Creating and Manipulating Models

Descriptor State-Space Models

Descriptor state-space (DSS) models are a generalization of the standard state-space models discussed above. They are of the form

The Control System Toolbox supports only descriptor systems with a nonsingular matrix. While such models have an equivalent explicit form

it is often desirable to work with the descriptor form when the matrix is poorly conditioned with respect to inversion.

The function dss is the counterpart of ss for descriptor state-space models. Specifically,

• sys = dss(A,B,C,D,E)
  

creates a continuous-time DSS model with matrix data A,B,C,D,E. For example, consider the dynamical model

with vector of angular velocities. If the inertia matrix is poorly conditioned with respect to inversion, you can specify this system as a descriptor model by

• sys = dss(-F,eye(n),eye(n),0,J)   % n = length of vector 
  

State-Space Models

Frequency Response Data (FRD) Models