Inport block name PortDimensions Dimension of signals accepted by the inport u Inport block input levels at the operating point, returned as a vector of length Nu. Description Inport block input description, returned as a character vector.
Time	Times at which any time-varying functions in the model are evaluated, returned as a vector.
Version	Object version number

Tips

• You can create new operating points of in three ways:

  • Construct a new object using the operpoint function.

  • Create a new variable by assignment with the equals (=) operator.

  • Copy an operating point object using the copy command.

  Using operpoint or copy creates a new, independent object. When you use assignment, there is a link between the old and new variable. For an example, see Copy an Operating Point.

• To extract state and input values from an operating point object, use getstatestruct and getinputstruct, respectively.

Alternative Functionality

The operpoint function returns an operating point with the initial state and input values of the model. To create an operating point that meets your application specifications, use the findop function. For more information, see Compute Steady-State Operating Points.

Version History

Introduced before R2006a

R2021b: PortWidth property of operating point inputs will be removed

The input PortWidth property of operating points will be removed in a future release. Use the new Nu property instead.

To update your code, change instances of PortWidth to Nu as shown in the following table.

Not Recommended	Recommended
op = operpoint("scdplane"); numIn = op.Inputs(1).PortWidth;	op = operpoint("scdplane"); numIn = op.Inputs(1).Nu;