Bode plot analysis for control engineering

Thread Starter


Joined Oct 20, 2014
Hello, I repeat the question again, kindly refer to this pdf file pages 6 & 7. How LM calculated on the last row of the tables on pages 6 & 7? thank you



Joined Dec 1, 2012
Just the last row? The slope of the graph is -20 db/dec. The first column was calculated to be 40 db. 1 decade corresponds to moving the decimal place by 1 so 0.1 rad/s + 1 decade = 1.0 rad/s, etc. Since you know the slope of the line is -20 db/dec you can calculate where it will be at the next point. So log(4/.1) = 1.6 decades, 1.6 decades * -20 db/dec is -32, 40 - 32 = 8 db. Repeat for the next columns in the table except the slope is different and the initial frequency is different.


Joined Jun 17, 2014

Sorry i didnt get to this until now...

Referring to your first post image controleng.png, they most likely want you to use the formula under "Eg" with the slopes given. This leads to the new LM points. So take the slopes as 'given' and just calculate the new LM points using the slopes and the previous LM point.

For the phase table it works the same way.