Multivariable controller design by signal-flow graph techniques

This paper describes a series of systematic steps to synthesize a multivariable controller. It is a particularly useful technique when there is required partial or full noninteraction in conjunction with invariance of certain of the outputs with respect to disturbance vectors. This is a structure oriented method where the critical plant parameters and variables are reflected in the controller structure. The resulting controller structure permits a simple final field adjustment of controller parameters during the initial operation period. In addition, these same properties allow adaptive methods that require adjustment of very few of the parameters in response to environmental or plant changes. The problems of physical realization of controller elements and of achieving the desired control specifications are handled by a technique that may operate on the structure as it is derived. These operations clearly show the alternatives available, both in structuring and in realizing elements. These features indicate that algorithms to aid the design procedure would be quite possible for use on digital computers.