Model construction

Model construction palette:

The VIs in this section are used to construct various types of Models like State Space, Transfer Function, andZero-Pole-Gain.

The Construct State Space Model and Construct Transfer Function Model functions are discussed below.

Cd construct state space model:

The terminals for the function are shown above. If the Sampling Time terminal is not connected, the systemis by default considered continuous. Connecting a value to Sampling Time will change the system to discrete time using the givensampling time. There are terminals for the A, B, C, and D matrices of the State Space model. Once LabVIEW creates the State-Spacemodel (available at the output terminal), it can be used for other functions and can be converted into other forms as is discussedfurther in this chapter.

Here is an example of creating a State Space model. The output can be connected as input to numerous otherfunctions in the Control Design toolkit.

The inputs can be either constants (on the Block Diagram) or controls (on the Front Panel). Most examplesshown will use constants on the Block Diagram to make this manual more readable, however oftentimes using controls on the Front Panelwill be more efficient. The constants, controls, and indicators can all be created by right-clicking on the desired terminal andselecting an option from the pop-up menu.

The many special functions and data structures used in Control Design make this a very useful shortcutfor creating the correct Controls and Indicators.

Many Control Design functions, including Construct State-Space Model, are polymorphic. A polymorphic VI willhave the additional menu structure below the icon (in this figure above, labeled Numeric). This indicates that the input to the modelis going to be in a numeric form.

Also available with the same function is the ability to enter the model in Symbolic form, meaning the input hasvariables in it, and the value of the variables is controlled from the Front Panel. To select this option, simply click on the bottomof the icon with the operating tool and select the Symbolic option.

Cd construct transfer function model:

The terminals are shown above. The important terminals are the Numerator and Denominator. As in the previouscase, once the model is created, it can either be displayed on the Front Panel or connected to other functions. There is also aSymbolic input option in this case, and examples of it are available in further chapters.

In LabVIEW, the first element of the array is the coefficient of s0, the second element is coefficient of s1, thethird is coefficient of s2, and so on.