Cross coupling between horizontal and vertical motion
Right now, we use three OSEM to measure three degrees of freedom (DOF) for the vertical motion of the floating plate. Apparently, there is a quite significant cross coupling between the horizontal motion and the vertical one. We have to use a strong eddy-current damping to damp the horizontal motion, otherwise the motion of the plate is highly oscillatory.
To remove the eddy-current damping, we need to sense the horizontal motion and feedback control it. The current three OSEMs are not enough to measure all six DOFs. There are two possible approaches to sense all DOFs.
- Add three more OSEM in the horizontal direction.
- Design new OSEM that is compact and able to measure multiple DOFs.
It is quite tricky to add 6 OSEMs in the current setup due to geometry constraint. Here we will use the second approach and design a new OSEM. The design goes as follows: