Control loop performance monitoring in an industrial setting

The wide range of applications for single input single output controllers have encouraged interest in monitoring their performance. Over the past two decades researchers in the area have found many performance enhancement opportunities by applying these techniques. These are most evident in large operational plants with hundreds of controllers being monitored at the same time. Early performance measures were based on minimum variance control as a benchmark for controller performance. Many other procedures have since emerged that have improved the level of accuracy in these performance measures. In addition, these improvements made it easier to implement control loop performance monitoring in large industrial settings. This thesis looks at the performance measures in use for single input single output controllers. The work here looks at incorporating these different measures for a specific manufacturing plant. Ways of identifying the goals and objectives of controllers in a system are presented. Furthermore, measures are proposed that most accurately indicate if these goals and objectives are being met. The concept is demonstrated on a distillation system in a gas plant. It is shown how using these objective driven techniques can provide the user with sound results. These results do not require much user analysis to identify sources of problems and areas of improvement

Development of systematic control loop performance monitoring tool

Teollisuuden prosesseja ohjaavat automaatiojärjestelmät ja niiden komponentit ovat mahdollistaneet kompleksisten kokonaisuuksien hallinnan. Tuotantotasojen kasvun, energiatehokkuuden ja ympäristöystävällisyyden myötä myös automaatiojärjestelmän toimintaan on alettu kiinnittää entistä enemmän huomiota. Muuttuneiden olosuhteiden tai vääränlaisen suunnittelun tuloksena automaatiojärjestelmä ei välttämättä toimi suunnitellulla tavalla. Heikko suorituskyky vaikuttaa yksittäisten säätöpiirien kautta koko prosessin tehokkuuteen ja se tulisi havaita, jotta kunnossapitotoimenpiteet ja kehitys osataan kohdistaa oikein. Teollisuuden prosessien tehokas ylläpito ja kehitys vaativat parempaa tilannetietoisuutta automaatiojärjestelmän toiminnasta. Tämän työn tavoitteena on kehittää säätöpiirien suorituskykytyökalu, jonka avulla voidaan havaita historiatietokantaan tallennetun datan perusteella kohteet, joissa on ongelmia ja joihin panostamalla on mahdollista parantaa prosessin toimintaa ja ennaltaehkäistä tulevia vikoja. Säätöpiirien suorituskykytyökalun ominaisuudet toteutetaan perustuen kaupallisiin ohjelmistoihin, tutkimustuloksiin ja prosessihenkilökunnan havaintoihin. Suorituskykytyökaluun toteutettaviksi tarkasteltaviksi suureiksi valitaan asetusarvon seuranta, asetusarvon muutokset, ohjauksen saturaatio, ohjauksen vaihtelu, oskillointi ja säätimen tilan tarkkailu. Säätöpiirien suorituskyky arvioidaan laskettujen ominaisuuksien perusteella. Suorituskykytyökalu toteutetaan osaksi Wedge prosessidiagnostiikkajärjestelmää. Toteutettua suorituskykytyökalua testataan Boliden Harjavallan yhdellä rikkihappotehtaalla ja tulokset käydään läpi prosessihenkilökunnan kanssa niiden validoimiseksi. Toteutetun suorituskykytyökalun avulla kyetään löytämään suuresta kokonaisuudesta sellaiset säätöpiirit, joiden toiminnassa on ongelmia. Suorituskykytyökalun avulla on myös mahdollista havaita toteutettujen kehitystoimenpiteiden vaikutus säätöpiirin suorituskykyyn. Suorituskykytyökalun käyttöönotto uudessa kohteessa vaatii prosessituntemusta ja tulosten tarkastelussa prosessituntemuksen merkitys kasvaa. Toteutetun suorituskykytyökalun tuloksista prosessituntemusta omaava henkilö kykenee näkemään kohteet, joiden kehittämisellä on suurin merkitys kokonaisprosessin toimintaan. Toteutettu suorituskykytyökalu täyttää sille asetetut vaatimukset ja sen toimintaa olisi järkevä kehittää ja laajentaa myös muihin prosesseihin

New methods for control loop performance monitoring and assesment

Tato disertační práce se zabývá problematikou monitorování a ohodnocování kvality řízení v jednoduchých regulačních smyčkách s PID regulátory. Cílem bylo vyvinout spolehlivé a efektivní algoritmy, které komplexně pokrývají tuto problematiku především v oblasti řízení průmyslových procesů a jsou schopné praktického nasazení. Dosažené teoretické výsledky jsou popsány ve třech kapitolách, které se věnují metodám automatického ladění PID regulátorů, ohodnocování regulačních smyček a identifikace řízeného systému v uzavřené smyčce. Představené metody byly otestovány jak v simulačním prostředí, tak na reálných laboratorních modelech.NeobhájenoThis thesis deals with assessment and monitoring of simple PID loop control quality. The goal was to develop reliable and effective algorithms for complex solution of selected problem in process control industry. Achieved theoretical results are described in three chapters dedicated to automatic PID tuning, control loop performance assessment and closed-loop system identification methods. The introduced methods were extensively tested both in simulation and real hardware environment

An industrial PID data repository for control loop performance monitoring (CPM)

Control loop performance monitoring methods to detect problems in PID loops are developed and tested using industrial data sets. The data is captured from the process, passed on to the researcher who tries out new detection and diagnosis methods. The data is not generally shared with other researchers working on similar problems. The authors therefore have implemented a data repository to categorise and store the data so that it becomes accessible to all researchers. Existing methods can be compared and enhanced using the data sets. This paper describes the context of CPM as well as the data repository. The repository is set up, hosted and maintained by the South African Council for Automation and Control using a professional web developer.https://www.journals.elsevier.com/ifac-papersonline2019-04-01hj2018Electrical, Electronic and Computer Engineerin

Utilização de ferramenta de control loop performance monitoring e Matlab para sintonia de malhas de controle / Use of control loop performance monitoring tool and Matlab for tuning control loops

A competição global e as preocupações dos acionistas pressionam as plantas a superar suas metas tanto quanto reduzir custos, aumentar produção, melhorar qualidade, segurança e confiabilidade. Neste cenário, uma das formas de reduzir custos variáveis é melhorar o controle regulatório. Um dos fatores que influenciam a performance das malhas de controle é a sintonia inadequada pois as malhas sofrem deterioração no seu desempenho devido a alterações normais na dinâmica do processo. A utilização de softwares para simulação e sintonia de malhas de controle tem se destacado nas indústrias uma vez que permite aumentar a estabilidade da planta. Neste contexto têm-se as justificativas necessárias para se pesquisar e aplicar ferramentas de sintonia de malhas de controle nas indústrias. Este trabalho apresenta um estudo de caso de sintonia da malha de controle de embebição realizado em uma unidade industrial da Tereos Brasil. A hipótese defendida neste trabalho é avaliar se as ferramentas control loop performance monitoring e Simulink do Matlab® são eficazes para sintonia de malhas de controle. O resultado mostrou que as ferramentas utilizadas são práticas e eficazes, pois, permitiram a sintonia para parâmetros ótimos o que resultou na redução na variabilidade da vazão de embebição (67,8% menor) e também na atividade da válvula (79,5% menor)

A technological demonstrator for cloud-based performance monitoring and assessment of industrial plants: present architecture and future developments

This paper presents the actual status and future developments of a technological demonstrator of key enabling technologies of Industry 4.0. The final scope of the project is the realization of a platform where different solutions addressing specific companies needs can be analyzed and their performance compared. Available Industry 4.0 technologies allows the realization of various architectures, even though the most appropriate solution has to be found by the company, accounting for different aspects, as economy, security, specific skills to be maintained or given in outsourcing. The first core of the platform, already working, consists in a Control Loop Performance Monitoring (CLPM) system which operates in cloud as a single module able to supervise routine data coming from different plants. This is an attractive solution for many companies allowing to avoid costs of local installations, linked to monitoring systems, human resources and additional effort for maintenance and upgrading. Some technical details about the application on a pilot-scale plant are given to illustrate the status of the activities. The scope of the project is to add new features to the system as: CLPM extended to plants located in different sites, equipment condition monitoring and environmental data analyses. To this aim, future developments of the platform are discussed in terms of improved technologies, different protocols and architectures

Performance assessment and diagnosis of refinery control loops

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 algorithm to every individual control loop. A procedure is illustrated for selecting default values which make it possible to implement the technology on a refinery-wide scale. For instance, it is shown that the prediction horizon perameter in the CLPA algorithm can be set so that the analysis is sensitive to the persistent signals that cause loss of performance. Default values are suggested for refinery applications.A frequent cause of loss of performance in a control loop is a persistent oscillation due to a valve nonlinearity or a tuning fault. The paper presents an operational signatures in the form of an estimate of the closed loop impulse response that suggest the causes of such oscillations

Practical solutions to multivariate feedback control performance assessment problem: reduced a priori knowledge of interactor matrices

Abstract 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 remains as a considerably challenging problem to obtain a minimum variance control benchmark from routine operating data for multivariable process since the solution relies on the interactor matrix (or inverse time delay matrix). Knowing the interactor matrix is tantamount to knowing a complete knowledge of process models that are either not available or not accurate enough for a meaningful calculation of the benchmark. However, the order of an interactor matrix (OIM) for a multivariable process, a scalar measure of multivariate time delay, is a relatively simple parameter to know or estimate a priori. This paper investigates the possibility to estimate a suboptimal multivariate control benchmark from routine operating data if the OIM is available. The relation between this suboptimal benchmark and the true multivariate minimum variance control benchmark is investigated. Analytical expressions for the lower and upper bounds of the true multivariate minimum variance are derived. Although not minimum variance control, this benchmark answers important practical questions like ''at least how much potential of the improvement does the control have by tuning or redesigning?'' It is further shown that the proposed suboptimal benchmark is achievable by a practical control provided that the system of interest is minimum phase. Simulation examples illustrate the feasibility of the proposed approach

Universal direct tuner for loop control in industry

This paper introduces a direct universal (automatic) tuner for basic loop control in industrial applications. The direct feature refers to the fact that a first-hand model, such as a step response first-order plus dead time approximation, is not required. Instead, a point in the frequency domain and the corresponding slope of the loop frequency response is identified by single test suitable for industrial applications. The proposed method has been shown to overcome pitfalls found in other (automatic) tuning methods and has been validated in a wide range of common and exotic processes in simulation and experimental conditions. The method is very robust to noise, an important feature for real life industrial applications. Comparison is performed with other well-known methods, such as approximate M-constrained integral gain optimization (AMIGO) and Skogestad internal model controller (SIMC), which are indirect methods, i.e., they are based on a first-hand approximation of step response data. The results indicate great similarity between the results, whereas the direct method has the advantage of skipping this intermediate step of identification. The control structure is the most commonly used in industry, i.e., proportional-integral-derivative (PID) type. As the derivative action is often not used in industry due to its difficult choice, in the proposed method, we use a direct relation between the integral and derivative gains. This enables the user to have in the tuning structure the advantages of the derivative action, therefore much improving the potential of good performance in real life control applications