No description available.

Unsatisfactory performance of a control system may have different root causes, of which diagnosis and control have been subjects of interest. Numerous approaches have been used to identify the source of the oscillatory behavior of control systems. This work will focus on the nonlinearities introduced by process equipment, more specifically, static friction (stiction) in control valves. Using shape-based stiction detection methods and surrogate testing for time series, a new detection method is proposed for systems containing one or more sticky valves. Performance of this method is validated by both simulation and industrial data. The existence of stiction in a control valve may lead to oscillations in all loops of the process. In this work, frequency analysis of multi-loop processes oscillating due to stiction will be presented. Derivation of a general mathematical representation of the condition, under which oscillations occur in a multi-loop system because of stiction, is the contribution of the proposed analysis. The proposed condition for occurrence of oscillations provides a compensation framework for this problem. In this scheme, given dynamics of the system and severity of stiction, the appropriate tuning for the controller will be found which reduces or removes oscillations from the system. An alternative compensation algorithm will also be proposed, which aims removal of oscillations from systems for which the previously proposed approach cannot permanently remove undesirable oscillations. Achieving a non-oscillatory output without making the valve stem to move more aggressively, is the main characteristic of this algorithm. / Process Control

Nowadays, the assembly of small (<1mm) components has become an industrial reality. Many domains like MEMS, surgery, telecommunications, car industry, etc. now have large use of micro-parts. At this scale, predominant forces are different than in macroworld. The pieces often undergo adhesion problems. The adhesion forces can be splitted in different components : van der Waals, electrostatics and capillary condensation. This work focuses on capillary condensation as it often can be the major component of the adhesion force. The first part of this work details a review of literature of different fields involved in capillary condensation. A simulation tool is then implemented and theoretically validated in the second part of the work. Finally, a test bed is presented; this bed is then used to experimentally validate the simulation results. Experiments and simulation results are shown to concord. Therefore, the simulation tool can be used to model the force due to capillary condensation.

The pressure between two parallel planar surfaces at equal electric potentials is derived using the modified Poisson-Boltzmann (MPB) equation to account for finite ion size. The effects of finite ion size are presented for a z:z symmetric electrolyte and compared with the pressure derived by the classical Poisson-Boltzmann (PB) equation. The pressures predicted by the two models differ more as the bulk ion concentration, surface potential, and ion size increase. The ratio of the pressures predicted by the two models is presented by varying the ion concentration, surface potential, ion size and distance of separation. The ratio of pressures is relatively independent of the distance of separation between the two surfaces. An elastic beam suspended horizontally over a substrate in liquid electrolyte is subjected to electric, osmotic, and van der Waals forces. The continuous beam structure, not a discrete spring, which is governed by four nondimensional parameters, is solved using the finite element method. The effects of ion concentration and electric potentials to the pull-in instability are especially focused by parametric studies with a carbon nanotube cantilever beam. The pull-in voltage of a double-wall carbon nanotube suspended over a graphite substrate in liquid can be less than or greater than the pull-in voltage in air, depending on the bulk ion concentration. The critical separation between the double-walled carbon nanotube (DWCNT) and the substrate increases with the bulk ion concentration. However, for a given bulk ion concentration, the critical separation is independent of the electric potentials. Furthermore, the critical separation is approximately equal in liquid and air. Stiction, the most common failure mode of the cantilever-based devices, is studied in a liquid environment, including elastic energy, electrochemical work done, van der Waals work done and surface adhesion energy. We extend the classical energy method of the beam peeling for micro-electro-mechanical systems (MEMS) in the air to an energy method for nano-electro-mechanical systems (NEMS) in liquid electrolyte. We demonstrate a useful numerical processing method to find the parameters to free the stiction of the beams and to obtain the detachment length of the beams.

No description available.

Data based abnormality detection is a growing research field focussed on extracting information from feature rich data. They are considered to be non-intrusive and non-destructive in nature which gives them a clear advantage over conventional methods. In this study, we explore different streams of data based anomalies detection. We propose extension and revisions to existing valve stiction detection algorithm supported with industrial case study. We also explored the area of image analysis and proposed a complete solution for Malaria diagnosis. The proposed method is tested over images provided by pathology laboratory at Alberta Health Service. We also address the robustness and practicality of the solution proposed. / Process Control

<p>This master thesis reviews advances in detection and diagnosis of static friction (stiction) in control valves. Control valves suffering from stiction results in oscillating control loops which in turn decreases both the process stability and reliability. Perstorp AB sees a necessity to automatically detect stiction in valves before the effects of the malfunctioning valves have become too severe. This thesis presents an introduction to maintenance, control loops and how stiction in valves can affect performance of control loops.</p><p>A selection of methods presented in the literature are introduced and examined using normal operating data from the site in Perstorp. Common for all selected methods is their intuitive ideas and that they are based on normal operating data and minimum amount of process knowledge. For the adaptive segmentation method a further development is presented where among other things a test quantity is proposed.</p><p>This thesis shows that none of the selected methods can reliably diagnose stiction in control valves from normal operating data. Noise in process value and irregular disturbances results in weakened trend characteristics.</p><p>Finally, the thesis has tested a root cause analysis of plant-wide oscillating control loops found on two plants in Perstorp AB.</p> / <p>Detta examensarbete är en undersökning av detektion och diagnos av kärvande reglerventiler. Kärvande reglerventiler ger upphov till att reglerkretsar börjar att självsvänga vilket leder till sämre processtabilitet och driftsäkerhet. Perstorp AB ser ett stort behov att automatiskt detektera kärvande ventiler innan deras inverkan har blivit för omfattande. Rapporten presenterar en grundläggande redogörelse för arbete med underhåll, reglerkretsar och hur kärvande reglerventiler som kan leda till sämre reglerprestanda.</p><p>Ett selektivt urval av de metoder som har presenterats i litteratur introduceras och analyseras för att utvärderas på driftsdata från anläggningen i Perstorp. Gemensamt för samtliga metoder är att de bygger på intuitiva idéer, normal driftdata och minimal kunskap om processen. För den adaptiva segmenteringsmetoden presenteras en vidareutveckling där bland annat en teststorhet har tagits fram.</p><p>Rapporten visar att ingen av de utvärderade metoderna kan tillförlitligt diagnosticera kärvande reglerventiler ur verklig driftsdata då brus i mätsignaler och oregelbundna störningar leder till att karakteristiken hos trenderna försvagas.</p><p>Slutligen görs en analys av en metod för att hitta grundorsaken till att flera reglerkretsar svänger på två fabriker inom Perstorp AB.</p>

This master thesis reviews advances in detection and diagnosis of static friction (stiction) in control valves. Control valves suffering from stiction results in oscillating control loops which in turn decreases both the process stability and reliability. Perstorp AB sees a necessity to automatically detect stiction in valves before the effects of the malfunctioning valves have become too severe. This thesis presents an introduction to maintenance, control loops and how stiction in valves can affect performance of control loops. A selection of methods presented in the literature are introduced and examined using normal operating data from the site in Perstorp. Common for all selected methods is their intuitive ideas and that they are based on normal operating data and minimum amount of process knowledge. For the adaptive segmentation method a further development is presented where among other things a test quantity is proposed. This thesis shows that none of the selected methods can reliably diagnose stiction in control valves from normal operating data. Noise in process value and irregular disturbances results in weakened trend characteristics. Finally, the thesis has tested a root cause analysis of plant-wide oscillating control loops found on two plants in Perstorp AB. / Detta examensarbete är en undersökning av detektion och diagnos av kärvande reglerventiler. Kärvande reglerventiler ger upphov till att reglerkretsar börjar att självsvänga vilket leder till sämre processtabilitet och driftsäkerhet. Perstorp AB ser ett stort behov att automatiskt detektera kärvande ventiler innan deras inverkan har blivit för omfattande. Rapporten presenterar en grundläggande redogörelse för arbete med underhåll, reglerkretsar och hur kärvande reglerventiler som kan leda till sämre reglerprestanda. Ett selektivt urval av de metoder som har presenterats i litteratur introduceras och analyseras för att utvärderas på driftsdata från anläggningen i Perstorp. Gemensamt för samtliga metoder är att de bygger på intuitiva idéer, normal driftdata och minimal kunskap om processen. För den adaptiva segmenteringsmetoden presenteras en vidareutveckling där bland annat en teststorhet har tagits fram. Rapporten visar att ingen av de utvärderade metoderna kan tillförlitligt diagnosticera kärvande reglerventiler ur verklig driftsdata då brus i mätsignaler och oregelbundna störningar leder till att karakteristiken hos trenderna försvagas. Slutligen görs en analys av en metod för att hitta grundorsaken till att flera reglerkretsar svänger på två fabriker inom Perstorp AB.

This research study talks about the possible influence of gray cast iron microstructure on the corrosion properties of the brake rotor and the effect of stiction. Three Gray cast iron rotors with fully pearlitic microstructure and below 5% volume content of ferrite were studied in this research to understand their microstructural influence over corrosion. The selected gray cast iron rotors were friction tested against a 2009 Original Equipment Manufacturer (OEM) Ford F150 brake pad using scaled-down SAE J2522 standard test. Tested samples were later subjected to GMW16696 standard test, to identify the breakaway forces indirectly defining the corrosion resistance of the friction material used. The results show that the degree of corrosion and breakaway forces observed are greatly influenced by the graphite content quantified from quantitative analysis techniques adopted. Rotor with higher graphite content observed higher breakaway force and higher oxygen content compared to the other two studied rotors. Higher graphite content is considered to provide more cathodes, it accelerates the corrosion of the iron element in the rotor. There is no reliable correlation between the pearlite and ferrite of the gray cast iron rotor stiction force. The poor correlation between stiction force and microstructure also shows that the size of stiction force is not determined by a single factor.

A variabilidade é um problema presente na maioria das malhas de controle de processos industriais, trazendo prejuízo ao causar perda de produtividade e utilização excessiva de matéria prima e energia. Muitas vezes ela é causada pela presença do atrito em válvulas de controle, os atuadores mais usados em processos industriais. Há uma série de métodos propostos para diagnosticar as perturbações causadas pelo atrito nas válvulas, classificados em intrusivos e não-intrusivos. Neste trabalho, foram estudados dois métodos intrusivos. Eles foram aplicados de maneira automática em simulações computacionais, que foram realizadas em um sistema híbrido de teste (HIL) de uma planta de vazão, com dois níveis de atrito da válvula, e também em um ambiente inteiramente simulado, visando analisar o desempenho dos dois métodos. Os resultados obtidos com ambos os métodos foram satisfatórios, muito embora um dos métodos tenha confundido os efeitos gerados pelo atrito com os produzidos por má sintonia do controlador da malha. / The variability is a problem present on the most of control loops in industrial processes. It causes losses in plant productivity and in material and energy usage. Many times it is caused by the presence of friction in control valves, the most used actuator in industrial processes. There are many methods proposed to diagnose the disturbances caused by control valve friction, which are classified in intrusive and non-intrusive. In this work, two intrusive methods are studied. They were applied automatically by computer simulations that were performed in a hybrid test system (HIL) of a flow plant, with two valve friction levels. Additionally they were applied in a completely simulated environment, aiming at analyzing the performance of both methods. The results with the two methods were satisfactory, although one of the methods has not separated the effects generated by the friction from the ones produced by a bad tuning of the loop controller.