Robust Sampled Regulators for Stable Systems From Plant Step Data

The discrete time integrating regulator introduced by Astrom is extended to cover the case of multivariable systems with non-monotonic step responses. The use of approximate models to increase the possible range of sampling rates is also considered

Design of tracking systems incorporating multivariable plants

The methodology for the design of error-actuated digitalset-point tracking controllers proposed by Porter andco-workers has emerged as a result of the pursuit of effective and practical solutions to the problem of designing digital control systems for unknown, dynamically complex multivariable plants with measurable outputs. In this thesis, such digital set-point tracking controllers and the resulting digital set-point tracking systems are enriched to embrace plants with unmeasurable outputs and plants with more outputs than manipulated inputs. In the study of the latter plants, the novel concepts of limit tracking (i.e. the tracking exhibited by plants with moreoutputs than inputs) is introduced and an associatedmethodology for the design of self-selecting controllers isproposed. Such controllers involve the selection of differentset-point tracking controllers to control the most criticalsubset of plant outputs based upon the developed rigoroustheoretical foundations for the limit-tracking systems. Insuch foundations, the classification of linear multivariableplants into Class I and Class II plants based upon theirsteady-state transfer function matrices facilitates theassessment of the feasibility of limit-tracking systems.Furthermore, the associated order-reduction techniquesimplifies the problem of deciding the minimum numbers ofdifferent subsets of plant outputs to be controlled bycorresponding set-point tracking controllers. In addition, the dynamical properties of limit-tracking systems are alsoinvestigated using the phase-plane method and a methodology for the design of supervisory self-selecting controllers is proposed so as to prevent the occurrence of dynamical peculiarities such as limit-cycle oscillations which might happen in limit-tracking systems. The effectiveness of all the proposed methodologies and techniques is illustrated by examples, and the robustness properties of set-point tracking systems and limit-tracking systems in the face of plant variations and unknown disturbances are tested. Finally, self-selecting controllers are designed for a nonlinear gas-turbine engine and their practical effectiveness is clearly demonstrated