Magnetorheological dampers: a new approach to seismic protection of structures

For almost half a century, control engineering has been making an increasing contribution to more and more interesting and important applications. A listing of these would constitute a veritable litany of moves to improve the quality of human life and to protect both the people and their environments from hazards of various sorts. Recently upon the scene is a most striking and fascinating new challenge: the protection of civil engineering structures from hazards such as earthquakes, winds, and related phenomena. With many of the same motives which have led to the surge of engineering interest in low-power electrical circuits and systems, this new application would also profit greatly from control means which can operate when power systems are down, and which cannot harm inherently stable structures by undergoing operational failures after their installation. A very exciting new class of actuators for such purposes is found in magnetorheological dampers. In this paper, we survey the physical background of this device, its mathematical modelling, and current control experiments on a 3 DOF laboratory structure equipped with such protection.