The UT-SIM framework consists of mainly three components: 1) Communication modules, 2) integration modules, and 3) substructure modules. Complete with a standardized communication protocol and data exchange format, communication modules allow seamless communication between different software. For dynamic problems, integration modules are the main integration software which runs numerical time integration to solve the system’s equation of motion. Substructure modules provide the integration modules with restoring forces of structural components (critical subdomain) whose behaviour needs to be simulated (numerically modelled or physically tested) in detail. The current development of the UT-SIM framework enables two types of decomposition methods (component-level decomposition and system-level decomposition) which are demonstrated as below.
Communication ProtocolThe standardized communication protocol and data exchange format are the main components that allow for the seamless integration of diverse software and physical specimens. At this stage, an extensible data exchange format and a simple communication protocol is developed. Currently improvements are being made on the communication protocols to reduce the lag during geographically distributed communication. Analog voltage signals are used for the communication between the software and actuator control systems, because most controller system support such functionalities.
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Integration Modules
An integration modules is a main Integration modules are software tools which run a numerical time integration scheme for a dynamic problem or serve as main solvers in static problems. Thus, an integration module is used to model the majority of the structural system. Substructure modules, on the other hand, include components that need to be modeled as physical specimens or sophisticated finite elements in other software packages. In network communications, the integration module acts as a client while substructure modules act as servers. Depending on the nature of the problems, one of the following integration modules can be used for hybrid or multi-platform simulations.
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Substructure ModulesSubstructure modules include models of relatively small regions in a structural system that need to be modeled in great detail. For example, one may want to model a link beam with detailed finite element models (or even physical specimens) while the rest of the structural system can be modeled with frame elements. At this stage, all substructure modules are assumed to be static modules which are rate-independent. There are a few examples of methods which allow for the integration of dynamic subsystems to other dynamic systems, but such algorithms are not yet mature for general application to nonlinear dynamic problems.
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Real-Time Hybrid Simulation
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The above architecture applies to the Real Time Hybrid Simulations (RTHS). In RTHS, however, the real-time synchronization of the numerical analysis and experimental test is one of the most important requirements. Thus, it is necessary to develop the integration modules, substructure modules, and even actuator controllers such that all these components can be perfectly synchronized with minimal delay in each time step. With this purpose, a real-time controller and FPGA based real time simulation method has been developed.
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