| P I'D Mp3, P I'D Music Lyrics
| |
P I'D biography, P I'D discography
PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly.By "tuning" the three constants in the PID controller algorithm the PID can provide control action designed for specific process requirements.PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions.Control loop basics
2 PID controller theory
2.Ideal vs Standard PID form
7.See also
9 External links
9.As a controller, one decides roughly how much to change the tap position (MV) after one determines the temperature (PV), and therefore the error.This first estimate is the equivalent of the proportional action of a PID controller.Derivative action can be thought of as making smaller and smaller changes as one gets close to the right temperature and stopping when it is just right, rather than going too far.PID controllers do not have the ability to learn and must be set up correctly.Selecting the correct gains for effective control is known as tuning the controller.Changes in feed water temperature constitute a disturbance to the shower process.Controllers are used in industry to regulate temperature, pressure, flow rate, chemical composition, level in a tank containing fluid, speed and practically every other variable for which a measurement exists.Automobile cruise control is an example of a process which utilizes automated control.Due to their long history, simplicity, well grounded theory and simple setup and maintenance requirements, PID controllers are the controllers of choice for many of these applications.For other forms please see the Section "Alternative notation and PID forms".The PID control scheme is named after its three correcting terms, whose sum constitutes the manipulated variable (MV).Pout, Iout, and Dout are the contributions to the output from the PID controller from each of the three terms, as defined below.The proportional response can be adjusted by multiplying the error by a constant Kp, called the proportional gain.If the proportional gain is too high, the system can become unstable (See the section on Loop Tuning).In the absence of disturbances pure proportional control will not settle at its target value, but will retain a steady state error that is a function of the proportional gain and the process gain.The magnitude of the contribution of the integral term to the overall control action is determined by the integral gain, Ki.For further notes regarding integral gain tuning and controller stability, see the section on Loop Tuning.PV
t: Time or instantaneous time (the present)
The derivative term slows the rate of change of the controller output and this effect is most noticeable close to the controller setpoint.An excessively large proportional gain will lead to process instability.Larger Ki implies steady state errors are eliminated quicker.Some processes must not allow an overshoot of the process variable beyond the setpoint if, for example, this would be unsafe.Other processes must minimize the energy expended in reaching a new setpoint.Generally, stability of response (the reverse of instability) is required and the process must not oscillate for any combination of process conditions and setpoints.This section describes some traditional manual methods for loop tuning.There are several methods for tuning a PID loop.Manual "tune by feel" methods can be inefficient.If the system can be taken offline, the best tuning method often involves subjecting the system to a step change in input, measuring the output as a function of time, and using this response to determine the control parameters.Tune By Feel
No math required.Some cost and training involved.Then increase I until any offset is correct in sufficient time for the process.PID loop tuning usually overshoots slightly to reach the setpoint more quickly; however, some systems cannot accept overshoot, in which case an "over damped" tune is required, which will require a P setting significantly less than half that of the P setting causing oscillation.Nichols method, introduced by John G.The "P" gain is increased until it reaches the "critical gain" Kc at which the output of the loop starts to oscillate.Instead, PID tuning and loop optimization software are used to ensure consistent results.Some software packages can even develop tuning by gathering data from reference changes.In loops with response times of several minutes, mathematical loop tuning is recommended, because trial and error can literally take days just to find a stable set of loop values.The rate of mechanical wear is mainly a function of how often a device is activated to make a change.The proportional and differential terms can produce excessive movement in the output when a system is subjected to an instantaneous "step" increase in the error, such as a large setpoint change.In the case of the derivative term, this is due to taking the derivative of the error, which is very large in the case of an instantaneous step change.As a result, some PID algorithms incorporate the following modifications:
derivative of output In this case the PID controller measures the differential of the output quantity, rather than the derivative of the error.The output is always continuous (i.For this to be effective, the derivative of the output must have the same sign as the derivative of the error.Setpoint weighting uses different multipliers for the error depending on which element of the controller it is used in.These parameters do not affect the response to load disturbances and measurement noise.Limitations of PID control
While PID controllers are applicable to many control problems, they can perform poorly in some applications.Any information or intelligence derived from the system state can be "fed forward" or combined with the PID output to improve the overall system performance.Forward value alone can often provide a major portion of the controller output.The PID controller can then be used to respond to whatever difference or "error" that remains between the controller setpoint and the feedback value.If a velocity loop PID controller is being used to control the speed of the load and command the force or torque being applied by the prime mover, then it is beneficial to take the instantaneous acceleration desired for the load, scale that value appropriately and add it to the output of the PID velocity loop controller.The PID loop in this situation uses the feedback information to effect any increase or decrease of the combined output in order to reduce the remaining difference between the process setpoint and the feedback value.Often PID controllers are enhanced through methods such as gain scheduling or fuzzy logic.These pneumatic controllers were once the industry standard.Nowadays, electronic controllers have largely been replaced by digital controllers implemented with microcontrollers or FPGAs.Software implementations have the advantages that they are relatively cheap, highly reliable and reasonably flexible with respect to the implementation of the PID algorithm.Ideal vs Standard PID form
Note that the form of the PID controller most often encountered in industry, and the one most relevant to tuning algorithms is the "standard form".However, it is also the form where the parameters have the least physical interpretation and is generally reserved for theoretical treatment of the PID controller.The "standard" form, despite being slightly more complex mathematically, is more common in industry.Another representation of the PID controller is the series, or "interacting" form.This form essentially consists of a PD and PI controller in series, and it made early (analog) controllers easier to build.Tutorial Overview
PID Tutorial
P.FAQ on PID controller tuning.This page was last modified 19:56, 3 January 2008.All text is available under the terms of the GNU Free Documentation License.Pus can be released into the peritoneum.Two thirds of patients with laparoscopic evidence of previous PID were not aware they had had PID.PID is often associated with sexually transmitted diseases, as it is a common result of such infections.PID is a vague term and can refer to viral, fungal, parasitic, though most often bacterial infections.PID should be classified by affected organs, the stage of the infection, and the organism(s) causing it.Although an STD is often the cause, other routes are possible, including lymphatic, postpartum, postabortal (either miscarriage or abortion) or intrauterine device (IUD) related, and hematogenous spread.It is unsure how much is due to a single organism and how much is due to multiple organisms; many other pathogens that are in normal vaginal flora become involved in PID.This rate of infertility increases with each infection.It is important to note that PID can occur and cause serious harm without causing any noticeable symptoms.Definitive criteria include: histopathologic evidence of endometritis, thickened filled fallopian tubes, or laparoscopic findings.Pelvic inflammatory disease is more likely to occur when there is a history of pelvic inflammatory disease, recent sexual contact, recent onset of menses, or an IUD in place or if the partner has a sexually transmitted disease.Pelvic and vaginal ultrasounds are helpful in the differential diagnosis of ectopic pregnancy of over six weeks.Laparoscopy is often utilized to diagnose pelvic inflammatory disease, and it is imperative if the diagnosis is not certain or if the patient has not responded to antibiotic therapy after 48 hours.No single test has adequate sensitivity and specificity to diagnose pelvic inflammatory disease.However, even the modified 2002 CDC criteria does not identify women with subclinical disease.Prognosis
Although the PID infection itself may be cured, effects of the infection may be permanent.Since early gonococcal infection may be asymptomatic, regular screening of individuals at risk for common agents (history of multiple partners, history of any unprotected sex, or people with symptoms) or because of certain procedures (post pelvic operation, postpartum, miscarriage or abortion).If the initial infection is mostly in the lower tract, after treatment the person may have few difficulties.Infertile women may wish to see a specialist, because there may be a possibility in restoring fertility after scarring.Traditionally tuboplastic surgery was the main approach to correct tubal obstruction or adhesion formation, however success rates tended to be very limited.In vitro fertilization (IVF) was developed to bypass tubal problems and has become the main treatment for patients who want to become pregnant.Treatment
Treatment depends on the cause and generally involves use of antibiotic therapy.If the patient has not improved within two to three days after beginning treatment with the antibiotics, they should return to the hospital for further treatment.Treating partners for STD's is a very important part of treatment and prevention.Anyone with PID and partners of patients with PID since six months prior to diagnosis should be treated to prevent reinfection.Psychotherapy is highly recommended to women diagnosed with PID as the fear of redeveloping the disease after being cured may exist.PID treatment was performed prior to the 2006 CDC sexually transmitted diseases treatment guidelines.Discussing sexual history with a trusted physician in order to get properly screened for sexually transmitted diseases.Regularly scheduling STD testing with a physician and discussing which tests will be performed that session.Understanding when a partner says that they have been STD tested they usually mean chlamydia and gonorrhea in the US, but that those are not all of the sexually transmissible diseases.Other diseases that can lead to or be involved in PID
Salpingitis, any infection of the fallopian tubes.Which tests are most useful for diagnosing PID?".Walker CK, Wiesenfeld HC (2007).This page was last modified 20:59, 7 January 2008.What are the complications of PID?What is the treatment for PID?How can PID be prevented?Where can I get more information?STDs before an IUD is inserted.Symptoms of PID vary from none to severe.Prompt and appropriate treatment can help prevent complications of PID.PID and other problems with similar symptoms.The symptoms may go away before the infection is
cured.Although sex partners
may have no symptoms, they may still be infected with the organisms that can
cause PID.If a woman has any of these symptoms, she should stop
having sex and consult a health care provider immediately.Order Publication Online at www.American College of Obstetricians and Gynecologists (ACOG).ACOG Patient Education Pamphlet, 1999.Westrom L and Eschenbach D.These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred.Clifton Rd, Atlanta, GA 30333, U.Help
Sorry, Internal Server Error.Please check the URL for proper spelling and capitalization.If
you're having trouble locating a destination on Yahoo!Picus (biology)Picus (disambiguation)Picus (genus)Picus awokeraPicus canusPicus chlorolophusPicus erythropygiusPicus flavinuchaPicus mentalisPicus mineaceusPicus puniceusPicus rabieriPicus squamatusPicus vaillantiiPicus viridanusPicus viridisPicus viridisPicus vittatusPicus xanthopygaeusPiCVPICVAPICYAPiczoPiczo.CH PID Office and The University of North Carolina at Chapel Hill.PID, how do I get my ONYEN?PID database, how can I change it?PID or Person ID) that is unique to the University of North Carolina at Chapel Hill.CH PID Office and The University of North Carolina at Chapel Hill.At least 1 million cases of PID occur annually in
the United States.The infection spreads from the cervix up into the uterus,
fallopian tubes, and ovaries.PID can develop anywhere from
several days to several months after infection with an STD.However, PID can cause permanent damage even when
it is completely painless.PID does not cause endometriosis,
as asked by a reader.If left untreated, some cases of PID may require hospitalization.If you suspect PID, go to
your health care provider or clinic at once.Otherwise, they will continue to pass the infection back and
forth.Avoid sex, or use condoms and spermicide during sex,
until all sex partners are completely cured.If you think you may have an STD, get
tested and treated right away, before the infection spreads.PID occur annually in the United
States.Of all infertile women, at least 15 percent are infertile
because of tubal damage caused by PID.Can Men Help Prevent
PID?Men should take all the medicine prescribed,
even if symptoms go away.All partners must be treated to stop the cycle
of infection.The more people you have sex
with, the greater your risk of getting an STD.No part of this web site may be reproduced in any form without the written consent of the publisher.PID refers exclusively to ascending infection of the female upper genital tract (the female structures above the cervix).PID can scar the fallopian tubes, ovaries, and related structures and lead to ectopic pregnancies, infertility, chronic pelvic pain, and other serious consequences.Many different organisms can cause PID, but most cases are associated with gonorrhea and genital chlamydial infections, two very common STDs.The gonococcus (Neisseria gonorrhea), which causes gonorrhea, probably travels up into the fallopian tubes, where it causes sloughing (casting off) of some cells and invades others.It multiplies within and beneath these cells.The infection then spreads to other organs, resulting in more inflammation and scarring.The presence of a cervical mucus plug normally helps prevent the spread of microorganisms to the upper genital tract, but it is less effective during ovulation and menses.The gonococcus may gain access more easily during menses, if menstrual blood flows backward from the uterus into the fallopian tubes, carrying the organisms with it.The more sexual partners a woman has, the greater is her risk of developing PID.Women who douche once or twice a month may also be more likely to have PID.The diagnosis of PID can be difficult to make.If symptoms such as lower abdominal pain are present, a physical exam may be done to determine its location, check for abnormal vaginal or cervical discharge and for evidence of cervical chlamydial infection or gonorrhea.About a quarter of women with suspected PID must be hospitalized.They should therefore be treated even if they do not have symptoms to prevent reinfection and another bout of PID.If used correctly and consistently, latex condoms prevent transmission of gonorrhea and partially protect against chlamydial infection.MedicineNet does not provide medical advice, diagnosis or treatment.
|
| |
|
 |
|
