motor control - ve2013
DESCRIPTION
This session provides insight into the operation of electric motor drive systems. Topics include electric motor operation and construction, motor control strategies, feedback sensors and circuits, power and isolation, and challenges of designing highly efficient motor control systems. A new high performance servo control FMC board will be introduced in the presentation, which provides an efficient motor control solution for different types of electric motors, addresses power and isolation challenges, and provides accurate measurement of motor feedback signals and increased control flexibility due to FPGA interfacing capabilities. The motor control hardware platform will be used to demonstrate rapid prototyping of motor control algorithms using Xilinx base platforms and the MathWorks development and simulation tools.TRANSCRIPT
Efficient Motor Control Solutions: High Performance Servo Control Reference Designs and Systems Applications
Andrei Cozma, Analog Devices
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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
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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®
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Motor Control Applications and Target Markets Section 1
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Electric Motor Applications
Electric motors are used in a wide range of applications Industrial
Medical
Transportation
Automotive
Integrated applications
Communications
Household appliances
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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.
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Market Sub Segments in Motor Control Partners and Systems Value from ADI
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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
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
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Motor Control Strategies Section 2
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Brushed DC Motor Control
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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
A
B C
BLDCCONTROLLER
+
-
HALL
A
HALL
B
HALL
C
Brushless DC Motor Control
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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.
A
B C
BLDCCONTROLLER
+
-
HAL
L A
HAL
L B
HAL
L C
Brushless DC Motor Control
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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
AC Motor Control
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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 MOTORCONTROLLER
+
-
Ia Ib
Spee
d
Field Oriented Control (FOC)
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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
TorqueController
PI
FluxController
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
Feedback Sensors and Circuits Section 3
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Current and Voltage Sensing
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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
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.
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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
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Isolation Section 4
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Safety and Functional Isolation
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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
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
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ADI High Performance Servo Control FMC Solution Section 5
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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
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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
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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
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ADI FMC Controller Board Block Diagram
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ADI Low Voltage Drive Board Block Diagram
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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
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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
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
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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
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
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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
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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
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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
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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
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Using the ADI High Performance Servo FMC Platform with Xilinx FPGAs and Simulink Section 6
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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
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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
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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
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BLDCPID 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
Simulink Speed Controller
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Speed Computation
PID Controller
Edge Detection
Simulink Speed Controller
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Speed Computation
PID Controller
Edge Detection
Simulink Speed Controller
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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
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BLDCPI Speed Controller
6 State Motor Driver
Speed Computation
Current Reference
PositionSpeed
SpeedReference
+
-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
Simulink Speed and Torque Controller
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Simulink Speed and Torque Controller
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Speed Computation
PI Speed Controller Current Computation
PID Torque Controller
Simulink Speed and Torque Controller
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Simulink Speed and Torque Controller
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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
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Design Resources Covered in This Session
Ask technical questions and exchange ideas online in our EngineerZone™ Support Community Choose a technology area from the homepage: ez.analog.com
Access the Design Conference community here: www.analog.com/DC13community
Download the motor control reference designs and documentation from the ADI wiki wiki.analog.com
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