My model has an seemingly unsolvable algebraic loop in it. It is continous-time, so I put in a quick filter in the loop to try to break it. All that did was make it run for less than a microsecond simulation time with many small steps ( < 1 ns). The total simulation time I trying to do is 0.25 s. Below is a picture of my model. The places in red are the places where I have tried to put the filters in and the blue is just to highlight where they are now. The S-function block seems to work as a lookup table. My controllers have worked when the plant I was working on was just a set of EOM's.