David I. Wilson

Eco-efficiency and control loop configuration for recycle systems

To integrate measurements of eco-efficiency with control loop configuration has become an important topic since all industrial processes/plants are requested to increase their eco-efficiency. The exergy eco-efficiency factor, a new measure of eco-efficiency for control loop configuration, has been developed recently [1]. The exergy eco-efficiency factor is based on the thermodynamic concept of exergy, which can be used to analyze a process in terms of its efficiency. The combination of the relative gain array (RGA), NI, CN, dynamic RGA, and the exergy eco-efficiency factor will help guide the process designer to find the optimal control design with low operating cost/eco-efficiency. In this paper, we validate the proposed exergy eco-efficiency factor for processes with recycles which are very common industrially.

Rigorously modelling steam utility systems for mixed integer optimization

Given that industrial utility systems are essentially large energy converters, it is surprising that they are so often forgotten or ignored when optimizing plant performance. Significant operational savings are possible simply by redistributing steam generation and consumption, without adding extra equipment, and with minimal investment. However due to the discrete nature of a utility system where equipment can switched in and out of service, steam flows redistributed, and zero-flow conditions are normal, the optimizing of utility system requires a rigorous model based on thermodynamics and state-of-the-art numerical algorithms. This paper proposes a mixed integer modelling strategy to approximate a rigorous simulator model, combining regressions from literature, industrial experience and process specific knowledge resulting in a model suitable for optimization. Two case studies are presented to demonstrate the efficiency of the modelling design, a hypothetical three header model with cogeneration and a four header refinery utility system. Both systems are optimized using BONMIN in less than a quarter of a second on a standard desktop PC and result in substantial economic improvements.

Optimising ferry routes

In open waters, the skippers of passenger ferries have some leeway to plot a course that balances fuel efficiency, safety, and passenger comfort whilst still maintaining a tight schedule. This paper describes the seeking of an optimal ferry course for a 400t vehicular and passenger ferry. Numerical dynamic optimal control studies based on the vessels actual operating data, bathymetry and tidal streams showed that depth under keel was important in periods of slack water which fortuitously in this location happens to be adequately approximated by a simple straight line. During times of strong tidal streams, the optimal trajectory improved travel time by about 3.5% compared to the simple hooked curve course.

Navigating the wilds of industrial optimisation

Abstract The continual search for solutions that are better, faster and more efficient is second nature to all engineers. This activity is known as optimisation. But industrial optimisation problems are like the mythical beast, the Jabberwocky: they are big, complex, mean, ill-tempered, and prickly. What is interesting though is how we arrive at optimal solutions; how we can rapidly discard non-contenders, reduce the search-space, and accelerate the passage to the optimum. Essentially how do we optimise the optimisation process? This paper reviews the recent developments in large-scale optimisation algorithms that are suitable for industrial problems. The important issues of correctly formulating the optimisation problem, judging when to add constraints, when to introduce binary variables, and which of the many numerical algorithms to choose are also highlighted with many actual industrial examples such as trajectory planning of the Waiheke ferry, to the optimal operation of steam utility boiler systems, to optimal design of microwave cavities, and the classification of the electrical power usage of suburbs from Dargaville to Wellsford. The take home message is this: with the right tools (many of which are free), all the world’s problems start to look like optimisation problems where even a slightly better solution is better than nothing at all.

Maintaining New Zealand's electrical reserve management tool

Managing the electrical reserves in a small, geographically elongated nation like New Zealand is a challenge. The Reserve Management Tool (RMT) developed over a decade ago optimally schedules the reserve load given the current and anticipated circumstances every half hour to ensure that the reserve requirement for electricity is always met. However with changes in the underlying computing platform, and the recognition that the tool needed to be more flexible to incorporate future generator development meant that this tool needed a revamp. This paper describes the present tool, the motivation for the redesign and demonstrates the new capabilities.

Control Performance Assessment for a class of Nonlinear Multivariable Systems

Abstract Control loops of importance in industrial applications are often multivariable and exhibit nonlinear dynamics stemming either from the plant, the transducers, the actuators, or even in some cases the controllers themselves. Both these issues, the multivariable nature of the control loop and the nonlinearities, mean that it is awkward to reliably assess the control loops performance using standard tools. This study extends control performance assessment tools to nonlinear multi-input multi-output (MIMO) systems. To make the problem tractable, we restrict our nonlinear MIMO system structure to be a system with additive linear disturbances and where the nonlinearity is in the form of valve stiction.

Research data supporting "Flow visualisation and modelling of solid soap extrusion"

MATLABFigs.zip contains the MATLAB files for all of the figures which are plots/charts in the manuscript. One can extract the numerical values from the MATLAB .fig file

A cost effective high-speed auto-coded embedded model predictive controller

Compared to PID control, model predictive controllers place high demands on the computing environment in terms of precision, speed, and memory, take time to design due to the embedded dynamic model, and do not scale particularly well. This paper describes a way to seamlessly implement a flexible MPC controller designed to operate in embedded hardware starting from a dynamic model in Matlab. The resultant controller runs stand-alone on the embedded hardware, is extremely fast, exhibits a modest memory footprint and best of all, requires no particular embedded programming experience from the user.

From Chalk Talk to Tablet Talk: Pedagogies for Control Engineering

Abstract Individual disciplines, and even subfields within those disciplines, typically exhibit distinctive pedagogical approaches that have developed over time, influenced by the content of the discipline and technology. In control engineering, mathematical symbolic and diagrammatic forms are a key element, and have been traditionally taught using oral and handwritten approaches (so called chalk-talk). The widespread use of computer display technology and PowerPoint has influenced the way in which the development of ideas is presented, leading to mathematics presented as solutions, rather than a process, and the isolation of the mathematics from the control engineering context. This paper reviews educational trends and personal experience that suggests the use of digital pen-enabled tablet technologies can facilitate the reintroduction of elements critical to developing an effective pedagogy for control engineering.