Help problem of particle position

[FZMv587]

Hi bro.
I make a rope and move it in runtime.
Now,i want to get some particles world position but i failed.

I use   

Code:

actorIndex = rope.blueprint.groups[0].particleIndices[0]

to get actor index of this particle.

And i use

Code:

solverIndex = actor.solverIndices[actorIndex]

to get solver index of this particle

Finally,i use

Code:

position = actor.GetParticlePosition(solverIndex);

to get world position of this particle

Problem is this position is not change when i move rope, so i think maybe it is a local position.
Could you help me to get world position of particle?
Think you,waiting for you repose.