Motor control

1. ID 610C: Introduction to BLDC Motor Control
Avnet
Jim Carver
Technical Director, Advanced Architectures
12 October 2010
Version 1.0

2. 2
Renesas Technology and Solution Portfolio
Microcontrollers
& Microprocessors
#1 Market share
worldwide *
Analog and
Power Devices
#1 Market share
in low-voltage
MOSFET**
Solutions
for
Innovation
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).

3. 3
3
Renesas Technology and Solution Portfolio
Microcontrollers
& Microprocessors
#1 Market share
worldwide *
Analog and
Power Devices
#1 Market share
in low-voltage
MOSFET**
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).
Solutions
for
Innovation

4. 4
4
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 process
 350 uA/MHz, 1uA standby
 Capacitive touch
 Up to 25 DMIPS, 150nm process
 190 uA/MHz, 0.3uA standby
 Application-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 Power
General Purpose

5. 5
5
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 process
 350 uA/MHz, 1uA standby
 Capacitive touch
 Up to 25 DMIPS, 150nm process
 190 uA/MHz, 0.3uA standby
 Application-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 Power
General Purpose

6. 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. 7
Motor Types

8. 8
Expanding BLDC Motor Control Applications
AC, DC
and
Universal
Motors
Transition to
BLDC
As consumers demand
more energy efficient
products, more BLDC
motors are being used.

9. 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. 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 motor
Cons:
 Rotor sensor OR sensorless methods
needed to commutate
 Requires six power transistors

11. 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

12. 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. 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
U
V
W

14. 14
Six-step Commutation
STEP1 STEP2 STEP3 STEP4 STEP5 STEP6 STEP1 STEP2 STEP3
U
V
W
U
V
W

15. 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. 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. 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. 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. 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. 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. 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. 22
Startup of BEMF System
 Since only a spinning motor generates BEMF signals
 Start the motor in open loop
 First align rotor to a known angle
 Then 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. 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

24. 24
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. 25

*
r

Speed Regulator
r


*
q
i
0
*

d
i
r

id PI
Regulator
iq PI
Regulator d,q
to

,
)
(
1


T
Motor Model
Based Flux and
Position Observer
q
i
d
i
*
q
U
*
d
U
*

U
*

U
Voltage
Source
3-phase
Inverter
SIN
PWM
PWM1~6
to
a, b, c

,
3-phase
PMSM
r

to
d,q

,
)
(
T
a
i
b
i
d
i
q
i

i

i
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. 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. 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
Control
Mechanism
Sensor
Reference
Command
Feedback
+
-

28. 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
PI
Controller
ω*
ω θ

29. 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
PI
Controller
ω*
ω θ

30. 30
Motor Kit for Trapezoidal Control
 BLDC Motor, Board, Software, Schematics, Tool and GUI
R8C/25

31. 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. 32
YMCRPR8C25 Block Diagram
Power Supply
&
Conditioning
R8C/25
MCU
International
Rectifier
( I P M )
E8
Debug
I / F
4-LED
PWM / PWR
Status
LCD Segment
Display
M
Hall Sensor
Inputs
Push-Button
Switch
R8C25 MCRP Kit
24v DC
Supply
Jumper-1
BLDC
Motor
V
B
U
S
Shunt
Current
Speed
Control 6-PWM
RS232
I/F
Shutdown
TP-1
TP-2
TP-3
TP-4
CN-2
CN-1
CN-3
CN-4
TP-5
OP-AMP
(Signal Conditioning)
Comparators
( Back-EMF)

33. 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. 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. 35
Commutation Options
 Back-EMF detection
comparators
 Jumper selection (no
soldering) between
Hall and BEMF
modes
 Input connector for
Hall signals from
motor

36. 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. 37
Motor Control Graphical User Interface
Stop
Target Speed Actual Speed
Speed Slider
Motor
Current
System
Status

38. 38
HEW Development Environment
Source Code Editor
Output Window
Project
Navigator

39. 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. 40
Questions?

41. 41
Appendix

42. 42
WiFi
SH, RX, R8C
High-end
Connectivity
V850ES
50MHz
SH-2A
200MHz
Ultra Low
Power
78K0
10MHz
78K0R
20MHz
V850ES
20MHz
R8C
20MHz
M16C
32MHz
R32C
50MHz
Application Focused Solutions
TFT LCD
Control
H8S/SX
50MHz
SH-2A
200MHz
General
Purpose
8-bit
16-bit
32-bit
Renesas MCU and MPU Solutions
32-bit
32-bit
32-bit
8-bit
16-bit
Application
Processor
SH-3
200MHz
SH-4
240MHz
SH-4A
600MHz
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
32-bit
Motor Control
SH, V850, RX,
78K0R, R8C
Capacitive
Touch
R8C
Industrial CAN
R8C, R32C, SH
Lighting
78K0
RX600
100MHz
RX600
100MHz

43. 43
Motor Control Applications & Renesas Solutions
High-End
Low-Range Mid-Range
SPEED + TORQUE
CONTROL
SPEED CONTROL
SPEED + DYNAMIC TORQUE
+ MOTION CONTROL
Fans, Kitchen Appliances,
Pumps, Power-Tools
Pool Pumps, Washers
Health-Equipment
Compressors
Medical
Industrial, Washers,
Compressors
Motion Control
Torque Control (Limited)
R8C
78K0R
SuperH
V850
RX

44. 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. 45
Motor Control Solution Summary
Motor Type Algorithm R8C 78K0R V850 RX
SH2/
SH2A
1-Ø ACIM (PSC) V/f, Open Loop Y
1-Ø BLDC
Fixed 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