Fundamental Research on Active Seismic Isolation With Proportional Negative Stiffness Damper

In base-isolated structures, negative-stiffness control actively inputs energy into the system, providing a high level of vibration suppression, yet inherently posing a risk of system instability. By contrast, skyhook control dissipates energy through damping, thereby imparting a stabilizing effect on the system. Consequently, these two control strategies exhibit fundamentally opposing characteristics; however, this opposition also results in a notable complementarity between them. Leveraging this complementary interaction, the present study proposes an active base-isolation control method based on the principle of maintaining the superstructure in an approximately stationary state. In this approach, ground displacement is inversely estimated from measured acceleration records, and the resulting restoring force of the isolation layer is actively counteracted by actuators. The performance of the proposed control strategy is evaluated using a single-degree-of-freedom (SDOF) model. Compared with conventional viscous damping, the method achieves approximately a 50% reduction in peak structural acceleration and a reduction of RMS acceleration to about 60% of that obtained under viscous damping, demonstrating its effectiveness in mitigating seismic responses.