A Frequency Domain Design for the Control of a Distributed Parameter System

This thesis presents a new approach to frequency domain design of robust controllers for distributed parameter systems. The central idea is to use techniques from complex analysis, that were developed for the solution of the Corona Problem, for the solution to the Bezout equation that arises in the parameterization of stable feedback controllers. An algebraic reformulation of the Bezout equation allows the solution to be computed from the solution of an auxiliary equation with a Carleson measure as the inhomogeneous term.We first show how the Bezout equation arises in the problem of feedback controller design, then we present techniques that are used for its solution. An example is given in which the solution to a Bezout equation derived from an unstable plant with a delay is calculated. Finally this example is extended to show how the techniques developed for the Bezout equation may be used to calculate a sub-optimal solution to the Nehari Problem for a single-input single output system

Estimation of Hidden Markov Models for Partially Observed Risk Sensitive Control Problems

We look at the problem of estimation for partially observed, risk-sensitive control problems with finite state, input and output sets, and receding horizon. We describe architectures for risk sensitive controllers, and estimation, and we state conditions under which both the estimated model converges to the true model, and the control policy will converge to the optimal risk sensitive policy

A Model of the Dynamics of a Lathe Toolpost that Incorporates Active Vibration Suppression

A simple, linear, system model is presented for a lathe with a toolpost that incorporates active vibration suppression. The toolpost model is built from linear dynamic models of the component parts of the toolpost design: the actuator and drive circuitry, and the mechanical toolpost. The toolpost model is then combined with linear models for the lathe dynamics and cutting process to produce a model of the entire mechanical system. This model is used as the basis for a controller design that uses a measurement of the actuator current for a sensor signal, and the voltage applied to the actuator by the power amplifier as a control signal. The controller design uses the H 1 design methodology. The performance criteria for the toolpost design are interpreted as measures on transfer functions associated with the system model, and predictions of the performance of the design are made on the basis of these measures. The conclusion drawn from this work is that with careful design, the active ..

A Computational Method for Hontroller Design in the Frequency Domain

A new approach to frequency domain design of robust controllers for distributed parameter systems is presented. The central idea is to use techniques that were developed for the solution of the Corona Problem, for the solution of both the Bezout equation and an auxiliary equation that arises form the Nehari interpolation problem. An algebraic reformulation of these equations allows the solution to be computed from the solution of an inhomogeneous Cauchy Riemann equation with a Carleson measure as the inhomogeneous term. The theory is applied to a single input single output system with delay to yield the transfer function of a stabilizing controller with guaranteed Hstability margin. Finally the framework is extended to handle multi-input multi- output system

Postoperative critical care and high-acuity care provision in the United Kingdom, Australia, and New Zealand

BACKGROUND: Decisions to admit high-risk postoperative patients to critical care may be affected by resource availability. We aimed to quantify adult ICU/high-dependency unit (ICU/HDU) capacity in hospitals from the UK, Australia, and New Zealand (NZ), and to identify and describe additional 'high-acuity' beds capable of managing high-risk patients outside the ICU/HDU environment. METHODS: We used a modified Delphi consensus method to design a survey that was disseminated via investigator networks in the UK, Australia, and NZ. Hospital- and ward-level data were collected, including bed numbers, tertiary services offered, presence of an emergency department, ward staffing levels, and the availability of critical care facilities. RESULTS: We received responses from 257 UK (response rate: 97.7%), 35 Australian (response rate: 32.7%), and 17 NZ (response rate: 94.4%) hospitals (total 309). Of these hospitals, 91.6% reported on-site ICU or HDU facilities. UK hospitals reported fewer critical care beds per 100 hospital beds (median=2.7) compared with Australia (median=3.7) and NZ (median=3.5). Additionally, 31.1% of hospitals reported having high-acuity beds to which high-risk patients were admitted for postoperative management, in addition to standard ICU/HDU facilities. The estimated numbers of critical care beds per 100 000 population were 9.3, 14.1, and 9.1 in the UK, Australia, and NZ, respectively. The estimated per capita high-acuity bed capacities per 100 000 population were 1.2, 3.8, and 6.4 in the UK, Australia, and NZ, respectively. CONCLUSIONS: Postoperative critical care resources differ in the UK, Australia, and NZ. High-acuity beds may have developed to augment the capacity to deliver postoperative critical care