Actuators for Vibration Stabilization

The Final Focus vibration stabilization system will require actuators with sub-nanometer resolution, and high bandwidths. Piezo-electric actuators are available which meet these requirements.  Note that the resonant frequency of the Quad on the Piezo actuators is likely to be in the 100Hz range. It may be desirable to reduce the stiffness of the quad support to reduce the coupling of high frequencies.

A typical high load piezo actuator has the following properties:

A set of 6 actuators is required to control the 6 degrees of freedom of a solid body. If the solid body mode which produces beam deflection is only weakly coupled to the other modes, it may be possible use only a single feedback actuator.

A typical actuator and sensor arrangement is shown below:

(CanvasFormat.cv5)

There is no obvious way to mount the sensors or actuators to be orthoginal. The software will need to decode the orthoginal modes of motion and control. This sould be possible with a combination of modeling and measurements.

If the internal modes of the magnets couple strongly to the motion of the magnetic center, it may be necessary to use additional actuators to control these modes.

Page by Josef Frisch frisch@slac.stanford.edu 04/22/2002