Real-Time Hybrid Testing of an MR Damper for Response-Reduction
This research focuses on the real-time hybrid testing of Magneto-Rhelogical (MR) fluid dampers for the seismic protection of building structures in large-scale, small-scale and distributed systems, with an emphasis on system stability and performance from control systems perspective. Real-time hybrid testing provides the capabiity to isolate and physically test critical components of a structure, while the rest of the structure is simulated in the computer. One of the major challenges of real-time hybrid testing is the system stability. To overcome this issue, both actuator control and virtual coupling can be employed to successfully conduct the real-time hybrid testing. Improved actuator control can reduce the time delay observed in the actuator. Virtual coupling as defined here is a parallel connection of virtual spring and damper components, which is placed between the numerical and physical component to provide the system stability. Large-scale real-time hybrid testing was conducted at the Network for Earthquake Engineering Simulation (NEES) Fast Hybrid Test (FHT) facility at the University of Colorado at Boulder (CU). The results show that MR dampers can effectively protect the non-linear Los Angeles 3-story SAC structure, which is numerical component. Virtual coupling is used to provide stability in these tests.
Small scale real-time hybrid testing is sucessfully conducted at the University of Connecticut. THe physical compnent in these tests is a small-scale MR damper [RD-1005-3] and numerical component is a two-story building with natural frequencies at 4.46 Hz and 11.96 Hz for the first and second mode, respectively. A lead-lag compensator is employed to improve the hydraulic actuator time delay from 18~20 msec to 8~10 msec. The validation of the small scale real-time hybrid testing system is implemented by comparing with the shake table tests. The results show that the performance of the real-time hybrid testing depends on the accuracy of the numerical components and that real-time hybrid testing can be achieved using standard numerical integration schemes and a system approach to achieve performance and stability.
A real-time multi-site hybrid testing methodology is propsoed to extend the potential of the real-time hybrid testing system. One of the major challenges of multi-site testing is to accommodate the communication time delay. In order to demonstrate the potential method to achieve real-time hybrid testing, a bench-scale experiment conducted at the University of Connecticut using a small-scale MR damper [RD-1097-01] and a 2-story numerical building model. This research first proposes a system architecture that applies techniques from haptics to overcome simulation to experiment interface and communication time delay anticipated in multi-site testing. Smith-based controller is employed to accommodate the communication time delay and virtual coupling is employed to accommodate the inherent local time delay. The results show that using a Smith-based controller reasonable performance and stability are achieved with a 20 msec simulated time delay.
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