Frequency Domain Control Structure Design Tools

摘要

Very important parts of a multivariable design are the input/output (I/O) selection and I/O assignment or pairing, which both define the so-called control system structure design problem. I/O selection is the problem of choosing the variables that are the most appropriate to control particular outputs. A good physical understanding of the plant to be controlled is always the initial step towards the solution of this problem. However, in many cases the designer is still left with more than one choice from which he has to choose the best according to some criteria. This is the case in many real world applications, such as in aircraft and process control, where a number of variables are observable, but it is well known that only a subset of those equal to the number of inputs, can be independently controlled. Thus, the designer has the freedom to choose the outputs from the available measurements, and in doing so in a systematic way. A few criteria exist, which will be considered below, to help with this problem. Once such a choice has been made, it is then necessary to assign an input variable to the control of a particular output variable, i.e. to choose the appropriate I/O pairs. Most of the methods are scaling dependent, hence an initial I/O scaling is necessary before any of the aforementioned analytical tools are employed.