National Instruments 370753C-01

Chapter 3 Building System Connections

is created by appending the inputs, outputs, and states of Sys1 and Sys2.

A larger number of systems can be appended by appending two at a time.

• Both systems must have the same sample rate.

• Improper dynamic systems—systems with more zeros than poles—are

not allowed, because Sys is represented in state-space form.

The output is a dynamic system in block form as shown in Figure 3-2.

Figure 3-2. Output of a Dynamic System

For an example of how to use append( ), refer to Example 3-2.

Example 3-2 Using append( )

s3 = system(makepoly([1,2]), makepoly([1,3,5,0]));

s4 = system(makepoly([1]), makepoly([1,4,4]));

sap = append(s3,s4);

In the following discussion, the component state-space matrices of Sys1 are

denoted by A1, B1, C1, and D1, and you follow the same convention for Sys2.

The algorithm for append( ) is done strictly using the state-space

representations of Sys1 and Sys2. For this reason, Sys1 and Sys2 cannot

be improper transfer functions (transfer functions having more zeros than

poles). The component A, B, C, and D matrices of Sys1 and Sys2 are

extracted using the abcd( ) function. The A, B, C, and D matrices

comprising Sys are obtained as shown in the following example, where the

zero matrix elements span as many rows and columns as necessary.

Sys