ID 610C: Introduction to BLDC Motor Control

Avnet

Jim Carver

Technical Director, Advanced Architectures

12 October 2010

Version 1.0

2

Renesas Technology and Solution Portfolio

Microcontrollers& Microprocessors

#1 Market shareworldwide *

Analog andPower Devices#1 Market share

in low-voltageMOSFET**

Solutionsfor

Innovation

Solutionsfor

InnovationASIC, ASSP& Memory

Advanced and proven technologies

* MCU: 31% revenue basis from Gartner "Semiconductor Applications Worldwide Annual Market Share: Database" 25 March 2010

** Power MOSFET: 17.1% on unit basis from Marketing Eye 2009 (17.1% on unit basis).

33

Renesas Technology and Solution Portfolio

Microcontrollers& Microprocessors

#1 Market shareworldwide *

Analog andPower Devices#1 Market share

in low-voltageMOSFET**

ASIC, ASSP& Memory

Advanced and proven technologies

* MCU: 31% revenue basis from Gartner "Semiconductor Applications Worldwide Annual Market Share: Database" 25 March 2010

** Power MOSFET: 17.1% on unit basis from Marketing Eye 2009 (17.1% on unit basis).

Solutionsfor

Innovation

Solutionsfor

Innovation

44

Microcontroller and Microprocessor Line-up

Superscalar, MMU, Multimedia Up to 1200 DMIPS, 45, 65 & 90nm process Video and audio processing on Linux Server, Industrial & Automotive

Up to 500 DMIPS, 150 & 90nm process 600uA/MHz, 1.5 uA standby Medical, Automotive & Industrial

Legacy Cores Next-generation migration to RX

High Performance CPU, FPU, DSC

Embedded Security

Up to 10 DMIPS, 130nm process350 uA/MHz, 1uA standbyCapacitive touch

Up to 25 DMIPS, 150nm process190 uA/MHz, 0.3uA standbyApplication-specific integration

Up to 25 DMIPS, 180, 90nm process 1mA/MHz, 100uA standby Crypto engine, Hardware security

Up to 165 DMIPS, 90nm process 500uA/MHz, 2.5 uA standby Ethernet, CAN, USB, Motor Control, TFT Display

High Performance CPU, Low Power

Ultra Low PowerGeneral Purpose

55

Microcontroller and Microprocessor Line-up

Superscalar, MMU, Multimedia Up to 1200 DMIPS, 45, 65 & 90nm process Video and audio processing on Linux Server, Industrial & Automotive

Up to 500 DMIPS, 150 & 90nm process 600uA/MHz, 1.5 uA standby Medical, Automotive & Industrial

Legacy Cores Next-generation migration to RX

High Performance CPU, FPU, DSC

Embedded Security

Up to 10 DMIPS, 130nm process350 uA/MHz, 1uA standbyCapacitive touch

Up to 25 DMIPS, 150nm process190 uA/MHz, 0.3uA standbyApplication-specific integration

Up to 25 DMIPS, 180, 90nm process 1mA/MHz, 100uA standby Crypto engine, Hardware security

Up to 165 DMIPS, 90nm process 500uA/MHz, 2.5 uA standby Ethernet, CAN, USB, Motor Control, TFT Display

High Performance CPU, Low Power

Ultra Low PowerGeneral Purpose

6

Agenda

Motor Types Overview

BLDC Motor Applications

Comparison of DC to Brushless DC Motors

Hall Sensors

Six-Step Commutation

Sensorless Commutation with Back-EMF

Vector Motor Control basics

Closed-Loop Speed Control

Introduction to BLDC Motor Control Evaluation Kit

Summary

7

Motor Types

8

Expanding BLDC Motor Control Applications

AC, DC and Universal Motors

Transition to

BLDCAs consumers demand more energy efficient products, more BLDC motors are being used.

9

Brushed DC Motors Review

A winding assembly (armature) within a stationary magnetic field

Brushes and Commutators switch current to different windings in correct relation to the outer permanent magnet field.

Pros: Electronic control is simple, no need to

commutate in controller Requires only four power transistors Cons: A sensor is required for speed control The brushes and commutator create sparks

and wear out Sparks limit peak power Heat in armature is difficult to remove Low power density

10

Brushless DC Motors

Permanent Magnet

Rotor

Stator windings

Permanent magnet rotor within stationary windings

Pros: No brushes or commutator to wear out No sparks and no extra friction More efficient than DC motor Higher speed than DC motor Higher power density than DC motorCons: Rotor sensor OR sensorless methods

needed to commutate Requires six power transistors

11

Brushed DC Commutation

The windings in the armature are switched to the DC power by the brushes and armature

Each winding sees a positive voltage, then a disconnect, then a negative voltage

The field produced in the armature interacts with the stationary magnet, producing torque and rotation

+

-

N S

U

+

-

U

12

DC Motor Bridge

The DC motor needs four transistors to operate the DC motor

The combination of transistor is called an H-Bridge, due to the obvious shape

Transistors are switched diagonally to allow DC current to flow in the motor in either direction

The transistors can be Pulse Width Modulated to reduce the average voltage at the motor, useful for controlling current and speed 0

1

1

1

0

0

0

13

Three-Phase Bridge to Drive BLDC Motor

The Brushless DC motor is really a DC motor constructed inside-out, but without the Brushes and Commutators

The mechanical switches are replaced with transistors The windings are moved from the armature, to the stator The magnet is moved from the outside to become the rotor

N S

N S

UVW

14

Six-step Commutation

STEP1 STEP2 STEP3 STEP4 STEP5 STEP6 STEP1 STEP2 STEP3

U

V

W

UVW

15

Six-Step Current Waveform

Here we see the individual steps in a real trapezoidal current waveform

The PWM ripple is visible when the phase is active

The rising and falling edges are sloped, giving the trapezoidal shape

The amount of slope is a function of the winding inductance

16

Hall Sensors

Hall Sensors detect magnetic fields, and can be used to sense rotor angle

The output is a digital 1 or 0 for each sensor, depending on the magnetic field nearby

Each is mounted 120-degrees apart on the back of the motor

As the rotor turns, the Hall sensors output logic bits which indicate the angle

H1

H2

H3

N

S

H1 H2

H3

17

Hall Sensor Commutation

H1

H2

H3

STEP1 STEP2 STEP3 STEP4 STEP5 STEP6 STEP1 STEP2 STEP3

The combination of all three sensors produce six unique logic combinations or steps

These three bits are decoded into the motor phase combinations

U

V

W

18

3-Phase PWM

U

V

W

We can divide up the phase data into individual transistor gate signals

Now we can see how we can modulate one transistor at a time to regulate the motor voltage, and also the speed

UP

UN

VP

VN

WP

WN

19

Sensorless Commutation

Instead of using sensors like Halls, we can let the motor tell us which phase should be energized

The Brushless DC motor acts as a generator when it rotates, creating voltages

The three phases produce three voltages 120-degrees apart

The voltage generated by the motor is called Back Electro-Motive Force, a.k.a. Back-EMF or just BEMF

20

Brushless DC Motor BEMF

The Back-EMF is the voltage generated in stator windings as the rotor moves

BEMF voltages are more or less sinusoidal (depending on the motor) and are symmetrical from phase to phase

We detect the zero crossings of each phase to commutate The motor MUST be moving to generate BEMF voltages

21

Brushless DC Motor BEMF

The Back-EMF is the voltage generated in stator windings as the rotor moves

BEMF voltages are more or less sinusoidal (depending on the motor) and are symmetrical from phase to phase

We detect the zero crossings of each phase to commutate The motor MUST be moving to generate BEMF voltages

22

Startup of BEMF System

Since only a spinning motor generates BEMF signals

Start the motor in open loopFirst align rotor to a known angleThen energize the windings to step rotor to next

step

Accelerate steps until speed is sufficient to “see” BEMF zero crossings reliably

Switch to BEMF commutation

Once operating, this is almost identical to six-step operation with Hall sensors

23

Sinusoidal Methods

Stepped commutation methods work well, but… The Back-EMF waveform is more sinusoidal than trapezoidal If we can match the sinusoidal waveform, we can improve

performance We will show two sinusoidal methods:

180-Degree Sinusoidal “Field Oriented” or “Vector” control

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180° Sinusoidal Commutation

Modulates sine waves in all three windings Pros: No square edges

Lower Torque Ripple then six-step drive Lower audible noise

Higher efficiency and torque Stator angle is rotated smoothly rather

than in 60 degree jumps Each phase is utilized all of the time

Cons: Needs higher resolution feedback to

calculate sine waves with low distortion Needs more sophisticated processing to

calculate sine PWM values on the fly Bandwidth of currents are limited due to

motor impedance, this hurts high speed performance

25

*r

Speed Regulatorr

*qi

0* dirid PI

Regulator

iq PIRegulator d,q

to

,)(1 T

Motor Model Based Flux and

Position Observer

qi

di

*qU

*dU

*U

*U

Voltage Source3-phaseInverter

SINPWM

PWM1~6

toa, b, c

,

3-phasePMSM

r

tod,q

,

)(T

ai

bidi

qi

ii

a,b,c to ,

Speed Estimation

DC Bus

Vector (Field Oriented Control) Drive

This method mathematically converts the 3-phase voltage and current into a simple DC motor representation

Uses this data to calculate the best angle for commutation Creates new 3-phase sinusoidal PWM based on calculation Repeats the calculations at PWM frequency Pros:

Highest Torque efficiency Highest Bandwidth Widest Speed Range Lowest Audible Noise

Cons: Complicated Algorithm Needs powerful processor

26

BLDC Motor Speed Control

The goal of most Electronic Motor Control Systems is Speed Control

Speed Control systems are more or less complicated, depending on accuracy required

The simplest speed control is Open-Loop, that is, without speed feedback

In this configuration, a speed command is converted to a fixed voltage (PWM duty) which is sent to the motor

The motor may go the right speed, or it may not, it depends on the load

Without feedback, there is no way to tell internally what the real speed is and so may require outside adjustment

Speed Command

Pulse Width Modulator Transistors Motor Load

27

Closed-Loop Control

To get automatic speed control, feedback is needed Feedback systems could be Hall Sensors, Encoders,

Resolvers, tachometers or other devices The resolution and bandwidth of the feedback sensor limit

the resolution and bandwidth of the speed loop Below is a block diagram of a simple control loop Our Reference Command is the speed we desire, and the

Control Mechanism is our motor and motor control

ControlMechanism

SensorReference Command

Feedback

+

-

28

Closed Loop Speed Control

The generic terms can be replaced with terms common to motor control

The speed is often referred to as the Greek Letter Omega and motor angle is Theta θ

The Reference input is shown as Omega star * The Control Mechanism is a mathematical function, usually

a Proportional-Integral (PI) algorithm The speed sensors can be the same Hall sensors used for

commutation, where the speed is calculated from the time between steps

Hall Sensors

Speed Calculation

Motor

PWM Generation

PIController

ω*

ω θ

29

Closed Loop Speed Control

The way the loop works is to first measure the difference between the commanded speed and the actual speed

If the speed is to low, the PI controller increases the PWM duty which sends more voltage to the motor, correcting speed

If the speed to too high, the PI controller reduces the PWM, reducing the average voltage, so the motor slows down to the correct speed

The Proportional and Integral parameters have to be tuned to optimized the speed loop response-prevent speed oscillations

Hall Sensors

Speed Calculation

Motor

PWM Generation

PIController

ω*

ω θ

30

Motor Kit for Trapezoidal Control

BLDC Motor, Board, Software, Schematics, Tool and GUI

R8C/25

31

Motor Control Evaluation Kit

In order to help users decide on what kind of motor control they need, Renesas has introduced the YMCRPR8C25 Motor Control Evaluation Kit

The kit includes all that is needed to try Hall and BEMF commutated Brushless DC motor control with closed speed loops including, the control board, motor, debugger, power supply and software

32

YMCRPR8C25 Block Diagram

Power Supply &

Conditioning

R8C/25MCU

InternationalRectifier( I P M )

E8 Debug

I / F

4-LEDPWM / PWR

Status

LCD SegmentDisplay

M

Hall SensorInputs

Push-ButtonSwitch

R8C25 MCRP Kit

24v DCSupply

Jumper-1

BLDC Motor

VBUS

ShuntCurrent

Speed Control 6-PWM

RS232I/F

Shutdown

TP-1

TP-2

TP-3TP-4 CN-2

CN-1

CN-3

CN-4

TP-5

OP-AMP(Signal Conditioning)

Comparators( Back-EMF)

33

Motor Control Board

IGBT module capable of 10 amps.

3-Phase output capable of running DC and BLDC motors

15V and 5V regulators on board.

Voltage input from a single 24V (18-36VDC) supply, no shock hazard.

34

Board User Interface

Large potentiometer for speed control setting

2x8 LCD display with contrast pot for monitoring speed, current, etc.

Four push-buttons Bus voltage monitoring

to MCU Current monitoring to

the module for automatic protection

35

Commutation Options

Back-EMF detection comparators

Jumper selection (no soldering) between Hall and BEMF modes

Input connector for Hall signals from motor

36

Debugging Capabilities

Optically Isolated RS-232 communication

Optically Isolated E8(a) connector

Prototyping areas (under LCD)

LED’s for monitoring PWM lines, and GPIO

Abundant test points

37

Motor Control Graphical User Interface

Stop

Target Speed Actual SpeedSpeed Slider

Motor Current

System Status

38

HEW Development Environment

Source Code Editor

Output Window

Pro

ject

Na

vig

ato

r

39

Summary

DC and BLDC motors were compared

BLDC motors were shown to offer better performance

A large number of applications are moving from other motor

types to BLDC motors

Electronic BLDC motor control can be as simple as six-step

or as complicated as Vector Control

Closed Loop Speed Control was explained

The Renesas BLDC Motor Control Evaluation Kit was

introduced as a way to help get started in BLDC motor

control development

40

Questions?

41

Appendix

42

WiFiSH, RX, R8C

High-end Connectivity

V850ESV850ES50MHz50MHz

SH-2ASH-2A200MHz200MHz

Ultra Low Power

78K078K010MHz10MHz

78K0R78K0R20MHz20MHz

V850ESV850ES20MHz20MHz

R8CR8C20MHz20MHz

M16CM16C32MHz32MHz

R32CR32C50MHz50MHz

Application Focused Solutions

TFT LCD Control

H8S/SXH8S/SX50MHz50MHz

SH-2ASH-2A200MHz200MHz

General Purpose 8

-bit

16

-bit

32

-bit

Renesas MCU and MPU Solutions

32

-bit

32

-bit

32

-bit

8-b

it

16

-bit

Application Processor

SH-3SH-3200MHz200MHz

SH-4SH-4240MHz240MHz

SH-4ASH-4A600MHz600MHz3

2-b

it

32

-bit

32

-bit

32

-bit

32

-bit

32

-bit

32

-bit

Motor ControlSH, V850, RX,78K0R, R8C

Capacitive Touch

R8C

Industrial CANR8C, R32C, SH

Lighting78K0

RX600RX600100MHz100MHz

RX600RX600100MHz100MHz

43

Motor Control Applications & Renesas Solutions

High-EndLow-Range Mid-Range

SPEED + TORQUECONTROLSPEED CONTROL

SPEED + DYNAMIC TORQUE+ MOTION CONTROL

Fans, Kitchen Appliances,Pumps, Power-Tools

Pool Pumps, WashersHealth-Equipment

Compressors

MedicalIndustrial, Washers,

CompressorsMotion Control

Torque Control (Limited)

R8C

78K0R

SuperH

V850

RX

44

Renesas Motor Control Solutions

Renesas covers every motor control application from low-end to high-end

Renesas can provide all motor algorithms from Trapezoidal control to Sensor-less Vector control

Wide product portfolio

16bit MCU (20MHz): R8C, 78K0R

32bit MCU (48MHz to 200MHz): RX, V850, SH

These products have peripherals dedicated for Motor Control such as Timers and ADC

45

Motor Control Solution Summary

Motor Type Algorithm R8C 78K0R V850 RXSH2/SH2A

1-Ø ACIM (PSC) V/f, Open Loop Y  

1-Ø BLDCFixed Duty (Hall) Y  

Closed Loop (Hall) Y  

Universal (Brushed) DC

TRIAC Control ( speed loop w/Tachometer) Y  

PWM Chopper (speed loop w/Tachometer) Y  

3-Ø ACIM

V/f, Open Loop Y Y

Speed Loop w/Tachometer   Y

Sensorless Vector Control   Y Y Y

3-Ø BLDC

120-deg Trapezoidal (Hall) Y Y

120-deg Trapezoidal (BEMF) Y  

180-deg Sine (HALL) Y  

Sensor based Vector Control Y Y

Position Control (Encoder + Hall) Y

Sensorless Vector Control, 2 DCCT, 3-shunt, 1-shunt Y Y Y Y

*

*

*

*: Under development