Past research on this subject has treated piezoelectric actuators as ideal devices that have tip displacements proportional to their input voltages, at any instant in time. This assumption neglected phase lag and amplitude change at high frequencies. This characteristic of any actuator may lead to coupled control system-structural system instability that limits the amount of active stiffness or active damping that can be obtained. The paper presents a method for simulating the coupled “electromechanical” system to predict rotordynamic stability and unbalance response along with control system stability. The piezoelectric actuators and their amplifiers are represented as equivalent linear electrical circuits. The electromechanical system modeling approach is utilized to correlate test results from a double overhung rotor rig at NASA Lewis. The test results also show the effectiveness of the control system for suppressing the unbalance response of two modes using active stiffness and active damping.

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