APMonitor Modeling Language Documentation

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(:title APMonitor Modeling Language Documentation:) (:keywords nonlinear, model, DASPK, DASSL, ode15s:) (:description Sequential simulation mode for large-scale DAE systems.:)

Sequential Simulation

The DBS file parameter imode is used to control the simulation mode. This option is set to 7 for dynamic simulation.

NLC.imode = 7

Like steady-state simulation, sequential simulation requires a square problem with no degrees of freedom (neqn=nvar). It is also different than the simultaneous approach in that only one time step ahead is solved successively. Sequential simulation has many useful purposes including

  • Run through a large amount of historical data
  • Investigate step response characteristics of a nonlinear model
  • Simulate process changes for design, trouble-shooting, or planning
  • Perform what-if scenarios
  • Simulate a virtual process

Sequential simulation is one of the easiest dynamic modes to configure and run. The requirement for a square problem facilitates model convergence as the solver has only to achieve feasibility with the equality constraints.