Abstract
This paper considers how the output measurements have relation to the set of transfer functions from external inputs to controlled outputs achievable by stabilizing controllers.
For the design of control systems model-matching technique plays a fundamental role. Recently, several control problems concerning the above have been solved. Generally there is a degree of freedom in designing a controller with which a specified external characteristic is achieved. It is to be desired from the viewpoint of maintenance and economy that as few output-measuring terminals as possible be used. As a result we obtained a criterion for judging whether a particular subset taken from among the presupposed measuring terminals includes redundancy for the control objective or not, by using explicit characterization of all controllers that achieve the specified transfer function. In the case where some desired characteristic is not achievable, we utilize additional sensor outputs. A necessary and sufficient condition under which the inclusion of additional sensors strictly enlarges the class of achievable transfer functions is given.
