Constrain input signal
Simulink / Math Operations
The Algebraic Constraint block constrains the input signal f(z) to z or 0 and outputs an algebraic state z. The block outputs a value that produces 0 or z at the input. The output must affect the input through a direct feedback path. In other words, the feedback path only contains blocks with direct feedthrough. For example, you can specify algebraic equations for index 1 differential-algebraic systems (DAEs).
f(z)— Input signal
Signal is subjected to the constraint f(z) = 0 or f(z) = z to solve the algebraic loop.
z— Output state
Solution to the algebraic loop when the input signal f(z) is subjected to the constraint f(z) = 0 or f(z) = z.
Constraint— Constraint on input signal
Type of constraint for which to solve. You can solve for
= 0 or
f(z) = z.
Solver— Algebraic loop solver
Choice between the Trust Region ,  or Line Search  algorithms to
solve the algebraic loop. By default this value is set to
auto, which selects the solver based on the
Tolerance— Solver tolerance
This option is visible when you explicitly specify a solver to be used
(Trust region or Line Search) in the Solver dropdown
menu. Specify a smaller value for higher accuracy or a larger value for
faster execution. By default it is set to
Initial Guess— Initial guess of solution value
Initial guess for the algebraic state z that is close to the expected solution value to improve the efficiency of the algebraic loop solver. By default, this value is set to 0.
 Garbow, B. S., K. E. Hillstrom, and J. J. Moré. User Guide for MINPACK-1. Argonne, IL: Argonne National Laboratory, 1980.
 Rabinowitz, P. H. Numerical Methods for Nonlinear Algebraic Equations. New York: Gordon and Breach, 1970.
 Kelley, C. T. Iterative Methods for Linear and Nonlinear Equations. Philadelphia, PA: Society for Industrial and Applied Mathematics, 1995.