Hi, Simone. Simbody's integrators interpolate when a reporting time doesn't coincide with a step completion.

That's on by default but can be controlled by Integrator methods like setAllowInterpolation().

Regards,
Sherm

Hi Simone. If you use one of SImbody's variable step integrators, it should be able to figure out to take small steps over the rapid transition automatically.

Regards,
Sherm

Awesome! Thanks, Walter.

Sadly, no. There is a nice Assembly analysis in Simbody but no InitialVelocity analysis (there should be!) You can work around that by adding a velocity constraint (or Motion object) to one of the dofs (assuming a net-1-dof system). Then constraint projection will figure out all the other velocities...

You could try:
- CPodes limited to Order 1 (that makes it implicit Euler)
- SemiExplicitEulerIntegrator
- Use fixed step or very loose accuracy requirement, like 10%
- Use less damping or large masses to avoid extreme stiffness

Optimization is still probably the most direct approach.

Assembly analysis is for satisfying position constraints. In this case it sounds like you would like the spring to minimize its stored potential energy, that is have the system relax so that it is in a steady state. That's a "static" or "equilibrium" analysis, if I understand your question. Simbody ...

I think all you need is a C-style cast like
SimTK::MobilizerQIndex(int)

Hi, Andrea. The entire System (including all its Subsystems) needs to be built before any computations are done. It looks like you are adding a Subsystem later, would be good to get that sorted out (might not be the problem but could cause trouble). Also, the GeneralContactSubsystem is old and super...

Hi, Simone. Apologies for the delayed reply. (b) There is currently no provision in Simbody to call a function at step completion. This would be a nice addition to the TimeStepper class in case anyone would like to submit a Simbody PR! (a) This is a great question. It's not clear to me whether a fix...

A quick look suggests you need to get a reference to the existing SimbodyMatterSubsystem rather than a copy:
Regards,
Sherm