Our connected world and environment make us interact every day with very complex devices. Driving our cars, monitoring health using smart phones, the extensive use of robots are all applications which involve large quantities of embedded functions and physics. To design and simulate efficiently such systems, individual physics simulators are not sufficient and coupled simulations are required. A new standard called FMI (Functional Mock-Up Interface)  has been created, allowing to federate these interactions between a wide variety of physical, digital and reduced models, either through a co-simulation approach or through model exchange strategy using a standardized and neutral interfacing mechanism. In this article, we illustrate through an example how it’s possible to simulate mechanical assemblies, kinematics, dynamics and control systems in the same system model. Each mechanical sub-assembly is represented by a FMU (Functional Mock-Up Unit) exported from a multibody dynamics solver and includes a mix of rigid and flexible components. Flexible components are reduced order models of the full fidelity finite element model using the well-known CMS (Component Mode Synthesis) method. 
We apply the coupling through the FMI standard to a robot model, composed of rigid parts and one flexible sub-assembly. The highly non-linear behavior of the equations of motion of the multibody assembly is captured and consumed as a co-simulation FMU. The actuators detailed model – from the voltage source to the electric motors – are modeled in the system simulation platform ANSYS Twin Builder, while the control loops use SCADE which offers different control laws. The co-simulation of these 3 sub-systems can then be performed in an efficient manner, without the prerequisite of having on-off coupling developed between each of the individual simulators.
Keywords: FMU, multibody dynamics, CMS, actuator, control
Proceedings of the 2nd Japanese Modelica Conference Tokyo, Japan, May 17-18, 2018
 Component Mode Synthesis, Jaap Wijker, in Mechanical Vibrations in Spacecraft Design, pp 369-398 Springer, Berlin, Heidelberg
 Nonsmooth Mechanics, Models, Dynamics and Control. Third Edition. Bernard Brogliato, Springer, Berlin, Heidelberg