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Polynomial Control Systems (2014)

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3.4.1 Left Matrix-Fraction Models

LeftMatrixFraction creates a left matrix-fraction model of a system from the denominator and numerator matrices, or another control object.

Left matrix-fraction data structure.

Make sure the application is loaded.

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Here are two polynomial matrices describing a left matrix-fraction model. Note that a matrix fraction does not necessarily have a matrix D that is diagonal.

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LeftMatrixFraction keeps its component matrices unchanged.

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This is the TraditionalForm of the same object.

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This output format shows one object that consists of two matrices. The first contains the inverse of the denominator matrix D(s), and the second contains the numerator matrix N(s). The | indicates that these two matrices constitute a LeftMatrixFraction object. Similarly to other polynomial control objects, you can apply the LeftMatrixFraction object to a variable to extract the underlying matrices in that variable.

This produces a list of the matrices D and N in the variable s.

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A left matrix-fraction model can also be created from an existing system model in transfer-function, zero-pole-gain, state-space, system matrix, or right matrix-fraction (see Section 3.4.2) form.

Left matrix-fraction object data structure for converting from other system forms.

Here is a StateSpace object.

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This constructs a left matrix-fraction object. Since no formal variable is supplied, the result is obtained in the pure function form, that is, in the variable #.

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You can also construct a LeftMatrixFraction object in the variable of your choice.

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In TraditionalForm, both systems use the same variable .

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A left matrix-fraction object can be transformed to any other model form by applying the appropriate wrapper.

Here is a TransferFunction object.

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This is the corresponding LeftMatrixFraction.

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This is a corresponding SystemMatrix model.

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The result highlights the correspondence between the system matrix object in left-fraction form and the left matrix-fraction object. Since the matrix T of the system matrix object is diagonal, it is easy to see that the model concerned is fourth-order, which corresponds exactly with the degree of the determinant of the left matrix-fraction model. This would also be the order of a minimal state-space realization.

This is a state-space realization of the system.

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The fourth-order realization is both controllable and observable and, therefore, minimal.

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