Predictive active control of MDOF structures

Abstract

SUMMARYThis paper presents a theoretical study of a predictive active control system used to improve the response of multi-degree-of-freedom (MDOF) structures to earthquakes. As an example a building frame equipped with electrorheological (ER) dampers is considered. The aim of the design is to "nd a combination of forces that are produced by the ER dampers in order to obtain an optimal structural response. The mechanical response of ER #uid dampers is regulated by an electric "eld. Linear auto-regressive model with exogenous input (ARX) is used to predict the displacements and the velocities of the frame in order to overcome the time-delay problem in the control system. The control forces in the ER devices are calculated at every time step by the optimal control theory (OCT) according to the values of the displacements and of the velocities that are predicted at the next time step at each storey of the structure.A numerical analysis of a seven-storey ER damped structure is presented as an example. It shows a signi"cant improvement of the structural response when the predictive active control system is applied compared to that of an uncontrolled structure or that of a structure with controlled damping forces with time delay. The structure's displacements and velocities that were used to obtain the optimal control forces were predicted according to an &occurring' earthquake by the ARX model (predictive control). The response was similar to that of the structure with control forces that were calculated from a &known' complete history of the earthquake's displacement and velocity values, and were applied without delay (instantaneous control).

Base‐isolated structures with selective controlled semi‐active friction dampers

“…However, if the magnitude of the ground motion is low or medium, there is no need in activating the dampers. Hence, it is proposed to use a selective control strategy (Gluck et al , 2000) for active base isolation systems with variable stiffness.…”

“…(2001) used amplifying devices and instantaneous control theory for increasing the efficiency of a damping system with VF. In order to overcome time delay in the control system, a predictive algorithm combined with instantaneous control (Gluck et al , 2000a) or a method developed from predictive and modal control (Lu 2004) may be used.…”

Chapter 7. Optimal control

“…If implemented, this kind of control would therefore ensure that the actuation system is yielding performance which is very close to the optimal physically-attainable performance. These controllers have attracted some attention the area of structural control (Gluck et al 2000;Huang and Betti 1999;Inaudi et al 1992;Mei et al 2001;Yang and Beck 1995). However, Receding Horizon controllers are computationally expensive, and in order to be appealing, there are some issues which must first be resolved.…”

Selective controlled base isolation system with magnetorheological dampers

“…Analysis of the building's response at discrete time steps during an earthquake yields the displacements, the velocities and the accelerations at each time increment. The value of the base displacement for next time steps can be predicted using, for example, an ARX algorithm [15] or other predictive techniques. According to the basic idea of the selective control strategy [16] the dampers are activated and the control forces are applied to the structure in order to reduce the base displacements and to keep them in the allowed limits in the case, if according to the prediction the base displacement exceeds the permitted value.…”