# response: relative displacement

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Hi,

I want to use the relative displacement (magnitude) between node-pairs as a constraint. The values/bounds of the constraints are all the same.

For that, I see at least two possible ways:

1) Create a dresp1 for each DOF (1,2,3) and each Node with the displacement. Let's assume, I have 20 pairs --> 40 Nodes --> 120 dresp1-Cards

Also I write an equation: f(a,b,c,d,e,f,)= sqrt( (d-a)² + (e-b)² + (f-c)² ) and create a dresp2 for every pair (-->20 dresp2)

Last step is to create 20 design-constrain-cards.

2) I'm not sure if this is really suitable:

Create 3 dresp1-cards (one for every translational DOF) for all nodes on one side (each is one node of a node-pair), and the same for the second nodes of the pairs. I get 6 dresp1-Cards, each includes 20 nodes.

The equation is the same. One dresp2 should be enough for the whole problem. And also only one constraint.

But the question is HOW or IF optistruct understands, which nodes belong together. Is it done by the correct / same order for each of the 6 dresp1-Cards?

Is there also a more simple way for the same result?

One side-question:

what system (x,y,z) is the dresp1 for displacements using? Global? May I change that in Hyperview?

Thanks for help...

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I also have same issue

want to have optimization based on relative displacement

Can you explain me how did you do it using DRESP2?

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Hi Sagar,

For creating a user defined response, create two responses for the displacements. Create a dequation

f(a,b) = a - b

Come back to responses, create a new response with type "function". Select the dequation.

Click Edit before create. Choose responses in the bottom panel. Number of responses = 2. Double click each response field in the top panel and select the two responses created earlier.

Click return, followed by create. Use this new response like any other response in setting up the objective, constraints etc.

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Thank you Prakash

I also figured the same and tried on it.

Thank you again

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