Model linear implicit systems
Simulink / Continuous
The Descriptor StateSpace block allows you to model linear implicit systems that can be expressed in the form$$E\dot{x}=Ax+Bu$$ where E is the mass matrix of the system. When E is nonsingular and therefore invertible, the system can be written in its explicit form $$\dot{x}={E}^{1}Ax+{E}^{1}Bu$$ and modeled using the StateSpace block.
When the mass matrix E is singular, one or more derivatives of the dependent variables of the system are not present in the equations. These variables are called algebraic variables. Differential equations that contain such algebraic variables are called differential algebraic equations. Their state space representation is of the form
$$\begin{array}{c}E\dot{x}=Ax+Bu\\ y=Cx+Du\end{array}$$
where the variables have the following meanings:
x is the state vector
u is the input vector
y is the output vector
Data Types 

Direct Feedthrough 

Multidimensional Signals 

VariableSize Signals 

ZeroCrossing Detection 
