IJSRD - International Journal for Scientific Research & Development Vol. 4, Issue 1, 216 ISSN (online): 2321-613 Close Loop Speed Response of BLDC Motor using Pi Controller Patel Milan V 1 Chaudhari Pooja B 2 1,2 ME Student 1,2 Department of Electrical Engineering 1,2 MGITER/GTU, Navsari/Surat, Gujarat, India Abstract Permanent magnet brushless DC motors (PMBLDC) find wide applications in industries due to their high power density and ease of control. These motors are generally controlled using a three phase power semiconductor bridge. For starting and the providing proper commutation sequence to turn on the power devices in the inverter bridge the rotor position sensors required. Based on the rotor position, the power devices are commutated sequentially every 6 degrees. To achieve desired level of performance the motor requires suitable speed controllers. Brushless dc (BLDC) motor drives are continually gaining popularity in motion control applications. Therefore, it is necessary to have a low cost, but effective BLDC motor speed/torque regulator. They are used in Residential and commercial appliances such as refrigerators and air conditioning systems with conventional motor drive technology. A Brushless DC (BLDC) drives are known for higher efficiency and lower maintenance. This paper presents a Modelling and performance analysis of PID controlled BLDC motor and different schemes of PWM controlled BLDC motor. This paper presents simple open loop response of speed, torque, stator current, back emf and verified the operation of BLDC motor. Keywords: Brushless DC motor (BLDCM) Speed Control MATLAB/SIMULINK, Back emf Fig. 1: Cross section of BLDC motor Basically BLDC motor is a PMSM motor but only difference is the rotor position sensors and trapezoidal back emf. Control algorithm provides gate pulses from the hall signals. Control algorithm may be of logical type or in form of programming (.m file). I. INTRODUCTION To replace the function of commutators and brushes, the BLDC motor requires an inverter and a position sensor that detects rotor position for proper commutation of current. The rotation of the BLDC motor is based on the feedback of rotor position which is obtained from the hall sensors. BLDC motor usually uses three hall sensors for determining the commutation sequence. In BLDC motor the power losses are in the stator where heat can be easily transferred through the frame or cooling systems are used in large machines. BLDC motors have many advantages over DC motors and induction motors. Some of the advantages are better speed versus torque characteristics, high dynamic response, high efficiency, long operating life, noiseless operation; higher speed ranges. BLDC motor consists of stator with number of poles and rotor with permanent magnet mounted on it. Stator winding is supplied with 3 phase inverter as required. And inverter switches are controlled by hall position sensors. They are placed 12 degree apart from each. Fig. 2: Basic block diagram of BLDCM Fig. 3: Ideal waveform of stator current and back emf All rights reserved by www.ijsrd.com 1382
(IJSRD/Vol. 4/Issue 1/216/383) II. MATHEMATICAL MODEL OF BLDC MOTOR Modeling of a BLDC motor can be developed in the similar manner as a three-phase synchronous machine. Since there is a permanent magnet mounted on the rotor, some dynamic characteristics are different. Flux linkage from the rotor depends upon the magnet material. Therefore, saturation of magnetic flux is typical for this kind of motors. As any typical three-phase motors, one structure of the BLDC motor is fed by a three phase voltage source. The source is not necessarily to be sinusoidal. Square wave or other wave-shape can be applied as long as the peak voltage does not exceed the maximum voltage limit of the motor. Similarly, the model of the armature winding for the BLDC motor is expressed as follows: Va=IaRa+(L-M) dia/dt+e...(1) Vb=IbRb+(L-M) dib/dt+eb...(2) Vc=IcRc+(L-M) dic/dt+ec...(3) L is armature self-inductance [H], R-armature resistance [Ω], Va, Vb, Vc terminal phase voltage [V], ia, ib, ic motor input current [A], and ea, eb, ec motor back-emf [V]. B friction constant [Nms.rad-1]. An easy way to comply with the conference paper formatting requirements is to use this document as a template and simply type your text into it. A. Proposed Speed Control System Of Bldc Motor: The complete block diagram of speed control of three phase BLDC Motor is below Fig. Two control loops are used to control BLDC motor. The inner loop synchronizes the inverter gates signals with the electromotive forces. The outer loop controls the motor's speed by varying the DC bus voltage. Fig. 4: Equivalent circuit of the BLDC motor The mechanisms of back-emf and electromagnetic torque are all the same with those of the traditional brushed DC motor, thus similar analysis methods can be adopted. ea = Kwf(θe)w...(4) eb = Kwf(θe -2π/3)w....(5) ec = Kwf(θe + 2π/3)w.. (6) Kw is back EMF constant of one phase[v/rad.s-1], θe -electrical rotor angle [ o el.], W= rotor speed [rad.s-1], The electrical rotor angle is equal to the mechanical rotor angle multiplied by the number of pole pairs p: θe=p/2 θm θm is mechanical rotor angle [rad]. Total torque output can be represented as summation of that of each phase. Next equation represents the total torque output: Te=(ea.ia+eb.ib+ec.ic)/w (7) Te is total torque output [Nm], The equation of mechanical part is represented as follows: Fig. 5: Block Diagram of speed control of BLDC Motor Driving circuitry consists of three phase power convertors, which utilize six power transistors to energize two BLDC motor phases concurrently. The rotor position, which determines the switching sequence of the MOSFET transistors, is detected by means of 3 Hall sensors mounted on the stator. By using Hall sensor information and the sign of reference current (produced by Reference current generator), Decoder block generates signal vector of back EMF. The basic idea of running motor in opposite direction is by giving opposite current. Based on that, we have Table I for calculating back EMF for Clockwise of motion and the gate logic to transform electromagnetic forces to the 6 signal on the gates is given Table. III. RESULTS AND DISCUSSIONS BLDC motor ratings Stator phase resistance Rs (ohm):1 Stator phase inductance Ls (H):4e-1 Flux linkage established by magnets (V.s):.7625 Voltage Constant (V_peak L-L / krpm):6.3879 Torque Constant (N.m / A_peak):.61 Back EMF flat area (degrees): 12 Inertia, friction factor and pole pairs [ J(kg.m^2) F(N.m.s) p() ]: [17.3e-6.2 4] Voltage:36V Speed:27rpm Te-Tl=Jdw/dt+Bw...(8) Tl is load torque[nm], J inertia of rotor and coupled shaft [kgm2], All rights reserved by www.ijsrd.com 1383
(IJSRD/Vol. 4/Issue 1/216/383) 2-2.1.2.3.4.5.6.7.8.9 1 1-1.1.2.3.4.5.6.7.8.9 1 2 TABLE 1: Gate Pulses From Hall Sensors -2.1.2.3.4.5.6.7.8.9 1 Fig. 8: Stator current waveform Fig. 9: Zoomed Stator current waveform.8 Fig. 6: Close loop simulation of BLDC motor torque.6.4.2.1.2.3.4.5.6.7.8.9 1 4 speed 3 2 1 Fig. 1: Back emf waveform.1.2.3.4.5.6.7.8.9 1 Fig. 7: Torque-Speed waveform without load torque All rights reserved by www.ijsrd.com 1384
(IJSRD/Vol. 4/Issue 1/216/383) Fig. 11: Zoomed Back emf waveform Fig. 14: Back emf waveform (with load torque) Fig. 12: torque-speed waveform (With load torque of.1n.m at t=.2s) Fig. 15: Load torque waveform of.1n.m at t=.2 s Fig. 13: Stator current waveform(with load torque) Fig. 16: Line to line output voltage of inverter IV. CONCLUSION The simulation and mathematical model present in this paper helps you to understand the theoretical and practical response of BLDCM in open loop response. All the characteristics of BLDC motor are verified in this paper. All rights reserved by www.ijsrd.com 1385
(IJSRD/Vol. 4/Issue 1/216/383) ACKNOWLEDGMENT I would like to thank all the people who contributed in some way to work described in this report. First & Foremost, I thank my academic advisor, Prof. Naresh C Kumavat, Electrical engineering department, for accepting me into the group. During my tenure, he contributed his experience, engaging me into new ideas and demanding high quality of work in all my endeavors. Also thankful to Miss. Pooja B Chaudhari, my co-author. Most importantly, I would like special thanks to my parents for everything that they have done throughout my life and their support. I would also like to thanks my friends for their endless and unconditional love. REFERENCES [1] Mohammed Abdelbar Shamseldin, Adel A. EL-Samahy, Speed Control of BLDC Motor By Using PID Control and Self-tuning Fuzzy PID Controller, 15th International Workshop on Research and Education in Mechatronics (REM), Elgouna, Egypt,IEEE 214. [2] M.S Evangelin blessy, Mr.M.Murugan, Modeling and Controlling of BLDC Motor Based Fuzzy Logic,IEEE 214. [3] Arundhathi Shyam,Fabin daya J L, A Comparative Study on the Speed Response of BLDC Motor Using Conventional PI Controller, Anti-windup PI Controller and Fuzzy Controller,IEEE 213. [4] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specification, IEEE Std. 82.11, 1997. [5] Tae-Hyung Kim, Mehrdad Ehsani, Sensorless Control of the BLDC Motors From Near-Zero to High Speeds. IEEE Trans., Power Electronics, vol. 19, no. 6, November 24. [6] S. Ogasawara and H.Akagi, An approach to position sensorless drive for brushless dc motor, IEEE Trans. J. Industry Application, vol.27, pp. 928-933, Sep/Oct. 1991. All rights reserved by www.ijsrd.com 1386