Experimental Identification and Control of a Frame Structure Using an Actively Controlled Inertial-Based Vibration Absorber

In this investigation, a method for reducing the externally induced vibrations of a frame structure is developed. The frame structure considered as a case study is a three-story shear building system with a pendulum hinged on the third floor. The pendulum serves as an actively controlled inertial-based vibration absorber and the applied torque is actively controlled by using a brushless motor driven by a programmable digital controller. A first-order state-space model of the frame structure is obtained from input-output experimental data without considering the control action of the pendulum. For this purpose, a numerical procedure based on the combination of the Observer/Kalman Filter Identification Method (OKID) with the Eigensystem Realization Algorithm (ERA) is used. The identified mathematical model of the frame structure is used to design an optimal feedback controller and an optimal state estimator based on a closed-loop control architecture by using the Linear Quadratic Gaussian (LQG) control and estimation method. Experimental results demonstrated that the introduction of the feedback controller combined with the state estimator designed employing the LQG method and based on the identified state-space representation leads to a considerable reduction of the vibrations of the frame structure.