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International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.

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  1. 1. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620612 | P a g eModeling and Simulation of Brushless DC Motor Using PWMControl Technique1vinod Kr Singh Patel, 2A.K.Pandey,1,2Department of Electrical Engineering, M.M.M. Engineering College, Gorakhpur (U.P.)1Research Scholar (Electrical Engineering, M.M.M. Engineering College)2 Associate Prof (Electronics Engineering, M.M.M. Engineering College)ABSTRACTThis paper describes a simpler way tocontrol the speed of PMBLDC motor using pwmcontrol method. The performance of thePMBLDC system is simulated. The speed isregulated by PI controller. Simulink is utilizedwith MATLAB to get a reliable and flexiblesimulation. In order to highlight the effectivenessof the speed control method used. The methodproposed suppresses torque oscillations. Thisdrive has high accuracy, robust operation fromnear zero to high speed.KEYWORDS: Hall position sensors, permanentmagnet brushless DC motor, pwm, PI controller.INTRODUCTIONLatest advance in permanent magnetmaterials, solid state devices and microelectronichave resulted in new energy efficient drives usingpermanent magnet brushless DC motors(PMBLDCM). Brushless DC motors are verypopular in a wide array of applications in industriessuch as appliances, automotive, aerospace,consumer, medical, industrial automation for itsreliability, high efficiency, high power density, lowmaintenance requirements, lower weight and lowcost. As the name implies, BLDC motor do not havebrushes for commutation. Instead they areelectronically commutated. BLDC motor have manyadvantages over brushed DC motor and inductionmotors, like better speed- torque characteristics,high dynamic response, high efficiency, noiselessoperation and wide speed ranges. Torque to weightratio is higher enabling it to be used in applicationswhere space and weight are critical factor [1]. ABLDC motor finds numerous applications in motioncontrol. A BLDC motor has windings on stator andalternate permanent magnets on rotor. Electroniccommutation of stator windings is based on rotorposition with respect to the stator winding [1]. Anew generation of microcontrollers and advancedelectronics has overcome the challenge ofimplementing required control functions, makingthe BLDC motor more practical for a wide range ofuses [2], [3], [4]. In this method the speed iscontrolled in a closed loop by measuring the actualspeed of the motor. The error in the set speed andactual speed is calculated. A proportional plusintegral (PI) controller is used to amplify the speederror and dynamically adjust the pwm duty cycle.When using pwm outputs toControl the six switches of the three- phasebridge, variation of the motor voltage can be got byvarying the duty cycle of the pwm signal. For low-cost, low-resolution speed requirements, the Hallsignals are used to measure the speed feedback.2. TYPES OF CONTROL TECHHIQUEOF PMBLDC MOTORThough various control techniques arediscussed in [5] basically two methods are availablefor controlling PMBLDC motor. They are sensorcontrol and sensor less control. To control themachine using sensors, the present position of therotor is required to determine the next commutationinterval. Motor can also be controlled by controllingthe DC bus rail voltage or by PWM method. Somedesigns utilize both to provide high torque at highload and high efficiency at low load. Such hybriddesign also allows the control of harmonic current[6]. In case of common DC motors, the brushesautomatically come into contact with thecommutatorof a different coil causing the motor tocontinue its rotation. But in case of BLDC motors thecommutation is done by electronic switches whichneed the rotor position. The appropriate statorwindings have to be energized when rotor poles alignwith the stator winding. The BLDC motor can also bedriven with predefined commutation interval. But toachieve precise speed control and maximumgenerated torque, brushless commutation should bedone with the knowledge of rotor position. In controlmethods using sensors, mechanical positionsensors,such as a hall sensor, shaft encoder orresolver have been utilized in order to provide rotorposition information. Hall Position sensors or simplyHall sensors are widely used and are popular. Threephase windings use one Hall Sensors each. Theyprovide three overlapping signals giving a 60° wideposition range. Whenever the magnetic poles passnear the sensors, they either give a high or low signal,indicating North or South Pole is passing the pole.The accurate rotor position information is used togenerate precise firing commands forpowerconverter. This ensures drive stability and fastdynamic response. The speed feedback is derivedfrom the position sensor output signals.Between thetwo commutations signals the anglevariation is
  2. 2. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620613 | P a g econstant as the Hall Effect Sensors are fixed relativeto the motor, thus reducing speed sensing to a simpledivision. Usually speed and position of a permanentmagnet brushless direct current motor rotor iscontrolled in a conventional cascade structure. Theinner current control loops runs at a larger width thanthe outer speed loop to achieve an effective cascadecontrol [7]. Various senseless methods for BLDCmotors are analyzed in [8-18.Modeling of BLDC isgiven in [3].[8] Proposes a speed control of brushlessdriveemploying PWM technique using digitalsignalprocessor. A PSO based optimization ofPIDcontroller for a linear BLDC motor is given in [9-10],Speed Control of BLDC based on CMAC &PIDcontroller is explained in [11]. Direct torquecontroland indirect flux control of BLDC motor withnon-sinusoidal back emf method controls thetorquedirectly and stator flux amplitude indirectlyusing daxiscurrent to achieve a low-frequency torqueripple freecontrol with maximum efficiency[12-13].Directback EMF detection method for sensorlesscontrol isgiven in [14]. [15] Proposes a novelarchitectureusing a FPGA-based system. Fixed gainPI speedcontroller has the limitations of beingsuitable for alimited operating range around theoperating pointand having overshoot. To eliminatethis problem afuzzy based gain scheduled PI speedcontroller isproposed in [16].A new module structureof PLLspeed controller is proposed by [17].A fixedstructurecontroller (PI or PID) using time constrainedoutputfeedback is given in [18]. The above literaturedoesnot deal with reduction of speed oscillationsinPMBLDC drive. This paper deals withcontrolmethod to reduce speed oscillations.To controla system, by any of these methods anaccuratemathematical model of the complete systemisrequired.3. MATHEMATICAL MODEL OF THE PMBLDC MOTORThe circuit model of PMBLDC motor is shown in fig1Fig 1: Motor circuit ModelThe voltage equations of the BLDC motor are as follows:𝑉𝑎 = 𝑅 𝑎 𝑖 𝑎 +𝑑𝑑𝑡𝐿 𝑎𝑎 𝑖 𝑎 + 𝐿 𝑎𝑏 𝑖 𝑏 + 𝐿 𝑎𝑐 𝑖 𝑐 +𝑑𝜆 𝑎𝑟 (𝜃)𝑑𝑡𝑉𝑏 = 𝑅 𝑏 𝑖 𝑏 +𝑑𝑑𝑡𝐿 𝑏𝑎 𝑖 𝑎 + 𝐿 𝑏𝑏 𝑖 𝑏 + 𝐿 𝑏𝑐 𝑖 𝑐 +𝑑𝜆 𝑏𝑟 (𝜃)𝑑𝑡𝑉𝑐 = 𝑅𝑐 𝑖 𝑐 +𝑑𝑑𝑡𝐿 𝑐𝑎 𝑖 𝑎 + 𝐿 𝑐𝑏 𝑖 𝑏 + 𝐿 𝑐𝑐 𝑖 𝑐 +𝑑𝜆 𝑐𝑟 (𝜃)𝑑𝑡In balanced system the voltage equation becomes𝑉𝑎𝑉𝑏𝑉𝑏=𝑅 0 00 𝑅 00 0 𝑅𝑖 𝑎𝑖 𝑏𝑖 𝑐+𝑑𝑑𝑡𝐿 𝑎 𝐿 𝑏𝑎 𝐿 𝑐𝑎𝐿 𝑏𝑎 𝐿 𝑏 𝐿 𝑐𝑏𝐿 𝑐𝑎 𝐿 𝑐𝑏 𝐿 𝑐𝑖 𝑎𝑖 𝑏𝑖 𝑐+𝑒 𝑎𝑒 𝑏𝑒𝑐………………. (1)The mathematical model for this motor is describedin Equation (1) with the assumption that themagnethas high sensitivity and rotor induced currents can beneglected [3]. It is also assumed that thestatorresistances of all the windings are equal. Thereforethe rotor reluctance does not change withangle. Now𝐿 𝑎 = 𝐿 𝑏 = 𝐿 𝑐 = 𝐿
  3. 3. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620614 | P a g e𝐿 𝑎𝑏 = 𝐿 𝑏𝑐 = 𝐿 𝑎𝑐 = 𝑀Assuming constant self and mutual inductance, thevoltage equation becomes𝑉𝑎𝑉𝑏𝑉𝑏=𝑅 0 00 𝑅 00 0 𝑅𝑖 𝑎𝑖 𝑏𝑖 𝑐+𝐿 − 𝑀 0 00 𝐿 − 𝑀 00 0 𝐿 − 𝑀𝑑𝑑𝑡𝑖 𝑎𝑖 𝑏𝑖 𝑐+𝑒 𝑎𝑒 𝑏𝑒𝑐……………… (2)In state space form the equation is arranged as𝑑𝑑𝑡𝑖 𝑎𝑖 𝑏𝑖 𝑐=−𝑅𝐿𝑖 𝑎𝑖 𝑏𝑖 𝑐_1𝐿𝑒 𝑎𝑒 𝑏𝑒𝑐+1𝐿𝑉𝑎𝑉𝑏𝑉𝑏The electromagnetic torque is given as𝑇𝑒 =(𝑒 𝑎 𝑖 𝑎 + 𝑒 𝑏 𝑖 𝑏 + 𝑒𝑐 𝑖 𝑐)𝑤𝑟The equation of motion is given as𝑑𝑤𝑟𝑑𝑡=(𝑇𝑒 − 𝑇𝐿 − 𝐵𝑤𝑟)𝐽4. BLDC MOTOR SPEED CONTROLIn servo applications position feedback isused in the position feedback loop. Velocityfeedback can be derived from the position data. Thiseliminates a separate velocity transducer for thespeed control loop. A BLDC motor is driven byvoltage strokes coupled by rotor position. The rotorposition is measured using Hall sensors. By varyingthe voltage across the motor, we can control thespeed of the motor. When using PWM outputs tocontrol the six switches of the three-phase bridge,variation of the motor voltage can be obtained byvarying the duty cycle of the PWM signal. Thespeed and torque of the motor depend on thestrength of the magnetic field generated by theenergized windings of the motor, Which depend onthe current through them. Hence adjusting the rotorvoltage and current will change motor speed.Fig 2: PWM Speed ControlFig .3 Schematic of a Speed controller
  4. 4. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620615 | P a g e.Commutation ensures only proper rotation of therotor. The motor speed depends only on theamplitude of the applied voltage. This can beadjusted using PWM technique. The required speedis controlled by a speed controller. This isimplemented as a conventional proportional-Integralcontroller. The difference between the actual andrequired speeds is given as input to the controller.Based on this data PI controller controls the dutycycle of the PWM pulses which correspond to thevoltage amplitude required to maintain the desiredspeed. When using PWM outputs to control the sixswitches of the three-phase bridge, variation of themotor voltage can be achieved easily by changingthe duty cycle of the PWM signal. In case of closedloop control the actual speed is measured andcompared with the reference speed to find the errorspeed. This difference is supplied to the PIcontroller, which in turn gives the dutycycle.PMBLDC motor is popular in applicationswherespeed control is necessary and the currentmust becontrolled to get desired torque. Figure4.shows thebasic structure for closed loop control ofthePMBLDC motor drive. It consists of an outerspeedcontrol loop, an inner current control loop forspeedand current control respectively. Speed loopisrelatively slower than the current loop.Fig.4.Closed Loop Speed Control4. SIMULATION RESULTSWith the help of the designed circuit parameters,the MATLAB simulation is done and resultsarepresented here. Speeds are set at 1650 rpm and the load torque disturbances areapplied at time t=.04 sec. Thespeed regulations areobtained at set speed and thesimulation results are shown. The waveforms of theback EMFare shown in Fig.6. it can beseen that the phasor voltages are displaced by 120°.The stator current waveformsare shown in Fig 7.They are quasi sinusoidal in shape and displaced by120°.Fig.5. BLDC MOTOR CONVENTIONAL PWM CONTROL USING HYSTERESIS CONTROLLERSimulink results for the conventional pwm control scheme for a BLDC motor are shown below.
  5. 5. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620616 | P a g eBackemf ABackemf B
  6. 6. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620617 | P a g eBackemf CPhase voltage APhase voltage BPhase voltage CFig.6. Back EMF and phase voltage in three phases
  7. 7. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620618 | P a g ePhase current APhase current BPhase current CFig.7. Phase current in three phases
  8. 8. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620619 | P a g eSpeed (rpm)Electromagnetic torqueFig.8. speed and electromagnetic torque5. CONCLUSIONClosed loop controlled VSI fed PMBLDCmotor using pwm control is modeled andsimulated. Feedback signals from the PMBLDCmotor representing speed and position are utilizedto get the driving signals for the inverter switches.The simulated results shown are at par with thetheoretical predictions. The simulation results canbe used for implementation of PMBLDC drive.The speed oscillations are minimized using closedloop system.REFERENCES1 T.J.Sokira and W.Jaffe, Brushless DCmotors:Electronic Commutation andControl, Tab Books,USA, 19892 Tay Siang Hui, K.P. Basu andV.SubbiahPermanent Magnet BrushlessMotor ControlTechniques, National Powerand EnergyConference (PECon) 2003Proceedings, Bangi,Malysia3 Nicola Bianchi,SilverioBolognani,Ji-HoonJang,Seung-Ki Sul,” Comparison ofPM Motorstructures and sensor lessControlTechniques for zero-speedRotorposition detection” IEEEtransactions on powerElectronics, Vol 22,No.6, Nov 2006.4 P.Thirusakthimurugan, P.Dananjayan,’ANewControl Scheme for The SpeedControl ofMBLDC Motor Drive’ 1-4244-0342-1/06/$20.00 ©2006 IEEE
  9. 9. vinod Kr Singh Patel, A.K.Pandey / International Journal of Engineering Research andApplications (IJERA) ISSN: 2248-9622 www.ijera.comVol. 3, Issue 3, May-Jun 2013, pp.612-620620 | P a g e5 R.Krishnan, “Electric Motor DrivesModeling,Analysis, and Control, Prentice-Hall InternationaInc., New Jersey, 2001.6 “New Approach to Rotor PositionDetection andPrecision Speed Control ofthe BLDC Motor”Yong-Ho Yoon Tae-Won Lee Sang-Hun ParkByoung-Kuk LeeChung- 1-4244-0136-4/06/$20.00 2006IEEE7 Ling KV, WU Bingfang HE Minghua andZhangYu, “A Model predictive controllerformultirate cascade system”, Proc.of theAmericanControl Conference, ACC 2004,USA, pp.1575-1579.2004.8G.Madhusudhanrao,B.V.SankerRam,B.SampathKumar,K.Vijay Kumar,” SpeedControl of BLDCMotor using DSP”,International Journal ofEngineeringScience and Technology Vol.2(3),2010.9 Yingfa Wang, Changliang Xia, ZhiqiangLi, PengSong,” Sensorless Control forBLDC motor usingsupport vector machinebased on PSO”, 2009IEEE10 Mehdi Nasri, HosseinNezamabadi-Pour,Malihemaghfoori, “A PSO-Basedoptimization of PID controller for aLinearBLDC Motor” Proc. Of Worldacademy ofScience Engg &Tech, Vol.20,April 2007.11 Zhiqiang Li &Changliangxia, “SpeedControl ofBLDC based on CMAC & PIDcontroller” Proc.Of 6th World congress onIntelligent Control &Automation. China,June 21-23, 2006.12 Salih Baris Ozturk, Hamid A.Toliyat,“SensorlessDirest Torque and IndirectFlux Control ofBrushless DC Motor withNon-Sinusoidal backemf”,978-1-4244-1766-7/08 ©2008 IEEE