An Experimental Study of the Active Control of a Building Model

The active control of large structural systems is a subject of growing worldwide interest. One of the reasons for the increasing attention is the successful application of passive structural control methods such as base-isolation approaches and damping augmentation techniques. Research activity in the civil engineering field has been primarily focused on theoretical studies with few, limited experimental investigations. This paper reports some of the results of an ongoing analytical and experimental study into the control of building-like structures subjected to nonstationary random excitations such as earthquakes. The structural model used resembles a 5-story building about 2.5 meters high. The building model was subjected to a variety of direct-force excitations. The control algorithm used employes an adaptive structural member at a pre-determined location in the model in order to attenuate the structural response relative to the moving building foundation. An electromagnetic actuator is used to generate the required control forces in the "smart" member. Among the key features of the algorithm under discussion are: 1. Only one active controller is required to attenuate the vibration response contributed by the first three modes; the damping factor is increased from virtually zero to about 20%. 2. Only two sensors are needed for this algorithm; this leads to simpler instrumentation and a more robust system. 3. Due to the optimization procedure used to select the controller location, a significant amount of damping augmentation is obtained from a relatively small amount of control energy. 4. The whole design procedure was demonstrated, especially attention was paid to time lag problem of the active controller and the stability of the system was discussed. As part of the design phase of this study, a system identification procedure was used to develop a suitable reduced-order mathematical model. The results of a simulation study using this identified model are compared to experimental measurements. Problems encountered in the experimental phase of the study are reported and discussed. It is shown that (1) the algorithm under discussion is capable of reliably controlling the motion of the test structure under arbitrary dynamic environments, and (2) the features of the algorithm makes it a promising candidate for application to large civil structures