SIMULINK BODE plot yields no response

Included in the ZIP file is a SIMULINK model of a 3 degree of freedom system along with the input data and appropriate gain values a, b, & c. The SIMULINK model generates both the pole/zero locations along with the corresponding BODE plots. 4 of the 5 BODE plots execute correctly. The 5th, "Product Bode", generates no response or output, yet viewing the output of mass1out.signal6 the timeseries output does exist.

Can anyone counsel me on how to get the BODE response of the signal that immediately follows the "Product" block in the top level block diagram "blkdiag3"? If the SIMULINK model requires more than what is included in the ZIP file let me know & I will try to provide the necessary files.

The following WARNING is generated pertaining to that signal:

Warning: The linearization input/output port specification of the 'blkdiag3/Product Bode' block resulted in linear system with a value of zero. Change the input/output specification, the blocks connecting the input and output points, or the snapshot time/event to yield a non-zero linear model. See the Simulink Control Design documentation for details on how to diagnose these conditions.

THANX, Jeff

[Jeff]

I changed my SNAPSHOT time & got something. I am somewhat new to SIMULINK so if anyone has any feedback to enlighten me on this issue I would be greatful.

THANX

[Michelle Wu]

Hi Jeff,

I think changing snapshot time is the right way to go. The warning is saying that the linearization of the 'Produce Bode' block resulted in linear system with a value of zero, which probably means that the linearization operating point was not chosen correctly. Using proper snapshot time should help extracting good operating points.

The documentation below is the resource center for Troubleshooting Linearization, and you might find it useful:

http://www.mathworks.com/help/releases/R2012b/slcontrol/ug/troubleshooting-linearization.html

Answer 1

[Jeff]

This was corrected by changing the SNAPSHOT time