Structural vibration reduction using self-tuning fuzzy control of magnetorheological dampers

Among the control devices considered for dissipating seismic energy and reducing structural vibrations is the magnetorheological (MR) damper which consists of a hydraulic cylinder filled with a suspension of micron-sized, magnetically polarizable iron particles capable of reversibly changing from free-flowing, linear viscous fluid to semi-solid with the application of a magnetic field. Several algorithms have been proposed for regulating the amount of damping provided by MR dampers. An attractive option is the use of fuzzy controllers because they are simple, intrinsically robust, and they do not depend on a model of the system. Tuning of these controllers, however, has shown to be a difficult task because of the large number of parameters involved. This paper proposes a self-tuning fuzzy controller to regulate MR dampers’ properties and reduce structural responses of single degree-of-freedom seismically excited structures. Robustness to changes in seismic motions and structural characteristics was assessed by subjecting a rigid and a flexible building to different earthquake records. Results show that the self-tuning controller proposed effectively reduced responses of both structures to all earthquakes considered. In addition, results were compared to those of a fuzzy controller with constant scaling factors and to those of two passive strategies: “passive on” and “passive off”, where the current to the MR dampers was set to its maximum allowable value, and zero, respectively.