Active control of earthquake-excited structure using a torsional servomotor active mass driver system

Abstract

Servomotor system has advantages of low cost, small size, good controllability, and less maintenance in driving mass movement. In this study, a torsional servomotor active mass driver (AMD) system is developed to actively control an earthquake-excited structure. A relation between the mass inertial force and servomotor rotational speed is established as the transfer function of an uncontrolled AMD. A control algorithm consisting of the linear quadratic regulator (LQR) and Kalman filter is designed to control the transfer function in real time only using acceleration measurements. With the help of LabVIEW platform, a user-programmable AMD controller including data acquisition, data processing, and motor control is developed. Finally, shaking table tests of a three-story steel frame equipped with developed AMD system subjected to earthquake excitations are conducted. The results show that the torsional servomotor AMD system performs quite well in reducing the displacement and acceleration responses of the earthquake-excited steel frame. The root-mean-square displacement and absolute acceleration of the top floor greatly decrease with nearly 70%. The damping ratio of the steel frame is greatly improved from 0.17%∼0.29% to 1.25%∼2.25% after implementing the torsional servomotor AMD control. Besides, a phenomenon of good control in both first-mode and second-mode vibrations is observed to validate the active control superiority.