International Journal of Engineering and Technology Volume 1 No. 3, December, 2011 153 Copyright IJET © 2011 - IJET Publications UK Design and Analysis of Smart Structures for Active Vibration Control using Piezo-Crystals Deepak Chhabra 1 *, Pankaj Chandna 2 , Gian Bhushan 3 1* Department of Mechanical Engineering, University Institute of Engineering &Technology Maharshi Dayanand University, Rohtak,Haryana, INDIA 2,3 Department of Mechanical Engineering, National Institute of Technology Kurukshetra,Haryana, INDIA ABSTRACT The present work considers the active vibration control of beam like structures with laminated piezoelectric sensor and actuator layers bonded on top and bottom surfaces of the beam. A finite element model based on Euler-Bernoulli beam theory has been developed. The contribution of the piezoelectric sensor and actuator layers on the mass and stiffness of the beam has been considered with modeling of entire structure in a state space form. The designing of state/output feedback control by Pole placement technique and LQR optimal control approach are demonstrated to achieve the desired control. From the analysis, it has been observed that the LQR control scheme is very effective in controlling the vibration. Numerical simulation shows that including and varying the location of the sensor / actuator mass and stiffness from the free end to the fixed end on the beam produces a considerable change in the system’s structural vibration characteristics. The study illustrates that sufficient vibration suppression can be attained by means of the proposed methods. Key words: Piezoelectric material, FEM, LQR optimal control, Pole placement 1. INTRODUCTION Smart structures consist of highly distributed active device which comprises sensors and actuators either embedded or attached with an existing passive structure coupled by controller. The piezoelectric sensor senses the disturbance and generates an electric charge due to the direct piezoelectric effects. The piezoelectric actuator in turn produces a control force/moment due to the converse piezoelectric effects. If the control force is appropriate, the structural vibration may be suppressed. This technology has several applications such as active vibration and buckling control, shape control and active noise control. The finite element method is powerful tool for designing and analyzing smart structures. Both structural dynamics and control engineering need to be dealt to demonstrate smart structures. A three-dimensional finite element model of a smart structure with embedded piezoelectric sensors and actuators is developed for analyzing the response of active damping structures to steady state input. The closed loop numerical simulation in the frequency domain and in the time domain is attempted (Lim et al., 1997& 1999). Beam, plate and shell type elements have been developed incorporating the stiffness, mass and electromechanical coupling effects of the piezoelectric laminates (Narayanan S., Balamurugan V., 2003). Xu S.X, Koko T.S. (2004) proposed the design method for intelligent structures with finite element code and control design is carried out in state space form established on finite element modal analysis. Karagulle et al. (2004) introduced the active vibration control using APDL (ANSYS Parametric Design language) in ANSYS. They analyzed the results obtained from the APDL for the two-degrees of freedom system and found superiority with the Laplace transform method. Further, application of APDL to smart structures has also been investigated. Xing-Jian Dong et al., (2006) proposed a general analysis and design scheme of piezoelectric smart structures by using ANSYS and observer/Kalman filter identification (OKID) approach, and to experimentally study the feasibility and efficiency of OKID approach in the vibration control of piezoelectric smart structures. Vasques C.M.A., Rodrigues J. Dias (2006) studied the effectiveness of control strategies, constant gain and amplitude velocity feedback, and optimal control strategies, linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) controller, in order to suppress vibrations in smart beams. Kumar, K.R. and. Narayanan S, (2008) used a model-based linear quadratic regulator (LQR) controller for the optimal placement of collocated piezoelectric actuator–sensor pairs on a thin plate. They have also formulated the problem using the finite element method (FEM) as multi-input–multi-output (MIMO) model control..Manjunath T.C, Bandyopadhyay B. (2009) presented the modeling and design of multirate output feedback based sliding mode control scheme for the vibration control. Malgaca Levent (2010) integrated the control methods into the finite element solutions (ICFES) with ANSYS. The author analyzed the active control of free and forced vibrations for a smart laminated composite structure (SLCS) using ICFES simulation and compared with the experiment results.