Sensorless Control of PMBLDC Motor Based on Speed Independent Position Function

Transcription

1 Sensorless Control of PMBLDC Motor Bse on Spee Inepenent Position Function C. Subb Rmi Rey 1 & M. Sury Klthi 2 1 Electril & Electronics Engineering Deprtment, K.S.R.M College of Engineering, Kp, In 2 Electril & Electronics Engineering Deprtment, J.N.T.U.H College of Engineering, Hyer, In E-mil : c_subbrmirey2020@yhoo.com 1, mungl12@yhoo.co.in 2 Abstrct - This pper presents the methoology n implementtion of noel sensorless control technique for the permnent mgnet brushless c (PMBLDC) motor. In this new sensorless control technique, noel flux linkge function is efine, which is spee inepenent. A physilly insightful spee-inepenent function of flux linkge long with the combintion of two fferentil equtions goerning the sttor phse winngs he been use for this purpose. The propose new sensorless metho soles the problem of sensorless PMBLDC motor t low spees. Keywors - permnent mgnet brushless c motor; position function; spee control; sensorless. I. INTRODUCTION A motion system bse on the clssic c motor proies goo, simple n efficient solution to stisfy the requirements of rile spee rie. Although c motors possess goo control chrcteristics n ruggeness, their performnce n pplitions in wier res is inhibite ue to sprking n commuttion problems [1]. Inuction motor o not possess the oe mentione problems, they he their own limittions such s low power fctor n non-liner spee torque chrcteristics [2]. With the ncement of technology n eelopment of moern control techniques, the permnent mgnet brushless c (PMBLDC) motor is le to oercome the limittions mentione oe n stisfy the requirements of rile spee rie [1,3]. The brushless c (BLDC) motor is incresingly being use in computer, erospce, militry, utomotie, inustril n househol proucts beuse of its high torque, compctness, n high efficiency [4-7]. The PMBLDC motor is inherently electronilly controlle n requires rotor position informtion for proper commuttions of current. Howeer, the problems of the cost n reliility of rotor position sensors he motite reserch in the re of position sensorless BLDC motor ries [8,9]. This pper presents noel sensorless position etection technique with new physil concept bse on spee inepenent position function for the PMBLDC motors. With the spee inepenent position function, the commuttion instnts n be estimte from ner zero (1.5% of the rte spee) to high spees. Since the shpe of the position function is ientil t ll spees, it proies precise commuttion pulse t stey stte s well s trnsient stte. The propose metho oes not rely on the mesure bck electro motie force (EMF) n hence the nee for externl hrwre circuitry for sensing terminl oltges is remoe. II. OERIEW OF SENSORLESS CONTROL TECHNIQUES Sensorless methos for the trpezoil bck EMF type of PMBLDC motors [10,11] n be clssifie s follows. Bck EMF sensing technique Bck EMF integrtion technique Flux linkge bse technique Freewheeling oe conuction All these methos rely on spee epenent bck EMF. Since the bck EMF is zero or unetectly smll t stnstill n low spees, it is not possible to use the bck EMF sensing metho in the low spee rnges. Also, the estimte commuttion points tht re shifte by 30 from zero crossing of bck EMF he position error in trnsient stte. The flux estimtion metho lso hs signifint estimtion error t low spee, in which the oltge eqution is integrte in reltiely lrge perio of time [8]. To oercome the oe rwbcks, Interntionl Journl of Smrt Sensors n A Hoc Networks (IJSSAN) ISSN No (Print) olume-1, Issue-2,

2 Sensorless Control of PMBLDC Motor Bse on Spee Inepenent Position Function noel metho, bse on new spee-inepenent function, is propose, one tht is bse on new physil insight. III. PROPOSED SENSORLESS CONTROL TECHNIQUE A. Principle The generl oltge eqution of one of the ctie phses is gien by x Ri x + n k 1 ψ kx ( θ, i ) Where x is the ctie phse oltge, R is the phse resistnce, i x is the phse current, θ is the rotor position, ψ kx (θ, i x ) is the totl flux linkge of the ctie phse n n is the number of phses. The flux linkge in the ctie phse inclues both self n mutul flux linkges. For three-phse BLDC motors, the totl flux linkge of the phse A is ψ A L (θ,i ).i + L (θ,i b ).i b + L c (θ,i c ).i c + λ r (θ) (2) Where, the first term, L (θ, i ).i, represents the self flux linkge of phse A, the secon n thir term stn for the mutul flux linkge with phses B n C n the fourth term, λ r (θ) stns for the flux linkge ue to the permnent mgnet tht is ttche on the rotor. The first three terms of (2) re function of current n position, n the λ r (θ) is the function of position. Therefore, the flux profile hs close reltionship with the ynmic performnces. Since the BLDC motor uses permnent mgnets, the permeility of the ttche permnent mgnet is consiere s tht of ir, n hence, typilly, the motor hs smll inuctnce rition. Therefore, if the motor is operte within the rte current, the sturtion effect of inuctnce ue to current leel is usully neglecte. For the surfce-mounte permnent mgnet (SMPM) type of BLDC motors, the permnent mgnets re rounly ttche on the roun surfce of the rotor, n hence, the inuctnce rition by rotor position is negligibly smll. Bse on the chrcteristics of the SMPM type of BLDC motors, the flux profile n be simplifie s in (3) long with the following ssumptions: The motor is operte within the rte contion n hence the sturtion effect ue to current leel is neglecte. The lekge inuctnce is negligibly smll n hence neglecte. Iron losses re negligible. ψ A L. i + L. i b + L c. i c + λ r (θ) (3) x (1) Substituting (3) into (1) gies λr Ri + ( Li + Lib + Lcic ) + (4) In blnce three-phse BLDC motors L L bb L cc L s (5) L b L L L c L L cb M (6) where, L s n M represent the self-inuctnce n mutul-inuctnce, respectiely. Substituting (5) n (6) into (4) gies λr Ri + ( Li + Mib + Mic ) + (7) For blnce str connecte BLDC motors, i + i b + i c 0 (8) Using (8), (7) is simplifie s λ r R i + L + (9) where L L s M is the phse inuctnce uner blnce contions. The lst term in the oltge equtions is so lle bck EMF, n the term is reefine s ( k f ) e r R i + L + (10) θ ( f r ) Ri + L + k e (11) θ where k e stns for the bck EMF constnt. It is seen tht λ r (θ) in (9) is expresse s constnt lue times flux linkge function tht is chnge only by the rotor position s shown in (10). The f r (θ) is flux linkge form function tht is function of rotor position. Since some mnufcturers o not proie motor neutrl point, the line-to-line oltge equtions re use s follows: ( i i ) { f ( θ) f ( θ) } b r br R( i ib ) + L + ke ω (12) θ ( i i ) f b r R( i ib ) + L + k e ω (13) θ Where ω stns for the instntneous spee. The f r (θ) is line-to-line flux linkge form function tht is function of the rotor position. Now we efine new function, H(θ), s Interntionl Journl of Smrt Sensors n A Hoc Networks (IJSSAN) ISSN No (Print) olume-1, Issue-2,

3 Sensorless Control of PMBLDC Motor Bse on Spee Inepenent Position Function f r θ Then, H(θ) n be erie s H ( θ) Since the H(θ) function itself hs one to one reltionship with rotor position, it is possible to use this function for position estimtion. But s shown in (15), to know the H(θ) function, the instntneous spee term, tht is unknown for ynmic opertions, is require to lculte the function. To eliminte the instntneous spee term, ω, tht uses trouble in using the H(θ) function for position estimtion, one line- to-line H(θ) functionn is ie by nother line-to- line H(θ) function, n the ie new spee inepenent function is nme G(θ). For exmple G ( ) θ / 1 ω ke H H ( θ) ( θ) Fig.1 shows the G(θ) functions G(θ) ) /, G(θ) / weform bse on (15). The stnr instnt is when the G(θ) functions re positie infinity to negtiee infinity s in n G(θ) /, commuttion chnge from Fig.1. ( b ) R ( i ib ) ( ) ( b ) b c R i R i ( i ) b ( i ) L c b (14) b (15) b c L (16) b From the sequentil combintionn of two line-to-line H(θ) functions t ech commuttion interl, the iel G(θ) function tht is inepenent of spee n contins continuous position informtion is erie. It mens tht only the positie prt of the G(θ) function weform in fig.1 is utilize. It is note tht the stnr commuttion point is the pek point of iel G(θ) functionn tht is the most sensitie prt of the function s shown in fig.2. Therefore, the position estimtion bse on the G(θ) function n proie the best ccurcy t commuttion points of the current which re the most importnt instnts for the sensorless opertion. Tle I shows the position estimtion equtions t ech moe in fig. 2. Two line-to-linee H(θ) functions re use in ech moe s Tle I. As shown in fig. 2, t moe 1, G(θ) 1 is use s position estimtion eqution n fter 60 electril ngle, t moe 2, G(θ) 2 is utilize. The time urtion of ech moe in fig.2 correspons to 60 by electril ngles. When the G(θ) function reches preefine threshol lue, the motor is commutte. From the sequentil combintionn of the H(θ) functions bse on Tle I, the G(θ) function n be me s shown in fig.2. It is note thtt the commuttion signl n be generte t the pek point tht is the most sensitie prt of the G(θ) function. From the ille sttor current n c link oltge, the G(θ) functionn is compute bse on the equtions of Tle I in rel time. Since the weform of the G(θ) function is ientil t the entire spee rnge, it n be chrcterize t stey stte in look-up tle, n use s position reference for sensorless opertion t ll spees. Fig. 1 : G Function weforms B. Commuttion Strtegy After reful inestigtion of the shpe of G(θ) function to proie the best inrect position-function tht is spee-inepenent with high sensitiity t ech commuttion point, the rtio of two line-to-line H(θ) functions is sequentilly utilize. Fig. 2 : Line-to-line H Functions, G Function, Phse Current using propose sensorless metho Interntionl Journl of Smrt Sensors n A Hoc Networks (IJSSAN) ISSN No (Print) olume-1, Issue-2,

4 Sensorless Control of PMBLDC Motor Bse on Spee Inepenent Position Function TABLE I : G FUNCTION AT EACH MODE Moe Moe 1 n 4 Moe 2 n 5 Moe 3 n 6 G θ ) ( 1 G θ ) ( 2 G θ ) ( 3 G Function C. Current Control To control currents, hysteresis controller n be use for the propose sensorless metho. Also, to lculte line-to-line oltges in equtions in Tle I t ech moe, eery phse current is ctiely controlle. It mens tht silent phse current is controlle s zero I. SIMULATION RESULTS The prmeters of the PMBLDC motor use for simultion re s follows. Power : 1 HP Rte spee : 3500 rpm Poles : 4 Rte current : 5 A Rte torque : 2 N-m Inerter oltge : 160 Armture resistnce : 0.75 Ω Armture inuctnce : 3.05 mh Bck EMF constnt : sec/r Torque constnt : Nm/A Rotor inerti : e-4 Kg-m 2 iscous friction coefficient : 0.02 Nm/r/ses. Fig. 3 shows the block grm of propose sensorless control of PMBLDC motor. The complete rie system consists of PMBLDC motor fe by three-phse PWM inerter, spee inepenent position G function block n controller. The inerter which is connecte to the c supply fees controlle power to the motor. The mgnitue n frequency of the inerter output oltge epens on the switching signls generte by the hysteresis controller. The stte of these switching signls t ny instnt is etermine by moe of opertion, spee error n winng currents. The controller synchronizes the winng currents with the moe gien by G function. It lso fcilittes the rile spee opertion of the rie n mintins the motor spee to reference lue een uring lo ritions [12-14]. The propose sensorless control lgorithm is erifie through simultion using MATLAB SIMULINK pckge. Figs. 4 n 5 illustrte the performnce of the propose sensorless metho t 1500 n 100 rpm. ω ref + - DC Supply ω r 3-Phse oltge Hysteresis Current PI Spee Controll Reference Current Moe I c PMBLD C Fig. 3 : Block grm of propose sensorless control of PMBLDC rie. Fig. 4() : G Function n current weforms for step chnge in lo of 1Nm t t1.8sec (Reference spee 1500 rpm). G c, I c, ω r Interntionl Journl of Smrt Sensors n A Hoc Networks (IJSSAN) ISSN No (Print) olume-1, Issue-2,

5 Sensorless Control of PMBLDC Motor Bse on Spee Inepenent Position Function Fig. 4(b) : rition of spee for step chnge in lo of 1Nm t t1.8sec (Reference spee 1500rpm). Fig. 5(b) : rition of spee for step chnge in lo of 0.2 Nm t t1.8sec (Reference spee 100rpm) Fig. 4(c) : Electromgnetic torque rition for step chnge in lo of 1Nm t t1.8sec (Reference spee 1500 rpm). Fig. 5(c) : Electromgnetic torque rition for step chnge in lo of 0.2 Nm t t1.8sec (Reference spee 100rpm).. CONCLUSION This pper presents noel sensorless rie metho for PMBLDC motors. This technique mkes it possible to etect the rotor position oer wie spee rnge. This metho proies commuttion een in trnsient stte beuse of the spee inepenent chrcteristics of G(θ) function. Fig. 5(): G Function n current weforms for step chnge in lo of 0.2Nm t t1.8sec (Reference spee 100 rpm). REFERENCES [1] W. Hong, W. Lee n B. K. Lee, "Dynmic simultion of brushless c motor ries consiering phse commuttion for utomotie pplitions", IEEE Interntionl Electric Mchines & Dries Conference, IEMDC pp , 3-5 My Interntionl Journl of Smrt Sensors n A Hoc Networks (IJSSAN) ISSN No (Print) olume-1, Issue-2,

6 Sensorless Control of PMBLDC Motor Bse on Spee Inepenent Position Function [2] T. J. E Miller, Brushless permnent mgnet n reluctnce motor ries, clrenon press, oxfor, [3] Pul C. Kruse, Anlysis of Electric Mchinery, McGrw Hill Book Compny, [4] B K Bose, Intelligent Control n Estimtion in Power Electronics n Dries, Electril Mchines n Dries Conference Recor, IEEE interntionl my 1997,pp.TA2/2.1- TA2/2.6. [5] H. Le-Huy, Moeling n simultion of electril ries using mtl/simulink n power system blockset, The 27thnnul conference of the IEEE Inustril Electronic Society (IECON 01), Denor/Coloro, pp [6] Lee, P.W n Pollock, C, Rotor Position Detection Techniques for Brushless Permnent- Mgnet n Reluctnce Motor Dries, Inustry Applitions Society Annul Meeting, 1992, Conference Recor of the 1992 IEEE, 4-9 Oct. 1992, pp ol.1 Digitl Object Ientifier /IAS [7] A. Kusko n S. M. Peern, Definition of the brushless DC motor, Proc. of the IEEE Inustry Applition Society Annul Meeting IAS 88, pp , [8] N. Ertugrul n P. Arney, A new lgorithm for sensorless opertion of permnent mgnet motors. IEEE Trns. on Inustry Applitions, ol. 30, pp , Jn./Feb [9] Johnson J. P, Ehsni M n Guzelgunler Y, Reiew of Sensorless Methos for Brushless DC, in Proc. IEEE IAS 99 Conf., ol. 1, 1999, pp [10] T. Kim n M. Ehsni, Ance sensorless rie techniques for brushless c motors, U.S. Ptent 60/438,949, [11] M. Cirste, A. Dinun n S. Repth, Moelling New Sensorless Control Strtegy for Brushless DC Motors, IEEE Interntionl Conference on Inustril Technology (ICIT), 2004, pp [12] B. K. Lee n M. Ehsni, Ance Simultion Moel for Brushless DC Motor Dries, Electric Power Components n Systems, ol. 31, pp , [13] R. Wu n G. R. Selmon, A permnent mgnet motor rie without position sensor, IEEE Trns. on Inustry Applitions, ol. 27, pp , Sept./Oct [14] P.Pilly n R.Krishnn, Moeling simultion n Anlysis of Permnent Mgnet Motor Dries, Prt-II: The Brushless DC Motor Drie, IEEE Trns. on Inustry Applition, ol. 25, No. 2, pp , Mrch/April1989. Interntionl Journl of Smrt Sensors n A Hoc Networks (IJSSAN) ISSN No (Print) olume-1, Issue-2,