Destabilization of velocity feedback controllers with stroke limited inertial actuators

It has been observed when using inertial actuators for the active reduction of structural vibration, that velocity feedback controllers are liable to become unstable if the actuator is subject to stroke saturation. This article presents a simple nonlinear, time domain model of an inertial actuator mounted on a single degree of freedom system. At low amplitudes the actuator, when used in a velocity feedback control loop, increases the effective damping of the structure. At higher amplitudes the system is shown to become unstable, however, and generates limit cycle oscillations having a predictable frequency.