System for solving differential equations with algebraic constraints

摘要

This invention uses a system model to take one integration step while disregarding algebraic constraints, followed by a correction step that uses the technique for computing consistent initial values for the reduced state. It also claims the integration of such a correction step into numerical solvers. In mixed-mode simulation, i.e., simulation of systems with piecewise continuous behavior, algebraic constraints may become active during simulation, requiring a consistent mapping of the system state onto the reduced state of the new piecewise behavior. The invented simulation interface uses the same technique to compute consistent initial values for the reduced state to compute consistent state variable values when such changes in the system occur during simulation. The invention is useful for the simulation of physical systems relying on differential and algebraic equations (DAE). IMAGE