3 phase sensorless bldc motor control using mc9s08mp16
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January 22 th , 2010. 3-Phase Sensorless BLDC Motor Control Using MC9S08MP16. Presentation. Libor Prokop System Application Engineer. Presentation Outline. BLDC Motor Control Generally Sensorless BLDC with BEMF Zero Crossing DRM117 Sensorless BLDC Motor Control Application.

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3-Phase Sensorless BLDC Motor Control Using MC9S08MP16

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3 phase sensorless bldc motor control using mc9s08mp16

January 22th, 2010

3-Phase Sensorless BLDC Motor Control Using MC9S08MP16

Presentation

Libor Prokop

System Application Engineer


Presentation outline

Presentation Outline

  • BLDC Motor Control Generally

  • Sensorless BLDC with BEMF Zero Crossing

  • DRM117 Sensorless BLDC Motor Control Application


3 phase sensorless bldc motor control using mc9s08mp16

BLDC Motor Control Generally

120o

60o

A

B

C


6 step commutation diagram

0%

0%

Phases voltage

6 - Step Commutation Diagram

  • Six Step BLDC Motor Control

    • Voltage applied on two phases only

    • It creates 6 flux vectors

    • Phases are power based on rotor position

    • The process is called Commutation

A

B

C

1.

3.

5.

2.

4.

6.

BLDC

ØA

ØC

ØB


6 step 120 degree 3 phase bldc motor control

6 step (120 Degree) 3-phase BLDC Motor Control

  • Stator field is maintained 60° to 120° relative to rotor field

  • Therefore the rotor position must be estimated

  • Right After Commutation

  • Right Before Commutation


Power stage motor topology

Power Stage – Motor Topology

3-PHASE POWER STAGE

B

PWM1

PWM3

PWM5

S

S

S

AT

BT

CT

POWER

C

A

SOURCE

DC VOLTAGE

PWM2

PWM4

PWM6

S

S

S

3-PHASE BLDC MOTOR

AB

BT

CT

MOSFET/IGBT DRIVERS

PWM1

PWM2

PWM3

PWM4

PWM5

PWM6

Controller


Quadrants of operation

Quadrants of Operation

Current

(Torque)

Second Quadrant

First Quadrant

negative speed-positive torque

positive speed-positive torque

“reverse-braking”

“forward-accelerating”

Generating

Motoring

I

Voltage

(Speed)

II

III

IV

Motoring

Generating

Fourth Quadrant

Third Quadrant

Positive speed - negative torque

negative speed - negative torque

“forward-braking”

“reverse-accelerating”


Bipolar bldc commutation 3 complementary pwm pairs

commutation

commutation

commutation

commutation

Bipolar BLDC Commutation (3 Complementary PWM pairs)

  • Allows energy recuperation

  • BOTTOM is opposite of TOP

  • Requires sophisticated PWM support

commutation

commutation

commutation

commutation

120o

60o

A - Off

A - Off

SAt

SBt

SCt

SAt

A - Off

A - Off

SAb

SAb

SBb

SCb

B - Off

B - Off

SBt

B - Off

B - Off

SBb

C - Off

C - Off

C - Off

SCt

ØB

3phase

Brushless

DC motor

C - Off

C - Off

C - Off

SCb

ØA

ØC


Bipolar bldc commutation complementary pwms detail

Bipolar BLDC Commutation (Complementary PWMs) Detail

  • BOTTOM is opposite of TOP

Dead

Time

Dead

Time

Dead

Time

Dead

Time

Dead

Time

Dead

Time

A - Off

SAt

A - Off

SAb

B - Off

SBt

B - Off

SBb

C - Off

B - Off

SCt

C - Off

B - Off

SCb

Swap

Dead

Time

Dead

Time

Dead

Time

Dead

Time


Unipolar bldc commutation 3 complementary pwm pairs

commutation

commutation

commutation

commutation

Unipolar BLDC Commutation (3 Complementary PWM pairs)

  • Allows energy recuperation

  • BOTTOM is opposite of TOP

  • Requires sophisticated PWM support

commutation

commutation

commutation

commutation

120o

60o

A - Off

A - Off

SAt

SAt

SAt

SCt

SAb

A - Off

A - Off

SAb

SBb

SCb

B - Off

B - Off

SBt

B - Off

B - Off

SBb

C - Off

C - Off

C - Off

SCt

ØB

3phase

Brushless

DC motor

C - Off

C - Off

C - Off

SCb

ØA

ØC


3 phase sensorless bldc motor control using mc9s08mp16

Sensorless BLDC with BEMF Zero Crossing


Synchronous pm motors

Synchronous PM Motors

  • Stator Field needs to be close to orthogonal (90°) to rotor field to get maximal torque and energy efficiency:

+Vp (PWM)

La

Running

Direction

Motor

Torque

S

N

Lc

90`

Lb

Stator Flux

GND (PWM)


Bldc motor back emf shape

A

C

H

4

0

V

B

C

BLDC Motor Back-EMF Shape

P

h

a

s

e

A

-

B

V

o

l

t

a

g

e

P

h

a

s

e

B

-

C

V

o

l

t

a

g

e

P

h

a

s

e

C

-

A

V

o

l

t

a

g

e

P

h

a

s

e

A

P

h

a

s

e

B

P

h

a

s

e

C


Bldc commutation specifics

A

B

C

1.

3.

5.

2.

4.

6.

0%

BLDC

ØA

ØC

ØB

0%

BLDC Commutation Specifics

  • After the commutatation current transient:

    • Ic = 0 and so UC = BEMFC

USc = UbackEMFc


Sensorless bldc motor control with bemf zero crossing detection

Sensorless BLDC Motor Control with BEMF Zero-Crossing Detection

Appropriate Phase Comparator Output selected

Zero Crossing event

detected


Sensorless commutation and bemf

Sensorless Commutation and BEMF

0

60

120

180

240

300

360

Rotor Electrical Position (Degrees)

Phase R

Phase S

Phase T

Zero crossings

PWM 1

PWM 3

PWM 5

PWM 2

PWM 4

PWM 6


Bldc central point is not accessible

BLDC Central Point Is Not Accessible

  • 3-phase invertor and DC bus current measurement

Inverter Stage

Udcbus

Not Accessible

Rshunt

Phase c

BLDC

Motor

Phase b

Idcbus

Phase a


Bldc motor voltages at bipolar switching phases

-

-

-

-

+

+

+

+

-

-

-

-

+

+

+

+

PhC

PhA

PhB

BLDC Motor Voltages at Bipolar Switching Phases

Regeneration

I

1

2

1

2

V

-V

Q2

Q1

Regeneration

Q4

Q3

3

4

3

4

-I

VDCB

Motor Phase A Voltage

VDCB/2

3

4

1

2

Motor Central Point

Voltage V0

GND

1(4) Top Bottom

in diagonal on

2(3) Top Bottom

in (inverse) diagonal on


Bldc motor voltage at unipolar switching phases

-

-

+

+

-

-

+

+

PhC

PhA

PhB

BLDC Motor Voltage at Unipolar Switching Phases

1

2

One cycle

in Quadrant 1

1 Top Bottom

in diagonal on

2 Two Bottoms on

3

4

One cycle

in Quadrant 3

3 Top Bottom

in diagonal on

4 Two Bottoms on

(inverse current)

Motor Phase Voltage

VDCB

VDCB/2

3

4

1

2

Gnd

Motor Central Point

Voltage U0


Zero crossing sensing reference

Zero Crossing Sensing Reference

HB1

+

HB1

Udcb

HB1

  • BLDC Motor Central Point is not accessible

A

-

+

+

HB2

0

A

A

-

-

B

V

HB2

HB2

+

0

0

B

V

B

V

-

+

+

-

-

+

HB3

HB3

C

-

+

+

HB3

C

-

-

  • ½ UDCB reference

  • GND reference

  • Virtual CP reference

Udcbus

Rshunt

HB1

HB2

A

BLDC

Motor

Idcbus

0

B

V

HB3

C


Bipolar commutation complementary pwms detail

Bipolar Commutation (Complementary PWMs) Detail

  • BOTTOM is opposite of TOP

Top and Bottom

in diagonal on

Top and Bottom

negative in diagonal on

A - Off

SAt

A - Off

SAb

B - Off

SBt

B - Off

SBb

B - Off

C - Off

SCt

C - Off

B - Off

SCb

Dead

Time

Dead

Time


Unipolar commutation complementary pwms detail

Unipolar Commutation (Complementary PWMs) Detail

  • BOTTOM is opposite of TOP

Top and Bottom

in diagonal on

Two Bottoms on

A - Off

SAt

A - Off

SAb

B - Off

SBt

B - Off

SBb

C - Off

B - Off

SCt

C - Off

B - Off

SCb


Zero crossing detection measurement window

Zero Crossing Detection Measurement Window

  • BOTTOM is opposite of TOP

Top and Bottom

in diagonal on

Two Bottoms on

SAt

SAb

SBt

SBb

C - Off

SCt

C - Off

SCb

Zero-Crossing

Sampling

Window


Back emf zero crossing sensing circuit

Back-EMF Zero Crossing Sensing Circuit

  • ½ UDCB reference

Phase Selection

According to PWM Sector

Phase a

Udcb

Positive

MUX

A

Phase b

0

V

B

Sampling

Cout

Phase c

+

-

C

Negative

MUX

Udcb/2

ZC Sampling Window

Ud/2

Sampling

Window

Generator

PWM Sync


Back emf detection window

Back-EMF Detection Window

CMT

CMT

ZC

Zero Crossing

Detected

BLDC

Commutation

Zero

Crossing

Detection

Process

BLDC

Commutation

Current

Recirculation


Bldc commutation with back emf zero crossing sensing

BLDC Commutation with Back-EMF Zero Crossing Sensing


Calculation of the commutation timing

Calculation of the Commutation Timing


3 phase sensorless bldc motor control using mc9s08mp16

Sensorless Commutation - Forced PLL2nd algorithmimplemented on3-phase Sensorless BLDC Motor Control Using MC9S08MP16

Regulator

Motor

ZC

Detector

3-phase

Power Stage

+

-


Sensorless commutation control states

Sensorless Commutation Control States

  • Sensorless commutation needs three commutation states :

    • Alignment

    • Open-Loop Start

    • Sensorless Run

  • Alignment must be performed before every start.

  • Alignment duration and current is dependent on motor electrical and mechanical time constant.

  • Because after alignment, motor is not spinning, there is state a Open-Loop Start between Alignment and Running, in which no Zero Crosses are detected and commutation must be performed manually.


Alignment vector

Alignment Vector


Bldc motor vectors at the start up

BLDC Motor Vectors at the Start-up

  • Starting ModeOpen Loop Ramp:

    • no feedback

  • Regular Running Mode– Close Loop:

    • Position estimation fedback

q

b

q

b

supposed rotor position

d

d

a

a


Open loop start

Open Loop Start

Velocity

Open Loop

Commutation velocity

Ramp Acceleration OL

Velocity

Desired

Closed Loop

Commutation velocity

Ramp Acceleration CL

Open Loop Start

Alignment

Run

Velocity

Threshold

OLtoRun

real speed

time

Alignment

Period


3 phase sensorless bldc motor control using mc9s08mp16

3-ph

BLDC Motor

Idc

Control

BLDC Current Control and Limitation


Speed controller with current limitation

Speed Controller with Current Limitation

  • Current (torque) limitation provided with:

    • “slow current limitation control” - 2 ms sampling

Current Limitation

PI Controller

Desired DC Bus

Current Limit

+

-

Actual DC

Bus Current

Speed

PI Controller

1/T

+

Velocity Required

To

PWM

Period

Zero Crossing

Filtered/Estimated

-

Velocity Actual


Current control limitation

+

-

Current Control/Limitation

  • Technique

    • SW current limitation with slow control loop

  • Issue:

    • Problematic current sensing during commutation transient

Controller

3-ph

BLDC Motor

SW

current

control

ADC

Idc

HW

OVC


Current sampling at back emf zero crossing

Current Sampling at Back-EMF Zero-crossing

  • Commutation Transient:

    • Current not sensed during commutation transient

Back-EMF

Zero-crossing

Phase Voltage

Phase Current

DC Bus Current Envelope

DC Bus Shunt Current

Current

Sampling

At Back-EMF

Zero Crossing


3 phase sensorless bldc motor control using mc9s08mp16

Freescale Reference Design DRM117

3-phase Sensorless BLDC Motor Control


Freescale applications for sensorless bldc motor control

Freescale Applications for Sensorless BLDC Motor Control

  • DRM117: 3-phase Sensorless BLDC Motor Control using MC9S08MP16:

    • Uses MC9S08MP16 MCU device with 8-bit S08 core

      • Some peripheral of the MC9S08MP16 are similar with MCF51AG128

        • FlexTimer module for 3-phase PWM

    • Application s/w written in C-language with some S08 assembler subroutines

    • Design Reference Manual DRM117 document

    • Modular h/w design:

      • 3-phase BLDC/PMSM Low Voltage Motor Control Drive board – 36V, 4A

      • The MC9S08MP16 daughter board module can be replaced with MCF51AG128 daughter board

    • Application demo available

    • New application - Released November 2009

  • MCF51AG128 application can be based on existing DRM117


3 phase sensorless bldc motor control using mc9s08mp161

Application Usage:

Fans

Compressors

Pumps

Industrial drives

Appliances

Application Features:

Targeted at the MC9S08MP16 8-bit microcontroller

Sensorless 3-phase trapezoidal BLDC motor control with six-step commutation (60, 120 degree control)

Three sensorless synchronized commutation control algorithms incorporating

One of unipolar or bipolar PWM commutation techniques possible

Back-EMF zero crossing used to synchronize six-step commutation with rotor position

Running on a Three-phase low voltage (24V) power board

MC9S08MP16 daughter controller board

FreeMASTER software control interface and monitor

Main application components

s/w - written in C-code using some library algorithms - available for the MC9S08MP16

h/w - based on Freescale universal motor control h/w modules

documentation - DRM

3-Phase Sensorless BLDC Motor Control Using MC9S08MP16


3 phase sensorless bldc motor control using mc9s08mp16

3-Phase Sensorless BLDC

Motor Control

Using MC9S08MP16

Design Reference

Manual

Application Code

Control page

Demo Hardware


3 phase sensorless bldc motor control using mc9s08mp16

SPI

3-Phase BLDC/PMSM Low-Voltage Motor Control Drive

3 Phase Inverter

DC Bus Voltage & Current Sensing

24V

DC Power Input

3 Phase BLDC Motor

3 Phase Voltages

Over-current

FAULT

Vdcb, Idcb

Vphasea,b,c

PWM1..6

FTM

HSCMP2

ZC Comparator

FTM2

PWM 3pps Generator

ADC Module

Simmilar

Peripheral to

MCF51AG128

PDB2

ZC to PWM

Synchronization

FTM1

Timer Cmt

(and) ZC

PDB1

Synchronization ADC to PWM

MC33927 driver

Config.

Zero Crossing Period & Position Recognition

Commutation

And PWM

Control

ADC

Sensing

Sensorless Commutation

I/O

Ports

PWM Duty cycle

GPIO Module

Superior

System

Application

Monitoring

and Control

Zero-crossing

Period

Application

Control

1/T

MTIM

Time Base

Desired speed

Actual speed

USB to

COM

Convertor

-

On Board Programming

SCI Module

Ramp Generation

+

Speed PI Controller

Required speed

Freemaster

BDM

Limitations

DC Bus Current

-

Torque PI Controller

MC9S08MP16

Required torque

+


S w data flow

S/W - Data Flow


S w bldc control state diagram

S/W - BLDC Control State Diagram


S w application flow chart 1

S/W – Application Flow chart (1)


S w application flow chart 2

S/W – Application Flow chart (2)


3 phase sensorless bldc motor control using mc9s08mp16

Sensorless BLDC Motor Control Using MC9S08MP16 – HCS08 Core Load(slow speed control loop is not considered)

Assumptions:

Core speed 20MHz

Motor Speed 4000rpm,

8 poles =>

625us commutation period

sensorless BLDC motor direct commutation using comparators

PWM frequency – 20kHz

Sensorless Run BLDC Direct Commutation

Timer Cmt

Commutation

Timeout

25us (*)

Timer Cmt

Current dec

Timeout

10us (*)

Timer ZC

Zero-Crossing

Detected

20us (*)

100%

625us

55usec -> 10% (*)

Ca 300us

12 bit Analog Variables Sensing and Filtering Service

ADC

service

14us

ADC

service

14us

ADC

service

14us

ADC

service

14us

ADC

service

14us

ADC

service

14us

100%

50us

55usec -> 30% (*)

50us (*)

Sensorless BLDC Commutationusing HSCMP comparators occupiesaround 10%and ADC service occupies around 30% (*) of HCS08 8bit processor computational power at 4000rpm with 8-pole motor and 50kHz pwm.


Thanks for your attention

Thanks for Your Attention

  • Questions and answers

  • Contact:

    • Libor ProkopFreescale1.maje 100975661Roznov pod RadhostemCzech Republic

    • E-mail:[email protected]

    • www.freescale.com/motorcontrol


3 phase sensorless bldc motor control using mc9s08mp16

Back-up slides


3 phase sensorless bldc motor control using mc9s08mp16

3-ph

BLDC Motor

Idc

Control

BLDC Current Control and Limitation 2


Sw current control

SW Current Control

  • Commutation Transient:

    • Current not sensed during commutation transient

Phase Voltage

Phase Current

DC Bus Current Envelope

Current

Control

Current

Sampling

Current

Control

DC Bus Shunt Current

Tregulator


Hw current limitation

HW Current Limitation

  • Commutation Transient:

    • Problematic current sensing

Phase Voltage

Phase Current

HW

Current

Limitation

DC Bus Current Envelope

DC Bus Shunt Current


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