Research on Advanced Earthquake Engineering Hybrid Simulation Technology - Vibration Isolation and Reduction of Structure and Hybrid Simulation - Seismic Design and Composite Experiment Technology of Metal-containing Seismic Device Frames (Main Project and Sub-Project 1) (I)

Passive isolation system is one of the common structural control techniques used to enhance the performance of structures/equipment subjected to severe earthquake excitations. By adding a flexible isolator under the equipment, the fundamental natural period of the passive isolation system can be extended to avoid devastating seismic impact. Relevant academic research and practical applications have proved that a well-designed passive isolation system can effectively reduce the absolute acceleration of the equipment and protect the equipment from damage due to earthquake loading. However, passive isolation system has non-stationary optimal damping for different seismic forces, and the isolation layer has to avoid moving when subject to non-seismic force. The passive isolation systems are often designed with a larger friction damping which reduced the performance and robustness of the passive isolation system. Especially for small-to-medium earthquakes, the restriction of the seismic isolation layer causes the isolation system to be unable to effectively isolate the seismic force. In view of this, this research aims to develop an active isolation system for equipment in high-tech factories. When an earthquake comes, the movement of the isolation sliding table is controlled by an actuator, so that the seismic impact can be isolated. The traditional skyhook isolation control law uses the absolute velocity of the system as feedback signal. However, in order to increase the performance and robustness of the active isolation system, this research proposes the state extended state space representation method. Therefore, the base acceleration direct integral feedback skyhook control law is developed. The dynamic characteristics and design control gain of active isolation system can then be fully analyzed and determined. In addition, the actuator applied for active isolation system can be used for displacement or velocity control mode to overcome the influence of undesired friction, thus the absolute acceleration of the equipment can be controlled more effectively especially for small-to-medium earthquakes. Since the developed control law takes into account the input of the excitation, the damping ratio of the active isolation system can be greatly improved by the control law without affecting the isolation effect. Moreover, when the equipment is subjected to external forces other than the base excitation, the seismic isolation layer can still be effectively controlled. This study further considers that since the active isolation system and equipment are installed on the structural floor, the main disturbance of the equipment is the absolute acceleration of the structural floor where it is located. Compared with the acceleration on the ground, it may be amplified by the structure as well as the frequency content. In addition, due to the heavy weight of equipment in high-tech factories, the reaction force of the active isolation system might interact with the structure during operation. In order to fully understand the overall dynamic response of the active isolation system and the structure. The real-time hybrid testing technology is adopted to fully verify the developed active isolation system.