A first successful solution has been made for strong coupling between flexible FEM body and rigid multibodies. The solution is designed for distributed co-simualtion using FMI. The two bodies are separate FMU packages and connected together through a master stepper.

A 2D rigid body pendulum, mechanically constrained to an elastic finite element body. The simulation slaves are independent and does only know that an external force may or may not be applied to it on a connector point. The finite element body is integrated using Crank-Nicolson and the rigid multibody system use a variant of the SHAKE stepper, called SPOOK, with particular constraint stabilization and regularization terms. The latter is also used for the master solve for the coupling constraint force. The master also involves pre-solve for the subsystems to compute the directional derivatives. The over all computational complexity is N*(2 + M) solves, where N is the number of subsystems (2 in this case) and M is the number of constraints on each subsystem. Realtime performance is met although code is far from optimized. For further details on the master stepper, see here.

Categories: Demos, Project News

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