[SOLVED] Is there any way to have tandem phases in dymos that don't share a t_initial and t

Is there any way to have tandem phases in dymos that don't share a t_initial and t_duration?

For example if there is one long phase, but some short fast dynamics need to be captured in tandem at the beginning of the phase at a higher level of discretization, but these fast dynamics still depend on some variables from the long slow phase.

Furthermore could there be two consecutive short fast phases that are linked and both draw variable from the slow long phase?

Solution

In the instance where you have a series of short phases to be conducted in tandem with a longer phase

Long phase

o-------------------------------------------o
t_0                                        t_f

Short Phases

o------------------- o ---------------------o
t_0                 t_1                    t_f

There isn't anything in dymos that handles this situation for you. Knowing the grids from the two shorter phases, it would be possible to build an interpolant that interpolates onto the grid of the long phase, but that's fairly complicated.

If there needs to be some intermediate boundary constraint in the middle of the fast phases (at t_1 above), then you're probably better off breaking the long phase up into multiple phases that share time bounds with the short phases.