Optimal PD/PID control of smart base isolated buildings equipped with piezoelectric friction dampers

Long-period pulses in near-field earthquakes lead to large displacements in the base of isolated structures. To dissipate energy in isolated structures using semi-active control, piezoelectric friction dampers (PFD) can be employed. The performance of a PFD is highly dependent on the strategy applied to adjust its contact force. In this paper, the seismic control of a benchmark isolated building equipped with PFD using PD/PID controllers is developed. Using genetic algorithms, these controllers are optimized to create a balance between the performance and robustness of the closed-loop structural system. One advantage of this technique is that the controller forces can easily be estimated. In addition, the structure is equipped with only a single sensor at the base floor to measure the base displacement. Considering seven pairs of earthquakes and nine performance indices, the performance of the closed-loop system is evaluated. Then, the results are compared with those given by two well-known methods: the maximum possive operation of piezoelectric friction dampers and LQG controllers. The simulation results show that the proposed controllers perform better than the others in terms of simultaneous reduction of floor acceleration and maximum displacement of the isolator. Moreover, they are able to reduce the displacement of the isolator systems for different earthquakes without losing the advantages of isolation.