Algebraic Constraint (Simulink Reference)

Constrain the input signal to zero

Library

Math Operations

Description

The Algebraic Constraint block constrains the input signal f(z) to zero and outputs an algebraic state z. The block outputs the value necessary to produce a zero at the input. The output must affect the input through some feedback path. This enables you to specify algebraic equations for index 1 differential/algebraic systems (DAEs).

By default, the Initial guess parameter is zero. You can improve the efficiency of the algebraic loop solver by providing an Initial guess for the algebraic state z that is close to the solution value.

For example, the following model solves these equations.

```
z2 + z1 = 1
z2 - z1 = 1
```

The solution is z2 = 1, z1 = 0, as the Display blocks show.

Data Type Support

An Algebraic Constraint block accepts and outputs real values of type double.

Parameters and Dialog Box

Initial guess: An initial guess for the solution value. The default is 0.

Characteristics

Direct Feedthrough
Yes

Sample Time
Inherited from driving block

Scalar Expansion
No

Dimensionalized
Yes

Zero Crossing
No

Direct Feedthrough	Yes
Sample Time	Inherited from driving block
Scalar Expansion	No
Dimensionalized	Yes
Zero Crossing	No

Action Port Assertion