ACTIVE VIBRATION CONTROL OF SHELL

Abstract

Recent advances in materials science have led to the development of a range of functional materials which when embedded into a structure can produce and monitor structural deformations. These structures have been labeled `smart structures' and such materials are known as `smart materials'. Smart materials have the ability to change shape or size dramatically thus have the capability to `feel' a stimulus and suitably react to it just like any living organism. Each individual type of smart material has a different property which can be significantly altered, such as viscosity, volume, and conductivity. The property that can be significantly altered influences the likely applications of the smart material. In the recent years, there has been great interest among engineers to builds `smart structure' that have capability of sensing and actuating in a controlled manner in response to an input and adjust their properties and shapes to the changing environment. The adjustments in such structures may be made through the use of actuators. The attenuation of vibrations is a problem of primary importance in many engineering fields, particularly so in aerospace applications. This work deals with the experimental assessment of suppression of vibration using piezoelectric patches as smart material. These patches are usually thin wafers, which are poled in the thickness direction and bonded to the surfaces of the host structures. Piezoelectric material such as PZT patch (Piezoceramic patch) is equally effective as sensor and actuator. PZT patch is useful in vibration control because of advantages of high stiffness, light weight, low power consumption and easy implementation.PZT patches are considered to be bonded on the top and bottom surfaces of the host structure. These patches act as sensors and actuators. An experimental setup has been fabricated to demonstrate the use of piezoelectric material like PZT patch in the active vibration control application. This setup includes the piezoelectric material i.e. PZT patches, data acquisition card, signal conditioner and a computer with LabVIEW software. The aluminum semi-circular cylindrical shell is mounted in the cantilever configuration and excited manually by tapping. The vibration of the shell is controlled by the piezo actuation system by increasing the gain. Control strategies such as proportional control have been implemented. In the control strategies, the feedback voltage is generated as a function of position quantities. As the shell deforms, due to external applied loads, the bonded piezoelectric film (sensor) also vi deforms, and due to its constitutive behavior, it develops a voltage proportional to the applied force. The voltage is then amplified by a control system, to obtain the feedback voltage. This feedback voltage is supplied to the other piezoelectric film (actuator) that induces a counteractive deformation to the shell structure and the amplitude of vibration is suppressed.