Multivariable Control Scheme Design for Discrete Systems Employing Multirate Sampling

Abstract

Multivariable frequency response methods which have been used widely and successfully for the design of continuous multi-input multi-output control systems, can be directly extended to the z domain to cope with digital computer control schemes provided a common sampling rate is used throughout. When a variety of sampling rates are used to accommodate differing physical requirements and speeds of response, a complete and explicit z transfer function matrix representation of the system can no longer be determined and the required mapping arrays cannot be generated.This paper outlines an approach to the design of schemes employing multirate sampling which combines both z domain and time domain techniques, The overall control structure is determined from a mapping approach. assuming single rate sampling, and the individual loop compensators are found via a discrete model adjustment method which takes account of the differing sampling periods involved.