Creating and Manipulating Models    

Precedence and Property Inheritance

You can apply operations to LTI models of different types. The resulting type is then determined by the rules discussed in "Precedence Rules" on page 2-5. For example, if sys1 is a transfer function and sys2 is a state-space model, then the result of their addition

is a state-space model, since state-space models have precedence over transfer function models.

To supersede the precedence rules and force the result of an operation to be a given type, for example, a transfer function (TF), you can either

Suppose, in the above example, you want to compute the transfer function of sys. You can either use a priori conversion of the second operand

or a posteriori conversion of the result

Another issue is property inheritance, that is, how the operand property values are passed on to the result of the operation. While inheritance is partly operation-dependent, some general rules are summarized below:


  Operations on LTI Models Extracting and Modifying Subsystems