Feedback control laws for proof-mass electro-dynamic actuators

This paper presents a simulation study about the stability and performance of a control system with five decentralized feedback control units mounted on a flat panel in order to reduce its vibration and sound radiation. Each control unit consists of a proof-mass electrodynamic actuator with a velocity sensor at its base. The aim is to design light, simple, robust and low cost control units which can be attached in large numbers to flexible structures in order to control their spatially averaged response and sound radiation at low audio-frequencies. Thus four basic feedback control functions have been studied: (a) proportional, (b) integral (c) derivative and (d) PID. Two types of controllers have been considered which drive the actuators either with current or voltage signals. This paper shows that proportional control loops generate active damping which effectively reduces the frequency averaged response of the plate except at the fundamental resonance frequency of the actuator and at higher frequencies where control spillover effects take place. The PID control loops can mitigate these control spillover problems with no loss of control performance. Finally, integral and derivative control loops are characterized by important stability issues and also produce little control effects since they generate active stiffness and active mass effects which just shift the resonances of the plate structure.