How Does Moving the Summation Block Affect the Equation in Control Systems?

[LauraMorrison]

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?

Thanks,
Laura Morrison

 

[donpacino]

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

notice how the V3*H3 term is completely independent 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?