## Servo System Applied in Industrial Sewing Machines

in the rapid development of the world textile industry,

the research on industrial sewing machines have been focused

on higher precision, more energy-saving, lower cost, higher

speed, multiple-function, more intelligence. In order to

achieve all these performance indexes, the main problem is to

develop an effective servo system. And the PMSM based

servo systems have attracted more and more researchers, for

which has several inherent advantages compared with other

types electric machinery, such as high power density, high

power factor, high torque to current ratio, high efficiency, low

inertia, rugged construction, easy for maintenance and so

on[1,2].

The PID control is one of the early developed control

strategies. Due to its simple algorithm, good robustness and

reliability, it has been widely used to design position, speed

and electric current loop controller in industrial sewing

machine servo system. And classic PID control based, such as

increment PI control, fuzzy PID control, Neural PID control ,

multi-segment PI control are also adopted[3,4]. However, the

classical control strategies have some disadvantages, such as,

large overshoot, long adjustment time and so on. It is difficult

for the PMSM servo system to realize high precision control.

PMSM servo system is a typical non-linear time-variant

control system. Many intelligent control methods such as

fuzzy control, self-adaptive control, neural network control,

sliding mode variable structure control, genetic algorithm

control are adopted to solve the problems. Many scholars have

done a lot of meaningful researches on these control methods

[5,6]. But it still has some difficult to realize.

The ADRC can not only arrange the transient process, but

also estimate and compensate the total disturbances on the

system, which can highly improved the performance of the

PMSM servo system. In this paper, ADRC is used as a speed

loop regulator in the industrial sewing machine servo control

system[7,8]. Simulation results indicated that, compared with

conventional PID control servo system, the proposed control

method has better dynamic performance, and stronger

robustness to the system disturbance.

II. MATHEMATICAL MODEL OF THE PMSM

PMSM is an important category of the electric machines,

in which the rotor magnetization is created by permanent

magnets attached to the rotor. Many mathematical models

have been proposed for different applications, such as the

abc-model and the two axis dq-model. Due to the simplicity of

the two axis dq-model, it becomes the most widely used model

in PMSM engineering controller design. The dq-model offers

significant convenience for control system design by

transforming stationary symmetrical AC variables to DC ones

in a rotating reference frame. vs enterprises

Based on the dq reference frame theory, the mathematical

model of the PMSM can be expressed as the following

equations:

1) Circuit equation

( ) d s d r q q

d

d u R i L i

dt

L di = − + ω (1)

( ) q s q r d d r f

q

q u R i L i

dt

di

L = − − ω − ω Ψ (2)

2) Electromagnetic torque equation:

[ ( ) ] e p f q d q d q T = n Ψ i − L − L i i (3)

3) Motion equation

e L d

r T T T

dt

J dω = − − (4)

Where d i , q i represent the current of the d-axis and

q-axis; d u , q u represent the voltage of the d-axis and

q-axis; d L , q L represent the inductance of the d-axis and

q-axis; s R is the stator resistance; r

ω is the rotor speed;