Load Torque Observer Based Sliding Mode Control Method for
Permanent Magnet Synchronous Motor
Changfan Zhang
1
, Lin Jia
1
, Jing He
1,2
1. College of Electrical and Information Technology, Hunan University of Technology, Zhuzhou, 412007, China
E-mail: zhangchangfan@263.net
2. College of Mechatronics and Automation, National University of Defense Technology, Changsha, 410073, China
E-mail: hejingzzcn@yahoo.com.cn
Abstract: Considering the control performance requirements of high-performance printing press, a sliding-mode speed
controller with torque feed-forward compensation is proposed in this paper. First, a sliding mode control method is pre-
sented for the permanent magnet synchronous motor(PMSM) of the printing press. Then, in order to reduces chattering
phenomenon caused by system parameter variations and external time-varying load torque disturbances, by using a cas-
cade observer design technique based on the sliding mode control, a load torque observer and a load torque derivatives
observer are designed respectively. Since the estimated load torque and its derivatives are considered as the feed-forward
compensation part to compensate sliding mode speed controller, the sliding mode controller may take a smaller gain for
switching functions without sacrificing load disturbance rejection performance. The stability of the proposed scheme
is verified using the Lyapunov method to determine the observer gain. The simulation result shows that the observer-
based control scheme can decrease the chattering phenomenon effectively and improve control performance of PMSM
remarkably.
Key Words: permanent magnet synchronous motor (PMSM), sliding mode, observer, time-varying torque, printing press
1 Introduction
It is well known that high servo performance for the drive
system is very important in the modern high-performance
printing press. A better tracking response plays a decisive
role on printing quality. PMSM has been widely used in
modern industrial applications due to its high power densi-
ty, high torque-to-current ratio, good dynamic response and
excellent tracking precision[1], which receiving increased
attention in the field of high-performance printing press.
However, PMSM is a complex object with nonlinearity,
multivariable and strong coupling[2]. In the filed of high
performance printing press with PMSM, the classical PID
controller cannot assure the requirements of control perfor-
mance[3].
Sliding-mode control (SMC) has found many applica-
tions in recent years, the most salient feature of this control
technique is its robustness to the system uncertainties and
disturbances in the so-called sliding mode[4]. Therefore,
its application in control of printing press has aroused great
concern[5]. The main problem for the application of SMC
in servo system is the well-known chattering phenomenon,
which can excite high-frequency dynamics[6]. Thus some
approaches have been proposed to overcome the chatter-
ing, which include classical method, intelligent method and
observer method. The classical method mainly includes
quasi-sliding mode approach, reaching law approach, fil-
tering approach and etc[7][8][9]. Classical method blazes
This work is supported by the Natural Science Foundation of China
(61273157 and 61104024), Hunan Natural Science Foundation of Chi-
na(13JJ8020), and Hunan Province Education Department(12A040).
the way for the application of SMC method in engineer-
ing while there are problems such as robustness is weak-
ened, the dependence of parameters is strong and so on.
Intelligent method includes fuzzy control, neutral network
and etc[10][11]. It applies advanced control theory in-
to weakening of chattering, which obtains good effective-
ness. However, the calculation is big and its difficult to
be used for fast real-time control. Chattering problem can
be solved better by adopting observatory method for e-
limination of chattering caused by uncertainty. Therefore,
observer-based control solution has been widely used in
practical application[12], which is also the focus in this pa-
per. Liu et.al. designed a load torque observer utilizing
rotate speed and torque current of system and combines
observation results and output of controller as compensa-
tion solution[13]. Good control effects have been achieved
by this way. Zhang et.al. designed a sliding mode load
torque observer[14]. It adopts the same compensation so-
lution as that in[13], which eliminates chattering well and
improves anti-interference performance of system. In all
existing observer-based references, load torques are con-
sidered as constants or load torques are constants in cer-
tain time while the load torque is fast time-varying in high-
precision printing press, therefore the application of cur-
rent observer solution in control system of high-precision
printing press is restricted to some extent.
In order to optimize the performance of the servo system
of the printing press, a sliding mode speed controller based
on the upper and lower bounds of load torque derivatives
is employed in this paper. The design method is simple
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978-1-4673-5532-2
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2013 IEEE