L thuyt KTchuyn thi cNgi vit: Bi Trung HiuNgnh iu khin t ngKhoa in-in tTrng HBK tp H Ch Minh

Li tha:Nh bit, vi Matlab, cng vic hc tp mn KT tr nn rt n gin v th v. Tuy nhin, i ph vi k thi, d bn l mt ngi hc rt tt l thuyt nhng khng ch trng n cch lm bi vn c th b im thp. mt ln b nh th, ti nh phi b ra mt khong thi gian c th thch nghi vi cng vic tt nhin ca SV: thi c! Trong bi ny, ti trnh by vi cc bn 2 bi ton rt c bn ca l thuyt KT.V biu Bode.Thit k mt khu ri rc.Tt nhin, chng s c trnh by gii vi Caculator, ti s dng FX570MS.

V gin Bodevi s tr gip ca FX570MSVi Matlab, cng vic ny rt n gin dng dng lnh: bode(hm_truyn) vi hm truyn c khai bo di dng:Hm_truyn=tf(t_s,mu_s)Hm_truyn=zpk(zero,cc, _li)cc thng s phTuy nhin, i ph vi k thi, bn phi v c biu Bode dng Caculator, l thuyt trong sch KT hng dn cc bn mt cch rt chi tit, ti ch nu cch cc bn dng Caculator tnh ra cc kt qu ch :

V gin Bode bin vi s tr gip ca FX570MSL thuyt c trnh by chi tit trong sch LT KT nh xut bn HQG tp H Ch Minh trang 112-113.Bc 2: Dng FX570MS Mode 2 (CMPLX) nhp hm truyn cn kho st, ch thay bng A*i. Vic kho st s cn cc tn s gy, ta ch n gin thay chng kim sot vic v ng hay sai.Xt v d sau lm r iu :Bc 1: Xc nh tt c cc tn s gy v xp chng theo trt t tng dn

V gin Bode bin vi s tr gip ca FX570MS (v d1)Bc 1: Cc tn s gy (lu hm m khng nh hng ti Bode bin )V biu Bode bin gn ng ca h thng c hm truyn:( thi hc k 2 nm 2004-2005)Nhn xt: Hm truyn c mt khu tch phn l tng

V gin Bode bin vi s tr gip ca FX570MS (v d1)Bc 2: Dng Caculator (FX570MS): Nhn Mode2(CMPLX) tc ComplexVic tip theo, bn nhn phm Calc, sau thay A bng cc gi tr Nhp s liu nh sau: (Tnh bng n v dB)20logAbs(100(Ai+10)(Ai)(Ai+1)(Ai+100))(Ti ly A l bin s trong v d trn)Calc: A? 0.01= 60Calc: A? 1= 17Calc: A? 10=-17Calc: A? 100=-42Calc: A? 1000=-80

V gin Bode bin vi s tr gip ca FX570MS (v d1)Ni cc im trn li, bn s c c bn Bode bin cn v.Kt qu nh sau:

Mu xanh: Bode dng MatlabMu : V xp x cc gi tr

V gin Bode pha vi s tr gip ca FX570MSTrn, ti trnh by cch v Bode bin , cn cch v Bode pha, sn y ti cng xin dn ra:Trong gio trnh KT, ta khng thy hng dn cch v Bode pha, mt mt v cc bc tin hnh ca n hi rc ri, m kt qu cho cng khng tht chnh xc (Khng m bo sai s nh Bode bin (

V gin Bode pha vi s tr gip ca FX570MSC s l thuyt:S dng FX570MS, Mode2 (CMPLX). Nhp hm s dng:

V gin Bode pha vi s tr gip ca FX570MSLu :Phi phn r cc tch s ca hm truyn thnh cc tng Arg.Chuyn Arg ca hm m v dng: Xt v d sau r hn:V biu Bode pha ca hm truyn cho V d1

V gin Bode pha vi s tr gip ca FX570MS (V d 2)Nhp hm kho st nh sau:(n v: )Cng vic tip theo:Calc A? 0.01 -90.8Calc A? 0.1 -98.05Calc A? 0.5 -128Calc A? 1 -158Calc A? 2 -200Calc A? 10 -421Calc A? 20 -697Calc A? 50 -1580Calc A? 100 -3000

arg(Ai+10)-0.5A*180/pi-arg(Ai)-arg(Ai+1)-arg(Ai+100)

Mu xanh: Bode dng MatlabMu : V xp x cc gi tr

V gin Bode pha vi s tr gip ca FX570MSCc sai lm thng gp:Khi lm vic vi hm m, khng a v dng T m vn dng arg(exp(-Tj)), bn lu l hm m min s phc c chu k tun hon l 2.Khi lm vic vi hm m qun chuyn n v t rad sang deg.Khng phn r cc tch ca hm truyn thnh cc tng Arg khi gp mt s hm bt thng gy sai kt qu.Vic tnh ton khi th cc gi tr rt nhanh, khng mt nhiu thi gian, ch khong 3-5 hon thnh bi Bode pha.

Kt lun v phng php v Bode:Nh phn tch trn, vic v Bode khng phi l cng vic qu kh khn, tuy nhin, n l cng vic nng v ton hc, v nu bn rt thnh thc vi cch v bng tay, dng l thuyt trang 112-113(Sd), khi bn xc nh cc khu ca hm truyn, c th bn s khng mt thi gian khi v Bode bin (khong 3), tuy nhin, vi bn khng cn xc nh cc khu ca hm truyn, vn c th v c m khng c trc trc g, bn nn nh rng cch v m yu cu ch l v gn ng. Tht ra, ti c th v chnh xc n 99% gin Bode nu dng FX570MS. Lc , ti ang lm li ci cng vic ca mt chic my, v ti cht ngh, lm tt cng vic ca mt ci my th c g phi t ho

Kho st h ri rc dng PP Kg trng thi:y cng l mt dng bi tp rt thng hay gp trong cc k thi, ti cng th dng FX570MS gii:Ti ly v d trong sch gio trnh n gin:(trang 280-281)C(t)+-r(t)e(t)e(kT)eR(t)TThnh lp h phng trnh trng thi m t h thng trn.Tnh p ng ca h i vi tn hiu vo l hm nc n v (nhn qu)

Kho st h ri rc dng PP Kg trng thi:Bc 1: Mt cch my mc, ta tm c cc ma trn A, B,D m t h lin tc:C(s)ER(s)Ch rng h phng trnh m t h lin tc c dng:

Kho st h ri rc dng PP Kg trng thi:Bc 2: Tnh ma trn qu .Cch tm ma trn nghch o:

Kho st h ri rc dng PP Kg trng thi:Vi Aij l det mt ma trn vung cp n-1 c tnh bng cch:B i hng i, ct j

Kho st h ri rc dng PP Kg trng thi:TnhCch tnh Laplace ngc: Gi s phng trnh cn bin i c dng t s/mu s. Vi bc t s b hn bc mu s. Ta chia ra 3 trng hp sau:Nghim mu s l nghim n.Nghim mu s l nghim thc kp.Nghim mu s l nghim phc lin hp.

Kho st h ri rc dng PP Kg trng thi:Nghim mu s l nghim thc n..

Kho st h ri rc dng PP Kg trng thi:Nghim mu s l nghim thc kp:

Kho st h ri rc dng PP Kg trng thi:Nghim mu s l nghim phc lin hp: s1,2= -j

Kho st h ri rc dng PP Kg trng thi:Ti ly mt v d n gin lm r vn ny:

Kho st h ri rc dng PP Kg trng thi:Tr li v d ca bi ton ri rc, by gi ta tnh cc ma trn Ad,Bd,Dd :Bc 3: Mt cch my mc, ta th Ad = (T)Vi lu rng, ta c th dng chc nng tch phn ca FX570MSBc 4: H pt trng thi m t h thng ri rc vi tn hiu vo r(kT)

Kho st h ri rc dng PP Kg trng thi:Dng chc nng ma trn ca FX570MS:

Kho st h ri rc dng PP Kg trng thi:Ta tm c phng trnh trng thi: Nhp ma trn A l ma trn va tm c. Gn ma trn C=(0 0)T sau gn ma trn Ans l ma trn C.(r rng, c th dng ti ma trn cp 3, tc o hm cp 3)Ta c nhn nt =n chng no k=n theo yu cu bi ton.n y, ta gii xong bi ton kho st h ri rc dng pp kg trng thi, tuy cc bc tnh u c th dng Caculator, nhng bn phi thc hnh vi ln th mi mong c th lm khng sai st.V ti xin nhc li rng, y ch l bin php i ph vi thi c, bn cn phi c s tm hiu thch hp khi dng Matlab. Hin ti, ti s dng chng trnh matlab 7.0 v Mathematica 5.0, cc chng trnh trn phc v rt tt cng vic tnh ton.

Nu bn c hng th trao i vi ti v phng php dng Caculator gii cc bi tp trong thi c cc mn trng H xin gi mail v a ch hp th: buitrunghieu@khvt.com, rt vui lng trao i kinh nghim s dng vi bn.

Ti rt bun khi ngi vit Slide ny, nhng l cch gii khuy duy nht sau khi thi LTKT, mn hc m ti tn rt nhiu cng sc trong hc k.Mi th trn i u c phi lun theo mnh, phi khng no? Cht bon chen, c th em v cho ta danh li y!Bn b ci ngh, mnh, cng dn th h 8X, c th lm mi th mnh mun i th nhiu khi li c vic hn, ngh rng: mnh c th lm mi vic ngi khc c th lm c, nhiu khi li hp thi trong mi trng H ny!Thnh ph H Ch Minh, ngy 25 thng 6 nm 2005!