FPGA Realization of a High-performance
Servo Controller for PMSM
Zhaoyong Zhou and Tiecai Li
Department of Electrical Engineering
Harbin Institute of Technology
Harbin, China
E-mail: zhouzy@hit.edu.cn
Toshio Takahashi and Eddy Ho
Digital Control IC Design Center
International Rectifier
California, USA
E-mail: ttakaha1@irf.com
Abstract—This paper proposes a fully digitized hardware design
scheme of a vector-controlled servo controller, which is verified
and implemented on one-chip field programmable gate arrays
(FPGA), for high-performance servo drives of the permanent
magnet synchronous motor (PMSM). This scheme integrates the
vector control strategy, the M/T speed measurement algorithm,
the PI regulating technique and the SVPWM principle as well as
the EDA design methodology, and it will be a good substitute for
traditional PMSM drives practice. The realized control IC also
contains a standard host communication interface, which enables
the on-line configuration for all kinds of control parameters. The
actual sample frequencies of the torque loop and the speed loop
are limited by the selected FPGA; with respect to the Altera
FPGA prototype mentioned in this paper, the two loops can
respectively obtain a sample frequency of 40kHz and 20kHz as
well as a bandwidth of 5kHz and 400Hz. Experimental results
indicate that the controller can provide a controllable speed
range from 0.2 RPM to 10,000 RPM with satisfactory dynamic
and static performances.
Keywords-vector control; servo; FPGA; PMSM
I. INTRODUCTION
High performance AC servo drive depends on the well
control of the currents; however, the strong coupling and
nonlinear natures of the AC motors make it impossible to
directly control the stator currents to obtain the desired
performances as the behavior of DC motors. Hence, a specific
algorithm must be introduced to realize the decoupling of
relevant variables. Fortunately this problem has been resolved
by the vector control technology. The principle of vector
control, often referred to as field-oriented-control, was first
proposed by F. Blaschke of Siemens in the early 1970s for
controlling induction motors, and after several years of efforts
this method had been developed into a complete theory system
[1], [2]. In the latest twenty years, the vector control
technology has been used wider and wider in high performance
AC drives due to the rapid progress in power electronics,
computer and microelectronics.
In engineering practice, because of the complexity of
servo control algorithm, it is basically implemented with
software based on DSP [3]; this approach can provide a
flexible skill, but suffers from a long period of development
and exhausts many resources of the CPU. In some cases, dual
DSPs have to be adopted to achieve superior performances [4].
In recent years, a novel design methodology has arisen, that is
FPGA-based hardware implementation technology [5].
Compared with ASIC, FPGA is only a collection of standard
cells, which have none of specific functions, but owing to its
field programmable characteristics and reuse of the IP cores,
user can design his own ASIC according to their schemes with
professional placement and routing tools in a shortest time,
instead of participation of the semiconductor manufacturers. In
addition, since FPGA can carry out parallel processing by
means of hardware mode, which occupies nothing of the CPU,
the system can get a very high speed level as well as an
exciting precision. This new design methodology has been
used in high performance motion control field, such as [6]-[8],
which realize different current controller. In [6], the designed
digital current controller integrates both nonlinear ∆ modulator
and linear PI regulator and can obtain a very high bandwidth.
Literature [7] provides a co-processor scheme based on the
indirect vector control with current feed forward, and literature
[8] proposes a digital hardware implementation where it can
operate under different instructions. All these digital current
controllers have achieved very high performances, however, it
is obvious that these schemes have a common property that the
current is considered as a co-processor and the speed or
position control is implemented by DSP. As known to all,
position control is very flexible and difficult to generalize, but
the speed control is universal just as the current control, and
high performance speed control can be impossible without the
current control. Thus, it is necessary to integrate the speed and
the current into a single chip, which can be separately used as a
speed controller or a current controller; furthermore, the two
controllers can also be incorporated into a position control
system, as shown in Fig.1. If the FPGA has integrated CPU,
the position, speed and current control can be all implemented
with only one single chip, which will lead to a real SOC
(system on a chip), the important trend of high performance
motion control integration design.
This paper studies the current vector control, PI
regulation, feed back speed measurement and space vector
PWM, and presents their digital structures. These algorithms
are designed in International Rectifier iMOTION products such
as the IRMCK201/IRMCK202 digital control ICs, and being
applied to the real industry application. In detail, it is organized
as follows. In section II, vector control principle of the PMSM
is briefly reviewed and the relevant expressions are derived.
0-7803-8269-2/04/$17.00 (C) 2004 IEEE. 1604