Distributed four-layer PVDF actuator/sensor arrangement for the control of beam motion

Lee, Young-Sup, Elliott, Stephen J. and Gardonio, Paolo (2001) Distributed four-layer PVDF actuator/sensor arrangement for the control of beam motion. Rao, Vittal S. (ed.) In Proceedings of SPIE. Smart Structures and Materials 2001: Modeling, Signal Processing, and Control in Smart Structures. SPIE - The International Society for Optical Engineering. pp. 284-294 . (doi:10.1117/12.436483).

Abstract

This paper presents a study of a distributed arrangement of double PVDF actuator/sensor pairs bonded on a cantilever beam for the control of vibration at the tip. The arrangement of a single PVDF actuator/sensor pair, in practice, is known to be non-minimum phase due to coupling between in-plane motion and out-of-plane motion. This means that a single pair arrangement does not have the conventional driving-point collocated system property. The stability and performance of the arrangement are limited by finite feedback gains, which can be used with direct velocity feedback control. A double pair arrangement using four layers of PVDF has thus been suggested to overcome this problem. Theoretically, when both the actuator pair and the sensor pair are working out-of-phase, then the response becomes minimum phase since in-plane motion cannot be excited or detected. A smart beam with double PVDF actuator/sensor pairs has been implemented. A triangular shaped actuator/sensor pair was bonded on each side of the beam. The initial experimental measurements with individual pairs of transducers showed a good reciprocity and a strong coupling between out-of-plane and in-plane responses. All the four layers have then been used as out-of-phase actuators and sensors to attempt to measure only the out-of-plane response. However, in practice, this compensation method was found not to discriminate against the in-plane response, due to the direct coupling between the actuation and sensing transducers due to their finite thickness and compliance. Therefore, the four layers smart beam does not have a minimum phase property. A new arrangement of actuator/sensor pair for in-plane compensation is then suggested and discussed.

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