Improved discrete-time, disturbance-accommodating control performance using discrete/continuous control theory. part I. Complete disturbance-cancellation (rejection)

The effective accommodation of immeasurable, persistently-acting, external disturbance-inputs is an important consideration in the design of virtually all control systems. Design methodologies for a broad variety of traditional, zoh-type, multivariable, discrete-time "disturbance-accommodating" (disturbance-rejecting, etc.) controllers have been available in the control literature since 1982. In this part I of a multipart paper, similar multivariable "disturbance-accommodating" controller design methodologies are developed for a new and more-general type of discrete-time controller called a discrete/continuous (D/C) controller. The unique dynamic characteristics of a D/C-type control-input make it possible to design "smart," multivariable, discrete-time controllers that, compared to conventional zoh-type discrete-time controllers, can achieve significant performance improvements in set-point ("pointing") and servo-tracking problems, as well as in cancellation ("rejection"), and other modes of disturbance-accommodation. The paper focuses on the design of D/C discrete-time controllers to achieve complete disturbance-cancellation (complete "rejection" of disturbances).