Online tuning of fractional order fuzzy PID controller in smart seismic isolated structures

Abstract

This paper aims at designing an adaptive fractional order fuzzy proportional–integral-derivative controller for seismic control of smart base-isolated structure by means of variable friction dampers (VFD). One main challenge occurs when large displacement of the isolator happens due to near-field motions. To overcome this challenge, a solution is to use VFDs. However, the floor accelerations of the superstructure can increase because of sudden changes in the damper friction force of VFDs. Therefore, a suitable control strategy is desired to handle the displacement of isolator without any increase in superstructure acceleration responses during both far-field and near-field earthquakes. First, a sub-level fractional order fuzzy PID (FOFPID) controller is designed to reduce the isolator displacement without significant increase in roof acceleration based on a multi-objective optimization algorithm. Using an adaptive strategy, the fuzzy rule weights of the FOFPID controller are then tuned on-line based on information sensed from both the earthquake and the building responses. Considering nine important performance criteria and several real-data earthquakes, numerical studies are carried out for a benchmark base-isolated structure equipped with VFDs. Simulation results show the superior performance of the proposed controller in mitigation of seismic responses of base-isolated structure against various types of earthquakes in comparison with other controllers presented in previous researches.