Amasu Okulawula i-PID Ekuzenzekeleni
Ezweni lokuzenzakalela kwezimboni, ukugcina inqubo ezinzile neqondiwe kuyimfuneko eyinhloko. Kungakhathaliseki ukuthi ukugcina izinga lokushisa lehhavini ngenani elithile, ukugcina izinga loketshezi ethangini, ukulawula ijubane lemoto yokuthutha, noma ukulawula ingcindezi ohlelweni lwe-pneumatic—konke kudinga isu lokulawula elithembekile. Enye yezindlela ezisetshenziswa kakhulu ngenxa yobulula bayo, ukusebenza kahle, kanye nokulula kokusetshenziswa kwayo ukulawula i-PID (Proportional–Integral–Derivative). Lesi sihloko sixoxa ngemiqondo eyisisekelo ye-PID, indlela ingxenye ngayinye esebenza ngayo, ukusetshenziswa kwayo ezenzakalelayo, kanye nemikhuba yokulungisa ukuze kusebenze kahle uhlelo.
Kuyini ukulawula i-PID?
I-PID iyi-algorithm yokulawula impendulo ebala isignali yokulawula ngokusekelwe emehluko phakathi kwenani lokubhekisela (i-setpoint) kanye nenani elilinganisiwe (i-process variable/PV). Lo mehluko ubizwa ngokuthi iphutha. Umgomo wokulawula i-PID ukunciphisa iphutha ngokushesha ngangokunokwenzeka ngaphandle kokubangela ukuthi uhlelo lushintshe kakhulu noma lube olungazinzile.
Ngokuvamile, isilawuli sizokhiqiza umphumela (isb., ukuvulwa kwe-valve, i-motor voltage, noma umjikelezo womsebenzi we-PWM) othinta inqubo. Izinzwa zifunda umphumela bese ziwuqhathanisa nendawo ebekwe kuyo. Lo mjikelezo uqhubeka njalo ku-PLC, DCS, noma isilawuli esifakiwe.
Ifomula eyisisekelo yefomu eliqhubekayo le-PID:
u(t) = Kp e(t) + Ki ∫ e(t) dt + Kd · (de(t)/dt)
Ezinhlelweni zedijithali (njenge-PLC), izibalo zenziwa ngokuhlukile ngokusekelwe ezikhathini ezithile zokuthatha amasampula.
Izingxenye ze-PID: P, I, kanye no-D
1) Okulinganayo (P)
Ingxenye elinganiselayo inikeza impendulo elinganiselayo ngobukhulu bephutha lamanje. Uma iphutha likhulu, umphumela wokulungisa nawo uzoba mkhulu. Inzuzo impendulo esheshayo nelula.
Kodwa-ke, ukulawula kwe-P kuphela kuvame ukushiya iphutha lesimo esizinzile (iphutha elihlala ngemva kokuba uhlelo seluzinzile). Isibonelo, ekulawuleni izinga lokushisa, izinga lokushisa lingase lime kancane ngaphansi kwe-setpoint ngoba amandla okulungisa i-P ayancipha njengoba iphutha lehla.
Ipharamitha yokhiye: Kp (inzuzo elinganayo)
– I-Kp incane kakhulu: impendulo ehamba kancane, isikhathi eside sokunyamalala kwephutha.
– I-Kp inkulu kakhulu: ingozi yokudubula ngokweqile kanye nokushukuma.
2) Okuhlanganisiwe (I)
Ingxenye ehlanganisiwe ihlanganisa amaphutha ngokuhamba kwesikhathi. Umsebenzi wayo ukususa amaphutha e-steady-state, ngoba ngisho namaphutha amancane azoqhubeka nokushayela umphumela kuze kube yilapho iphutha lisondela ku-zero.
Okubi ukuthi ama-integral anganciphisa isivinini sempendulo futhi angase adale ukushaqeka noma ukushukuma uma enolaka kakhulu. Enye inkinga evamile i-integral windup, lapho ama-integral "akha" kakhulu lapho i-actuator ifinyelela umkhawulo wayo omkhulu/ophansi (ukugcwala).
Amapharamitha ayisihluthulelo: I-Ki (inzuzo ehlanganisiwe) noma ngezinye izikhathi evezwa njenge-Ti (isikhathi esihlanganisiwe)
– I-Ki incane kakhulu: iphutha lesimo esizinzile liyanyamalala kancane kakhulu.
– I-Ki inkulu kakhulu: i-overshoot ephezulu, ukushukuma, futhi ithambekele ekuqhekekeni.
3) Okususelwe (D)
Ingxenye esuselwe kokunye ibikezela ukuthambekela kwamaphutha ngokubheka izinga layo lokushintsha. I-D ingasiza ekunciphiseni ukushaqeka ngokweqile futhi ithuthukise ukuzinza, ikakhulukazi ezinhlelweni ezivame ukushukuma.
Kodwa-ke, ama-derivatives azwela kakhulu umsindo wezinzwa. Ekulinganisweni okunomsindo, i-D ingabangela ukuthi umphumela uqhume. Ngakho-ke, ukusetshenziswa kwe-D kuvame ukuhambisana nesihlungi (isb., isihlungi esidlula kancane) noma kusetshenziswe njenge-derivative ye-PV (esikhundleni sephutha) ukunciphisa imiphumela yokushintsha kwe-setpoint okungazelelwe.
Amapharamitha ayisihluthulelo: Kd (i-gain derivative) noma i-Td (i-time derivative)
– I-Kd incane kakhulu: umphumela wokudambisa awubonakali kakhulu.
– I-Kd inkulu kakhulu: umphumela uyazwela umsindo, uhlelo lungase lungakhululeki noma lungazinzile.
Kungani i-PID idumile ekuzenzekeleni?
Ama-PID athandwa ngezizathu eziningana ezisebenzayo:
1. Kulula ukuyisebenzisa: Cishe wonke ama-PLC nama-DCS anamabhulokhi omsebenzi we-PID akhelwe ngaphakathi.
2. Iguquguquka kakhulu: Ingasetshenziswa ezinqubweni eziningi (izinga lokushisa, izinga, ukugeleza, isivinini, ingcindezi).
3. Akudingi amamodeli anemininingwane yezibalo: Ngokungafani nokulawula okusekelwe kumodeli, i-PID ingalungiswa kusetshenziswa indlela yokuhlola.
4. Ukusebenza okwanele kwezidingo eziningi zezimboni: Ezinqubweni eziningi, i-PID “ilungile ngokwanele” ngentengo ephansi.
Kodwa-ke, i-PID ayilona ikhambi lazo zonke izimo—isibonelo, ezinqubweni ezingezona eziqondile kakhulu, lezo ezinezikhathi ezinkulu ezifile, noma izinqubo ezineziguquguquki eziningi ezisebenzisana kakhulu. Kulezi zimo, ukulawula okuthuthukisiwe (isb., i-MPC) ngezinye izikhathi kufaneleke kakhulu.
Izibonelo zezinhlelo zokusebenza ze-PID embonini
1. Ukulawula izinga lokushisa (i-heater/i-oven/i-boiler)
I-PV: izinga lokushisa le-thermocouple/RTD
Umphumela: amandla okushisa (i-SSR/thyristor) noma ukuvulwa kwevalvu yomusi
Izinselele: i-inertia yokushisa kanye nesikhathi esifile.
2. Lawula izinga lethangi
I-PV: izinga loketshezi (isidluliseli se-ultrasonic/sokucindezela)
Umphumela: ukuvulwa kwe-valve yokungena noma isivinini sephampu
Izinselele: ukuphazamiseka okubangelwa ukuphuma kwamanzi kanye nokushintsha kobuningi.
3. Ukulawula isivinini semoto
I-PV: i-RPM ye-encoder/tachometer
Okukhiphayo: isignali ku-VFD/servo drive
Izinselele: ukushintsha imithwalo, ukungqubuzana, kanye nokungasebenzi kahle kwemishini.
4. Ukulawula ingcindezi
I-PV: umthumeli wokucindezela
Umphumela: i-actuator ye-valve noma i-compressor
Izinselele: ukucindezelwa kwegesi kanye nokuguquguquka kwamapayipi.
Umgomo wokulungisa i-PID (ukulungisa)
Ukuhlela kuyinqubo yokukhetha amanani e-Kp, Ki, kanye ne-Kd ukuze uhlelo luhlangabezane nezindinganiso zokusebenza: okusheshayo ukufinyelela endaweni yokusetha, ukudubula okuncane kakhulu, okuzinzile, nokumelana nokuphazamiseka.
Kunezindlela eziningana ezivamile zokulungisa:
1) Ukuhlela ngesandla (ukuhlola kanye nephutha)
Izindlela ezisebenzayo ezivame ukusetshenziswa ensimini:
– Kusukela ku-Ki = 0 kanye ne-Kd = 0.
– Khulisa i-Kp kuze kube yilapho impendulo ishesha, kodwa ingakashintshi kakhulu.
- Faka i-Ki kancane ukuze ususe iphutha lesimo esizinzile.
– Engeza i-Kd uma kudingeka ukuze unciphise ukugxumagxuma nokunyakaza.
Isihluthulelo sokulungisa ngesandla ukwenza izinguquko ezincane, ukubheka impendulo yesinyathelo (ushintsho lwendawo noma ukuphazamiseka), nokuqinisekisa ukuthi uhlelo luhlala luphephile.
2) I-Ziegler–Nichols (indlela yokunyakaza)
Indlela yakudala: khulisa i-Kp kuze kube yilapho uhlelo lushintshashintsha ngokuqina (i-ultimate gain), qopha isikhathi sokushintshashintsha, bese ubala amapharamitha e-PID kusuka etafuleni. Le ndlela iyashesha, kodwa ivame ukukhiqiza ama-overshoots amakhulu, ngakho-ke ayifaneleki njalo ezinqubweni ezibucayi.
3) Ukuhlela okuzenzakalelayo kubalawuli besimanje
Ama-PLC/abalawuli abaningi bokushisa banikeza izici zokulungisa okuzenzakalelayo. Ngokuvamile, idivayisi izonikeza isignali yokuhlola, ihlonze impendulo yenqubo, bese ibala amapharamitha okuqala e-PID. Imiphumela ivame ukuba mihle ngokwanele njengendawo yokuqala, kodwa ingadinga ukulungiswa ngokusekelwe ezidingweni zenqubo.
Izinto ezibalulekile ekusetshenzisweni kwe-PID yedijithali
1. Isikhathi sokuthatha amasampula (Ts)
Ukusampula kancane kakhulu kungabangela ukuthi ukulawula kusabele kancane. Ukusampula ngokushesha kakhulu kungakhulisa umsindo futhi kugcwalise i-CPU ngokweqile. Khetha u-Ts ngokuya ngezinqubo: izinqubo ezisheshayo zidinga u-T omncane, kuyilapho izinqubo ezisheshayo zingasebenzisa u-Ts omkhulu.
2. Ukugcwala kokukhipha kanye nokulwa nokuphelelwa yisikhathi
Uma umkhiqizo ufinyelela umkhawulo (isb., 0–100%), i-integral ingaqhubeka nokukhula futhi ibangele ukukhukhumala ngokweqile lapho uhlelo lubuyela esimweni esijwayelekile. I-Anti-windup ivimbela ukuqongelela okungadingekile kwama-integral.
3. Ukuhlunga ama-derivatives kanye ne-PV
Izinzwa zivame ukuba nomsindo. Isihlungi esidlula kancane siyasiza, ikakhulukazi uma kusetshenziswa izingxenye ze-D.
4. Irempu ye-setpoint/ukuqala okuthambile
Izinguquko ze-setpoint ezizumayo zingabangela ukushesha ngokweqile. Ukushintsha i-setpoint kwenza ushintsho lube lula.
Izindinganiso zokusebenza ezivamile zihlolwe
Ekwenzeni okuzenzakalelayo, ukulungiswa kwe-PID kuvame ukulandela inhlanganisela yalokhu:
– Isikhathi sokukhuphuka ngokushesha (isikhathi sokukhuphuka siye endaweni ehleliwe).
– Ukudubula okuncane kakhulu (akudluli kakhulu endaweni ebekwe kuyo).
– Isikhathi esifushane sokuphumula (sizinzile ngokushesha).
– Iphutha elincane lesimo esizinzile.
– Ukuqina okuhle (kuhlala kuzinzile ngisho noma kukhona izinguquko emthwalweni/eziphazanyisweni).
Akuzona zonke izinto ezingathuthukiswa ngesikhathi esisodwa. Isibonelo, ukulwela izikhathi zokukhuphuka ngokushesha kuvame ukwandisa ukuqhuma ngokweqile. Ngakho-ke, ukulungisa kuncike ezintweni eziza kuqala enqubweni: ukuphepha, ikhwalithi yomkhiqizo, ukusebenza kahle kwamandla, noma induduzo yokusebenza.
I-Penutup
Amasu okulawula i-PID ayinsika yezinhlelo eziningi ezenzakalelayo ngenxa yekhono lawo lokulawula ngempumelelo izinqubo ngokusetshenziswa okulula. Ngokuqonda izindima zezingxenye ze-P, I, kanye ne-D, nokusebenzisa imikhuba emihle yokulungisa nokusebenzisa—njengokuvimbela ukuvala, ukuhlunga, kanye nesikhathi sokuthatha amasampula—i-PID inganikeza ukusebenza okuzinzile, okuphendulayo, kanye nokumelana namaphutha ezinhlobonhlobo zezicelo zezimboni. Naphezu kokutholakala kwezindlela zokulawula zesimanje eziyinkimbinkimbi, i-PID isalokhu iyisinqumo esikhethwayo sezinqubo eziningi ngenxa yokulinganisela kwayo okuhle kokusebenza, ubulula, kanye nezindleko.
Uma ufisa, ngingavumelanisa lesi sihloko nesimo esithile (isib. i-PID ku-Siemens/Omron PLC, ukulawulwa kwezinga lokushisa ngama-SSR, noma isibonelo sokubala kokulungisa uhlelo lwezinga le-motor/tank).
