ACTIVE VIBRATION •CONTROL OF SMART BEAM AND CIRCULAR PLATE

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 simply by adding or removing a little bit of energy. Thus, they 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 field of smart structures and its control has come up as an emerging area of research especially in aerospace industry. This dissertation deals with the experimental and numerical assessment of the vibration suppression of smart structures using piezoelectric materials. These materials 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. Active, control methods use external active devices to generate a second set of disturbance of equal amplitude but opposite phase to cancel the targeted unwanted disturbance. Unlike passive control, active control needs an external power supply to its control system. A typical active control system is composed of three basic component; sensors, actuators and controller. An experimental setup is developed to , measure and control the vibration of a cantilevered aluminum straight beam (L=263mm, W=29mm & T= 1.5mm). One pair of piezoelectric patches of size (25 x 25 x 0.5) is mounted on the beam near the fixed side and other pair of piezoelectric patches is mounted on the beam near the midpoint. The patches are bonded in a symmetrical fashion on the opposite sides of the beam. One of the patch acts as a sensor and the other acts as an actuator. The experimental setup consist of piezoelectric material, i.e., PZT patches, an Aluminium cantilever beam, Vibration control unit (Piezo sensing and actuation system), USB based Data acquisition card (NI make), a function generator and a computer with LAB View software version 8.6. The beam is excited by iii function generator at the free end in order to vibrate it in the first mode. As the beam deforms, an electric potential difference develops across the thickness of the sensor patch. The electric signal from the sensor is amplified by the control system to obtain the feedback voltage. This feedback voltage is supplied to the actuator patch. The force applied by the actuator induces a counteractive deformation to the beam structure and the amplitude of vibration is suppressed. Using this setup, Proportional Feedback Control was investigated for the cantilever beam, and a close co-relation was found between the theoretical predictions and experimental observations, thus establishing the authenticity of the theoretical derivations.