Semi-active fuzzy control for variable damping devices for seismic protection

Oliveira, Cristina; Guerreiro, Luís

http://hdl.handle.net/10400.26/49951

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Authors

Oliveira, Cristina

Guerreiro, Luís

Abstract(s)

Dynamic actions, in general, and earthquakes, in particular, can transmit very high forces to structures. Protection control systems have been developed to reduce the damaging effect of those actions. Semi-active control devices may generally be referred to as controllable passive devices. The semi-active control approach consists of the indirect application of variable control forces whose energy derives directly from the motion of structures and is obtained by instantaneous change of the parameters and dynamic characteristics according to a predetermined control criterion. No mechanical energy is inputted directly into the structure, making the entire system intrinsically dynamically stable. The efficiency of the protection will depend on the efficiency of the control algorithm. Fuzzy control has been widely implemented in many fields due to its efficiency, while having simple and straightforward rules. In structural control, fuzzy logic has an interesting potential for mitigating earthquake vibrations. The reaction of a fuzzy control system can suitably adapt to the high randomness of seismic accelerations, so algorithms of this type of control should be developed, analyzed and studied for structural application. An algorithm using fuzzy control has been developed for application in a semi-active variable damping device for controlling seismic actions in structures. Input membership functions were selected using ground acceleration feedforward control and displacement and velocity feedback control. The output pertinence functions set the damping value to be selected for the device using the centroid method. All membership functions were defined using a triangular function. In this paper, the proposed algorithm is presented, described and tested with numerical simulations. The tests were performed using artificial accelerograms representative of the Portuguese Seismic Action in a one degree of freedom and two degrees of freedom models. The results are then compared with traditional passive protection using a viscous damper, allowing to compare the efficiency of the proposed original fuzzy control algorithm.