STK 12.4 FMI/FMU Feature

For those of you who are not familiar with the functional mock-up interface (FMI) and functional mock-up unit (FMU), let me take a minute to describe the concept. The FMI is an open standard for sharing dynamic models. This interface enables users across organizations, or even between organizations, to collaborate at a whole new level. The simple idea is to create a standardized wrapper around any digital model —which then becomes an FMU —) and then execute that model in any other tool that understands the interface. 

So how does this apply to Systems Tool Kit (STK) and Ansys? Well, many Ansys physics solvers already have a native capability to export FMUs representing the complex responses associated with loads applied (thermal, mechanical, electronic, etc.). Now, in conjunction with STK 12.4, we made a protype plugin that reads FMUs directly into STK as Calculation Scalars. This combination of features provides a streamlined workflow for capturing the complex physics of the Ansys solvers as FMUs and then makes those available to the STK mission simulation environment.  

For example, suppose you are designing a new airframe for a UAV and want to evaluate the stresses and strains on the wing based on a series of mission simulations of the expected flight profiles.  Exporting the flight characteristics (velocity, angle of attack, wing loading, etc.) for each flight profile and then importing them into time-based mechanical simulations would use significant computational resources. You would need to rerun each simulation for every new mission and duplicate efforts, since many missions may have similar profiles.  

Instead, by designing the mechanical simulation to evaluate across the full spectrum of loads that could be applied to the airframe, we can capture the response surface of the resulting stresses, strains, and deflections as an FMU (which only needs to be generated once) and then use that FMU in any number of mission profiles. This enables you to evaluate these responses directly in STK with any new flight profile imaginable and it runs as an extremely fast reduced order model (ROM), saving time and effort.  

In addition to running a single model in the STK environment, you can also load any number of other FMU models to interact with each other. Perhaps your UAV is battery operated, so you have a propulsion model and a sensor model linked to a battery model, all driven by the same mission and collection schedule. This will help you evaluate your power state and validate your requirements. 

So, with all that said, we are excited to preview this new capability in STK to link models across the entire Ansys software ecosystem and from external sources, too. The initial STK FMU capability is available as a prototype plugin while we work toward a new integrated feature in STK’s Analysis Workbench capability.