1. technology and computing

ST’s SOFTWARE AND HARDWARE TOOLS
FOR MOTION CONTROL
Gianluigi Forte, Dino Costanzo, Antonino Bruno
INTRODUCTION
 Fully configurability of the library to support any device of the
One of the major features inherent to the automation and
industrial
segment
is
the
electrical
motor
drive.
STMicroelectronics’ (ST) focus on motor control is enabling the
company to develop a wide portfolio of dedicated HW and SW
solutions. The ST MC (Motor Control) Ecosystem includes a
complete set of solutions like evaluation boards, a firmware (FW)
library, and collateral materials to meet the various applications’
requirements.
A new version of the Motor Control FW library for
Permanent Magnet Synchronous Motors (PMSM), called STM32
PMSM FOC SDK v4.0, now enriches the ST MC Ecosystem.
These tools, the result of deep knowledge and system expertise
accrued in digital and power system solutions for over ten years,
speed up the time to market and evaluation of ST products. In fact,
the company supports all kinds of motors used in the automation
and industrial fields thanks to a portfolio of innovative products
ranging from power transistors to intelligent power modules, motor
driver ICs, and the latest microcontrollers.
The PMSM FOC SDK features and dedicated algorithms add
value to the evaluation of ST products for industrial motion drives.
To implement this function, a synergy between hardware and
firmware solution is required. In addition, to achieve the best
performance in this field, the well-known field oriented control
technique (FOC) for three phases brushless motor is enhanced with
an offer of diverse specific algorithms.
STM32F microcontroller family (F0, F1, F2, F3 and F4), each
with peculiar characteristics, and to support any power stages
based on ST power products like the intelligent power module
(SLLIMM™) or discrete solutions with Power MOSFET,
IGBTs and gate drivers.
 Configuration allowed by PC software (the ST MC Workbench)
that has the dual functionality of assisting the user in the setup of
the system and establishing real time communication with the
FW,
 “Dual drive” motor control, which means driving two motors
simultaneously with the same microcontroller.
 Additional features like flux weakening, MTPA (maximum
torque per ampere) for internal permanent magnet motors, and
feed forward current regulation.
The firmware, combined with the HW tools - control stage
plus power stage or a complete solution - allows the customer to
get a jumpstart with their prototyping phase.
Figure 2: MC ecosystem for PMSM
Figure 1: Automation and industrial motor control
STM32 FOC SDK V4.0 WHAT IS NEW?
ST has been in the field of FOC control from many years. The
first release of the library supporting STM32 devices and
supporting the STM32 Motor Control kit for three phase motors
was delivered in 2009. Since then, the solution has been improved
with new features:
 Sensorless control of permanent magnet motors (two
complementary algorithms, the back-emf state observer and the
High Frequency Injection).
The most recent version of the STM32 FOC SDK released by
ST, at the end of 2014 is the 4.0. This release focuses on an
architectural change done with one keyword in mind:
“accessibility”. This increase of accessibility will help the user
speed up the design and reduce the time-to-market one of the key
factor for success in the electronics market. To improve the
accessibility of the SDK, a set of arrangements and new features
have been implemented in the “ecosystem” starting from the
source code, through the PC GUI, and culminates with a complete
set of collateral materials: technical document, FAQs,
presentations, software examples, “use cases”, tutorials, and
videos. All are provided together with the standard software and
firmware package, and can be found on-line on www.st.com. Full
C language source code will be released by direct request to the
user’s local STMicroelectronics office.
The new STM32 FOC SDK v4.0 ecosystem includes the two
pillars necessary for swift, efficient design: the firmware library
and the PC software GUI.
The well-established STM32 field oriented control firmware
library supports the full range of ST microcontroller families.
Starting with the cost effective 48Mhz Cortex-M0 STM32F030x,
up to the cutting edge 180Mhz Cortex-M4 STM32F4 with the
support of floating point instructions, and through the STM32F30x
family with its broad series of integrated analog IP, the STM32
covers a wide range of motor control applications, from the small
miniaturized motor for such applications as medical, up to big
servomotors in factory automation or in electric motor traction.
The ST FW Library supports all of those different devices thanks
to a peculiarity that distinguishes the STM32 FOC library from
other solutions: the object-oriented approach.
Version 4.0 keeps the benefit of the well-structured software
abstraction layer defined in the previous versions, so what is new?
Workspaces are simplified, reducing the numbers of projects inside
each specific configuration. Additionally, the supported IDE,
historically only offered by IAR Embedded Workbench, is also
available by from KEIL Microvision.
The flagship of the previous version, the motor control
application program interface (API), is now extended with new
functionality. Moreover, a set of ready examples has been included
in the packages; they make use of the functions exported by the
motor control API to implement typical “uses cases” that users can
employ with their final applications. For example:
 setting the speed reference according to an input analog voltage;
 putting a PWM signal in output that is proportional to the
measured speed;
 changing parameters like the controller bandwidth in real time;
 changing the speed and position sensor used to execute the
control loop in real time.
All the code required to implement such functions is present inside
the examples. They can be used as a starting point to build more
complex projects or they can be seen as a reference guide to
understand the logic behind the API itself. The motor control
library can act as a black box to show how to assert commands to
the motor, like start, stop or execute a speed ramp. It can be used to
get feedback from the motor such as measured speed, torque or
power. It also provides a way to focus only on the upper layer of
the application and differentiate one solution from the other with
the specific strategic know how.
Figure 3: MC SDK 4.0 user interfaces
In version 4.0, the user interaction with the firmware has been
improved with two channels. If the control board embeds an LCD
screen, it is possible to enable a new light-weight (smaller code
size) LCD graphical user interface. The reduced version of LCD
gives the user more flexibility to customize the GUI itself by
adding extra interactions with the firmware. If the control board is
not provided with an LCD screen, the other opportunity is to
establish real time communication via USART. In v4.0, it is
possible to enable “fast unidirectional communication”. In this
modality, the data is continuously sent from the firmware to the PC
at the maximum speed rate and without any other control bytes,
which allows the user to monitor variables with fast variation.
Some other features new to the Workbench:

The setting window of the sensor-less startup has been
renewed with a graphical representation of the imposed
current and acceleration adding the benefit of a visual
depiction.

The set of workbench projects’ configurations released
in bundle with the tool, which cover a broad range of
supported reference design boards, have been enriched.

The link between the Workbench and the documentation
has been reinforced. A new entry in the program menu
brings the user directly into technical documentation:
quick start, user manual, developer manual and API
reference manual.

Moreover, the complete support for the digital PFC plugin introduced in the last version of the Workbench can
now setup the AC input range in the power stage section
and cope with implemented safety features like over
currents and over voltage, allowing the user to set proper
thresholds in the drive management section.
ZERO SPEED CONTROL WITH HIGH FREQUENCY
INJECTION
The improvements of the new release of the firmware are not
limited to user experience and accessibility. The 4.0 version
contains a new sensor-less algorithm added to the already “stateof-the-art” BEMF state observer present in the previous versions.
The new sensor-less algorithm is called “High frequency injection
(HFI)” and can be applicable for a permanent magnet synchronous
motor (PMSM) with internal magnets.
Figure 4: Motor magnetic structures
In this machine, the magnets are not glued to the surface of
the rotor but are buried inside the iron of the rotor. This kind of
motor, the interior permanent magnet synchronous motor
(IPMSM), presents an electrical anisotropy in the inductances, seen
from the windings’ respect to the quadrature and direct axis (Lq
different from Ld).
High Frequency Injection exploits the anisotropy of the
magnetic structure to detect rotor angular position at very low
speeds and at standstill. This new sensorless technique extends the
speed range with respect to the Back Electromotive Force (BEMF)
observer or by any other technique based on the back
electromagnetic force detection. Because the BEMF amplitude is
proportional to the speed of the motor, when the motor is in
standstill or at very low speed, the BEMF amplitude is not
appreciable. The HFI can control the low speed operation because
it is based on a very different physical principle. A roto-pulsating
field is injected into the motor and the actual electrical angle is
computed from the current flowing through the magnetic structure
of the machine. The injected frequency has to be set sufficiently
higher than the fundamental in order to not produce any additional
torque. It is like an x-ray scanning of the motor to detect the
electrical position of the rotor from the anisotropy of this magnetic
structure. The method is valid from stand still phase to low speed,
and it works in synergy with the BEMF observer, switching onthe-fly automatically from one method to the other according to the
speed of the motor. This new algorithm is added to the list of
patented innovations that ST offers to its customers within the
motor control SDK and provides several benefits:
 Full toque at zero speed
 Very low speed operations
 Startup sensorless without any backward rotation
 Fastest sensorless startup ever
 Sensorless Speed reversal from positive (clock wise) to negative
(counter clockwise)
Moreover, it adds value to any application that can benefit from
startup efficiency like compressors, low speed operation or speed
reversal like washing machine or industrial automation, e-bike or
electrical traction, and the field of applications is still in discovery.
ST HW tools
ST offers a complete set of boards supported by the MC library,
enabling users to evaluate ST products like its Intelligent Power
Module (SLLIMM™), IGBTs, Gate drivers, Motor control ICs,
and microcontrollers in a real motor control system. For three
phase motors we highlight:
1. Its modular, flexible system, composed of a control board,
which – features an STM32 of any of the F0,F1,F2,F3,F4
families plus a rich set of additional functionalities such as
MEMS, temperature sensors, external memories, LCD,
transceivers, cameras etc – and a power stage featuring an ST
inverter stage based on SLLIMM™ (Small Low Losses
Intelligent Molded Module) power modules or discrete power
MOSFETs or IGBT and gate drivers.
Control boards and power boards can be linked through ST’s
standard “Motor Control Connector”, ensuring full
compatibility.
Figure 3: Flexible system control board plus power board
2. Its complete motor drive in a single board for addressing
specific applications such as air conditioning, ceiling fan,
dishwasher, and others. For example, the STEVALIHM034V2, which is able to drive a PMSM up to 1.4 kW,
and by connecting another board can drive two motors
simultaneously (FOC).
Figure 4: Complete motor drive
For more information on st.com:
Motor control board
Control board
Conclusions
We have presented the new features of the latest release of
ST’s MC FOC SDK. Every year, ST enriches the offerings for the
automation and industrial segments with new features, new
technologies, and new products, enlarging STMicroelectronics’
Motor Control Ecosystem to meet new trends in terms of
accessibility, ease, and fast evaluation, while maintaining the same
attention to efficiency, integration, and cost optimization.