Controller Design for a Permanent Magnet Linear
Synchronous Motor: a Singular Perturbation Method
YANG Chunyu, HAN Yuchen, SHI Yuxiang, ZHOU Linna
School of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221116, P. R. China
E-mail: chunyuyang@cumt.edu.cn, han19900206@sina.com, zs13060105@cumt.edu.cn, linnazhou@cumt.edu.cn
Abstract: This paper considers the design problem of a three-closed-loop controller for a permanent magnet linear synchronous
motor. Taking into account the multiple time-scale property of the system, the design is achieved in two stages. In the first one,
the inner loop (current-loop) controller is designed based on the singular perturbation theory and pole assignment technique. The
controller gains can be constructed by solving a set of well-defined linear matrix inequalities. In the second stage, with the ob-
tained controller gains, a homotopy algorithm is formulated to design the velocity- and position-loop controllers simultaneously.
Simulation is given to illustrate the proposed results.
Key Words: Permanent magnet linear synchronous motor, Singularly Perturbed system, Pole assignment, Homotopy algorithm
1 Introduction
Compared with rotary motors, permanent magnet lin-
ear synchronous motors (PMLSMs) have many advantages,
such as no backlash and less friction, high acceleration and
high precision and no conversion device [1, 2]. Thus differ-
ent PMLSMs have been used in numerous engineering ap-
plications, for example, electromagnetic aircraft launch sys-
tems (EMALS) [3], machine tools [4], maglev vehicles [5],
and workshop transportation [6].
Controller design for PMLSMs has attracted much atten-
tion and many advance control methodologies have been
modified to control PMLSMs. In [7], an iterative learning
variable structure controller was established and achieved
the fast point-to-point motion. In [8], an H
∞
robust con-
trol method was proposed in term of linear matrix inequal-
ities (LMIs). To deal with the state-dependent uncertainties
and bounded nonlinearities, a nonlinear adaptive robust con-
troller with saturated actuator authority was designed in [9].
A sliding mode controller basing on fuzzy neural network
(RFNN) was proposed in [10]. The RFNN can estimate
the real-time lumped uncertainty for the position control of
PMLSMs. In [12], a discrete adaptive sliding-mode (DASM)
controller was proposed, which can guarantee system stabil-
ity for both regulation and tracking tasks.
Although the above mentioned design methods have been
shown to have certain advantages in some aspects, PID or PI
control is the most popular scheme in practical applications
and most of the commercial motion controllers adopt PID or
PI control structure [13]–[15]. This paper will consider the
design problem of the three-closed-loop controller shown in
Fig. 1. The three-closed-loop control system consists of a
current-loop, a velocity-loop and a position-loop. The cur-
rent error and velocity error are regulated by PI controller
separately and position error is regulated by a proportional
controller. In this control system, there is not a differential
controller because it usually amplifies the effect of external
This work was supported by the National Natural Science Foundation
of China (61374043), the Jiangsu Provincial Natural Science Foundation of
China (BK20130205), the China Postdoctoral Science Foundation funded
project (2013M530278, 2014T70558), the Fundamental Research Funds for
the Central Universities (2013QNA50, 2013RC10, 2013RC12, 2013XK09)
and the Natural Science Foundation of Liaoning Province (201202201).
disturbances. PI controllers have been shown to be compe-
tent to regulate the current and velocity. In position-loop,
only a proportional controller is used since a PI controller
may cause large overshoot. Thus most commercial motion
controllers, for example, ACS motion controller, adopt such
a structure.
The aim of this paper is to propose an efficient method
to construct the controller gains K
1
,K
2
,K
3
,K
4
,K
5
. First,
the model of the PMLSM is recalled and the model for the
three-closed-loop control system is established. There ex-
ist some nonlinear terms on K
i
in the closed-loop model,
thus it is difficult to design the five gain matrices simultane-
ously. Then, in view of the multiple time-scale property of
the system, we separate the current-loop from the whole con-
trol system, which leads to a linear singularly perturbed sys-
tem with a standard state feedback controller. By using the
singular perturbation theory and pole assignment technique,
the current-loop PI controller design is reduced to solving a
set of LMIs. With the obtained gain matrices, a homotopy
algorithm is formulated to design the velocity- and position-
loop controllers simultaneously. Finally, simulation is made
to illustrate the proposed results.
2 System description
2.1 PMLSM model
Under standard assumptions [11], the PMLSM model in
d-q coordinates is as follows.
di
d
dt
= −
R
L
d
i
d
+
L
q
L
d
π
τ
vi
q
+
1
L
d
u
d
, (1)
di
q
dt
= −
R
L
q
i
q
−
π
τ
v(L
d
i
d
+ ψ)+
1
L
q
u
q
, (2)
dv
dt
=
3nπ
2τM
(ψi
q
+(L
d
− L
q
)i
d
i
q
) −
1
M
(F
l
+ F
d
), (3)
ds
dt
= v, (4)
Proceedings of the 34th Chinese Control Conference
Jul
28-30, 2015, Han
zhou, China
4453