DESIGNfeature
ROGER ALLAN, Contributing Editor
Smart Motor Controllers Take
Charge Of Expanding Applications
Advances in packaging and
performance spawn a variety
of low-cost, intelligent motor
controllers for an expanding
range of consumer and industrial applications
T
ake a look at a modern motor controller and one of the first things
you’ll notice is that the control circuit is about the same as the motor
it controls. That ís a far cry from the 10X or size bigger sizes of just
a few years ago. It’s also less expensive and smarter. Credit IC chip
advances in the form of more powerful and lower-cost DSPs, microcontrollers, amplifiers, encoders, power ICs, etc., for this.
This comes against a background of increasing demand for motor
controls in many more sectors like the automotive, computer, industrial, medical,
toys, as well as emerging white goods, power tools, and vacuum cleaner consumer
appliances.
Motor control is a complex task involving not only understanding for the designer
of complex operations, but also advanced hardware and software algorithms. Thus,
it is not surprising to see field-programmable gate array (FPGA) vendors and vendors
of intellectual property (IP) algorithms entire this field more recently. IC microcontroller unit (MCU) and DSP vendors are actively working with these aforementioned
suppliers to present complete system development kits and platforms, particularly for
users of embedded MCU and DSP users who are more software knowledgeable than
hardware oriented.
In using stepper motors, engineers are challenged to maximize control algorithms
for greater efficiency. This means boundary conditions of the complete electromechanical system must be mapped. This can be daunting since all system variables
such as temperature, mechanical degradation, acceleration, velocity, supply voltage,
vibrations, etc. must be accounted for.
The types of motor drives are widespread in both ac and dc varieties. These
include universal ac and dc motors, high-frequency pulse-width modulated (PWM)
universal types, brushed and brushless motors, induction motors, scalar variable frequency drives (VFD) motors, vector drive motors, as well as stepper motors.
Intelligent motor control ICs provide advanced control capabilities for multiphase motors, most commonly brushless dc motors and three-phase induction
motors. Microprocessors and DSPs are providing relatively inexpensive intelligent
Sine Wave
Power
Variable
Frequency
Power
Mechanical
Power
AC Motor
1540
Variable
Frequency
Controller
Power Conversion
Operator
Interface
www.powerelectronics.com
Power Conversion
Fig. 1. Energy savings can be
achieved for motor control
circuits using variable frequency drives (VFDs). A VFD
controls the rotational speed
of ac electric motors by controlling the frequency of the
electrical power supplied to
the motor.
March 2011 | Power Electronics Technology
31
MOTORcontrollers
Fig. 2. texas Instrumentsí DRV8412C2-kIt is an evaluation platform for
the design of scalable motor drivers
and brushed dc stepper motors.
field-oriented control (FOC), or vector control, a mathintensive technique for controlling brushless dc and ac
induction motors more efficiently. It reduces motor size,
cost and power consumption. It achieves this by directly
measuring the field position within the motor.
Another variant technique being used is indirect FOC.
Here, the motor’s field position is measured indirectly via
slip calculations using a mathematical model of the motor.
A big push is on for more energy efficient motor control
and the key to this is smart control. Smart motor control is
indeed helping boost energy savings. This is particularly the
case with the use of VFD circuits. These circuits optimize
motor acceleration and deceleration ramps, slow down the
motor, and turn it off when not in use.
A VFD is a system for controlling the rotational speed
of ac electric motor by controlling the frequency of the
electrical power supplied to the motor (Fig. 1). VFDs are
also known as adjustable-frequency drives (AFD), variablespeed drives (VSDs), ac drives, micro-drives or inverter
drives. Since the voltage is varied along with frequency,
they are sometimes also called variable-voltage variablefrequency (VVVF) drives.
A VFD can also be used to save regenerated energy.
For example, when a motor is trying to stop a high-inertia
load, it acts as a generator by dynamically converting the
kinetic energy in a motor into useful heat energy using highwattage braking resistors. Many modern motors feature
VFD capabilities.
for driving brushless dc stepper motors running up to 6
A continuous and 12 A peak at 50 V. It is aimed at
medical pumps, gate openers, stage lighting, textile
manufacturing tools, and industrial and consumer
robotics applications.
The platform includes the DRV8412 motor
driver, a real-time C-200 Piccolo MCU control-card module, a quick-start graphical-user
interface (GUI), full development source code,
Code Composer Studio integrated development environment (IDE), as well as motors.
Microchip Technology Inc. recently announced
two new low-cost development boards, one for the control of high-voltage motors (the dsPICDEM MCHV) and
another for stepper motors (the dsPICDEM MCSM).
Along with related application notes and free source-code
FOC software, they enable rapid designs using Microchip
Technology’s dsPIC33 motor control digital signal controller families.
“These development tools jumpstart our customers’
advanced high-voltage motor control and stepper motor
control designs, and brings the benefits of high-efficiency control to their products quickly,” explains Sumit
Mitra, vice president of Microchip Technology’s highperformance motor control division. “They provide our
customers with a winning combination of price, features
and reduced time to market for the motor-control applications,” he adds.
The dsPICDEM MCHV is said to be the industry’s
most cost-effective tools for the rapid evaluation and
design of a wide variety of high-voltage closed-loop control applications using ac induction motors, brushless dc
motors, or permanent-magnet synchronous motors. The
board includes in-circuit debugging circuitry, eliminating
the need for a separate debugger for development with
Microchip Technology’s dsPIC33 product. The board also
combines a proven motor-control system and power factor
A SySteM Look
Texas Instruments (TI) was one of the first to offer a
new line of scalable motor driver evaluation platforms
for brushed dc stepper motor with its DRV8412-C2-KIT
(Fig. 2). It provides all the hardware and software needed
32
Power Electronics Technology | March 2011
Fig. 3. Performance Motion Devices’ 58000 series Magellan motion IC provides
an oscilloscope-style trace of 64 separate motion variables for high-performance control applications.
www.powerelectronics.com
Fig. 4. AlteraÕs Cyclone
III FPGA together with
AlizemÕs motor control
IP with a proprietary
DSP algorithm are used
in developing a costeffective motor control
approach for home appliances.
Main Application
Loop
Other system
components (user
interface, network
connectivity)
DC bus
PMS motor
Sensorless motor
vector current
controller with
optimal PWM
Washing mode
Motor speed
profliles
(programs) Speed controller Torque
command
command
Estimated
position
Esimated
Water temperature
signal
speed signal
and level controller
Motor speed
and position
estimators
Nios II processor
Output
pins
Optically coupled
3-phase 2 level
inverter
One shunt current
measurement
Input
pins
Analog-to-digital
converter
Cyclone III FPGA
correction(PFC) for regulatory requirements.
The dsPICDEM MCSM is said to be the industry’s most
cost-effective tool for creating unipolar and bipolar stepper
motor applications. This board enables the development
of both open-loop and current closed-loop micro-stepping
routines using the dsPIC product. It also provides designers with a GUI, which allows them to focus on integrating
the other application features and fine-tuning the motor’s
operation.
Typical of modern motor control processors is the 58000
series Magellan motion processor from Performance Motion
Devices Inc. (Fig. 3). This IC provides an oscilloscope-style
trace of 64 separate motion variables for high-performance
control applications. It captures and stores real-time signals
from eight different functional areas such as trajectory
generation, encoder feedback, servo control, commutation,
motor output, general-purpose input, signal status and system clock into hardware buffers for future retrieval.
The IC works with the company’s ProMotion software
which facilitates servo tuning and trace-capture analysis via
a graphical user interface. Trace and display can be tailored
to the motion applications by programming trace start,
trace stop, data-capture frequency, external signal triggers
and other relevant parameters.
Motor drivers are available for a wide range of stepper
motor type fractions. For example, the BD638xxEV series
of micro-step motor drivers from Rohm Semiconductor
offer selectable excitation modes - from full step to 1/16th
step with 1.0 or 2.0 of output current at full step and 2.5A
at 1/8th step. Available in ultra-thin HTSSOP-B28 packages, they feature a unique ghost-supply prevention feature
that eliminates motor malfunctions, as well as built-in voltage, current and thermal protection.
Galil Motion Control, an industry pioneer in motion
control technology, recently introduced the DMC-41x3
motion controller series boards and packages for Ethernet
applications. Part of Galil’s Econo series of controllers,
www.powerelectronics.com
the new product offers many enhancements over previous
products including operation over 100Base-T Et Ethernet,
a USB 2.0 port, higher-speed performance, larger program
memory, analog inputs and an optically isolated I/O.
“Compared to the older DMC-21x3, the new DMC41x3
controller offers many speed improvements and can accept
encoder inputs up to 15 MHz and close the loop in as
quickly as 62 µs,” claims Lisa Wade, vice president of
sales and marketing at Galil. “It also offers twice as much
memory for user programs and arrays,” she adds.
The DMC-41x3 operates in a standalone mode or
interfaces to a PC with Ethernet 10/100-Base-T or USB
connectivity. An auxiliary RS232 port is also provided.
The product is available in one- through eight-axis formats
each of which is user configurable for stepper or servo
motor operation. It can be connected with external drives
or any power range or with Galil’s multi-axis (500 W/axis)
servo drives or 60-V, 3-A micro-stepping drives. Standard
I/O includes 16 optically isolated I/Os for the four-axis
models and 32 I/Os for the five- to eight-axis models.
Eight analog inputs are provided in addition to optically
isolated forward and reverse limits and home input for
each axis.
The DMC-41x3 comes in an 8.1-by-7.25-by-1.5-in.
package for the one- through four-axis model and 11.5-by7.25-by-1.5-in. package for five- through eight-axis models.
A ROLE FOR FPGAS
Increasingly, low-volume OEMs are turning to FPGAs
together with IP ICs for motor control development.
FPGAs allow specific one-size fits-all/generic PWM blocks
and transducer interfaces (to be configured by the system
designer) to specific pre-configured motor control blocks
including software drivers on an FPGA embedded processor. Unlike a DSP or microcontroller where each device
has its own tools that must be learned and much time
is invested in component integration, an FPGA provides
March 2011 | Power Electronics Technology
33
MOTORcontrollers
motor control designers with a single design environment
where the complete system - hardware and software - can
be developed.
The key to an FPGA’s advantage is to use motor control
IP from companies like Alizem. This company offers a
complete range of advanced control and fault-diagnosis IP
for motors designed to provide very high energy efficiency
and safety in home appliances. The company offers three
products: Zem-PWM IP for integrating high-performance
PWM for voltage actuation, ranging from standard spacevector PWM to custom-optimized PWM; Zem-CC IP for
enabling the correct cost/performance compromise for
motor current regulation, ranging from standard scalar
control to adaptive sensor-less vector control; and ZemDiag IP to monitor measurement signals and machine
states to proactively detect and diagnose faults in the
motor, power converter, sensors and the load.
Marc Perron, Alizem’s president, likens the shift toward
FPGAs for motor control to the evolution from mobile
cell phones to smart phones like the iPhone. “Apple has
decoupled the phone’s platform and functionality which
allows me to apply third-party applications that customize
the iPhone,” Perron said.
Altera found the kind of IP that Alizem makes very
helpful working with them in developing a motor control
approach for home appliances using Altera’s Cyclone III
FPGA (Fig. 4). It found that all Alizem motor-control IP
cores are designed with a proprietary DSP algorithm that
offers the best compromise of performance and FPGA
resources such as logic elements. A complete motor drive
for a permanent-magnet synchronous motor including
PWM and current control includes less than 500 logic elements on an Altera Cyclone III low-cost FPGA.
Actel (now part of Microsemi) uses its SmartFusion
intelligent mixed-signal FPGAs for embedded motor
control. The company says they are the only devices that
integrate an FPGA, ARM Cortex-M3 processor, and programmable analog functions, offering full customization,
IP protection, and ease-of-use. The SmartFusion mixedsignal FPGA is based on Actel’s proprietary flash process
(Fig. 5).
SmartFusion FPGAs are ideal for hardware and embed-
Fig. 5. Actel’s SmartFusion intelligent mixed-signal FPGA is aimed at embedded motor control applications development. It integrates an FPGA, ARM Cortex-M3 processor, and programmable analog functions, offering full customization,
IP protection, and ease-of-use.
Supervisor
ARM ™ CORTEX ™ -M3
PLL
OSC
RC
WDT
32 KHz
RTC
JTAG
+
3V
PPB
NVIC
SWD
ENVM
MPU
APB
UART 1
EFROM
I2 C 1
IAP
ESRAM
S
SmartFusion
D
Microcontroller Subsystem
Programmable Analog
–
SPI 1
SysReg
SysTick
I
FPGA Fabric
APB
SPI 2
Timer1
UART 2
Timer2
I2 C 2
AHB Bux Matrix
PDMA
SCB
Temp. Volt. Mon
(ABPS)
Mon.
Curr.
Mon. Comparator
SCB
Temp. Volt. Mon
Mon.
(ABPS)
Curr.
Mon. Comparator
34
APB
EMC
10/100
EMAC
Analog Compute
Engine
ADC
ADC
Sample Sequencing
Enine
Post Processing
Engine
Power Electronics Technology | March 2011
DAC
(SDD)
Versa Tiles
DAC
(SDD)
SRAM SRAM SRAM
SRAM SRAM SRAM
www.powerelectronics.com
peratures of -40ºC to +125ºC.
Rohm Semiconductor has used
silicon-carbide (SiC) technology to
develop the industry’s first SiC trench
MOSFET and Schottky barrier mod-
ules for automotive vehicle motor
control. The 600-V 450-A devices
take up less than 50% of equivalentperformance silicon modules and can
operate at up to 200ºC.
Fig. 6. RenishawÕs AM4096 12-bit magnetic encoder
chip provides UVW outputs with 16 poles (8 pole
pairs), incremental, absolute, linear (potentiometer), tacho generator and sinusoidal outputs.
ded designers who need a true system-on-chip (SoC) solution that gives
more flexibility than traditional fixedfunction microcontrollers - without
the excessive cost of soft processor
cores on traditional FPGAs.
Another FPGA supplier, Xilinx,
is using its FPGAs to develop what
it considers is the most advanced
FPGA-based motor control system.
The Targeted Design Platform is
scheduled to be unveiled this quarter.
smarter, faster, smaller
IMPROVED ENCODERS, POWER DEVICES
Check out the latest addition to CUI’s power line:
Key motor control components are
also making performance improvements. Take the AM4096 12-bit magnetic encoder chip from Renishaw,
for example. The chip (Fig. 6.) takes
Renishaw’s OnAxis encoder technology a step further with more
functionality and lower costs. The
encoder ( provides UVW outputs
with 16 poles (8 pole pairs), incremental, absolute, linear (potentiometer), tacho generator and sinusoidal
outputs. Resolution is 12 bits (4096
steps/turn) with a programmable
zero position. The encoder operates
from 3.3 V or 5 V and features a
sleep mode for battery operation. It
can be supplied pre-programmed or
customer-programmed with settings
stored in its on-chip EEPROM. The
encoder can operate up to 60,000
rpm and withstand operating tem-
www.powerelectronics.com
At CUI, our approach is to develop smarter, faster, smaller power modules.
Whether it’s an embedded ac-dc power supply, a board level dc-dc converter,
or a level V external adapter, we continuously strive to keep our power line, that
ranges from 0.25 W to 2400 W, ahead of the curve.
Novum digital dc-dc power POL modules
Smarter
¬ Auto compensation
¬ Dynamically adjustable
¬ System intelligence
Faster
¬ Greatly reduce your design cycle
Smaller
¬ Reduced footprint:
12 A - 0.50" x 0.925"
25 A - 0.50" x 1.075"
NDM1-250
NDM1-120
cui.com/power
March 2011 | Power Electronics Technology
35