Hybrid simulation combines physical testing and computer modeling, offering a more efficient and affordable way to examine how large civil structures respond to seismic loading.
-Image courtesy of NEES and the University of Colorado Boulder
Leveraging Hybrid Simulation for Structural Testing ApplicationsExtending the benefits of computer modeling and component level testing for large or full scale testing applications.
Civil and seismic test engineers face increasingly challenging scenarios. Sophisticated control systems and higher PC processing speeds have enabled forces and motions to be exerted on test specimens in a complex manner. While the temptation is to evaluate larger test specimens in order to produce the most true-to-life test results possible, large test specimens are expensive to manage and procure. In addition, every test system and test facility can only accommodate test specimens of a certain size.
To address such space and cost challenges, many laboratories are employing hybrid simulation capabilities for conducting their testing programs. Hybrid simulation involves the mechanical testing of a physical component or substructure, while using computer modeling to represent the surrounding structure.
Although hybrid simulation is widely used for testing, test laboratories often use actual test specimens for controller tuning, test rehearsals and other mandatory procedures performed prior to testing, as well as for training. This is not ideal. Configuration errors are often present during the tuning and rehearsal stages which can damage the test articles. Similar risks also accompany using a physical test rig for training purposes, in addition to tying up valuable time on a test station.
Creating the virtual plant model
New controller software advances are now extending the benefits of computer modeling to test preparation and operator training. These advances go a critical step beyond hybrid simulation, using modeling alone to simulate the entire test rig and specimen in a simulated test. Nothing physical is required for test preparation or training.
To achieve this virtual state, a plant model is produced, providing a complete and accurate digital representation of the actuators, servovalves and specimen present in test (physical plant). Plant models are developed with Simulink, a popular software tool for simulating dynamic systems.
The plant model is beneficial to several essential processes surrounding a test, including:
Tuning. By tuning controller settings in simulation mode, test engineers have flexibility to change parameters multiple times and see the simulated system response. With an accurate plant model, the results of the physical test should be similar to those generated when using the virtual plant model.
Test rehearsals. Running test rehearsals against a plant model exposes design flaws before a physical test specimen is used, allowing errors in test procedures to be remedied before they pose risks to anything physical. As a real-world example, MTS recently helped a customer develop a plant model for testing a multi-column bridge. A virtual test rehearsal was run, identifying an out-of-phase actuator that would have almost certainly damaged the physical test specimen.
Operator training. Plant models make it possible to offer a complete testing experience for training purposes in a virtual environment — from test creation and execution through data acquisition and post-test analysis. This type of training can occur in any room with a networked PC, freeing up your valuable lab floor space for other uses.
Once you create a plant model, it also has potential uses for fault detection and test system health monitoring. By running the plant model in parallel with the physical plant (test system) - health status can be monitored by comparing the physical feedback from the physical plant to the virtual feedback from the virtual plant model. If the test system is running efficiently, the physical and virtual feedback should be similar.
Create your plant model with MTS
MTS offers unmatched simulation solutions and expertise for civil and seismic structural testing, including new features that allow plant models to be created and tightly integrated within the controller. Contact us today to learn more about all the ways virtual modeling can benefit your civil or seismic testing.
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