National Instruments 370753C-01 Manual De Usuario

afeedback( )

, 

append( )

, 

connect( )

, and 

feedback( )

 connect 

dynamic systems in state–space or transfer–function form to produce a 
larger system in state-space form. The following restrictions apply to all 
of these functions:

•

Both systems must have the same sample rate.

•

Improper dynamic systems (systems with more zeros than poles) are 
not allowed.

•

If the systems to be connected are in transfer-function form, they must 
be expressed in the same dependent variable.

In describing the algorithms used in these connection functions, we will 
often refer to the component matrices of a state-space system 

Sys

1

 as 

A

1

, 

B

1

, 

C

1

, and 

D

1

.

Sys = afeedback(Sys1,{Sys2})

The

 afeedback( )

 function connects two dynamic systems in a feedback 

loop, and obtains a single system representation for the complex loop. 

Sys

is organized as shown in Figure 3-1. Additional external inputs to the 

feedback path are included with outputs from the feedforward path. 
Figure 3-1 illustrates that outputs of the feedback path system are included 
with forward path outputs

. 

For an example of how to use 

afeedback( )

, 

refer to Example 3-1. 

Figure 3-1.  afeedback System Configuration

e

1

e

2

u

1

u

2

y

1

y

2

Sys

1

Sys

+

+

+

–

Sys

2