www.ietdl.org
Published in IET Control Theory and Applications
Received on 29 April 2014
Revised on 18 August 2014
Accepted on 15 September 2014
doi: 10.1049/iet-cta.2014.0477
Special Issue on Co-operative Multi-Agent
Systems with Engineering Applications
ISSN 1751-8644
Virtual line-shafting control for permanent
magnet synchronous motor systems using
sliding-mode observer
Changfan Zhang
1
, Jing He
1,2
, Lin Jia
1
, Chengjie Xu
1
,Yuanyuan Xiao
1
1
College of Electrical and Information Engineering, Hunan University ofTechnology, Zhuzhou, Hunan 412007, People’s
Republic of China
2
College of Mechatronics Engineering and Automation, National University of DefenseTechnology, Changsha, Hunan
410000, People’s Republic of China
E-mail: hejing@263.net
Abstract: This study presents a novel observer-based electronic line-shafting control strategy for permanent magnet syn-
chronous motor systems. Adopting the sliding-mode variable structure technology, the proportional–integral speed controller
for every servo unit is designed, followed by design of two cascades connected observers, in order to improve the system
synchronisation performance when a large load disturbance occurs. The load torque observer transmits the observed load
torque value instead of the calculated one back to the virtual shafting, which reflects the dynamic relationships of all the
virtual or slave shafts more accurately. Another load torque derivative observer feeds the observed value forward to the corre-
sponding sliding-mode controller for reducing the switching gain. The proposed control system is proved stable by Lyapunov
stability theory, and simulation results show the strategy is effective on reducing sliding-mode chattering and achieving higher
synchronisation precision.
1 Introduction
With simplified system architecture and improved sys-
tem performance, multi-motor technology has become an
important replacement for conventional mechanical cou-
pling in the printing press, steel rolling, robotics and
other modern electromechanical industrial fields [1]. For
a multi-motor system, the conventional control of trans-
mission performance has been transformed into the con-
trol of multi-shaft synchronous precision. To achieve
high synchronous performance, the speed and position
of a single shaft should be controlled with high pre-
cision, besides, the coordination relationships of syn-
chronous movements should be given full considera-
tion [2].
Multi-shaft synchronisation control methods can be
divided into two categories according to the topologies
among shafts. The uncoupling synchronisation control meth-
ods include parallel control, master slave control and
electronic line shafting (ELS) control [3–5], whereas the
coupling ones include cross-coupling control and bi-axial
cross-coupling control [6–8]. Lorenz and Meyer first pro-
posed the ELS control idea, then Valenzuela and Lorenz
[9] carried out its further development. Since ELS control
technology simulates the physical properties of mechani-
cal transmission and has the similar inherent synchroni-
sation behaviour with mechanical shafting system, it has
been widely applied in practical engineering. Studies have
shown that, ELS control can maintain good synchronisation
performance in the steady state. However, in the dynamic
process caused by the large load disturbance, asynchroni-
sation will occur because the calculating of virtual value
feedback to the virtual shaft leads to the time delay on
the feedback of load disturbance [10]. Therefore this paper
presents a novel observer-based ELS control strategy, with
which the improvements of the multi-shaft synchronisation
performance are realised by employing the sliding-mode
variable structure technology.
The remainder of the paper is organised as follows.
Section 2 presents a novel observer-based ELS control strat-
egy on the basis of conventional ELS control. Section 3
describes the mathematical model of servo motor, followed
by the single-shaft controller design. The design of two
observers is discussed in Section 4. Simulation examples
illustrating the results are presented in Section 5 and a brief
conclusion in Section 6 following.
2 ELS control
2.1 Conventional ELS control
In the ELS control strategy, virtual electronic-shaft plays
the role of mechanical line shaft and drives the other slave
shafts by means of the transmission of control signals instead
456 IET Control Theory Appl., 2015, Vol. 9, Iss. 3, pp. 456–464
© The Institution of Engineering and Technology 2015 doi: 10.1049/iet-cta.2014.0477