Nonlinear vibrations of a stroke-saturated inertial actuator

Proof-mass actuators are typically used to supply an external control force to a structure,for the purpose of vibration suppression. These devices comprise a proof-mass suspended in a magnetic field that is accelerated in order to provide a reaction force on the actuator casing and the structure itself. If the actuator stroke length is reached or exceeded, the proof-mass will hit the end stops, resulting in a nonlinear phenomenon known as stroke saturation. In this paper, a theoretical and experimental investigation into the actuator’s dynamical behaviour is undertaken. First, the blocked inertial force of the actuator in response to an input voltage was measured experimentally using a variety of excitation amplitudes and frequencies. An analysis was conducted in the time- and frequency-domains, and the first-order force-voltage FRF of the actuator was ascertained for each excitation amplitude. The information provided by the analysis was then used to estimate the parameters for a linear piecewise stiffness model of the actuator, in order to simulate the time-domain response. Finally, a comparison of the simulated and measured signals is conducted to establish the accuracy of the model.