11084 FOC - amoBBSd1.amobbs.com/bbs_upload782111/files_10/ourdev_288142.pdf · sensorless Field Oriented Control (FOC) of Permanent Magnet Synchronous Motors ... 11084 FOC Slide 22

© 2007 Microchip Technology Incorporated. All Rights Reserved. 11084 FOC Slide 1

11084 FOC

Sensorless FOC for PMSM with dsPIC® DSC


Class ObjectivesWhen 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


Agenda

PMSM OverviewHands-On ExerciseFOC for PMSM controlHands-On ExercisesSensorless techniquesHands-On ExerciseWrap up, Q&A


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


Agenda

PMSM Overview− PMSM Applications− PMSM v BLDC− PMSM Construction− PMSM Characteristics− PMSM Operation


PMSM ApplicationsHigh Efficiency & ReliabilityDesigned for high-performance Servo ApplicationsRuns with/without Position EncodersMore compact, efficient and lighter than ACIMCoupled with FOC control produces optimal torqueSmooth low and high speed performanceLow Audible Noise & EMI


PMSM Applications

Air Conditioner & Refrigerator (AC) compressorsDirect-drive washing machinesPrecision Machining ToolsAutomotive Electrical power steeringTraction controlData Storage


PMSM v BLDCHistory…. the motors originated from different areas The fundamentals of Torque production are identicalBLDC is a variant of the PM BDCPMSM describes a AC synchronous motor whose field excitation is provided by PMsControl Methods are different (Six Step v FOC)


Motor Classification


PMSM Construction

Radial Axial

Rotor

Rotor

StatorStator


PMSM Construction


PMSM ConstructionRotor Assembly possibilities


PMSM Construction

PM Characteristics


PMSM Construction

The PMSM is similar to the BLDC but the Back EMF signals are sinusoidal and trapezoidal respectivelyMathematical treatment is differentDesigned to be driven with a sine waveLike a 3-phase ACIM but air gap flux is produced by rotor mounted magnets


BLDC

PMSM CharacteristicsPMSM

Stator Flux

Linkage

Back EMF


PMSM Characteristics

Wave shape is largely influenced by Stator designNumber of slots per pole per phase is keyFractional slot, coil and pole motors enable wave shapingWaveform quality determined by manufacturing tolerances

eb

ωt



Brushless motor with sinusoidal Back EMFSynchronous AC motorBLACPMSM

ea eb ec

ωt

Back EMF shape of PMSM

v



The Back EMF ideally contains no harmonicsLeads to a reduction in audible noise And better efficiency – reduction of parasitic energy that excites mechanical components in an uncontrolled way


PMSM CharacteristicsTorque

Speed0

Continuous operation

Short time operation VSI voltage line

Demagnetization limit

VSI current limit

ωr

T0


PMSM Operation

s

ss

iTTei

∝= ω

e

Motor

R L

v

i

PMSM Electric Model

Instantaneous power− Torque x Speed = Back EMF x phase

current


PMSM Operation

Torque production

Taking direction of F into account T=Fr sin θ


Stator Field

Rotor Field

PMSM Operation

S

N

S

N

N

S

N

S

θ

S

N


PMSM OperationStator field can be decomposed into components which are parallel and orthogonal to the rotor fieldOnly the orthogonal (quadrature) field produces torqueThe parallel (direct) field produces force which compresses the bearingsPhase current produces stator field and can be measured


BEMF (V)

Current (I)

Torque

θ

T = Fs*Rs*sinθ

S

N

N

S

θ

S

N

N

S

N

S

Without FOC

PMSM Operation


PMSM Operation

BEMF (V)

Current (I)

With FOC

Torque

θ

T = Fs*Rs*sinθ

S

N

N

S

90°

S

N

NS

NS


PMSM Operation

90°

0

π/2

-π/2


PMSM with FOCKeep load 90°ahead of rotor positionKnowledge of rotor position required at all timesBetter torque productionNo torque ripple

S

N

N

S

90°

S

N

N

S

NS


Agenda



Lab 1. Running Sensorless Demo


Objectives of Lab 1Getting to know the hardware in front of youWhere are the Labs located?− C:\Masters\11084\Lab1\PMSM.mcwHow to load the lab projectsProgramming the dsPIC® DSC devicesRunning the program on dsPIC DSC


You should have….1. MPLAB® IDE v7.60 or higher

installed2. C30 Compiler3. Complete MPLAB ICD 2 setup4. dsPICDEM™ MC1 Board5. Low Voltage Power Module6. dsPIC30F6010A PIM7. 24V power supply for the board8. Hurst (NTDynamo) BLDC motor


LAB 1 What we will do:− 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 2


Lab1Instructions for 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 ...


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


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 folderUse the created workspace for each lab


Agenda



Agenda

FOC for PMSM− FOC Overview− Signal processing− FOC for PMSM


FOC OverviewSinusoidal excitation with applied current space vector referenced to rotor positionStator current & rotor (magnet) flux interact to produce mutual torque and speedElectronic control required to keep phase at 90 degrees (quadrature) with respect to the rotor in order to optimize torque productionT ∞ Current Space Vector


FOC Overview

Improved Dynamic ResponseReduced Torque RippleExtended Speed Range Operation is possibleLow Audible Noise & EMI


Signal Processing

a

b

c

α

β

d

q

3-Axis Stator Reference 2-Axis Stator Reference 2 -Axis Rotating Reference

Vector-Coordinate Systems


Signal Processing

3-phase voltages to control the current space vectorTransformations simplify equations and allows control of 3-Phase Motors with conventional techniques as in a DC motor3-phase time variant into a 2-axis time invariant


Signal Processing

a

c

iaic

ib

is

b 3-Phase Coordinate System(Stator current space representation)


Signal Processing

Real α and imaginary β components is = isα + jisβ. Transformation to an orthogonal, stationary system.

Projected Onto 2-Phase System (Clarke Transformation)


Signal Processing

Transformation from stationary to a rotating reference frame. Direct-axis and Quadrature-axis stator current representation

α

β

θd

q

Projected Onto Rotating System (Park Transformation)


Signal Processing

Transformation from stationary to a rotating reference frame (turned at the rotor speed)

Projected Onto Rotating System (Park Transformation)


Signal Processing

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

Vectors in the Rotating Reference Frame


Signal Processing

d

q

isiq

id

Torque ∝∝ iqiq Flux ∝∝ idThey are time-invariant and can be treated as DC parameters, which allows them to be controlled independently.

Vectors in the Rotating Reference Frame


FOC for PMSM

ΣΣ

ΣΣ

ΣΣ 3-Phase

Bridge

QEIQEI

SVMPI PI

PI

-

- -

d,q

α,β

θ

iq

id

d,q

α,β

A

BEncoder

iα

iβ

ia

ib

Motor

α,β

a,b,c

Vα

Vβ

Vq

Vd

iq ref

id ref

N ref

Speed and Position

This allows optimal torque production.


FOC for PMSMPI 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 speedsIq is servoed to equal the Torque demand and Id is servoed to zero. This gives optimal torque productionThe PI Controller Outputs are transformed to produce three phase voltage signals to the bridge (inverse Park, inverse Clarke folded into SVM)


BEMF (V)

Current (I)

S

N

N

S

θ

S

N

N

S

N

S

Without FOC Torque

θ

T = Fs*Rs*sinθ

FOC for PMSM

BEMF (V)

Current (I)

S

N

N

S

90°

S

N

NS

NS

With FOC


FOC for PMSM

PI Speed Control

PI Speed + FOC Control

Phase Current Responses


FOC for PMSM

PI Speed Control

PI Speed + FOC Control

Speed Responses


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


FOC for PMSMFOC provides smooth control at low speeds as well as efficient control at high speedsTrapezoidal (BLDC) commutation can be efficient at high speed but introduces torque ripple at low speed and produces audible noiseSinusoidal drive produces smooth control at low speed but is inefficient at high speedsFOC provides the best of both worlds


Agenda



Agenda

Hands-On exercises − Lab 2 – Enabling Graphs Using

DMCI− Lab 3 – Tuning PI Parameters


DMCI

Data Monitor and Control InterfaceSmart Watch Window9 Slider35 Input Control4 Graphs


Sliders

Assigns control variablesSuitable for PID control loop tuningDynamic data control9 Booleans available for flags


Input Controls

Text box typeConfigurable incrementsDynamic Data InputHex, Decimal, Fractional and Enum List data types


Graphs

Up to 4 plotsFeatures include− Zoom in/out− Mark data points− Print− Export as data

Dynamic Data View


Lab 2. Enabling Graphs Using DMCI


Objectives of Lab 2Getting to use DMCIHow to enable a graph using DMCIPlotting variables


Lab2Instructions for Lab2:− On MPLAB® IDE, open DMCI, select “Tools -

> Data Monitor And Control Interface”


Lab2 (contd.)Instructions for Lab2 (contd.):− Select “Dynamic Data View” tab− Check “Graph 1” box


Lab2 (contd.)Instructions for Lab2 (contd.):− Right click over Graph 1 area− Select “Configure Data Source”


Lab2 (contd.)Instructions for Lab2 (contd.):− Select “SnapBuf1” for data source array− Select “Fractional” for Display Format− Click OK


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.


Lab2 ResultsEstimated Theta PlotUsage of plots in DMCI Tool


Lab 3. Tuning PI Parameters


Objectives of Lab 3Tuning PI Parameters for Currents and SpeedUsing Sliders on DMCI tool





Lab3Instructions for Lab3:− On DMCI, Click Open Icon, and select:

“Lab3\Lab3.dmci” File

Lab3.dmci


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


Lab3 ResultsPI TuningUsage of Sliders in DMCI Tool


Agenda



Agenda

Sensorless Techniques− Six step for BLDC− FOC for PMSM


Six step for BLDC

Commutation is implemented in six discrete steps per electrical revolutionHall sensors can be used to indicate when commutation is requiredBack EMF can be used to provide the same information


Six step for BLDC

A

C B

DC+

DC-

Back EMF

Phase A and C are energizedInactive Phase B has induced Back EMFNormally the phase which is not energized, is monitored for Back EMF

BLDC Motor Back EMF


T30

T60

5 0 1 2 3 4 5 0 1SECTOR

0

0

0

Six step for BLDCBLDC Back EMF Crossing Diagram


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

Six step for BLDCThe Back EMF “zero crossing” method in detail


Six step for BLDC -Summary

Six step control creates comparatively more torque ripplePhase currents are rectangularLess processing power requiredRotor position is not accounted for between commutation pointsStarting ramp parameters must uncover Back EMF signalBLDC produces more Torque than PMSM


Sensorless FOC for PMSM

ΣΣ

ΣΣ

ΣΣ 3-Phase

Bridge

Position and Speed

Estimator

SVMPI PI

PI

-

- -

d,q

α,β

θ

iq

id

d,q

α,β

Speed

iα

iβ

ia

ib

Motor

α,β

a,b,c

Vα

Vβ

Vq

Vd

iq ref

id ref

N ref

Position Vα

Vβ



es

ωt

-π/2

π/2

Position Estimation− Rotor position is calculated with

BEMF information



( )ssss evL

iLRi

dtd

−+−=1

e

Motor

R L

v

i

PMSM Electric Model

Position Estimation− PMSM motor shares the same basic

electric model as the Brushed DC (BDC), BLDC and AC Induction Motors

ssss eidtdLRiv ++=



( ))()(1)()()1( nenvL

niLR

Tnini

ssss

ss −⋅+⋅−=−+

( ))()()(1)1( nenvLTni

LRTni ss

ssss −⋅+⋅⎟

⎠⎞

⎜⎝⎛ ⋅−=+

Position Estimation



-K

+K

( )zevL

iLRi

dtd

ssss −−+−= *** 1

Vs PMSMIs

I*s

* Estimated variable

+

-

Sign (I*s – Is)

Slide-Mode

Controller

z

Hardware

Current Observer


Sensorless FOC for PMSMCurrent Plots



( )zevL

iLRi

dtd

ssss −−+−= *** 1

LPF

e*s

⎟⎟⎠

⎞⎜⎜⎝

⎛

β

α

eearctan

θ*zLPF

efiltered*s


Back EMF Estimation


Sensorless FOC for PMSMBack EMF Plots



⎟⎟⎠

⎞⎜⎜⎝

⎛

β

α

eearctan

θ*

( ) ( )( ) speedK⋅⎟⎠

⎞⎜⎝

⎛= ∑

=

7

0i1-n-n θθω

+

+ θ*comp

ω*

LPFω*filtered


Position and Speed estimation



Phase Compensation− The inherent position filtering is

compensated− Speed range is divided into parts

with compensation applied to each− Spread sheet calculator supplied



Vs PMSMIs

I*s


+

- -1

+1Sign (I*s – Is)

Slide Mode Controller

z

Hardware

( )zevL

iLRi

dtd

ssss −−+−= *** 1

LPF

e*s

zLPF

efiltered*s

⎟⎟⎠

⎞⎜⎜⎝

⎛

β

α

eearctan

θ*

( ) ( )( ) speedK⋅⎟⎠

⎞⎜⎝

⎛= ∑

=

7

0i1-n-n θθω

+

+θ*comp

ω*LPF

ω*filtered



Encoder Rotor Position

Estimated Rotor Position

Practical Results


ΣΣ

ΣΣ

3-Phase

BridgeSVM

PI

PI

-

-

d,q

α,β

θ

iq

id

d,q

α,β

iα

iβ

ia

ib

Motor

α,β

a,b,c

Vα

Vβ

Vq

Vd

iq ref

id ref

Motor Startupθ

t

θ

t

Initial Torque Demand




Reset

Initialize Variables and Peripherals

Motor Stopped

Initialize Variables for

Running Motor

Initialize PI Controller

Parameters

Enable Interrupts

Motor Running Start Up

Read Reference

Torque from VR1

Measure Winding Currents

Convert Currents to Iq

and Id

Execute PI Controllers for

Iq and Id

Increment Theta Based

on RampSet New Duty Cycles using

SVM

Motor Running

Sensorless FOC Read

Reference Speed from

VR2

Measure Winding Currents

Convert Currents to Iq

and Id

Estimate Theta using SMC

Calculate Speed

Compensate Theta Based

on Speed

Execute PI Controllers for Speed, Iq and

Id

Set New Duty Cycles using

SVM

Stop Motor

A/D Interrupt

A/D Interrupt

End of Start Up Ramp

S4 Pressed

S4 Pressed or FAULT

S4 Pressed or FAULT

Motor Stopped

Open LoopFOC

Sensorless FOC

Main Software State Machine


No Extra Cost Added


Agenda



Agenda

Hands on exercises − Lab 4 – Tuning Sensorless

Parameters


Lab 4. Tuning Sensorless Parameters


Objectives of Lab 4Tuning Sensorless Parameters for Open Loop. Lock Times and End Speed.Tuning Sensorless Parameter for Closed Loop. Slide Mode Controller Gain.





Lab4Instructions for Lab4:− On DMCI, Click Open Icon, and select:

“Lab4\Lab4.dmci” File

Lab4.dmci


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?


K Slide = 0.9 / 500 RPM K Slide = 0.1 / 500 RPM

Lab4


Lab4K Slide = 0.1 / 2000 RPMK Slide = 0.9 / 2000 RPM


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.


Agenda



Agenda

Wrap up, Q&A− Summary− Dev Tools used in this class− Resources


Summary

PMSM− High efficiency and smooth torque

are advantageousFOC− Provides optimal torque control− Can be run with or without Position

Sensors− Applicable for ACIM


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)


ResourcesFor resources and information regarding designing motor-control applications, visit Microchip’s motor-control design center at: www.microchip.com/motorMicrochip Application Notes for Motor-Control Applications:

PIC18CXXX/PIC16CXXX Servomotor AN696Brushless DC Motor Control Made Easy AN857Brushless DC (BLDC) Motor Fundamentals AN885Brushless DC Motor Control Using PIC18FXX31 AN899Using the dsPIC30F for Sensorless BLDC Control AN901Using the dsPIC30F for Vector Control of an ACIM AN908Sensored BLDC Motor Control Using dsPIC30F2010 AN957Using the PIC18F2431 for Sensorless BLDC Motor Control AN970An Introduction to ACIM Control Using the dsPIC30F AN984Sensorless BLDC Motor Control Using dsPIC30F2010 AN992Sinusoidal Control of PMSM Motors with dsPIC30F AN1017Sensorless Control of PMSM Motors AN1078Sensorless BLDC Control with Back EMF Filtering AN1083Getting started with the BLDC Motors and dsPIC30F GS001Measuring speed and position with the QEI Module GS002Driving ACIM with the dsPIC® DSC MCPWM Module GS004Using the dsPIC30F Sensorless Motor Tuning Interface GS005


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.


TrademarksThe Microchip name and logo, the Microchip logo, Accuron, dsPIC, KeeLoq, KeeLoq logo, microID, MPLAB, PIC, PICmicro, PICSTART, PRO MATE, rfPICand 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 inthe 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.

Documents

11084 FOC - amoBBSd1.amobbs.com/bbs_upload782111/files_10/ourdev_288142.pdf · sensorless Field Oriented Control (FOC) of Permanent Magnet Synchronous Motors ... 11084 FOC Slide 22