Model Construction Palette:

The VIs in this section are used to construct various types of Models like State Space, Transfer Function, and Zero-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 system is by default considered continuous. Connecting a value to Sampling Time will change the system to discrete time using the given sampling time. There are terminals for the A, B, C, and D matrices of the State Space model. Once LabVIEW creates the State-Space model (available at the output terminal), it can be used for other functions and can be converted into other forms as is discussed further in this chapter. Here is an example of creating a State Space model. The output can be connected as input to numerous other functions in the Control Design toolkit.

The inputs can be either constants (on the Block Diagram) or controls (on the Front Panel). Most examples shown will use constants on the Block Diagram to make this manual more readable, however oftentimes using controls on the Front Panel will be more efficient. The constants, controls, and indicators can all be created by right-clicking on the desired terminal and selecting an option from the pop-up menu. The many special functions and data structures used in Control Design make this a very useful shortcut for creating the correct Controls and Indicators.

Many Control Design functions, including Construct State-Space Model, are polymorphic. A polymorphic VI will have the additional menu structure below the icon (in this figure above, labeled Numeric). This indicates that the input to the model is 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 has variables in it, and the value of the variables is controlled from the Front Panel. To select this option, simply click on the bottom of the icon with the operating tool and select the Symbolic option. The symbolic option is discussed in further detail later.

CD Construct Transfer Function Model:

The terminals are shown above. The important terminals are the Numerator and Denominator. As in the previous case, once the model is created, it can either be displayed on the Front Panel or connected to other functions. There is also a Symbolic input option in this case, and examples of it are available in further chapters. Transfer Function and associated inputs for the numerator and denominator are shown below. Notice the order of the coefficients.

In LabVIEW, the first element of the array is the coefficient of s0, the second element is coefficient of s1, the third is coefficient of s2, and so on. Only the State Space and Transfer function representation have been represented in the tutorial. Many other model types exist.