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Past Projects

Back to Stephen Duncan

Control of Temperature Profile during Sprayforming

The sprayform process creates tools and dies by spraying molten metal from arc spray guns onto a ceramic former. The key step in this technology is to ensure that as the metal cools, it undergoes a specific expansive phase transformation that offsets the thermal contraction experienced by the metal. This allows the formation of dimensionally accurate tools. In order that the metal undergoes the required transformation, the temperature profile of the surface has to be accurately controlled throughout the spraying process. This is achieved by measuring temperature variations in real time with a thermal imaging camera and then using this information to adjust the rate of spraying as the guns are moved over the surface by a robot. A full-scale spray cell has been built and an online control system has been successfully demonstrated along with offline path planning tools. A commercial version of the system has been developed. Discussions are currently being held with Ford Motor Company to continue this research for a further three years during which time, the process will be scaled up to allow larger tools to be sprayed. This will involve extending the cell to enable metal to be sprayed simultaneously form guns mounted on two robots. The ideas are also being used to control a plasma spraying process.

Participants: Paul Jones, Vassilios Tsachouridis, Pubudu Pathirana, Stephen Duncan, Tim Rayment, Sarah Hoile, Zoran Djuric, Patrick Grant

Partners: Department of Materials Science, University of Oxford; Ford Motor Company; Novarc Limited; Sulzer Metco; Kuka Robots.

Duration: 2000-2006

Process Control of Vacuum Plasma Coating

Vacuum plasma spraying is an industrial technique used to coat substrates onto a wide range of materials. Historically, vacuum plasma spraying processes have been open-loop processes with, at the most, closed-loop control of the spray parameters. The key control variable for these processes is the coating quality and in particular, the microstructure of the coated material. It has been shown that control of surface temperature during spraying has a direct effect on the microstructure and this project is designing and implementing a system for controlling temperature online so that the improvements in coating quality and process repeatability can be assessed.

Participants: Ewan Davis, Stephen Duncan, Patrick Grant

Partner: Department of Materials Science, University of Oxford

Duration: 2004 - 2007

Control of Concentration in Fluid Flow

Industrial process tomography systems can measure the concentration profile of different components or phases of a fluid flow within a pipe. The tomographic system works by measuring the capacitance or impedance between successive pairs of electrodes within an array that is mounted around the pipe. A state estimation scheme is then used to determine the concentration profile. 2-dimensional simulation studies carried out in conjunction with the Department of Applied Physics at the University of Kuopio, Finland, have indicated that a tomographic sensor can be combined with an array of injectors in a feedback loop to regulate the concentration profile in the pipe. The results of this research have been used in the project to control fluidised-bed dryers.

Participants: Anna Ruuskanen, Stephen Duncan, Jari Kaipio

Partners: Department of Applied Physics, University of Kuopio, Finland

Duration: 2003-2005

Control of Ultra-sound Treatment for Cancer

Cancer can be treated by using ultra-sound to heat tumours. A key component of the treatment is the ability to control the temperature profile during heating as it is necessary to ensure that the temperature within the tumour is sufficiently high to kill the cancerous cells without affecting the surrounding healthy tissue. A feedforward strategy for determining the power that should be applied to an array of ultra-sound sources has been developed, together with a feedback mechanism that uses images from an MRI scanner to control the temperature profile within and around the tumour. An alternative system, that uses ultra-sound for both sensing and actuation, is currently being investigated.

Participants: Matti Malinen, Stephen Duncan, Jari Kaipio

Partner: Department of Applied Physics, University of Kuopio, Finland

Duration: 2003-2005

Control of Gas Flows during Anaesthesia

Many systems for monitoring and regulating the flow of gases during anaesthesia are relatively crude and there is a considerable scope for using modern sensing technology to improve both the concentration of gases delivered to the patient and the overall amount of gas used during the procedure. In conjunction with the Nuffield Department of Anaesthetics, a prototype control system is being developed that will be tested. It is intended that the system will be used to determine the fraction of the blood that is not oxygenated as it passes through the lungs, directly from the difference between the composition of the inspired and expired air. Currently, this has to be inferred from the composition of the blood taken from a separate measurement.

Participants: Sara van der Hoeven, Stephen Duncan, Andrew Farmery, Clive Hahn

Partner: Nuffield Department of Anaesthetics, University of Oxford

Duration: 2004-2008

Modelling the Spread of Epidemics

The spread of a disease through a population can be modelled by as a dynamic spatio-temporal system. My work has concentrated on the spread of smallpox and interest in modelling the spread of this disease has increased recently, due to the possibility of smallpox being used in a bio-terrorist attack. The design of strategies for vaccination and quarantine and other public health measures to combat an outbreak of smallpox started by bio-terrorist action is critically dependent on an accurate measure of the transmissibility of the virus. By modelling the dynamics of the disease as a linear system with a non-linear feedback term, the transmissibility of the virus can be estimated from the frequency of outbreaks in populations where the disease is endemic. This approach has been used to derive an estimate of the value for the transmissibility for London in the 18th Century.

Participants: Stephen Duncan, Susan Scott

Partners: School of Biological Sciences, University of Liverpool

Duration: 2001-2009

Active and Inferential Sensing for Two-dimensional processes

Participants: Peter Randall, Jim Skelton, Stephen Duncan, Peter Wellstead

Partners: 3M, NDC/Infrared Engineering

Duration: 1996 – 2000

Design of a Track through Zoom System

Participants: Tom Roberts, Stephen Duncan

Partner: Pilkington Optronics

Duration: 1996 – 1999

Control and Estimation for Web Forming Processes

Participants: David Gacon, Martin Zarrop, Peter Wellstead, Stephen Duncan

Duration: 1994 – 1997

The Application of Basis Function Techniques to the Control of 2-D Processes

Participants: Ken Corscadden, Stephen Duncan

Partners: ICI Films

Duration: 1994 – 1997

Control of Radio-frequency Heating

Participants: Chris Cottee, Stephen Duncan

Partners: EA TEchnology

Duration: 1994 – 1997