1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Block Diagram Manipulation

  1. Dec 11, 2014 #1
    Screen Shot 2014-12-11 at 18.12.51.png
    Hi there,

    I am struggling to understand how moving the summation (with H3) to before G1 will cause H3 to have to be divided by G1. I tried writing down how the equations would work to make sense of it but I still can't see how it works out.

    Please can someone explain this to me?

    Laura Morrison
    Last edited by a moderator: Dec 11, 2014
  2. jcsd
  3. Dec 11, 2014 #2


    User Avatar
    Gold Member

    If you move the summation block backwards, then the ENTIRE result of the summation block will be multiplied by G1, not just one of the terms

    you are multiplying V3 by H3, then subtracting it from V1*G1, so your expression looks like

    notice how the V3*H3 term is completely independant of the value of G1.

    If you move the summation block before G1, then the expression will be

    (V1-V3*H3)*G1 which is also V1*G1-V3*H3*G1

    notice how the second term will change as G1 changes.

    make sense?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted