ACTUATOR WITH BUILT-IN VISCOUS DAMPING FOR ISOLATION AND STRUCTURAL CONTROL

The development and experimental application of an actuator with built -in viscous damping are described. A passive damper was modified to cr eate a novel actuation device for two applications: isolation and stru ctural control. The device uses the same fluid for damping and as: a h ydraulic lever for a voice coil actuator. For vibration suppression, a ctive enhancement of the inherent passive damping can optimize broadba nd damping or target certain frequencies. For vibration isolation appl ications, the passive stiffness can be chosen for small gravity sag an d the active control designed to provide reduced mount transmissibilit y over a broad- or narrow-frequency range. Lumped parameter models cap turing structural and fluid effects are presented. Component tests of free stroke, blocked force, and passive complex stiffness are used to update assumed model parameters. The structural damping effectiveness of the new actuator is shown to be that of a typical passive viscous d amper and that of an actively damped piezoelectric strut with load cel l feedback in a complex truss structure. Open- and closed-loop results are presented for a force isolation application showing an 8-dB passi ve and a 20-dB active improvement over an undamped mount.