Vibration Reduction of a Simply Supported Beam with Electromagnetic Actuator

Abstract

Structural vibration is one of the major problems in the field of structural engineering. The vibration of structures can be minimized in two ways namely passive vibration control and active vibration control. Passive vibration control doesn’t depend upon the output of the system. Generally springs, viscous dampers etc. are used for reducing the amplitude of vibration. Active vibration control depends upon the output of the system. In this study an attempt will be made to minimize the amplitude of vibration of simply supported beam structure using active vibration control method. For this purpose magnetic actuator is used to minimize the amplitude off vibration. An electromagnetic actuator will be used to apply the electromagnetic actuating force. The electromagnetic actuating force will be applied in opposite phase of the displacement of the structure. In this study an attempt will be made to apply such non-contact actuating force to minimize vibration of structure. This non-contact force is important because it will not damage the structure. The electromagnet is placed below the beam structure at mid span position. The constant dc current is passed through coil of electromagnet to generate electromagnetic actuating force which is applied on the beam and in the direction opposite to the exciting force. A simply supported beam is considered in this study and its equation of vibration is expressed in state space model in MATLAB Simulink environment. The single degree of freedom model of the beam is considered in this study. The first natural frequency of the beam as well as mode shape of the structure will be calculated. A disturbing force is applied on the beam at the mid span of the beam. The concentrated force whose frequency is changing with time is applied in such a manner that the natural frequency of the beam lies in the range of the frequencies of the exciting force. Due to the application of this force, resonance is observed when the frequency of the exciting force matches with the natural frequency of the beam. The electromagnetic actuating force is applied on the beam to minimize its amplitude of vibration. The electromagnetic force is applied only during the upward movement of the beam. During the downward movement of the beam the electromagnet is switched off and no actuating force is applied on the beam. It is shown in his study that the proposed actuator is successfully minimizing the amplitude of vibration even at the resonance also.