This document discusses efficient motor control solutions and Analog Devices' high performance servo control field programmable gate array (FPGA) module (FMC) board. It provides an overview of motor control strategies, feedback sensors, isolation requirements, and Analog Devices technologies that improve motor control system performance. The Analog Devices FMC solution addresses power, isolation, measurement, and control challenges in motor control applications. It allows accurate measurement of motor feedback signals and interfacing with Xilinx FPGAs.
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Motor Control - VE2013
1. Efficient Motor Control Solutions:
High Performance Servo Control
Reference Designs and Systems Applications
Andrei Cozma, Analog Devices
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2
3. Today’s Agenda
Motor control applications and target markets
Motor control strategies
Feedback sensors and circuits
Isolation
ADI high performance servo control FMC board
Using the ADI high performance servo FMC board with Xilinx®
FPGAs and Simulink® from Mathworks
3
4. Objectives
Provide insight into the operation of electric motor
drive systems and show where ADI technology adds
value to the system
Understand motor control strategies and the challenges
of designing efficient motor control applications
Show how some ADI motor control solutions can be used
with Xilinx FPGAs
Show how some ADI motor control solutions can be used
with Simulink from MathWorks®
4
6. Electric Motor Applications
Electric motors are used in a wide range of applications
Industrial
Medical
Transportation
Automotive
Integrated applications
Communications
Household appliances
6
7. Electric Motor Drives
Motor Drive
A system that varies the motor electrical input power to
control the shaft torque, speed, or position.
Types of Drives
Application specific drive—designed to run a specific
motor in a specific application (e.g., variable speed pump
drive).
Standard drive—designed as a general-purpose motor
speed controller capable of running a variety of motors
within a given power range.
Servo drive—designed to deliver accurate and high
dynamic control of position, speed, or torque down to
zero speed. Typically used in automation applications.
High performance servos—designed to deliver best in
class accuracy and connectivity. Typically used in CNC
and pick and place machines.
7
8. Market Sub Segments in Motor Control
Partners and Systems Value from ADI
8
High End Servos/CNC
ADI + FPGA Vendors
Xilinx
Focus ADI Parts:
Isolation (Gate Drivers/Discrete)
AD740x + AMP
RDC + SAR ADC
Transceivers
Power
Accelerometers/Sensors
Servos and Premium
Drives
ADI Has Complete Signal
Chain + Select Partners
Focus ADI Parts:
ASSPs/SHARC/BF
Isolation (Gate Drivers/Discrete)
AD740x + AMP
RDC + SAR ADC
Transceivers
Power
Accelerometers/Sensors
Standard and Midrange
Motor Drives
ADI Has Complete Signal
Chain + Select Partners
Focus ADI Parts:
ASSPs/BF
Isolation (Gate Drivers/Discrete)
AD740x + AMPs
RDC + SAR ADC
Transceivers
Power
Applications Specific
Motor Control
ADI Has Part of Signal
Chain + Select Partners
Focus ADI Parts:
ASSPs / ADuC Family
Isolation (Gate Drivers/Discrete)
AMPs
SAR ADC
Transceivers
Power
Highest Value for
High Performance
FPGA and AFE
9. Market Trends
Save Energy
Drive for performance and quality in motor control
More than 40% of global energy consumed by motors
The requirement for higher system efficiency means
there is a need to move from standard induction
machines to permanent magnet motors
Shift from analog to digital control—focus on highest
possible efficiency
Impact of Trends
Increases need for new performing technologies on:
converters, amplifiers, processors, isolation, power,
interfaces
The need for higher controller performance makes
room for new technologies like FPGAs and other
advanced controllers to be used in motor control
systems
9
11. Brushed DC Motor Control
11
Vary the dc supply, and the motor speed
will follow the applied voltage
Pulse width modulation
Constant amplitude voltage pulses of varying
widths are provided to the motor: the wider the
pulse, the more energy transferred to the motor
The frequency of the pulses is high enough that
the motor’s inductance averages them, and it
runs smooth
A single transistor and diode can control
the speed of a dc motor
The motor speed (voltage) is proportional to the
transistor ON duty cycle
Positive torque only—passive braking
An H-bridge power circuit enables four
quadrant control
Forward and reverse motion and braking
Complementary PWM signals applied to the high
and low side switches in the bridge
12. A
B C
BLDC
CONTROLLER
+
-
HALLA
HALLB
HALLC
Brushless DC Motor Control
12
Brushless dc motors windings generate a
trapezoidal back EMF synchronized to the
position of the rotor magnet.
Hall effect sensors detect the rotor magnet
position and provide signals indicating the
“flat top” portion for each winding’s back
EMF.
Six switching segments can be identified.
Star Connection Control
For any one segment, two windings will be in the
“flat top” portion of the back EMF and a third
winding will be switching between a positive and
negative output.
Electronic control leaves one winding open circuit,
connects one winding to the lower dc rail, and
controls the voltage applied to the third winding
using PWM.
The fill factor of the applied PWM controls the
speed of the motor.
13. A
B C
BLDC
CONTROLLER
+
-
HALLA
HALLB
HALLC
Brushless DC Motor Control
13
Delta Connection Control
For any one segment, two windings are connected
to the positive voltage supply and a third winding is
connected to the negative voltage supply.
The fill factor of the applied PWM controls the
speed of the motor.
Sensorless control can be achieved by
detecting the zero crossings of the BEMF
for each phase
Sensorless control benefits
Lower system cost
Increased reliability
Sensorless control drawbacks
BEMF zero crossings can’t be reliably
detected at low motor speeds
14. AC Motor Control
14
Volts per Hertz Control
Variable frequency drive for applications like
fans and pumps
Fair speed and torque control at a
reasonable cost
Sensorless Vector Control
Does not require a speed or position
transducer
Better speed regulation and the ability to
produce high starting torque
Flux Vector Control
More precise speed and torque control, with
dynamic response
Retains the Volts/Hertz core and adds
additional blocks around the core
Field Oriented Control
Best speed and torque control available for ac
motors
The machine flux and torque are controlled
independently
U
V
W
AC MOTOR
CONTROLLER
+
-
Ia
Ib
Speed
15. Field Oriented Control (FOC)
15
Separates and independently controls the motor flux and torque
Applies equally well to dc motors and ac motors and is the reason “dc
like” performance can be demonstrated using field oriented control on
ac drives
Torque
Controller
PI
Flux
Controller
PI
Inverse
Park
Transform
d,q → α,β
Space
Vector
PWM
3 Phase
Inverter
Forward
Clarke
Transform
a,b → α,β
Forward
Park
Transform
α,β → d,q
Vsq
Vsd
Vsα
Vsβ
Vsa PWM
Vsb PWM
Vsc PWM
AC
Motor
isa
isb
isα
isβ
isd
isq
Vsq
Vsd
VsqRef
VsdRef
_
+
+
_
VDC
Rotor Flux
Angle θ
17. Current and Voltage Sensing
17
Shunt Resistor
Linear, wide BW, zero offset
Power loss at high currents and
no isolation
Current Transformer
Isolating
AC only with poor linearity at low current
Hall Effect Current Sensor
Isolating, dc operation and less expensive
than CT
Nonlinearity and zero offset
Nulling Hall Effect Sensor
Isolating, dc operation and better linearity
than HE sensor
More expensive and zero offset
Voltage isolation
Used to remove CM signal from dc bus,
motor voltage, and current shunt voltages
Isolating
18. Shaft Position and Speed Sensing Devices
Speed
AC and DC tachometers are permanent
magnet generators that produce a
voltage proportional to speed.
The ac tachometer output frequency is
also proportional to speed.
Commutation (Rotor Angle)
Brushless dc motors require low
resolution feedback derived from the
motor magnets using Hall effect sensors.
A Hall effect based magnetic encoder
generates a pulse train for speed and
incremental position.
Precision Shaft Angle
Optical encoders with precision pattern
printed on a glass disk provide very high
resolution shaft position and speed data.
Resolvers generate sine/cosine relative
to position. They are the analog
counterpart of the rotary encoder.
18
19. Sensorless Control
Eliminate mechanical speed/position sensors by calculating
feedback signal from other information
Often used for rotor position estimation in PMSM and BLDC motors
Very useful in estimating rotor flux position in ACIM FOC control
In some cases, can provide better results than real sensors
Techniques
BEMF detection to estimate rotor position in BLDC motor control
Rotor angle detection based on motor model using measured phases currents
and voltages
Problems
Variation of motor/model parameters over time, temperature
Usually need special handling of low speed/zero speed and/or start-up
19
21. Safety and Functional Isolation
21
Functional isolation protects electronic control
circuits from damaging voltages
Isolate high voltage output from control circuits
connected to Power_GND
Safety isolation protects the user from dangerous
voltages
Protects user and electronic circuits
International standard apply
Typically requires double insulation barrier: single
device with two insulating layers OR two single
insulating layer devices in path to EARTH
Isolation options
Isolate power circuits from the control and user I/O
circuits
Common in “noisy” high power systems
Required when there is high BW communications
between control and communications process
Isolate power and control circuits from user I/O
circuits
Common in low power systems
Simplifies signal isolation when there is limited
communications between control and user
22. Motor Control Signal Isolation—Isolated Power
Circuit
Feedback isolation
Measure winding current using
isolating ADC
Isolated RS-485 position data from
encoder ASIC
Inverter drive isolation
Isolated high- and low-side gate
drivers
DC bus signal isolation
Serial I2C ADC for analog signal
isolation
Digital isolation of hardware trip
signals
Field Bus isolation
Isolate CAN outputs from field bus
network
22
24. FPGAs in Motor Control
FPGAs are becoming more popular for
motor control
Wide integration capabilities
Higher performance, reduced latency
Cost reduction
FPGAs are used in a large number of
industry fields for efficient motor control
Industrial servos and drives
Manufacturing, assembly, and automation
Medical diagnostic
Surgical assist robotics
Video surveillance and machine vision
Power efficient drives for transportation
24
25. ADI FMC High Performance Servo Solution
Purpose
Provide an efficient motor control solution for different types of
electric motors
Address power and isolation challenges encountered in motor
control application
Provide accurate measurement of motor feedback signals
FPGA interfacing capability
Added Value
Complete control solution showing how to integrate hardware for:
Power
Isolation
Measurement
Control
Increased control flexibility due to FPGA interfacing capabilities
Increased versatility to be able to control different types of
motors
Example reference designs showing how to use the control
solution with Xilinx FPGAs and Simulink
25
26. ADI FMC High Performance Servo Solution
Drive Board
Drives BLDC / PMSM / Brushed DC / Stepper motors
Drives motors up to 48V at 18A
Integrated over current protection
Current measurement using isolated ADCs
Bus voltage, phase currents and total current analog
feedback signals
PGAs to maximize the current measurement input rage
BEMF zero cross detection for sensorless control of
PMSM or BLDC motors
Controller Board
Compatible with all Xilinx FPGA platforms with FMC
LPC or HPC connectors
2 x Gbit Ethernet PHYs for high speed industrial
communication
Hall + Differential Hall + Encoder + Resolver interfaces
Current and voltage measurement using isolated ADCs
Xilinx XADC interface
Fully isolated control and feedback signals
26
29. Key Parts Features That Improve System
Performance
Efficient Motor Control Prerequisites
High quality power sources
Reliable power, control, and feedback signals isolation
Accurate currents and voltages measurements
High speed interfaces for control signals to allow fast controller response
29
Measurement
AD7401A 5 kV rms, isolated 2nd order Sigma-Delta modulator
AD8207 Zero drift, high voltage, bidirectional difference amplifier
AD8137 Low cost, low power differential ADC driver
Power
ADuM5000 isoPower® integrated isolated dc-to-dc converter
ADP1614 1000 mA, 2.5 MHz buck-boost dc-to-dc converter
ADP1621 Low quiescent current, CMOS linear regulator
Isolation
ADuM7640 Triple channel digital isolator
Voltage Translation
ADG3308 8-channel bidirectional level translator
30. AD7400A/7401A: 5 kV rms, Isolated 2nd Order
Sigma-Delta Modulator
Features
High performance isolated ADC
16-bit NMC
±2 LSB (typ) INL with 16-bit resolution
1.5 mV/°C (typ) offset drift
±250 mV differential analog input
−40°C to +125°C operating temperature
range
5 kV rms, isolation rating (per UL 1577)
Maximum continuous working voltages
565 V pk-pk: ac voltage bipolar waveform
891 V pk-pk: ac voltage unipolar
waveform (CSA/VDE)
891 V: dc (CSA/VDE)
Ideal for motor control and dc-to-ac inverters
Shunt resistor current feedback sensing
Isolated voltage measurement
External clocked version simplifies
synchronization
30
Product Data Rate Clock SNR ENOB INL Package
AD7400A 10 MHz Internal 80 dB 12.5 ±2 LSB SOIC-16
Gull Wing-8
AD7401A 20 MHz External 83 dB 13.3 ±1.5 LSB SOIC-16
31. AD8207: Zero-Drift, High Voltage, Bidirectional
Difference Amplifier
Features
Ideal for current shunt applications
EMI filters included
1 μV/°C maximum input offset drift
High common-mode voltage range
−4 V to +65 V operating (5 V supply)
−4 V to +35 V operating (3.3 V supply)
−25 V to +75 V survival
Gain = 20 V/V
3.3 V to 5.5 V supply range
Wide operating temperature range: −40°C to
+125°C
Bidirectional current monitoring
<500 nV/°C typical offset drift
<10 ppm/°C typical gain drift
>90 dB CMRR dc to 10 kHz
Qualified for automotive applications
Applications
High-side current sensing in
Motor control
Solenoid control
Engine management
Electric power steering
Suspension control
Vehicle dynamic control
DC-to-DC converters
31
32. ADuM5000: Isolated DC-to-DC Converter
Features
isoPower® integrated isolated dc-to-dc
converter
Regulated 3.3 V or 5 V output
Up to 500 mW output power
16-lead SOIC package with >8 mm
creepage
High temperature operation
105°C maximum
High common-mode transient immunity
>25 kV/μs
Thermal overload protection
Safety and regulatory approvals
UL recognition
2500 V rms for 1 minute per UL 1577
CSA component accept notice #5A
(pending)
Applications
RS-232/RS-422/RS-485 transceivers
Industrial field bus isolation
Power supply startups and gate drives
Isolated sensor interfaces
Industrial PLCs
32
33. ADP1614: 650 kHz/1.3 MHz, 4 A, Step-Up, PWM,
DC-to-DC Switching Converter
Features
Adjustable and fixed current-limit options:
Adjustable up to 4 A
Fixed 3 A
2.5 V to 5.5 V input voltage range
650 kHz or 1.3 MHz fixed frequency option
Adjustable output voltage, up to 20 V
Adjustable soft start
Undervoltage lockout
Thermal shutdown
3 mm × 3 mm, 10-lead LFCSP
Supported by ADIsimPower design tool
Applications
TFT LCD bias supplies
Portable applications
Industrial/instrumentation equipment
Design tools
ADIsimPower - DC-DC Power
Management design tool
33
34. ADuM7640: 1 kV RMS Six-Channel Digital
Isolator
Features
Small 20-lead QSOP
1000 V rms isolation rating
Safety and regulatory approvals (pending):
UL recognition (pending) 1000 V rms for
1 minute per UL 1577
Low power operation
3.3 V operation
1.6 mA per channel maximum at 0 Mbps
to 1 Mbps
7.8 mA per channel maximum at 25Mbps
5 V operation
2.2mA per channel maximum at 0 Mbps
to 1 Mbps
11.2mA per channel maximum at 25Mbps
Bidirectional communication Up to 25 Mbps
data rate (NRZ)
3 V / 5 V level translation
High temperature operation: 105°C
High common-mode transient immunity:
>15 kV/μs
Applications
General-purpose, multichannel isolation
SPI interface/data converter isolation
RS-232/RS-422/RS-485 transceivers
Industrial field bus isolation
34
35. ADG3308: Low Voltage, 1.15 V to 5.5 V, 8-
Channel Bidirectional Logic Level Translator
Features
Bidirectional logic level translation
Operates from 1.15 V to 5.5 V
Low quiescent current < 1 μA
No direction pin
Applications
Low voltage ASIC level translation
Smart card readers
Cell phones and cell phone cradles
Portable communication devices
Telecommunications equipment
Network switches and routers
Storage systems (SAN/NAS)
Computing/server applications
GPS
Portable POS systems
Low cost serial interfaces
35
36. Using the ADI High Performance
Servo FMC Platform with Xilinx
FPGAs and Simulink
Section 6
36
37. ADI High Performance Servo Development
Platform
Target FPGA Platforms
Xilinx Virtex FPGA platforms
Xilinx Kintex FPGA platforms
Xilinx Zynq FPGA platforms
Control Algorithms
Simulink models for controller ready for code
generation using HDL Coder™ from MathWorks
and Xilinx System Generator
Reference design showing BLDC motor speed
control
Reference design showing BLDC motor speed
and torque control
Simulation and Monitoring
Controller simulation and tuning in Simulink
ChipScope™ interface for internal signals
monitoring
37
38. Motor Control Reference Design FPGA Blocks
Motor Controller generated from Simulink
6 State Motor Driver
SINC3 Filters for current and voltage
measurement
BEMF position detector
Hall position detector
ChipScope blocks
38
39. Speed Control Reference Designs
Speed Control Reference Design
Target motor: BLDC
Speed control using Hall sensors
Sensorless speed control using
BEMF
Simulink controller model
ChipScope interface for internal
signals monitoring
Implementation Flow
39
BLDC
PID
Controller
6 State
Motor Driver
Speed
Computation
PWM
PositionSpeed
Reference
Speed
+
-
Design and Tune
the
Motor Controller
in
Simulink
using the
Xilinx Blockset
Generate the HDL Netlist
for the
Simulink Motor Controller
using
Xilinx System Generator
Integrate
the
Motor Controller HDL Netlist
in the
Speed Control Reference
Design
43. Motor Control Reference Designs
Speed and Torque Control
Reference Design
Target motor: BLDC
Speed and torque control
Simulink controller model
ChipScope interface for
internal signals monitoring
Implementation Flow
43
BLDC
PI Speed
Controller
6 State
Motor Driver
Speed
Computation
Current
Reference
PositionSpeed
Speed
Reference
+
-
PID Current
Controller
PWM
Current
Computation
Total Current
Measurement
Total
Current
+ -
Design and Tune
the
Motor Controller
in
Simulink
using
Simulink Native Blocks
Generate the HDL Netlist
for the
Simulink Motor Controller
using
Xilinx System Generator
Integrate
the
Motor Controller HDL Netlist
in the
Speed and Torque Control
Reference Design
Generate the HDL code
for the
Motor Controller
using
HDL Coder
Replace in the Simulink model
the Motor Controller
with
Xilinx Black Boxes
containing the
HDL generated by
HDL Coder
48. Conclusions
The ADI high performance servo development platform showcases
a full motor control solution that shows how to integrate all the
necessary hardware components for efficient motor control in one
system
The FPGA interfacing capabilities provide a high degree of flexibility
in developing high performance motor control algorithms
By using the MathWorks simulation and development tools, high
performance control algorithms can be developed and simulated on
the PC and transferred directly into the FPGA
The ADI motor control reference designs provide a starting point for
developing enhanced motor control algorithms using MathWorks
and Xilinx FPGAs
48
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Design Resources Covered in This Session
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from the ADI wiki
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49