is an option to StateSpaceModel and StateSpaceTransform that specifies whether to use descriptor or standard representation.


DescriptorStateSpace
is an option to StateSpaceModel and StateSpaceTransform that specifies whether to use descriptor or standard representation.
Details

- In StateSpaceModel[{a,b,c,d,e}], the matrix e is the descriptor matrix.
- The equations governing continuous-time standard and descriptor state-space models are:
-
standard state space descriptor state space - Discrete-time systems have analogous forms.
- The option can take the following values:
-
Automatic automatically determine the representation False use standard state-space representation True use descriptor state-space representation - With the setting DescriptorStateSpace->Automatic, StateSpaceModel uses the descriptor representation only if a standard representation cannot be obtained, and StateSpaceTransform does not alter the representation.
Examples
open all close allBasic Examples (7)
Invert the descriptor matrix to create a standard state-space model:
Add an identity matrix to create a descriptor form:
Obtain the descriptor StateSpaceModel:
By default, the standard form is obtained:
For some singular systems, the descriptor form is obtained by default:
This is because it is not possible to obtain the standard form:

When possible, the standard form is obtained:
In some cases, the standard form can have fewer states:
However, the order of the system is the same in both cases:
Obtain the result from StateSpaceTransform in the descriptor form:
Scope (6)
Create a standard state-space model from a descriptor state-space model:
Create a descriptor state-space model from a standard state-space model:
Convert a proper transfer-function model to a descriptor state-space model:
Create a descriptor state-space model from an ODE:
Obtain the state transformation of a standard StateSpaceModel in descriptor form:
It gives the same result as an explicit descriptor specification:
Similar results can be obtained with the inverse transformation as well:
A descriptor StateSpaceModel with an invertible descriptor matrix:
Properties & Relations (2)
Improper transfer-function models will create descriptor state-space models by default:
There is no standard state-space realization:

A descriptor StateSpaceModel with a noninvertible descriptor matrix:
StateSpaceTransform produces a descriptor model:
The state transformation cannot be obtained in standard form:

See Also
Related Guides
Text
Wolfram Research (2012), DescriptorStateSpace, Wolfram Language function, https://reference.wolfram.com/language/ref/DescriptorStateSpace.html (updated 2014).
CMS
Wolfram Language. 2012. "DescriptorStateSpace." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/DescriptorStateSpace.html.
APA
Wolfram Language. (2012). DescriptorStateSpace. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/DescriptorStateSpace.html
BibTeX
@misc{reference.wolfram_2025_descriptorstatespace, author="Wolfram Research", title="{DescriptorStateSpace}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/DescriptorStateSpace.html}", note=[Accessed: 16-August-2025]}
BibLaTeX
@online{reference.wolfram_2025_descriptorstatespace, organization={Wolfram Research}, title={DescriptorStateSpace}, year={2014}, url={https://reference.wolfram.com/language/ref/DescriptorStateSpace.html}, note=[Accessed: 16-August-2025]}