Cascade Control. 1. Introduction 2. Process examples 3. Closed-loop analysis 4. Controller design 5. Simulink example

Transcription

1 Caae Control. Introution. Proe exale 3. Cloe-loo analyi 4. Controller eign. Siulink exale

2 Introution Feebak ontrol» Corretie ation taken regarle of iturbane oure» Corretie ation not taken until after the outut ha eiate fro the etoint» Probleati for roee with large tie ontant an/or long tie elay Feeforwar ontrol» Corretie ation an be taken before the outut ha eiate fro the etoint» Diturbane ut be exliitly eaure» Tyially require a roe oel

3 Caae Control Caae ontrol an roie iroe erforane for uneaure iturbane Bai harateriti» A eon eaureent an a eon ontroller are ue in an inner feebak loo» The etoint for the inner ontrol loo i roie by an outer ontrol loo eigne to regulate the ontrolle outut» The iturbane an be ore raily ientifie with the eonary eaureent than with the riary eaureent Partiularly ueful when the iturbane i aoiate with the aniulate inut

4 Flow Control Exale Control roble» Regulate flow rate through ontrol alue eite hange in utrea an/or owntrea reure Control alternatie» Seify the alue oition to iniretly ahiee the eire flow rate» Utilize a eaureent of the flow rate to eign a feebak ontroller that exliitly regulate the flow rate Aliation» Any ontrol roble in whih a flow rate i ue a a aniulate ariable» Outer ontroller roie the etoint for the inner flow ontroller in a aae arrangeent

5 Furnae Exale Conentional ontrol» Diretly regulate hot oil teerature with fuel ga alue oition» Poor erforane for hange in fuel ga uly reure» Diturbane i relate to the aniulate inut Caae ontrol» A an inner ontroller that regulate fuel ga reure by aniulating the alue oition» Hot oil teerature ontroller roie etoint for inner ontroller» Iroe erforane for hange in fuel ga uly reure

6 Cheial Reator Exale Seonary (inner) ontroller» Maniulate ariable ooling water akeu alue oition» Controlle outut ooling jaket teerature» Diturbane ooling water inlet teerature Priary (outer) ontroller» Maniulate ariable ooling jaket teerature etoint» Controlle outut reator teerature» Diturbane reatant fee flow rate

7 Caae Control Blok Diagra

8 Cloe-Loo Tranfer Funtion eneral forula for loe-loo tranfer funtion» Z = any ariable in feebak yte» Z i = any inut ariable in feebak yte» P f = rout of all tranfer funtion between Z an Z i» P e = rout of all tranfer funtion in feebak loo Cloe-loo tranfer funtion for inner iturbane (D ) e f Z i Z P P ~ D D

9 Cloe-Loo Stability Charateriti equation for aae ontrol Charateriti equation for onentional ontrol ( =, = ) If inner loo ha fater ynai then the outer loo, then aae ontrol uually ha iroe tability harateriti

10 Cloe-Loo Stability Exale Tranfer funtion Inner loo for aae ontrol ( = 4) Inner loo for onentional ontrol.. 3 ) )( ( () (.)(4) () (4) ~ ()() () () ~

11 Cloe-Loo Stability Exale ont. Charateriti equation for aae ontrol Charateriti equation for onentional ontrol Can ue larger gain in outer ontrol loo with aae ontrol than with onentional ontrol , 3 u , 3 u

12 Caae Controller Deign Inner loo» Tyially a P or PI ontroller» Tune firt with outer ontroller in anual» Tune to roie fat reone to etoint hange Outer loo» Tyially a PI or PID ontroller» Tune eon with inner ontroller in autoati» Tune to roie aetable reone to etoint hange an/or iturbane» Mut be retune if inner loo i retune

13 Diret Synthei Deign Inner loo Outer loo Inner roe If ~ Outer roe If

14 Caae Controller Deign Exale Tranfer funtion Inner ontroller eign Outer ontroller eign 4 I I.. I I 4

15 Conentional Controller Deign Proe tranfer funtion IMC tuning ( = ) Siulink PID ontroller araeter ) )( ( ) ( ) ( ) ( ) ( ) (.9. D I... D I D I P

16 Outut Siulink Ileentation etoint To Workae Diturbane Diturbane Setoint PID 4 outut PID + + A 3 Outer Controller A A To Workae A Inner Controller Vale Proe. Inner Diturbane Caae Conentional Setoint Tie

17 Outut Outut Cloe-Loo Perforane. Outer Diturbane Caae Conentional Setoint.4. Setoint Caae Conentional Setoint Tie Tie