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## Re: [Question #707278]: Servo control of flexible membrane using ServoPIDController

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```Question #707278 on Yade changed:

Status: Open => Answered

Jan Stránský proposed the following answer:
> the number of nodes is not consistent with what I expected

You have to question whether expectation or realization is wrong.
Here the expectation seems correct, so the there is a problem in realization.

> more than one node can be created at the same position

Of course then can have same position, but they should not have same position.
The purpose of flexible membrane (or using PFacets in general) is that the PFacets are sharing the nodes.

> it is correct to use ' confining Stress * cylinder surface / number of
nodes' to represent the average force applied on each node?

Yes, it is correct to use the formula for "average force applied on each node".
However, if you have more nodes in one position, the result is meaningless..
So first you have to fix the usage of nodes.

> for r in range(nw):
>  for h in range(nh):
>     ...
>     V1=(O.bodies.append(gridNode(v1,rNode,...)))
>     V2=(O.bodies.append(gridNode(v2,rNode,...)))
>     V3=(O.bodies.append(gridNode(v3,rNode,...)))
>     V4=(O.bodies.append(gridNode(v4,rNode,...)))

The problem is here.
You need first to create nodes, one (not four) per each nw-nh cycle.
That way your nodes would not be duplicated.
Then you use these unique nodes to create gridConnections and PFacets.

Cheers
Jan

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