11084 FOC Sensorless FOC for PMSM with dspic DSC

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2 Class Objectives When you finish this class, you will: Understand some of the latest motor control design solutions available Be aware of a new algorithm for sensorless Field Oriented Control (FOC) of Permanent Magnet Synchronous Motors (PMSMs) Know where to find more information on this algorithm 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 2

3 Agenda PMSM Overview Hands-On Exercise FOC for PMSM control Hands-On Exercises Sensorless techniques Hands-On Exercise Wrap up, Q&A 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 3

4 Hands-On Exercises LAB Sessions: Lab 1 Running Sensorless Demo Lab 2 Enabling Graphs Using DMCI Lab 3 Tuning PI Parameters Lab 4 Tuning Sensorless Parameters 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 4

6 PMSM Applications High Efficiency & Reliability Designed for high-performance Servo Applications Runs with/without Position Encoders More compact, efficient and lighter than ACIM Coupled with FOC control produces optimal torque Smooth low and high speed performance Low Audible Noise & EMI 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 6

7 PMSM Applications Air Conditioner & Refrigerator (AC) compressors Direct-drive washing machines Precision Machining Tools Automotive Electrical power steering Traction control Data Storage 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 7

8 PMSM v BLDC History. the motors originated from different areas The fundamentals of Torque production are identical BLDC is a variant of the PM BDC PMSM describes a AC synchronous motor whose field excitation is provided by PMs Control Methods are different (Six Step v FOC) 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 8

14 PMSM Construction The PMSM is similar to the BLDC but the Back EMF signals are sinusoidal and trapezoidal respectively Mathematical treatment is different Designed to be driven with a sine wave Like a 3-phase ACIM but air gap flux is produced by rotor mounted magnets 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 14

16 PMSM Characteristics eb ωt Wave shape is largely influenced by Stator design Number of slots per pole per phase is key Fractional slot, coil and pole motors enable wave shaping Waveform quality determined by manufacturing tolerances 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 16

17 PMSM Characteristics v ea eb ec ωt Back EMF shape of PMSM Brushless motor with sinusoidal Back EMF Synchronous AC motor BLAC PMSM 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 17

18 PMSM Characteristics The Back EMF ideally contains no harmonics Leads to a reduction in audible noise And better efficiency reduction of parasitic energy that excites mechanical components in an uncontrolled way 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 18

19 PMSM Characteristics Torque Demagnetization limit VSI current limit Short time operation VSI voltage line T0 Continuous operation 0 ωr Speed 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 19

20 PMSM Operation PMSM Electric Model v i R L Motor e i s e s T = T ω i s Instantaneous power Torque x Speed = Back EMF x phase current 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 20

23 PMSM Operation Stator field can be decomposed into components which are parallel and orthogonal to the rotor field Only the orthogonal (quadrature) field produces torque The parallel (direct) field produces force which compresses the bearings Phase current produces stator field and can be measured 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 23

27 PMSM with FOC Keep load 90 ahead of rotor position N S S Knowledge of rotor position required at all times N N 90 S S S Better torque production N N No torque ripple 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 27

30 Objectives of Lab 1 Getting to know the hardware in front of you Where are the Labs located? C:\Masters\11084\Lab1\PMSM.mcw How to load the lab projects Programming the dspic DSC devices Running the program on dspic DSC 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 30

31 You should have. 1. MPLAB IDE v7.60 or higher installed 2. C30 Compiler 3. Complete MPLAB ICD 2 setup 4. dspicdem MC1 Board 5. Low Voltage Power Module 6. dspic30f6010a PIM 7. 24V power supply for the board 8. Hurst (NTDynamo) BLDC motor 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 31

32 What we will do: LAB 1 Configure board hardware connections Open a workspace in MPLAB IDE Compile or Build a simple first project in MPLAB IDE Follow a procedure to Program the dspic DSC using MPLAB ICD 2 Follow a procedure to Run the program using MPLAB ICD Microchip Technology Incorporated. All Rights Reserved FOC Slide 32

33 Instructions for Lab1: Lab1 On MC1 board, move DIP switch to ICD position Connect power to MC1 board Open MPLAB IDE by double clicking on the icon In MPLAB IDE, select File -> Open Workspace Browse to \Lab1\PMSM.mcw Select PMSM.mcw and open workspace Contd Microchip Technology Incorporated. All Rights Reserved FOC Slide 33

34 Lab1 (contd.) Instructions for Lab1 (contd): In MPLAB IDE, Select Project -> Build All IF NO errors then... In MPLAB IDE, Select Debugger -> Program to program dspic DSC On MC1 board, move DIP switch to Analog position Install wire jumper from AN2 to VR1 on J6 In MPLAB IDE, Select Debugger -> Run Pot VR1. Arrow should be at position Pot VR2 should be all the way to CW Press S4 on MC1 board and Motor will start spinning 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 34

35 Lab1 Results Follow Lab1 for programming and running software: Before programming dspic DSC, move DIP to ICD position Before running, move DIP to Analog position Each Lab has a already created workspace in the appropriate folder Use the created workspace for each lab 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 35

38 FOC Overview Sinusoidal excitation with applied current space vector referenced to rotor position Stator current & rotor (magnet) flux interact to produce mutual torque and speed Electronic control required to keep phase at 90 degrees (quadrature) with respect to the rotor in order to optimize torque production T Current Space Vector 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 38

39 FOC Overview Improved Dynamic Response Reduced Torque Ripple Extended Speed Range Operation is possible Low Audible Noise & EMI 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 39

40 Signal Processing Vector-Coordinate Systems b β q d a α c 3-Axis Stator Reference 2-Axis Stator Reference 2 -Axis Rotating Reference 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 40

41 Signal Processing 3-phase voltages to control the current space vector Transformations simplify equations and allows control of 3-Phase Motors with conventional techniques as in a DC motor 3-phase time variant into a 2-axis time invariant 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 41

43 Signal Processing Projected Onto 2-Phase System (Clarke Transformation) Real α and imaginary β components is = isα + jisβ. Transformation to an orthogonal, stationary system Microchip Technology Incorporated. All Rights Reserved FOC Slide 43

44 Signal Processing Projected Onto Rotating System (Park Transformation) q β d θ α Transformation from stationary to a rotating reference frame. Direct-axis and Quadrature-axis stator current representation 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 44

45 Signal Processing Projected Onto Rotating System (Park Transformation) Transformation from stationary to a rotating reference frame (turned at the rotor speed) 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 45

46 Signal Processing Vectors in the Rotating Reference Frame Properly phased winding currents will result in a current space vector which rotates with and is orthogonal to the rotor. Iq should be maximized and Id minimized for optimal control 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 46

47 Signal Processing Vectors in the Rotating Reference Frame q iq is id d Torque iq Flux id They are time-invariant and can be treated as DC parameters, which allows them to be controlled independently Microchip Technology Incorporated. All Rights Reserved FOC Slide 47

48 FOC for PMSM N ref Σ PI iq ref - - id ref Σ Σ PI PI Vq Vd d,q α,β Vα Vβ SVM 3-Phase Bridge - θ iq d,q iα α,β ia id α,β iβ a,b,c ib Speed and Position QEI A B Encoder Motor This allows optimal torque production Microchip Technology Incorporated. All Rights Reserved FOC Slide 48

49 FOC for PMSM PI Controllers operate in the d-q reference frame of the rotor, they are isolated from the sinusoidal variation of motor voltages and currents and so perform equally well at low and high motor speeds Iq is servoed to equal the Torque demand and Id is servoed to zero. This gives optimal torque production The PI Controller Outputs are transformed to produce three phase voltage signals to the bridge (inverse Park, inverse Clarke folded into SVM) 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 49

50 Without FOC N N S θ S S FOC for PMSM Torque N N With FOC S 90 S S θ N N S T = Fs*Rs*sinθ N N S S N S N BEMF (V) BEMF (V) Current (I) Current (I) 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 50

53 FOC for PMSM Field Weakening What happens when the Back EMF approaches the supply voltage? To enable more speed the rotor field must be weakened The stator d axis current is set to a negative value Torque reduces and speed increases with field weakening 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 53

54 FOC for PMSM FOC provides smooth control at low speeds as well as efficient control at high speeds Trapezoidal (BLDC) commutation can be efficient at high speed but introduces torque ripple at low speed and produces audible noise Sinusoidal drive produces smooth control at low speed but is inefficient at high speeds FOC provides the best of both worlds 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 54

66 Lab2 (contd.) Instructions for Lab2 (contd.): Select SnapBuf1 for data source array Select Fractional for Display Format Click OK 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 66

67 Lab2 (contd.) Instructions for Lab2 (contd.): Assign SnapBuf2 and SnapBuf3 to Plots 2 and 3. Halt, Reset and Run application using MPLAB IDE Run motor by pressing S4 After letting the motor run for about 5 seconds, halt execution Data should be on Graph 1 plot. This data corresponds to estimated rotor angle Microchip Technology Incorporated. All Rights Reserved FOC Slide 67

73 Lab3 (contd.) Instructions for Lab3 (contd.): Open Lab3 Project Program dspic DSC Run motor by pressing S4 By Pressing S6, Speed reference will be doubled Analyze transient response on Plots Tune Speed PI Parameters to reduce overshoot Tune Iq PI Parameters to achieve minimum oscillations on Speed 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 73

77 Six step for BLDC Commutation is implemented in six discrete steps per electrical revolution Hall sensors can be used to indicate when commutation is required Back EMF can be used to provide the same information 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 77

78 Six step for BLDC BLDC Motor Back EMF DC+ A Back EMF DC- C B Phase A and C are energized Inactive Phase B has induced Back EMF Normally the phase which is not energized, is monitored for Back EMF 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 78

80 Six step for BLDC The Back EMF zero crossing method in detail In every electrical cycle, there are periods when each phase is not being driven. During these regions one end of the inactive phase is referenced to the star point and the other is monitored. The monitored voltage will cross the 1/2 VDD point at 30 electrical degrees. Knowing the last zero crossing time we know the 60 electrical degree time (T60) T60 divided by 2 = T30 is loaded in TMR2. The ISR of TMR2 then commutes the next pair of windings at T30 seconds later 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 80

81 Six step for BLDC - Summary Six step control creates comparatively more torque ripple Phase currents are rectangular Less processing power required Rotor position is not accounted for between commutation points Starting ramp parameters must uncover Back EMF signal BLDC produces more Torque than PMSM 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 81

82 Sensorless FOC for PMSM N ref Σ PI iq ref - - id ref Σ Σ PI PI Vq Vd d,q α,β Vα Vβ SVM 3-Phase Bridge - θ iq d,q iα α,β ia id α,β iβ a,b,c ib Position Speed Position and Speed Estimator Vα Vβ Motor 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 82

84 Sensorless FOC for PMSM i PMSM Electric Model R L e d v s = Ris + L is + dt e s v Motor d dt i s = R L i s + 1 L ( v e ) s s Position Estimation PMSM motor shares the same basic electric model as the Brushed DC (BDC), BLDC and AC Induction Motors 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 84

85 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 85 Sensorless FOC for PMSM ( ) ) ( ) ( 1 ) ( ) ( 1) ( n e n v L n i L R T n i n i s s s s s s + = + ( ) ) ( ) ( ) ( 1 1) ( n e n v L T n i L R T n i s s s s s s + = + Position Estimation

86 Sensorless FOC for PMSM Current Observer Hardware Slide-Mode Vs PMSM Is Controller - +K d dt i R = i L * * 1 s s + L * ( v e z) s s I*s + Sign (I*s Is) z -K * Estimated variable 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 86

88 Sensorless FOC for PMSM Back EMF Estimation d dt i R L * * 1 s = is + L ( * v e z) s s e * s z LPF LPF e filtered * s e arctan e α β θ * * Estimated variable 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 88

90 Sensorless FOC for PMSM Position and Speed estimation e arctan e α β θ* ω* + + θ*comp 7 ω = i= 0 ( θ ( n) -θ ( n -1)) Kspeed LPF ω* filtered * Estimated variable 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 90

91 Sensorless FOC for PMSM Phase Compensation The inherent position filtering is compensated Speed range is divided into parts with compensation applied to each Spread sheet calculator supplied 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 91

92 Sensorless FOC for PMSM Hardware Vs PMSM Is Slide Mode Controller - -1 d dt i R = i L * * 1 s s + z LPF L * ( v e z) * Estimated variable s e * s s LPF e filtered * s e arctan e 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 92 α β I*s 7 ω = i= 0 θ* + ( θ ( n) -θ ( n -1)) K speed Sign (I*s Is) z ω* LPF +1 θ*comp + + ω* filtered

94 Sensorless FOC for PMSM Initial Torque Demand iq ref id ref Σ - Σ PI PI Vq Vd d,q α,β Vα Vβ SVM 3-Phase Bridge - θ iq d,q iα α,β ia id α,β iβ a,b,c ib Motor Startup θ Motor t 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 94

95 Sensorless FOC for PMSM S4 Pressed Measure Winding Currents Convert Currents to Iq and Id Reset Initialize Variables and Peripherals Motor Stopped Initialize Variables for Running Motor Initialize PI Controller Parameters Enable Interrupts Read Reference Torque from VR1 Motor Running Start Up A/D Interrupt Open Loop FOC Set New Duty Cycles using SVM Execute PI Controllers for Iq and Id Increment Theta Based on Ramp Motor Stopped Stop Motor S4 Pressed or FAULT S4 Pressed or FAULT End of Start Up Ramp Motor Running Sensorless FOC A/D Interrupt Read Reference Speed from VR2 Main Software State Machine Set New Duty Cycles using SVM Sensorless FOC Measure Winding Currents Execute PI Controllers for Speed, Iq and Id Compensate Theta Based on Speed Calculate Speed Estimate Theta using SMC Convert Currents to Iq and Id 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 95

100 Objectives of Lab 4 Tuning Sensorless Parameters for Open Loop. Lock Times and End Speed. Tuning Sensorless Parameter for Closed Loop. Slide Mode Controller Gain Microchip Technology Incorporated. All Rights Reserved FOC Slide 100

103 Lab4 (contd.) Instructions for Lab4 (contd.): Open Lab4 Project Program dspic DSC Run motor by pressing S4 Motor will not transition to closed loop Halt and analyze Plots Set K slide to.9. Run and analyze Set K slide to.1. Run and analyze Change End Speed from Slide Bars. What happens to Estimated Current? What happens to Theta? 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 103

106 Lab4 Results K Slide tuning. Slide Mode Controller Gain should be high enough to track measured current. Gain should be low enough to keep Theta as clean as possible. Estimated current and measured current should be on the same scale. End Speed should be enough to get a clean Theta Microchip Technology Incorporated. All Rights Reserved FOC Slide 106

109 Summary PMSM High efficiency and smooth torque are advantageous FOC Provides optimal torque control Can be run with or without Position Sensors Applicable for ACIM 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 109

110 Dev Tools used in this class dspicdem MC1 Motor Control Development Board (DM300020) dspicdem MC1L 3-Phase Low Voltage Power Module (DM300022) 3-Phase BLDC Low Voltage Motor 24V (AC300020) MPLAB ICD 2 In-Circuit Debugger/Programmer (DV164005) 2007 Microchip Technology Incorporated. All Rights Reserved FOC Slide 110

111 Resources For resources and information regarding designing motor-control applications, visit Microchip s motor-control design center at: Microchip Application Notes for Motor-Control Applications: PIC18CXXX/PIC16CXXX Servomotor Brushless DC Motor Control Made Easy Brushless DC (BLDC) Motor Fundamentals Brushless DC Motor Control Using PIC18FXX31 Using the dspic30f for Sensorless BLDC Control Using the dspic30f for Vector Control of an ACIM Sensored BLDC Motor Control Using dspic30f2010 Using the PIC18F2431 for Sensorless BLDC Motor Control An Introduction to ACIM Control Using the dspic30f Sensorless BLDC Motor Control Using dspic30f2010 Sinusoidal Control of PMSM Motors with dspic30f Sensorless Control of PMSM Motors Sensorless BLDC Control with Back EMF Filtering Getting started with the BLDC Motors and dspic30f Measuring speed and position with the QEI Module Driving ACIM with the dspic DSC MCPWM Module Using the dspic30f Sensorless Motor Tuning Interface AN696 AN857 AN885 AN899 AN901 AN908 AN957 AN970 AN984 AN992 AN1017 AN1078 AN1083 GS001 GS002 GS004 GS Microchip Technology Incorporated. All Rights Reserved FOC Slide 111

112 Thank You Note: The Microchip name and logo are registered trademarks of Microchip Technology Inc. in the U.S.A. and other countries. All other trademarks mentioned herein are property of their respective companies Microchip Technology Incorporated. All Rights Reserved FOC Slide 112

113 Trademarks The Microchip name and logo, the Microchip logo, Accuron, dspic, KeeLoq, KeeLoq logo, microid, MPLAB, PIC, PICmicro, PICSTART, PRO MATE, rfpic and SmartShunt are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. AmpLab, FilterLab, Linear Active Thermistor, Migratable Memory, MXDEV, MXLAB, SEEVAL, SmartSensor and The Embedded Control Solutions Company are registered trademarks of Microchip Technology Incorporated in the U.S.A. Analog-for-the-Digital Age, Application Maestro, CodeGuard, dspicdem, dspicdem.net, dspicworks, ECAN, ECONOMONITOR, FanSense, FlexROM, fuzzylab, In-Circuit Serial Programming, ICSP, ICEPIC, Mindi, MiWi, MPASM, MPLAB Certified logo, MPLIB, MPLINK, PICkit, PICDEM, PICDEM.net, PICLAB, PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, REAL ICE, rflab, Select Mode, Smart Serial, SmartTel, Total Endurance, UNI/O, WiperLock and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies Microchip Technology Incorporated. All Rights Reserved FOC Slide 113