Co-simulation or Hybrid Co-simulation?

co-simulation

hybrid co-simulation

As you have probably noticed, there are only slight differences between co-simulation and Hybrid Co-simulation. In both cases, the Simcenter Amesim solver is included. Nevertheless, there are some significant features that differ between the "libcosim" and "usercosim" ways of performing co-simulation. These points are summarized in table Table 5:

	"libcosim" use case	"usercosim" use case
Coupling type	Co-simulation	Hybrid Co-simulation
Number of executables	Number of applications involved in co-simulation	1
Simcenter Amesim solver embedded in model	Yes	Yes
Solver available	Both Simcenter Amesim fixed and variable step	Both Simcenter Amesim fixed and variable step
Co-simulation step	Decided at runtime from master. Simcenter Amesim can be master or slave	DLL function call Simcenter Amesim is slave
Master starts slave too	No	Yes
Take advantage of Multi-core, Multi-CPU architectures	Yes	No
Network compatibility	Yes	No

This table shows that "libcosim" and "usercosim" do not share the same philosophy.

On the one hand, a Simcenter Amesim model featuring "libcosim" is configured in the usual way. Solver type, parameters and simulation printout intervals are set from the Simcenter Amesim main window. Every executable involved in co-simulation has to be launched separately.

On the other hand, with the "usercosim" interface, it is possible to create a single executable which sets solver parameters and then pilots the whole co-simulation loop.

To make it clear, "libcosim" is a very easy way to set up co-simulation between Simcenter Amesim and an external executable. It keeps the Simcenter Amesim graphical user interface available to set up the model. "usercosim" is a more advanced way to perform co-simulations that can be fine-tuned.

To better understand the differences between co-simulation and Hybrid Co-simulation, let us take the example of two identical mass/spring/damper systems associated in series, each of them being modeled and simulated separately but communicating with the other one, as for the boundary conditions at their common interface:

Figure 10: Example of double mass/spring/damper co-simulation

Figure 11: Differences between co-simulation and Hybrid Co-simulation