The Algebraic Constraint block constrains the input signal f(x) to zero and outputs an algebraic state x. The block outputs the value necessary to produce a zero at the input. The output must affect the input through some direct feedback path, i.e., the feedback path should only contains blocks with direct feedthrough (without internal states). This enables the user to specify algebraic equations for index-1 differential/algebraic systems (DAEs).
By default, the initial value of the state which is used as initial guess values is zero. If the solver cannot converge towards the solution at the beginning of the integration, the user can help the solver by providing an initial guess that is close to the solution value. If f(x) has several solutions, the initial guess helps the solver to select the desired solution.
