National Instruments 370753C-01 Manual De Usuario

© National Instruments Corporation

Sys = feedback(Sys1,{Sys2})

The 

feedback( )

 function connects two dynamic systems together in a 

feedback loop as shown in Figure 3-4.

•

By default, feedback is defined to be negative.

•

Both systems must have the same sample rate.

•

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

•

When only one system is specified, it must be square (it must have an 
equal number of inputs and outputs).

Figure 3-4.  Feedback System Configuration

For an example of how to implement unity gain feedback using the 

feedback( )

 function, refer to Example 3-4.

tfsys2 = polynomial(-1)/polynomial([-2,-3]);

feedback(tfsys2)  # Note that this implements 

# negative unity gain feedback

ans (a state space system) =

A

-2 1

1 -4

B

0

1

C

e

1

u

1

y

1

Sys

1

Sys

+

–

Sys

2