1 / 27

Adaptive control and process systems . Design and methods and control strategies

Adaptive control and process systems . Design and methods and control strategies. Sensitivity and precision.

juliet-wise
Download Presentation

Adaptive control and process systems . Design and methods and control strategies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Adaptive control and processsystems. Design and methods and control strategies

  2. Sensitivity and precision • For a control system to carry out the mission for which it is designed, it should be sensitive to changes that occur so that it can actuate, if the variation is at the input, or correct it if it is at the output. At the same time a system has to be precise and accurate in its response.

  3. Sensitivity and precisionDefinitions • Sensitivity: we define sensitivity as the ability of response to very small excitations, stimuli or causes. E. Dorf defines the sensitivity of a system as the ratio of change in the transfer function of the system with respect to the change in the transfer function of the process, for a small incremental change. • Precision: it is defined as the ability to produce accurate results. This concept is linked to the ability to produce the same result under the same conditions, that is, for the control case, the ability to generate the same output in different occasions at the same input.

  4. Sensitivity and precisionDefinitions • Accuracy: it is defined as the accuracy on executing something. This concept would be more related to the ability to get the output to be as close as possible in value to the desired value. • Reliability: it is the quality of reliable, probability of good functioning of something. S. Martinez takes it up as the concept of reliability of equipment, in its current technical sense, as the probability of continuity of operation under certain conditions.

  5. Sensitivity and precisionSensitivitytoparametervariations • Every process is subject to changing conditions in their environment (imbalances, aging, etc.). • Open loopsystem: verysensitivetovariations. • Closedloopsystem: lesssensitive/insensitivetoparametervariations.

  6. Sensitivity and precisionSensitivitytoparametervariations • Suppose a change in the process so that the new transfer function isG(s)+ΔG(s). Then, the output willchangeaccordingtothetype of system • Open loop: • Closed loop Si G(s)H(s)>>ΔG(s)H(s) lessvariation

  7. Sensitivity and precisionSensitivitytoparametervariations • According to R. Dorf, the sensitivity of the system is defined as the ratio of the percentage change in the transfer function of the system compared to the percentage change in the transfer function of the process. • Ifthe transfer function of thesystemis Thesensitivity of thesystemisdefined as

  8. Sensitivity and precisionSensitivitytoparametervariations • Variations in directloop: • Open loopsystems: sensitivity = 1 • Closedloopsystems: Thesensitivity in a system in open loopisreducedifthe factor G(s)H(s) increases

  9. Sensitivity and precisionSensitivitytoparametervariations • Variations in the feedback loop: • Closed loop: The changes in H(s) directly affect the output. It is important that the components used in the feedback do not vary with environmental changes and remain constant.

  10. Sensitivity and precisionDisturbances • A disturbance is a signal that can affect the value of a system output. • Internal: it is generated within the system. • External: It is generated outside the system. It should be considered as another entry. • In both cases they are uncontrolled. • Open loopsystems are verysensitivetodisturbances. • Closedloopsystems are lesssensitivesincetheyaffectthe output and thesystemtendstocorrectthem.

  11. Sensitivity and precisionDisturbances • Disturbancesshouldbeconsidered as inputs of thesystem. Thesuperpositionprincipleisapplied in ordertoworkwiththem . • It can appear at anypoint of thesystem. • Themainproblemisitsvariability.

  12. Sensitivity and precisionDisturbances • Disturbance in direct loop: • If D(s) is zero the system behaves normal • If R(s) = 0, the process is readjusted as

  13. Sensitivity and precisionDisturbances • Disturbance in direct loop: by the superposition principle The sensitivity of the system to G2 and the effect of the disturbance with R(s)=0 are

  14. Sensitivity and precisionDisturbances • Disturbance in thefeedbackloop: whichisequivalentto:

  15. Sensitivity and precisionErrors • The errors in the control systems are attributable to many factors. The variations in the input reference cause inevitable deviations during the transient periods and even in steady state. The imperfections of the components, the deterioration of the elements of the systems (sensors and actuators), the friction between mechanical parts, the rolling, the temperature drift of the electronic components, the aging, etc., cause the system to deviate from the expected results. • Other types of errors are those that occur when the systems are not able to follow certain types of inputs. Any control system has in steady state an error in response to certain types of inputs.

  16. Sensitivity and precisionErrors • Errors in steady state: in a system with a unity feedback we have • The error will be

  17. Sensitivity and precisionErrors • Error in steadystatefor a step input: • Thestatic position error constant: • The error in steadystatewillbe:

  18. Sensitivity and precisionErrors • Error in steadystateforramp input: • Thestatic position error constant: • The error in steadystatewillbe:

  19. Sensitivity and precisionErrors • Error in steadystatefor a parabolic input: the error in steadystatewillbe

  20. Sensitivity and precisionErrors • Errorson a systemwith open loop: Kc= 1/K • The error willbe: as changes in environmental variables oraging of thecomponents are produced G(0) will stop beingtheunity, provockingthatthe error will no longerbezero.

  21. Sensitivity and precisionErrors • Errorsonthesystem in closedloop: KpK>>1 The error willbe: The error onthesystem in closedloopwillbe, ifweestablishKp=100/K,

  22. Sensitivity and precisionPrecision • S. Marcos defines the precision as the accuracy of a system in the tracking of an input signal. • The precision is represented by the error in steady state. The designer always wants the system not to present any error, however, each system has a certain inability to follow certain types of inputs. • It can be concluded that a system is more precise the smaller the errors in steady state are.

  23. Sensitivity and precisionReliability • Reliability: It is a measure of its compliance with a correct specification of its behavior. • Fault: it is a deviation of the behavior of a system with respect to its specification. • Error: it is the cause of the faults. • Failure: it is the mechanical or algorithmic cause of an error. The presence of a fault does not need to cause an error.

  24. Sensitivity and precisionReliability • Types of failures: • Steady state: they are present until they are repaired. They generally cause the systems to stop. • Transients: they disappear by themselves, so they have less serious consequences. • Intermittents: they appear and disappear from time to time or with a certain periodicity

  25. Sensitivity and precisionReliability • Prevention and tolerancetofailures: • Reduce thefailures: • Avoidthem. • Try themnottobeproducedduringthedesign and constructionphases. • Eliminatethemwhentheyappear. • Techniquestoavoidfailures: • Basedon hardware • Basedon software • Checks • Tests

  26. Sensitivity and precisionReliability • Redundancy: By this method additional components are used that perform simultaneously the same function or are able to detect incorrect behavior and restore functionality, it is what is called as masking of errors. However, the introduction of additional elements increases the possibility of failure. • static redundancy: with this type of redundancy, redundant components are always active. • Dynamic Redundancy: Redundant components are activated only when a fault occurs.

  27. Bibliography • K. Ogata, Modern Control Engineering. • R. Dorf, R. Bishop: Sistemas de control moderno. • B. Kuo, F. Golnaraghi: Automatic Control Systems. • P. Bolzern: Fundamentos de control automático. • S. Martínez: Electrónica de potencia. Componentes, topologías y equipos Links of interest • http://www.araba.ehu.es/depsi/jg/RAREPASO.pdf • http://www.isa.cie.uva.es/~felipe/docencia/ra12itielec/tema1_trasp.pdf • http://www.disa.bi.ehu.es/spanish/ftp/material_asignaturas/Ing_Sistemas_I/Transparencias%20de%20Clase/Tema%2001%20-%20Introducci%F3n%20a%20los%20Sistemas%20de%20Control.pdf • http://catarina.udlap.mx/u_dl_a/tales/documentos/lep/nunez_e_f/capitulo1.pdf • http://web.udl.es/usuaris/w3511782/Control_de_procesos/Unidades_files/apuntes_10-11.pdf • http://web.usal.es/~sebas/TEORIA/TEMA8-REGULACION.pdf • http://it.aut.uah.es/danihc/DHC_files/menus_data/SCTR/ToleranciaFiabilidad.pdf • http://laurel.datsi.fi.upm.es/~ssoo/STR/Fiabilidad.pdf • http://www.est.uc3m.es/esp/nueva_docencia/leganes/ing_industrial/estadistica_industrial/doc_grupo1/archivos/Fiabilidad%20presentacion.pdf

More Related