Functional mock-up interface support in Chrono

Abstract Adoption of a standardized co-simulation model exchange interface offers several advantages, including “one-time only” code development for model encapsulation, access to existing or future subsystem models with no changes to the co-simulation framework, and access to proprietary models and libraries. While there are several attempts at providing standard interfaces for model coupling and model exchange, the Functional Mock-up Interface (FMI) is arguably the standard with the largest user base, advocated by a large number of academic, governmental, and commercial entities. For these reasons, we opted to adopt FMI and implement a new Chrono::FMI module to provide the necessary functionality to both wrap Chrono models and simulations in so-called Functional Mock-up Units (FMU) and couple Chrono simulations to FMUs. We target both FMI 2.0 (because of its widespread use) and 3.0 (for new capabilities, useful in creating FMUs for models with large intput/output bandwidth, such as deformable terrain and sensors). This contribution describes the utility general-purpose library fmu-forge, its use in Chrono::FMI, and illustrates the use of Chrono FMUs in vehicle co-simulation as well as coupling external FMUs to Chrono simulations.