Impedance matching control design for executing conventional earthquake-simulator experiments and real-time hybrid simulations

Graduate Student: Sai Sharath Parsi

Principal Investigators: Mettupalayam V. Sivaselvan and Andrew S. Whittaker

Project Completion Date: September 2022

Real-time hybrid simulations (RTHS), also referred to as model-in-the-loop (MIL) simulations, involves physical testing of a structure, a system, or components, with its surrounding environment represented virtually using numerical models, and loading devices (actuators) controlled to simulate the effect of the virtual environment at the boundary of the test article. Such testing is appropriate when the dynamics of the test article is significantly influenced by its interaction with the boundary environment. Designing robust actuator controls that are capable of imitating different virtual environments is key for executing MIL tests. A novel strategy for designing robust MIL controls has been developed by Sivaselvan and his co-workers at the University at Buffalo: referred to as impedance matching, wherein the actuator is not merely viewed as a device imposing prescribed boundary conditions between the physical and virtual systems but as a dynamic system that is controlled such that its force-motion behavior (impedance/admittance/immittance) at the test article-actuator interface matches closely that of the virtual environment it is representing. This novel approach results in MIL controls that are simple, easy to implement, and stable.

This project is a cradle-to-grave demonstration of the impedance matching approach in an example configuration of 1D base-isolated equipment, from conceptualization, through design, verification, implementation, and validation. A fluid-filled vessel is the test article and a servo-hydraulic earthquake simulator, driven by impedance-based MIL controls, is used to impose acceleration boundary conditions corresponding to different isolation systems at the base of the vessel. Results show that the simulator, when equipped with the designed MIL controls, accurately imitates different isolation systems. The MIL controls designed herein are by-and-large standardized, meaning that they are implemented, with few modifications, for a diverse combination of physical and virtual systems: a significant advance in real-time hybrid simulation. Importantly, this experimental program utilized commercial off-the-shelf controller hardware for implementing MIL, thereby making the technology non-laboratory specific, applicable to earthquake simulators of different sizes and capacities, and readily deployable at scale for earthquake-related and other applications.

This project was supported by Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000978.