Support for Sundials is limited in SimBiology. There is no hint that this will be more broadly available anytime soon.
Hint and tips:
- Use the Simscape modeling language to define DAE's of problems in a way that MATLAB/Simulink can better understand and reformulate the DAE for solving. For instance, SimMechanics is optimized to deal with Index 3 DAE's that arise in rigid motion of multiple bodies moving together. There is no need to algebraically remove the constraints.
- If you must work in Simulink, then add states with known dynamics in places that have the algebraic states. For instance, replace an algebraic state with a first order transfer function with 10-1000 times faster dynamics than the rest of the model. This adds stiffness to the ODE system but the DAE already added stiffness in the first place. Choosing the dynamics so they are just faster than the rest of the system will allow the model to run reasonably while minimizing solver performance penalties because of added stiffness.