# Help for solving a block Diagram algebra - Control Systems

#### IlpolpoPaul

Joined Nov 20, 2015
6
I am having some difficulties with solving this block diagram. It is required that the node 1 goes at point 2 and the block S moves out of the feedback loop (to 3 and 4). Can anyone help me and draw the next equivalent block diagrams. What should I do, what will happen when I move the node 1 at the point 2?
I tried to solve this problem but I am not sure if it is correct! Any kind of information will be of great help Thanks in advance!

#### WBahn

Joined Mar 31, 2012
28,469
Your block diagram makes no sense. Look at the (p+2) block in the upper left and the multiplication junction to the right of it. You have signals coming into the junction from below and from the right, so the line connecting the junction to the (p+2) block must be an output from the junction to the block. But that means that the (p+2) block has three signals coming into it and none coming out of it. If the line connecting it to the junction is going the other way, then you have three signals going into the junction and none coming out of it. Plus, having two signals coming into the (p+2) block to begin with is nonsensical -- what signal is getting multiplied by (p+2)?

#### IlpolpoPaul

Joined Nov 20, 2015
6
Your block diagram makes no sense. Look at the (p+2) block in the upper left and the multiplication junction to the right of it. You have signals coming into the junction from below and from the right, so the line connecting the junction to the (p+2) block must be an output from the junction to the block. But that means that the (p+2) block has three signals coming into it and none coming out of it. If the line connecting it to the junction is going the other way, then you have three signals going into the junction and none coming out of it. Plus, having two signals coming into the (p+2) block to begin with is nonsensical -- what signal is getting multiplied by (p+2)?
Indeed! I see now that the block diagram is kinda weird, thank you for the clarification. But, maybe this homework is given to us just to show that we have understood the block diagram reduction/simplification operations/rules (move blocks and nodes). Even though I know that the block diagram is not as it should be, for me it is very important to make the two operations, node 1 moves to point 2 and the block S to points 3,4 (as shown in the diagram with lines). I tried it but I doubt that it is 100% correct! It would be of great help if you can help me

#### IlpolpoPaul

Joined Nov 20, 2015
6
I tried again after watching some tutorials on Youtube! I hope that this is a better solution. I would kindly ask anyone who has knowledge on Block Diagrams to give me some suggestions and to tell me if the block diagram I attached is correct or not! I am asking particularly for the movement of the node 1 to point 2!

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#### WBahn

Joined Mar 31, 2012
28,469
How can we tell you if it is correct when the diagram you started with is not valid to begin with?

#### IlpolpoPaul

Joined Nov 20, 2015
6
How can we tell you if it is correct when the diagram you started with is not valid to begin with?
I fully understand you Sir, I know that there many mistakes (signals directions, summing points are missing) but unfortunately I do not have what to do It is my professor's fault, and I'm afraid that this diagram might be part of my next week's exam! I'm pissed off but I have to do something just to get those damn points because my grade will get lower because of my professor's fault!
I just want to have your opinion about the movement of the node 1 to point 2 that I made in the picture I attached in the previous post (please assume that the other part of the diagram is correct).

#### hht

Joined Jan 19, 2017
6
I am new in this forum. I found this thread via google but I try to understand at what subforum it is. Would you like to help me.It seems it is just under the "threads". So from the home page of the forum how could I find this topic?

Thank you.

#### ScottWang

Joined Aug 23, 2012
7,342
I am new in this forum. I found this thread via google but I try to understand at what subforum it is. Would you like to help me.It seems it is just under the "threads". So from the home page of the forum how could I find this topic?

Thank you.
Our discussion main forum is http://forum.allaboutcircuits.com/
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