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COMPANY CONFIDENTIAL 1 eBike Sensorless Motor Control Alex Lollio, Global Rotation Engineer tomotive Products Business Unit ovence Design Centre, France y, 2013 - Jul, 2013 oject Manager : Andre Mourrier ogram Mentor : Massimo Grasso
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Page 1: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL 1

eBike Sensorless Motor Control

Alex Lollio, Global Rotation Engineer

Automotive Products Business UnitProvence Design Centre, France

May, 2013 - Jul, 2013

Project Manager : Andre MourrierProgram Mentor : Massimo Grasso

Page 2: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

e-Bike Overview

Market Info:

• $8.4 billion in 2013*

• 90% of e-Bike sales in China*

General Specifications:

•Battery 40-48V (10AH)

•Power 150W - 500W

•Input Current 10-15ARMS

•BLDC Motor

48V Lit Battery

Control Board BLDC Motor

*http://www.navigantresearch.com/research/electric-bicycles

IR Interests:

• 6 Power MOSFETS (IRFB3607)

• IC Controller and Gate Driver (IR3230)

Page 3: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

BLCD Motor Working Principle: 2 Pole

Page 4: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

IR Controller for e-Bike: IR3230

Main Features:•Brushless DC Motor Sensor Decoder & HVIC MOSFET Driver•Charge pump operation (No bootstrap capacitor)•Up to 30Khz PWM switching capability (on the low switches)

•Programmable over current and over temperature protections

Green = sensor2

Green = Ph2

Yellow = Ph3

Battery power supply -Battery power supply +

Blue = Ph1

Blue = sensor1

Yellow = sensor3

+5V

GNDIR32

30

+5V

GND

Page 5: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

Project Goal: Sensorless Implementation

Power FETs: 0.2$ x 6 ≈ 1.2$

Discrete Components ≈ 0.5$

Microcontroller ≈ 0.6$

Hall Sensors: 0.4$ x 3 ≈ 1.2$

Electronic Board BLDC Motor

Goal of the Project:

• Adapt IR3230 Controller & HVIC driver for a Sensorless implementation

Sensorless Cost Saving

Costumer Request:

• Sensorless driving strategy: reducing costs, simplify motor assembly and reducing failure (most failure = Hall sensors)

Sensors(0.15$)+Assembly(0.15$)+Cabling(0.1$)

Page 6: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

IR3230 Typical Schematic

Basic Idea: replacing the Hall Sensor with a Micro which senses the generated BEMF

+5v

Gnd_p

+V b a t

G ro u n d

I / O

5.6V

Power _mosf et

Vb

att

ery

Gn

d

P h 1

P h 2

P h 3

G h s 1

S k _ p h 1

G ls 1

G h s 2

S k _ p h 2

G ls 2

G h s 3

S k _ p h 3

G ls 3

Cpump

CTN Rshunt

IR3230

Gn

d

V s s

V s 1

V s 2

V s 3F lt _ rs t

M o t / R e g e n

F lt

1 2 0 / 6 0

R e v / F wd G n d p wr

S h t p

O u t _ S u p p ly

Vc

c

P wm

E nS e n s 1

H o 1

S e n s 2

H o 2

Tp

S e n s 3

H o 3

L o 1

L o 2

S h t m

Pm

p

L o 3

+5v

Di gi t al

Cd

Gnd

R d ig _ in

+ +

M 1

P h 1

P h 2

P h 3

S e n s 1S e n s 2S e n s 3

+5 v

G n d

R d ig _ in 1

R d ig _ in 2

R d ig _ in 3

R d ig _ in 4

R d ig _ in 5

R d ig _ in 6

Gnd_p

Gnd

Gnd

+5v

SOIC28

TºC

Mea

sure

men

t

5V Power Supply

Charge pumpShunt

Sensors interface

Diagnostic and Reset

Order input and Selection

Power Mosfet

BLDC Motor

IR3230

Page 7: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

What is Back Electromagnetic Force?

turning rotor

GND

Floating

Example: Trapezoidal Motor Driving

Faraday Law:

The induced Electromagnetic Force (EMF) is the voltage produced by changing magnetic flux into the windings

A

B

C

Floating phase, C, can be used to measure the Back EMF generated by the turning rotor.Generated Back EMF is proportional to angular rotation speed

A

B

C BEMF+-

VCC

Page 8: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

Back EMF when duty cycle is 100%

BEMF crosses VDD/2 in the middle of the switching period

Switching Period

VDD/2

VDD

Low Side ON

High Side ON

Z 0 Z1 1PHA

High Side ON

Inductive transient

Inductive transient

Step 1

0Step 2 3 4 5 6 1

Trapezoidal Driving6 Step Sequence

A A

A A

A A

C C

B

B

B

B

B

C C

C B C

PHAStep 2

Step 3 Step 4

Step 5 Step 6

THIS GRAPH SHOWS THE VOLTAGE OF NODE PHA

Page 9: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

Back EMF @Duty=20% (low side modulation)

Switching Period

VDD/2

Low Side PWM

High Side ON

Z PWM Z1 1PHA

High Side ON

Step 1

PWMStep 2 3 4 5 6 1

Trapezoidal Driving6 Step Sequence

A A

A A

A A

C C

B

B

B

B

B

C C

C B C

PHAStep 2

Step 3 Step 4

Step 5 Step 6

THIS GRAPH SHOWS THE VOLTAGE OF NODE PHA

Page 10: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

BEMF in Trapezoidal Motor Driving

PH1-A

PH2-B

PH3-C

Sens1

Sens2

Sens3

1 2 3 4 5

0

1

1

0

0

1

1

0

1

1

0

0

1

1

0

0

1

0

1

Z

0

Z

1

0

0

1

Z

0

Z

1

Z

0

1

1

0

Z

66 STEPS

Algorithm Strategy: VDD/2 crossing point in the middle of the switching cycle

VDD/2

VDD

T/2 T

Page 11: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

TSBEMF

Voltage

TS/2

time

VREF

Basic Idea: Circuital Implementation

zero-cross

POWER MOSFET

A

B

C

RA1RB1 RB3

SNS1SNS2SNS3

PWM

RE0RE1RE2

RD5

MOTORWINDINGSPICF1937 IR3230

RA3

VSUP

VREF

• Microcontroller compares the BEMF voltages to the reference voltage VREF

• When BEMF<VREF the internal comparator generates an interrupt (let’s call this event “zero-cross”)

Page 12: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

Basic Idea: Algorithm working principle

Time

FFFFh

0000h

-N

-N/2

error

errorPerfect zero-cross

Late zero-cross

-N’ = -(N+error)

-N’/2

Perfect zero-cross

Commutation periods

Full commutation preset

Half commutation preset

TIMER1

Timer1 overflow

The Back EMF tracking Algorithm works like a PLL: adjusting the commutation period in order to keep zero-cross in the middle

Page 13: eBike Sensorless Motor Control

COMPANY CONFIDENTIAL

Demoboard Image

BEMF Voltage Divider

BEMF Voltage Divider are tested for input supply voltage into the range 12-48V

PWM Trimmer

Connector to ICD3 programmer

PHA

PHB

PHC

IR3230