UE5 Control Rig - Make controls move bones localy and following them controlled by the parent

[Online_Learner_Iqpjr (PEZERIL Erwann)]

Hello, I’m currently trying to rig a robotic arm composed of an IK for the arm, a ball joint for the “hand”, and 2 rails driving 4 hooks.

The IK is ok, the hand aim a target, the hooks get closer with a float control, same for the 2 rails. The problem is when I move and rotate the hand (with IK or with Aim), rails and hooks don’t follow. I tried to make them parent-child, invert and add transforms, etc… Nothing works.

Here’s images of the way i make rails and hooks move. Bones are attached to their floats translation so here’s why it doesn’t move with the parent.

I think it has to move in the space with the cube control and locally with the arrows but it means making the arrow move with the cube and notmaking bones move with them.
I’m not experimented with rigging nor with blueprint, i try to learn.

[Enter_Reality]

You can try to lerp the movement of the rails based on the handIK location.
Get the handIK XY values ( assuming Z is Up ) and set a Lerp for both values, where over a value you start moving the rail by using the handIK traslation value ( using the same axis ), maybe multiplying the HandIK traslation by 0.75 or 0.5, so that the rail will follow along.
So basically, if the hand goes too far, the rail will move accordingly.
From the image is not clear which are the hooks.