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Motor Control - VE2013

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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, …

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.

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  • 1. Efficient Motor Control Solutions: High Performance Servo Control Reference Designs and Systems Applications Andrei Cozma, Analog Devices
  • 2. Legal Disclaimer  Notice of proprietary information, Disclaimers and Exclusions Of Warranties The ADI Presentation is the property of ADI. All copyright, trademark, and other intellectual property and proprietary rights in the ADI Presentation and in the software, text, graphics, design elements, audio and all other materials originated or used by ADI herein (the "ADI Information") are reserved to ADI and its licensors. The ADI Information may not be reproduced, published, adapted, modified, displayed, distributed or sold in any manner, in any form or media, without the prior written permission of ADI. THE ADI INFORMATION AND THE ADI PRESENTATION ARE PROVIDED "AS IS". WHILE ADI INTENDS THE ADI INFORMATION AND THE ADI PRESENTATION TO BE ACCURATE, NO WARRANTIES OF ANY KIND ARE MADE WITH RESPECT TO THE ADI PRESENTATION AND THE ADI INFORMATION, INCLUDING WITHOUT LIMITATION ANY WARRANTIES OF ACCURACY OR COMPLETENESS. TYPOGRAPHICAL ERRORS AND OTHER INACCURACIES OR MISTAKES ARE POSSIBLE. ADI DOES NOT WARRANT THAT THE ADI INFORMATION AND THE ADI PRESENTATION WILL MEET YOUR REQUIREMENTS, WILL BE ACCURATE, OR WILL BE UNINTERRUPTED OR ERROR FREE. ADI EXPRESSLY EXCLUDES AND DISCLAIMS ALL EXPRESS AND IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHTS. ADI SHALL NOT BE RESPONSIBLE FOR ANY DAMAGE OR LOSS OF ANY KIND ARISING OUT OF OR RELATED TO YOUR USE OF THE ADI INFORMATION AND THE ADI PRESENTATION, INCLUDING WITHOUT LIMITATION DATA LOSS OR CORRUPTION, COMPUTER VIRUSES, ERRORS, OMISSIONS, INTERRUPTIONS, DEFECTS OR OTHER FAILURES, REGARDLESS OF WHETHER SUCH LIABILITY IS BASED IN TORT, CONTRACT OR OTHERWISE. USE OF ANY THIRD-PARTY SOFTWARE REFERENCED WILL BE GOVERNED BY THE APPLICABLE LICENSE AGREEMENT, IF ANY, WITH SUCH THIRD PARTY. 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
  • 5. Motor Control Applications and Target Markets Section 1 5
  • 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
  • 10. Motor Control Strategies Section 2 10
  • 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
  • 16. Feedback Sensors and Circuits Section 3 16
  • 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
  • 20. Isolation Section 4 20
  • 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
  • 23. ADI High Performance Servo Control FMC Solution Section 5 23
  • 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
  • 27. ADI FMC Controller Board Block Diagram 27
  • 28. ADI Low Voltage Drive Board Block Diagram 28
  • 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
  • 40. Simulink Speed Controller 40 Speed Computation PID Controller Edge Detection
  • 41. Simulink Speed Controller 41 Speed Computation PID Controller Edge Detection
  • 42. Simulink Speed Controller 42
  • 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
  • 44. Simulink Speed and Torque Controller 44
  • 45. Simulink Speed and Torque Controller 45 Speed Computation PI Speed Controller Current Computation PID Torque Controller
  • 46. Simulink Speed and Torque Controller 46
  • 47. Simulink Speed and Torque Controller 47
  • 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
  • 49. Tweet it out! @ADI_News #ADIDC13 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 49