Closed-loop identification with a quantizer (2005)
Wang, M., Thornhill, N.F., Huang, B.
This paper proposes a new closed-loop identification scheme for a single-input single-output (SISO) control loop based upon a quantizer inserted into the feedback path. The quantizer can be used to...
Huang, B., Ding, S.X., Thornhill, N.F.
The research on control loop performance monitoring and diagnostics has been and remains to be one of the most active research areas in process control community. Despite of numerous developments, it...
Diagnosis of poor control loop performance using higher order statistics (2004)
Higher-order statistical (HOS) techniques were first proposed over four decades ago. This paper is concerned with higher-order statistical analysis of closed-loop data for diagnosing the causes of...
Specifying the directionality of fault propagation paths using transfer entropy (2004)
Bauer, M., Thornhill, N.F., Meaburn, A.
In continuous chemical processes, variations of process variables usually travel along propagation paths in the direction of flow. The aim of this study was to find a data-driven method for...
The impact of compression on data-driven process analyses (2004)
Stored process data in the form of high fidelity time trends are a resource for data-driven process analyses such as statistical monitoring, minimum variance control loop benchmarking, fault...
Principal components analysis of nonlinear chromatography (2004)
Pate, M.E., Turner, M.K., Thornhill, N.F., Titchener-Hooker, N.J.
Principal component analysis (PCA) has been used for the modeling of nonlinear chromatography under overload conditions. A 10-fold range of crude erythromycin samples were loaded onto columns with...
A frequency domain measurement diagnostic technique for plasma-tools (2004)
Law, V. J., Kenyon, A.J., Thornhill, N.F., Pagliarani, A., Lea, L., Watkins, M.
The design of a 10–500 MHz bridge is described and also its use with a tracking generator and spectrum analyser to form a scalar network analyser for the investigation of the internal...
Diagnosis of plant-wide oscillation through data-driven analysis and process understanding (2003)
Thornhill, N.F., Cox, J.W., Paulonis, M.A.
Disturbances that propagate throughout a plant due to recycle streams, heat integration or other means can have an especially large impact on product quality and running costs. There is thus a...
Controller performance assessment in set point tracking and regulatory control (2003)
Thornhill, N.F., Shah, S.L., Huang, B.
Recent critiques of minimum variance benchmarking for single-input-single-output (SISO) control loops have focused on the need for assessment of performance during set point changes and also on the...
Harmonic monitoring of the switched silicon etched process (2003)
Law, V.J., Kenyon, A.J., Thornhill, N.F., Pagliarani, A., Lee, K., Watkins, M., ...
A new non-invasive radio frequency technique for real-time monitoring of the STS ASE (TM) deep silicon etch process, or other forms of the Bosch switched etch process, is reported. The technique...
Detection of multiple oscillations in control loops (2003)
Thornhill, N.F., Huang, B., Zhang, H.
This article addresses the detection of oscillations in measurements from chemical processes including the case when two or more oscillations of different frequency are present simultaneously. The...
A data-driven model for valve stiction (2003)
The presence of nonlinearities, e.g., striction, hysteresis and backlash in a control valve limits the control loop performance. Striction is the most common problem in spring-diaphragm type valves,...
Harmonic monitoring of the switched silicon etched process (2003)
Law, V.J., Kenyon, A.J., Thornhill, N.F., Pagliarani, A., Lee, K., Watkins, M., ...
A new non-invasive radio frequency technique for real-time monitoring of the STS ASETM deep silicon etch process, or other forms of the Bosch switched etch process, is reported. The technique...
Amplitude and phase measurement of plasma harmonics in a photoresist etching process (2003)
Pagliarani, A., Kenyon, A.J., Thornhill, N.F., Lee, K., Law, V.J., Lea, L.
Remote-Coupled Oxygen Plasma Harmonic Measurements for Process Monitoring (2003)
Law, V.J., Bergamini, S., Kenyon, A.J., Thornhill, N.F., Lee, K., Watkins, M., ...
About the book: This book presents state-of-the-art analysis of developments in plasma physics.
Inferential measurement of SAG mill parameters III: inferential models (2002)
Apelt, T.A., Asprey, S.P., Thornhill, N.F.
This paper discusses inferential measurement models for semiautogenous grinding (SAG) mills. Inferential measurements of SAG mill discharge and feed streams and mill rock and ball charge levels are...
Inferential mearurement of SAG mill parameters II: state estimation (2002)
Apelt, T.A., Asprey, S.P., Thornhill, N.F.
This paper discusses the combined state and parameter estimation of SAG mill inventories and model parameters. Recognised simulation models are utilised for the rock and water charge state equations....
Tan, C.C., Thornhill, N.F., Belchamber, R.M.
This paper discusses principal component analysis (PCA) of integral transforms (spectra and autocovariance functions) of time-domain signals. It is illustrated using acoustic emissions from...
Spectral principal component analysis of dynamic process data (2002)
Thornhill, N.F., Shah, S.L., Huang, B., Vishnubhotla, A.
This article describes principal component analysis (PCA) of the power spectra of data from chemical processes. Spectral PCA can be applied to the measurements from a whole unit or plant because...
Path analysis for process troubleshooting (2002)
Huang, B., Thornhill, N.F., Shah, S., Shook, D.
In this paper, a model-free data-driven approach to process troubleshooting is proposed. The method is simple and can handle both univariate and multivariate processes. The only information needed...
Analysis of plant-wide disturbances using conditional entropy (2002)
Plant-wide disturbances in chemical plants have an impact on product quality and running costs, thus there is a need for automated diagnosis of the root cause. This short paper reports work in...
Detection and diagnosis of system nonlinearities using higher order statistics (2002)
This paper is concerned with the statistical analysis of closed loop data for diagnosing the causes of poor control loop performance. Higher Order Statistical (HOS) techniques have been developed...
Closed loop identification based on quantization (2002)
Wang, M., Thornhill, N.F., Huang, B.
This paper proposes a new closed-loop identification scheme for a single-input-single-output control loop. It is based upon a quantizer inserted into the feedback path. The quantizer can be used to...
Analysis of plant-wide disturbances through data-driven techniques and process understanding (2002)
Thornhill, N.F., Xia, C., Howell, J., Cox, J., Paulonis, M.
Plant-wide disturbances can have an impact on product quality and running costs. Thus there is a motivation for automated detection of a plant-wide disturbance and for diagnosis of the root cause. In...
Plasma harmonics Lissajous measurements (2002)
Bergamini, S., Law, V.J., Kenyon, A.J., Thornhill, N.F., Lea, L.
RF probe technology for the next generation of technological plasmas (2001)
Law, V.J., Kenyon, A.J., Thornhill, N.F., Seeds, A.J., Batty, I.
We describe radio frequency (rf) analysis of technological plasmas at the 13.56 MHz fundamental drive frequency and integer narrow-band harmonics up to n = 9. In particular, we demonstrate the use of...
Inferential measurement of SAG mill parameters (2001)
Apelt, T.A., Asprey, S.P., Thornhill, N.F.
Semi-autogenous (SAG) mill total load and ball load have a marked influence on mill performance. Direct measurement of these inventories is difficult, hence inferential measurement is an attractive...
Detection of distributed oscillations and root-cause diagnosis (2001)
Thornhill, N.F., Shah, S.L., Huang, B.
This article addresses the detection and diagnosis of oscillations in process measurements. Principal components analysis (PCA) can be applied to the power spectra for detection of groups of...
L.I.G.Kovaznay - Laminar flow behind a two-dimensional grid (2001)
N. F. Thornhill, S. L. Shah, B. Huang
This article addresses the detection and diagnosis of oscillations in process measurements. Principal components analysis (PCA) can be applied to the power spectra for detection of groups of...
Remote-coupled sensing of plasma harmonics and process end-point detection (2000)
Law, V.J., Kenyon, A.J., Thornhill, N.F., Srigengan, V., Batty, I.
A remote-coupled dual-directional coupler used in the single-directional mode for process harmonic end-point detection is described. Harmonic end-point detection of photoresist stripping and chamber...
Pate, M.E., Turner, M.K., Thornhill, N.F., Titchener-Hooker, N.J.
Principal component analysis (PCA) was used to analyse the behaviour of a chromatographic separation as its scale increased. Three 4.6 mm diameter columns identical in every respect except for column...
Koh, A.T-C., Thornhill, N.F., Law, V.J.
A principal component analysis (PCA) of plasma-generated harmonics monitored using a non-invasive ex-situ probe is reported. PCA trends due to gas pressure and RF power were demonstrated. Changes in...
Refinery-wide control loop performance assessment (1999)
Thornhill, N.F., Oettinger, M., Fedenczuk, P.
This paper discusses the application of control loop performance assessment (CLPA) in a refinery setting. The CLPA algorithm has several parameters that have to be adjusted correctly to give the best...
Near infra red spectroscopy for bioprocess monitoring and control (1999)
Yeung, K.S.Y., Hoare, M., Thornhill, N.F., Williams, T., Vaghjiani, J.D.
This article describes the calibration of a spectroscopic scanning instrument for the measurement of selected contaminants in a complex biological process stream. Its use is for the monitoring of a...
Pre-processing of chromatographic data for principal component analysis (1998)
Pate, M.E., Thornhill, N.F., Chandwani, R.M., Hoare, M., Titchener-Hooker, N.J.
This paper examines the selection of the appropriate representation of chromatogram data prior to using principal component analysis (PCA), a multivariate statistical technique, for the diagnosis of...
Cost benefit analysis of refinery process data: case study (1998)
Alheritiere, C., Thornhill, N.F., Fraser, S., Knight, M.J.
This paper applies the methodology developed previously to quantify the contribution of process data to performance measures. It describes a refinery case study in which measurements are ranked...
Performance assessment and diagnosis of refinery control loops (1998)
Thornhill, N.F., Oettinger, M., Fedenczuk, P.
This paper discusses the application of control loop performance assessment (Desborough and Harris, 1992) in a refinery setting. In a large process it is not feasible to tailor the parameters of the...