CONTRIBUTIONS TO THE STUDY OF TUBULAR

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1 TECHNICAL UNIVERSITY OF CLUJ-NAPOCA IOANA-CORNELIA VESE CONTRIBUTIONS TO THE STUDY OF TUBULAR LINEAR ELECTRIC ACTUATORS PH.D. THESIS Ph.D. Supervisor: Prof.Dr.ing. Mirce M. RADULESCU ABSTRACT OCTOBER

CHAPTER 1 refers to liner electric ctutors (LEAs), tht re electromgnetic devices tht convert electric energy with impressed informtion into controlled progressive or oscilltory (reciprocting)

2 CHAPTER 1 refers to liner electric ctutors (LEAs), tht re electromgnetic devices tht convert electric energy with impressed informtion into controlled progressive or oscilltory (reciprocting) trnsltionl mechnicl motion of limited trvel. The bove defining fetures (i) of both energy nd informtion electromechnicl conversion, nd (ii) of trnsltionl motion over limited rnge distinguish LEAs from liner electric motors, nd mke them the core constituents of direct-drive liner motion control (DDLMC) systems. Experts estimte tht bout 75% of ll motion-control industril pplictions require moving lods in stright line, but DDLMC systems presently ccount for reltively smll portion (up to 10 %) of ll LMC pplictions. Nevertheless, industry is seeing n nnul growth rte of % for DDLMC systems, while the rise of generl motion control technologies is round 6 % per yer. There is generl greement tht DDLMC systems emerged in mchine-tool industry pplictions, such s high-qulity mchining, honing, grinding, punching, nd cutting, nd recently expnded into mteril hndling, metl forming, electronic pckging nd utomted sorting, robotic mnufcturing, printing, textile weving, nd food processing. One cn sy tht DDLMC systems re now in mturing industril development, which requires engendering their bility to innovte. In DDLMC systems, LEAs develop directly electromgnetic forces between sttionry member (sttor) nd trnsltionlly-moving member (trnsltor, slider or runner) to drive pylod (plnt) long n imposed reference trjectory without mechnicl gers nd trnsmission systems, thus offering significnt dvntges over their rotry-to-liner counterprts, such s simpler overll structure, higher efficiency, better dynmic behviour, wider thrust-force control bndwidth, improved relibility, longer operting life nd lower mintennce (Fig.1). Fig. 1. Structure nd operting principle of TLEA (exemplified by TLBLPMA). The most recent dvnce in direct-drive liner-ctution technology is represented by the tubulr LEA (TLEA), which benefits from high thrust-force cpbility, therml efficiency, no end-windings nd zero net ttrctive force between sttor nd trnsltor. TLEA dvntges of incresed throughput, esy instlltion nd integrtion, very good ccurcy, consistent repetbility, high thrust-force density, light weight/force rtio, quiet opertion, nd high overll efficiency, open DDLMC systems to pplictions where on-line chnges to the motion profile re required or where relibility is t premium. 2

It my be pointed out tht of the three min TLEA technologies, tubulr liner brushless permnent mgnet ctutors (TLBLPMAs) dominte the mrket due to the following fvourble fetures s compred to its

3 It my be pointed out tht of the three min TLEA technologies, tubulr liner brushless permnent mgnet ctutors (TLBLPMAs) dominte the mrket due to the following fvourble fetures s compred to its competing TLEAs: higher thrust force density, higher overll efficiency, greter output force per coil re, smller size, simpler power supply with brushless commuttion, simpler mechnicl design, higher ccurcy, lower udible noise nd more user-cceptnce. It is likely tht future pplictions will crete need for TLEAs more innovtive, ever-smller nd bus-comptible with interfcing built into the pckge. Newer developments, design refinements, nd downwrd trend in mnufcturing costs seek to open DDLMC systems with TLEAs to wider udience. CHAPTER 2 dels with the electromgnetic design nd nlysis of TLBLPMA prototype with thrust-rod (inductor) xilly-mgnetized PMs nd three-phse-winding slotted rmture. The electromgnetic design of TLBLPMA prototype ws crried out on the bsis of simplified one-dimensionl field nlysis, in order to determine the min dimensions of the ctutor, for given specifictions. The design equtions for the considered TLBLPMA re developed using the min geometric prmeters of Fig.2 nd the following ssumptions: one-dimensionl field nlysis; infinite iron permebility; cylindricl symmetry; negligible end-effects. Despite some of these ssumptions seem to be very restrictive, they result from relistic pproximtions for the TLBLPMA topology under study. For exmple, the second stted simplifiction considers tht the TLBLPMA mgnetic behviour is dominted by the presence of PMs, thus the iron reluctnce is less importnt nd cn be neglected; the cylindricl symmetry is n inherent property of this ctutor; the end-effects cn be neglected if proper mitigtion techniques re used; finlly, iron sturtion does not occur when the ctutor is designed so tht the mgnetic lod is within the liner prt of the iron mgnetiztion chrcteristic. d m d i d e Fig. 2. Min geometric prmeters of the TLBLPMA under study. 3

4 The obtined solution procedure for the bove design cn be performed for different geometricl vlues nd designs, within resonble rnge. A complementry more-detiled nlysis of the mgnetic flux distribution in the TLBLPMA prototype using xi-symmetric FE simultions ws performed to refine the electromgnetic design, determine the electromgnetic thrust-force, s well s the rmture-winding inductnces for further dynmic modelling nd simultion. The TLBLPMA design ws bsed on simplifying ssumptions regrding the mgnetic flux pths, so tht it is worthy performing complementry more-detiled nlysis of the mgnetic flux distribution using finite-element (FE) field nlysis of the TLBLPMA prototype. The xi-symmetric model of the TLBLPMA prototype for FE mgnetic field nlysis is shown in Fig.3. Fig. 3. TLBLPMA prototype nd its xi-symmetric model for FE mgnetic field nlysis.. Using JMAG-Studio [7] softwre, nonliner mgnetic field 2D-FE simultions re crried out by tking into ccount the xil symmetry of the studied TLBLPMA topology, s well s its stedystte nd trnsient opertion modes. An xi-symmetric field model ws creted for 2D-FE simultion of the TLBLPMA under nolod nd rted-lod opertion conditions correlted with the imposed velocity on the trnsltor (slider) nd the current wveform through the rmture windings. The nonliner B-H chrcteristic for iron regions ws lso included. Symmetry ws exploited to reduce the field domin to hlf of the xil cross-section of the overll ctutor by imposing periodicity nd Dirichlet boundry conditions. FE-simultions were crried out for sinusoidl rmture-winding current nd ctive thrust-rod PMs. The FE-computed mgnetic flux distribution in the TLBLPMA prototype under rted-lod condition is given in Fig.4. The electromgnetic thrust force (due to the interction of the thrust-rod PM-excittion nd rmture-rection mgnetic fields) developed by the TLBLPMA prototype ws lso obtined from FEsimultions. Fig.4. shows the developed thrust force s function of trnsltor position, ssuming constnt currents flowing in the rmture windings (J = 6 [A/mm 2 ] 4

5 Fig.4.. FE-computed mgnetic flux distribution in the TLBLPMA prototype under rted-lod condition, for given trnsltor position nd electromgnetic thrust-force of the TLBLPMA prototype s function of the trnsltor position Modelling TLBLPMA from therml point of view is complex problem with severl spects to be tken into ccount, from the type of the therml sources to the type of het movement, nd het relesing prts considered, subject resolved in CHAPTER 3. For the heting sources, there is difficulty to predict the losses in trnsient opertion mode of the ctutor by mens of empiricl reltions. A good pproximtion is creted, with very good vlidtion from the experimentl results. Although simple, the proposed therml (Fig.5) model tkes into ccount the most importnt losses of this type of mchine. Fig.5. Therml circuit of TLBLPMA mchine under trnsient opertion. The tempertures of both iron nd copper prts re correlted with the corresponding therml resistnces nd cpcitors, which dynmiclly chnge in time. The prticulrity of this ctutor is the geometry itself tht brings some chnges in the therml model, since prt of the trnsltor helps the het exchnge with the externl ir. The vlidtion of nlyticl vs. Experimentl results re presented in Fig.6. 5

6 Fig.6. Computed vs. mesured tempertures of copper nd iron The multiphysics pproch to FE field nlysis of TLBLPMA represents crucil stge of the ctutor design optimiztion nd performnce improvement for industril pplictions nd it is proved in this section tht it represents vible tool for chrcterizing the interdependencies between electromgnetic nd therml field ppered in ctutors opertion. Anlyses of electromgnetic nd therml behviours hve been crried out for TLBLPMA prototype, using nlyticl-experimentl nd multiphysics pproches. The obtined results contribute to good chrcteriztion of the TLBLPMA mgneto-therml behviour, thus offering globl disply of TLBLPMA performnces nd reveling vluble informtion for the design optimiztion. In CHAPTER 4 Direct Thrust-Force Control strtegy for two-phse TLBLPMA ws developed nd implemented. The clssic strtegy, comprising inverter nd pproprite switching tble ws presented, long with the detiled description of possible inverter topologies nd mthemticl model for two-phse TLBLPMA prototype. Minly, there re two clssic topologies of voltge inverter tht suit the feeding of two-phse TLBLPMA. There is the four-leg two-phse inverter (FLTPI) (full H-bridge), in Fig.7, nd the threeleg two-phse inverter (TLTPI) (semi-h-bridge). A B Vdc/2 V1 S1 S2 S5 S6 n L R A -Vdc/2 V2 S3 S4 bl S7 br S8 B Fig.7.Four-leg two-phse inverter structure FLTPI 6

FLTPI structure comprises two single-phse full-bridge inverters, i.e. eight switching modules. The two windings re seprtely connected to ech of the two single-phse full-bridge inverters.

7 FLTPI structure comprises two single-phse full-bridge inverters, i.e. eight switching modules. The two windings re seprtely connected to ech of the two single-phse full-bridge inverters. It results in 16 switching sttes, 12 ctive nd four zero sttes. The 8 sectors, ech of 45 0, re formed by 4 vectors with length of 2V dc nd 8 spce vectors with length ofv dc. There is perfect squre formed by the 12 spce vectors, nd lso there re 4 null vectors, in the center of it. A current-bsed model ws implemented in order to estimte the two-phse TLBLPMA quntities, nd to void the inccurcies introduced in clssicl voltge-bsed model. F ψ = L i b s b b ( ψ ) 2 + ( ψ ) 2 ψ = L i ψ = π = ψ p PM + ψ + ψ ib cos PM PM cos sin b π p π x i sin π p p x x π p x (1) It hs been proved tht, for two-phse TLBLPMA DTFC scheme with current-bsed model, the position informtion is mndtory. Due to the very smll time-constnt of the two-phse rmture of the TLBLPMA prototype, the constnt-force DTFC dynmic response revels significnt thrustforce nd current ripples (Fig.8). Hence, SVM technique is required in order to reduce these ripples in DTFC two-phse TLBLPMA opertion. Fig.8. Experimentl thrust-forcend rmture phse currents responses. Prcticl vlidtion of the DTC TP-PMTA strtegy is implemented nd crried out in this chpter. A dspace bsed HIL Simultion provides prcticl evidence of the DTC two-phse TLBLPMTA strtegy, using full-h inverter bridge, s presented in CHAPTER 5. The tests were performed using the test bench presented in Fig.9, which comprises the following prts: PC with dspace interfce, two-phse TLBLPMTA (LinMot Prototype) under study, two 7

8 Semikron-mde SSTPI, DC power sources, inverter mplifier box (interfce between dspace signls nd gte drivers of inverter IGBTs), mesurement box nd cbles connecting ll devices. Fig.9. Photogrph of the experimentl set-up The djustments needed when switching from simultion to rel-time experiment re, eventully, simplifying foundtions for ccurte dynmic chrcteriztion; tht is becuse most of the pproximted vlues become, in experiment, mesured quntities furnished directly from the drive system. The dvntges of implementing the simultion into rel time system bring out the ccomplishment of the DTC two-phse TLBLPMTA direct-drive system, with the regrded involvement in industril prototype-pplictions. CHAPTER 6 presents the mjor contributions of the thesis nd some suggestions for the future reserch work s follows: The mjor contributions brought by the uthor to the present reserch work re the following: the electromgnetic design of xilly-mgnetized PM thrust-rod TLBLPMAs with refinement by two-dimensionl mgnetic field nlysis using FEM, nd vlidtion ginst experiments on built prototype; 3D-FE therml nlysis vlidted through nlyticl-experimentl results nd completed by multiphysics pproch to TLBLPMA prototype s crucil stge for design optimiztion nd performnce improvement; development nd implementtion by mens of dspace-bsed hrdwre-in-the-loop simultion nd experiment of sinusoidl commuttion scheme nd inverter supply, s well s DTFC of two-phse TLBLPMAs for industril pplictions. As future developments of the thesis reserch work, it is suggested to investigte the behviour of TLBLPMA with soft mgnetic composite mterils replcing the sttor nd slider iron prts; to further study mitigtion techniques ginst detent (cogging) force components of TLBLPMA with xilly-mgnetized PM thrust-rod topology; to introduce slider-position sensorless scheme for the electronic commuttion nd inverter supply of TLBLPMA; to extend the DTFC strtegy to three-phse rmture-winding TLBLPMAs for both constnt-thrust nd constnt-power (flux-wekening) opertion modes. 8

ELE B7 Power Systems Engineering. Power System Components Modeling

ELE B7 Power Systems Engineering. Power System Components Modeling Power Systems Engineering Power System Components Modeling Section III : Trnsformer Model Power Trnsformers- CONSTRUCTION Primry windings, connected to the lternting voltge source; Secondry windings, connected