Study of the shearer for the possibility of stabilizing
the load current in the cutting electric drive
Shprekher D.M.
Kolesnikov E. B.
Zelenkov A.V.
Tula State University
Tula, Russia
shpreher-d@yandex.ru
Novomoskovsk branch (institute) of D.
Mendeleyev University of Chemical
Technology
Novomoskovsk, Tula region, Russia
Kolesnikov55@mail.ru
Tula State University
Tula, Russia
sashazelnkv@mail.ru
Abstract — A mathematical model of a shearer-loader with an
integrated forward motion drive and an automatic control system
(ACS) with a PI controller has been developed. It is shown that
ACS allows reducing dynamic loads on the mechanical parts of a
shearer-loader electric drives in conditions of a sudden change in
coal strength. The results of transient processes arising from a
stepwise change in the strength of coal are presented. It is shown
that when the combine is working on weak coals, there is a
decrease in the ACS speed by almost 1.5-2.0 times relative to the
speed of the ACS when the combine is working on strong coals. To
stabilize the speed of the ACS of the cutting current regulator, it is
proposed to adjust the parameters of the regulator depending on the
resistance of the coal to cutting. The conclusion is made about the
need for the use of intelligent regulators.
Keywords — shearer-loader, forward motion drive, cutting
drive, mathematical model, transients, coal strength, control system
I. INTRODUCTION
One of the areas of the technical process in the coal
industry is the widespread introduction of systems and means
of automation of mining equipment and, first of all, shearers.
Existing mining shearer-loader extracting minerals (coal,
silvinites) have drive of shearer drum and drive of forward
motion which interact among themselves at destruction of a
layer of a mineral through executive body- fig. 1 [1.2].
A coal seam is a heterogeneous mass with the presence of
solid inclusions of the rock, which, when destroyed, lead to
the appearance of strong shock loads on the executive body of
the shearer. Thus, the cutting drive is one of the weakest parts
of the shearer [3].
Automation of the operation of the shearer should increase
their productivity due to a more complete use of the energy
capabilities of the electric drive and reduce the likelihood of
"induction motor stalling", increase durability due to reduced
overloads of the electric motor and the mechanical part, and
hence their accident rate.
In the control system of the mining shearer-loader, a
cutting current (load) regulator can be applied, the purpose of
which is to prevent overload or stalling of the cutting drive
motor, by changing the feed rate of the combine when the
resistance of the mineral to cutting and the working conditions
of the combine [4].
Executive body
Drive of shearer drum
Drive of forward motion
Fig. 1. The appearance of the mining shearer-loader
However, this control system is forced to work under the
conditions of parametric disturbances, which are caused by
changes in the strength of coal, which is of a random nature,
wear and blunting of the cutters of the executive body of the
shearer.
The action of perturbations causes a change in the
transmission coefficient of the control object, which leads to a
deterioration in the quality of transients in the system and can
lead to a loss of stability of the control system.
A control object in such a system is a shearer together with
industrial process, control – the speed of forward motion of
the shearer, and the main disturbance is the change in the
strength of the coal.
II. LITERATURE ANALYSIS
the shearer, its electromechanical system must be considered
as several constituent energy parts. A frequency converter for
powering an adjustable electric motor, an electromechanical
converter (induction motor) for converting electrical energy
into mechanical energy, a mechanical converter (transmission)
to ensure the technological process.
The executive body of the shearer is connected to an
asynchronous squirrel-cage rotor motor and through the
transmission carries out the destruction of the rock mass.
The interaction between the cutting electric drive and the
drive of shearer drum takes place through the coal face, and
the loads are controlled by the operator in manual or automatic
mode, analyzing the signals from the sensors. Changing the
forward speed of the shearer is implemented by means of a
frequency-adjustable drive of shearer for motion forward [10].
The work of domestic and foreign scientists is devoted to
the development of control systems that increase the
productivity of the shearer in a in the conditions of change of
disturbing influences in wide limits. However, a number of
unresolved issues remain that determine the direction for
improving the control systems of the shearer (coal mining
technological processes) [3-7]. In addition, additional research
is required to clarify the mathematical model for the joint
operation of the shearer and the coal face.
The electrical part of the drive. Matlab Simulink was
used as a modeling tool. To speed up the simulation, it was
proposed that the induction motors of the forward motion and
cutting drives be presented in the form of known transfer
functions with the following parameters: moment of inertia
JIM, electromagnetic time constant TE, and momentum transfer
coefficient β (Fig. 2) [11].
The control system of the shearer while limiting the cutting
current in automatic mode is characterized by increased
complexity. Firstly, the shearer is a complex object consisting
of the following closely interacting mechanical and
electromagnetic systems: an asynchronous electric motor (IM)
and a transmission of drive for motion forward, an
asynchronous electric motor (IM) and a transmission of drive
for cutting, executive body and the shearer's body. Secondly, a
change in the perturbing effects by which the regulation is
carried out leads to a change in the static characteristics of the
executive body, namely, its angle of inclination. Thirdly, the
motion forward speed of the shearer sets the rate of change in
time of disturbing influences, which is the low-frequency
component of the resistance of coal to cutting. In such
automatic control systems, complicated by the presence of
feedback with a variable gain in the disturbance function and
the presence of a variable in a wide range of gain of one of the
components of the control object (also in the disturbance
function), the stability of control systems and the quality of
transient processes is especially urgent task [9].
(1  TE p) M IM  (0  IM );
III. THE MAIN CONTENT
The most effective analysis tool is the method of
mathematical modeling. For this, it is necessary to develop a
correct mathematical model of the dynamic functioning of all
subsystems in the shearer when forming maximum loads,
which have a significant negative impact on the reliability
parameters of the shearer. In this work, the UKD300 coal
processor [9] was adopted as an object of transient research.
To draw up a structural diagram describing the
electromechanical processes that occur during the operation of
The equations describing the operation of an induction
motor are as follows:
M IM  M red  J IM pIM .
(1)
In its turn

J
2М max
1
2f
; 0 
; TM  IM ,
; TE 

0 smax
0 smax
pp
(2)
where M max - is the critical (maximum) moment of the
induction motor to drive cutting or drive moving forward;
smax - critical slip of an induction motor to drive cutting or
drive to moving forward; p p - the number of pole pairs of the
electric motor;  0 - the angular frequency of the ideal idle
speed of the induction motor; IM - the angular frequency of
rotation of the rotor of an induction motor, TM electromechanical time constant.
This system of equations is implemented in the form of the
structure shown in Figure 2.
Since the induction motor of the cutting drive is
unregulated, and it is important for us to know the value of its
current only (the frequency of rotation is constant), it can be
represented by the transfer function proposed in [12, 13, 14],
assuming that the moment in the working part of the
mechanical characteristic cutting motor is proportional to its
current ( M c  1 I c ) we get:
kI
WIM.c  p  
I c ( p)
1 / KI

,
M c ( p) TЭTМ p 2  TМ p  1
(3)
where k I - is the by current transfer coefficient of the
asynchronous motor for cutting drive.
The calculation procedure of k I - is presented in [15], and
the parameters of an induction motor for cutting drive are
given in [9].
The transfer function of the frequency converter (FC) can
be represented by the gain:
WFC ( p)  K FC .
(4)
The implementation of the model of the transmission drive
to motion the shearer forward according to (5) is shown in Fig.
3.
The mechanical part of the drive for moving the
shearer forward. The subsystem for moving the combine
body is described by the following equation [10, 16], and its
implementation is shown in Fig. 4.
msh
dVm
 Сst (st Rst  xm )  st (st Rst  Vm )  Fr ,
dt
(7)
where Fr is the force of resistance to movement of the shearer
mass mc, equal to the sum of the forces from resistance to
movement of the screw and resistance to movement of the
combine along an inclined axis [9, 13].
Fr  k f (
Fig. 2. Block diagram of the drive of shearer for forward motion (or cutting)
of induction motor (исправить)
Transmission for driving the shearer for motion
forward. In the mining shearer loader, two reduction of
transmission are used: between the cutting electric motor and
the screw and between the electric motor providing motion for
the combine forward and the shearer propeller. The drive of
shearer for forward motion rotates the asterisk cycloid gear.
The model transmission of shearer for forward motion is
implemented according to the classical system of equations
[10, 16]:
J tr
dst
 M tr itr tr  M r.tr ,
dt
M tr  ctr (IM  st itr )  btr (IM  st itr ),
(5)
Where M tr - is the moment on the input shaft of the
transmission; M r .tr - moment of resistance on the output shaft
of the transmission; IM, IM - respectively, the angle of
rotation and the rotation speed of the rotor of induction motor
at forward motion the shearer, st st - respectively, the angle
of rotation and the rotation speed of the drive star (pinion
gear) for forward motion the shearer; itr - gear ratio of the
transmission for the drive forward motion; J tr - moment of
inertia of the transmission for the drive forward motion; сtr, btr
- respectively, the stiffness and viscosity coefficients of the
transmission for drive of shearer forward motion; tr transmission efficiency.
M r.tr  Сst Rst (st Rst  xm )  st Rst (st Rst  Vm ),
(6)
where сst, bst - respectively, the stiffness and viscosity
coefficients of the pinion gear ( star) of the shearer; xm, Vm respectively, the movement and linear speed of the combine
(speed movement forward); Rst - is the radius of the drive star
(pinion gear).
Frm
 msh gfk cos),

(8)
where  - is the overall efficiency of the movement
mechanism of the shearer; fk - coefficient of friction of the
shearer on the guides of the conveyor; - angle of incidence
(rebellion) of the reservoir; G - is the weight of the shearer;
Frm - is the force of resistance to the forward movement of the
combine; g is the acceleration of gravity; kf - coefficient taking
into account additional resistance to movement of the combine
is taken equal to 1.4.
Transmission for cutting drive. The Executive body and
the transmission for the cutting drive have their eigenvalues
own rigidity and viscosity. To obtain the transfer function of
the transmission for the cutting drive ( Wtr .c ), we rewrite the
system (5) in the operator form, taking the control action by
speed equal to zero (  IM  0 ) . As a result, we obtain:
Wtr .c  p   М tr  p  / М r.tr  p   [(btr.c / ctr.c ) p  1]/{(itr.c J tr .c / ctr.c ) p 2 
 [tr.c (btr.c / c tr.c ) p  1]}.
(9)
Executive body. A shearer is a element whose output
values are the moment of cutting resistance forces MEB and the
component of these forces in the direction of the combine
forward movement, and the input quantities are the control
action (forward speed of the combine Vm) and external
disturbance forces (coal resistance to cutting
A ).
The transfer function of the executive body for the control
action [10]:
WEB ( p )  M EB ( p)/Vm ( p ) 
 K EB / [( 1 / 12) 2 p 2  (1 / 2)p  1]
(10)
where KEB is the transfer coefficient of the executive body on
managing influence;  - is the delay constant by the formation
of coal shavings (   1 / ( z c ) ); z - the number of incisors in
one cutting line; c - frequency of rotation of the screw of the
cutting drive.
Fig.3. Model of the transmission drive to motion the shearer forward
Fig. 4. Model of the mechanical part of the forward motion drive (housing) of the shearer
The process of forming land shavings is subject to the law
[17]
t
h( t ) 
 Vп ( t )dt
or h( p )  Vп  p   ( 1  e p ) / p
t 
(11)
where kp - is the coefficient taking into account the weakening
of the resistance to cutting of the material in the cutting zone
and the parameters of the auger cutters; REB - radius of the
screw (executive body), h(t) - the thickness of the coal
shavings
In turn, the process of formation (creation) of coal
shavings is determined by the transfer function of the form
[14]:
Wc .sh  p   h( p) / Vm ( p)  (1  e  p ) / p 
  / [( 1 / 12 ) 2 p 2  (1 / 2)p  1].
(12)
Combining equations (10) - (12), we obtain the transfer
function of the interaction of cutting electric drive and the
electric drive of forward movement of the combine
WEB ( p)  M EB ( p) / Vm ( p) 
 A  k p  z  REB   / [(1 / 12 ) 2 p 2  (1 / 2)p  1].
where Bc - is the parameter characterizing the interaction of
the cutting electric drive, the electric drive for moving the
combine and the coal face.
Current sensor. The analog signals from the primary
converters of the stator current are converted using an analogto-digital converter into digital signals.
The moment of resistance to cutting is [13]:
M EB  A  k p  z  h(t )  REB ,
FEB / Frm  ( M EB / REB )/( M rm / Rst )  Bc  1 / 0,7 , (14)
(13)
The relationship of the influence of the mechanical
properties of the coal face on the power parameters of the
cutting electric drive and the electric drive for moving the
combine can be taken constant [15]:
The current sensor gain is the ratio of the output voltage to
the measured input parameter. The transfer function of the
current sensor is presented in the form:
WCS ( p)  K CS  uCS / I C ,
(15)
where uCS - is the output voltage of the current sensor
corresponding to the current value the current of the cutting
motor; IC - current of the cutting motor.
Based on the above considerations, using the formulas (1)
- (15), a simulation model of the control system (CS) of the
shearer with the calculated parameters for the stabilization
mode of the cutting current was compiled (Fig. 5).
In the simulation model of the control system of the
shearer (Fig. 5), a block has been introduced to simulate
changes in the resistance of coal to cutting.
When cutting a homogeneous coal seam, the resistance to
cutting can be modeled at a constant value. When the
formation with solid inclusions is destroyed, the resistance to
cutting increases sharply, exceeding the nominal one by 1.7–2
times [2].
Fig. 5. The simulation model of the control system of the shearer in the stabilization mode of the cutting current with a PI controller
In the work, the obtained model was used to study the
electromechanical processes occurring in a shearer with
automatic control of the current of the cutting drive electric
motor and with a stepwise change in the resistance of coal to
cutting and the work of the combine on weak and strong coals.
As a result, we obtained the oscillograms shown in Fig. 6, 7.
From the oscillograms (Fig. 6) it can be seen that with a
stepwise change in the resistance of coal to cutting in the
range from 350 N/mm to 500 N/mm, the speed of the cutting
current regulator is 0.4 s with a load surge, at reset a load- 0.5
s. Furthermore, the maximum current value of the cutting
motor is 170 A.
It can be seen from the oscillograms (Fig. 7) that with a
stepwise change in the resistance of coal to cutting in the
range from 250 N/mm to 400 N/mm, the speed of the cutting
current regulator is 0.6 s with a load surge and 1.0 s, at reset a
load. Wherein, the maximum current value of the cutting
motor is 195 A.
t,c
Fig. 6. Oscillograms of the automatic control system under a stepwise change in the resistance of coal to cutting in the range from 350 N/mm to 500 N/mm
t,c
Fig. 7. Oscillograms of the automatic control system under a stepwise change in the resistance of coal to cutting in the range from 250 N/mm to 400 N/mm
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