Ian K. Craig

When to initiate HIV therapy: a control theoretic approach

This paper shows an application of control theory to human immunodeficiency virus (HIV)/AIDS models. Minimum singular value decomposition is applied to HIV/AIDS models to measure the extent to which the different stages in the progression of HIV/AIDS disease are controllable and, consequently, when best to initiate therapy such that the general objectives of therapy are satisfied. Simulations are used to demonstrate the effect of treatment at various stages. Comparisons are made between mono-class and combination therapies and between when therapy is initiated at the acute infection, asymptomatic and the advanced stages.

Model predictive control of an electric arc furnace off-gas process

Abstract This paper shows that an electric arc furnace off-gas system can provide valuable manipulated variables for feedback control which can improve furnace efficiency and contribute to safety in the workplace. Model predictive control (MPC) is used to illustrate this concept using practically motivated control objectives. An initial verification of a non-linear furnace model with plant data is shown. The design of MPC controllers for the furnace is discussed and results are shown by way of simulation. Evaluation of the final controller against traditional manual operation is done, and the setpoint tracking capability of the controller is tested.

Robust Nonlinear Model Predictive Control of a Run-of-Mine Ore Milling Circuit

This brief investigates the feasibility of applying a robust nonlinear model predictive controller to a run-of-mine ore milling circuit, and the conditions under which such a controller might be worthwhile implementing. The run-of-mine ore milling circuit model used consists of nonlinear modules for the individual components of the milling circuit, allowing for arbitrary milling circuit configurations to be modeled. The model is cast into a robust nonlinear model predictive control framework, and a practically motivated simulation of the mill model being controlled by an robust nonlinear model predictive control (RNMPC) controller is presented. Issues related to implementing such a controller are investigated.

Economic evaluation and design of an electric arc furnace controller based on economic objectives

Controllers are often designed to satisfy functional objectives, without a thorough analysis of the resulting economic impact. A model predictive controller, designed based on economic objectives, is used to control electric arc furnace variables that are usually under manual control. To make the controller simulation as realistic as possible, the economic data used are taken from an operating furnace, and measurements are only fed back as and when they typically become available. The economic benefits of model predictive control over manual control are also quantified in a simulation study. Potential savings in excess of 5% are predicted by more efficient feed material utilisation and by preventing unscheduled delays.

Introducing HIV/AIDS education into the electrical engineering curriculum at the University of Pretoria

This paper describes how HIV/AIDS education is being introduced into the curriculum of the Department of Electrical, Electronic, and Computer Engineering at the University of Pretoria, Pretoria, South Africa. Third- and fourth-year students were provided with an HIV/AlDS Educational CD developed at the university. Their knowledge of the subject was tested via two quizzes-one written before they were exposed to the material on the CD and one after. In addition, a mathematical HIV/AIDS model is being incorporated into a third-year control systems course. This model is used to illustrate standard control systems engineering concepts, such as linearization, system stability, feedback, and dynamic compensation. This paper is an example of how topical nonengineering material can effectively be made part of a high-level undergraduate engineering course. Students benefit not only from the topical nature of the subject, but also from an improved understanding of control engineering concepts which can be applied to many different fields.

Evaluation of advanced industrial control projects: a framework for determining economic benefits

A framework for the evaluation of advanced control projects is illustrated in this paper by way of a case study on level control in mineral flotation. The approach taken is to investigate how improvements brought about by advanced control can be measured to a required level of statistical significance, after the controller has been commissioned. Measured improvements are translated into increases in cash flow that result from implementing an advanced controller, which is then used for project evaluation. As an introduction to the case study, a framework for establishing advanced controllers for industrial processes, which culminates in determining economic benefits, is discussed. Ways of obtaining controller benefits through the reduction of downtime and product variations, are also described. The risk of implementing an advanced control project is discussed together with typical scenarios under which such projects are often undertaken.

A contemplative stance on the automation of continuous casting in steel processing

Abstract This paper gives a contemplative stance on the automation of continuous casting in steel processing. It gives a brief overview of the control techniques used in this industry, typical applications of such techniques, and discusses supportive technologies that form a critical part of the implementation of such techniques. The casting process and operational issues are described. Particular attention is paid to production planning and scheduling, computer-aided quality control, and the crucial role that instrumentation plays in the automation of a caster. The importance of integrating casting automation systems into plant wide production systems, and the development of new instrumentation, are highlighted.

Robust controller design and implementation for a run-of-mine ore milling circuit

Abstract A new approach to the problem of designing a multivariable controller for a run-of-mine (ROM) ore mill is described. Doyles μ-controller synthesis and analysis methodology is applied to a general formulation of this problem that includes plant model uncertainties and performance specifications. The design process, including the weight iterations required to meet performance robustness specifications, is explained. The results of testing the μ-controller on an industrial ROM milling circuit are presented and the practical problems encountered are discussed.

Experimental design for the economic performance evaluation of industrial controllers

Experimental design techniques are routinely used in the social and biological sciences to determine the relative performance of different factors. However, it appears that these techniques are not commonly used by the industrial control community. As a consequence, incorrect conclusions are often reached from inappropriately designed plant improvement trials. This presentation introduces experiment design concepts as part of a framework for determining the economic benefits of advanced industrial control projects. Using improved level control in mineral flotation as an example, common incorrect experiments are demonstrated and examples of correct experimental designs are given. The contention is that greater use of these tools by the industrial control community would significantly enhance the validity of comparative trials.

AN OVERVIEW OF THE AUTOMATION OF LOAD-HAUL-DUMP VEHICLES IN AN UNDERGROUND MINING ENVIRONMENT

Abstract This work is a survey on the automation of load-haul-dump trucks in underground mining. Background on the purpose of LHD vehicles is given and the need to automate LHDs discussed, with emphasis on the underground mining environment. Safety issues regarding mine personnel and mine vehicles are considered. Dynamic and kinematic modelling techniques including slip and no-slip models are discussed. Navigation of the LHD through the mine using absolute and reactive navigation are given and sensor technology is perused.