Use the Indicator States node () to define state variables that the solver uses to trigger implicit events, which occur at a zero crossing of an indicator state variable if the implicit event condition changes from false to true.

Multiple indicator state variables can be defined in the table together with corresponding g-coefficients and initial values. A state variable, u, gets its value by solving the following equation:

with the initial conditions u(t0) = u0 (where the dot notation indicates time derivatives). You use the state variables in the implicit event condition that you specify for the Implicit Event node. The g-coefficients are written similarly as when defining Global Equations; for example, any global state variables or operators in the model can be used as well as the time or discrete state variables defined by the Events interface. However, the expressions cannot contain any indicator state variables. The nojac operator makes sure that the state variables do not enter into the Jacobian matrix, avoiding fill-in of the matrix.

Enter values or expressions in the table for the Name, g-coefficients g(v,vt,vtt,t), Initial value (u0), and (optionally) enter a Description.