ALBERT

Description: The performance aspects of a wireless 'active' sensor, including the reliability of the wireless communication channel for real-time data delivery and its application to feedback structural control, are explored in this study. First, the control of magnetorheological (MR) dampers using wireless sensors is examined. Second, the application of the MR-damper to actively control a half-scale three-storey steel building excited at its base by shaking table is studied using a wireless control system assembled from wireless active sensors. With an MR damper installed on each floor (three dampers total), structural responses during seismic excitation are measured by the system's wireless active sensors and wirelessly communicated to each other; upon receipt of response data, the wireless sensor interfaced to each MR damper calculates a desired control action using an LQG controller implemented in the wireless sensor's computational core. In this system, the wireless active sensor is responsible for the reception of response data, determination of optimal control forces, and the issuing of command signals to the MR damper. Various control solutions are formulated in this study and embedded in the wireless control system including centralized and decentralized control algorithms. Copyright © 2007 John Wiley & Sons, Ltd.

Description: Structural control technology has been widely accepted as an effective means for the protection of structures against seismic hazards. Passive base isolation is one of the structural control techniques to enhance the performance of structures subjected to severe earthquake excitations. Isolation bearings employed at the base of a structure naturally increases its flexibility, but concurrently results in large base displacements. The combination of base isolation with active control, i.e. active base isolation, creates the possibility of achieving a balanced level of control performance in reductions of either floor accelerations or base displacements. Many theoretical papers have been written by researchers regarding active base isolation. A few experiments have been performed to verify these theories; however, challenges in appropriately scaling the structural system and modeling the complex nature of control-structure interaction (CSI) have limited the applicability of these results. This paper presents the development and experimental verification of an active base isolation system for a seismically excited building. First, the general problem formulation and control design procedure are provided. Subsequently, the experimental setup is described; unique features include low-friction pendular bearings and custom-manufactured low-force hydraulic actuators. A new system identification procedure that can effectively capture the phenomena of CSI is then presented and used to realize control-oriented models of the system. H 2/LQG control strategies employing different performance objectives are developed and experimentally evaluated on a six degree-of-freedom shake table in the Smart Structures Technology Laboratory at the University of Illinois at Urbana-Champaign. The proposed control strategies are shown to perform effectively for a wide range of seismic excitations. © 2010 John Wiley & Sons, Ltd.