A Remote Laboratory Experiment for 4-Quadrant Control of a DC Motor ERDAL IRMAK, 1 RAMAZAN BAYINDIR, 1 ILHAMI COLAK, 1 MUSTAFA SOYSAL 2 1 GEMEC-Gazi Electric Machines and Control Group, Faculty of Technical Education, Department of Electrical Education, Gazi University, Ankara, Turkey 2 Department of Electric, I ˙ skitler Vocational High School, I ˙ skitler, Ankara, Turkey Received 3 November 2008; accepted 6 April 2009 ABSTRACT: This study presents development of the system architecture to perform laboratory experiments over the Internet for electrical engineering education. Design and implementation of four-quadrant speed control experiment for a direct current (DC) motor is given in the article as a sample remote experimental study. The system designed consists of four main parts as a client, a server, a data acquisition unit and an experimental set with a control unit. MATLAB web server (MWS) is used to send and receive data or graphics over the Internet. While the experiment is being operated, the real experimental set placed in the laboratory can be monitored by the remote user. Evaluation results show that the system designed accelerates the learning period, increases the concentration on the experiment and provides a safe environment for four-quadrant speed control experiment of a DC motor. ß 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20361 Keywords: web-based laboratory; remote experimentation; real-time systems; DC motor; speed control INTRODUCTION Remote laboratories are increasingly being gained popularity according to rapid developments of the Internet technology. Since they can be considered as a serious alternative to the classical local laboratories, many institutions all over the world use remote laboratory techniques. Thanks to the remote laboratories, increasing learners’ motivation and enhancing learning effect can be provided. Remote laboratories offer users to use more expensive laboratory devices which cannot be available in conventional local laboratories because of the hard- ware inadequacy, to access them without time and place limitation, to share these devices with more people geographically remote located, to ensure a safe laboratory environment. Recently, usage of the web-based laboratory in engineering education has been growing. A lot of Correspondence to I. Colak ([email protected]). ß 2009 Wiley Periodicals Inc. 1
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A Remote LaboratoryExperiment for 4-QuadrantControl of a DC Motor
ERDAL IRMAK,1 RAMAZAN BAYINDIR,1 ILHAMI COLAK,1 MUSTAFA SOYSAL2
1GEMEC-Gazi Electric Machines and Control Group, Faculty of Technical Education,
Department of Electrical Education, Gazi University, Ankara, Turkey
2Department of Electric, Iskitler Vocational High School, Iskitler, Ankara, Turkey
Received 3 November 2008; accepted 6 April 2009
ABSTRACT: This study presents development of the system architecture to perform
laboratory experiments over the Internet for electrical engineering education. Design and
implementation of four-quadrant speed control experiment for a direct current (DC) motor is
given in the article as a sample remote experimental study. The system designed consists of
four main parts as a client, a server, a data acquisition unit and an experimental set with a
control unit. MATLAB web server (MWS) is used to send and receive data or graphics over
the Internet. While the experiment is being operated, the real experimental set placed in
the laboratory can be monitored by the remote user. Evaluation results show that the
system designed accelerates the learning period, increases the concentration on the
experiment and provides a safe environment for four-quadrant speed control experiment of
a DC motor. �2009 Wiley Periodicals, Inc. Comput Appl Eng Educ; Published online in Wiley InterScience
(www.interscience.wiley.com); DOI 10.1002/cae.20361
Keywords: web-based laboratory; remote experimentation; real-time systems; DC motor;
speed control
INTRODUCTION
Remote laboratories are increasingly being gained
popularity according to rapid developments of the
Internet technology. Since they can be considered
as a serious alternative to the classical local
laboratories, many institutions all over the world use
remote laboratory techniques. Thanks to the remote
laboratories, increasing learners’ motivation and
enhancing learning effect can be provided. Remote
laboratories offer users to use more expensive
laboratory devices which cannot be available in
conventional local laboratories because of the hard-
ware inadequacy, to access them without time and
place limitation, to share these devices with more
people geographically remote located, to ensure a safe
laboratory environment.
Recently, usage of the web-based laboratory
in engineering education has been growing. A lot ofCorrespondence to I. Colak ([email protected]).
� 2009 Wiley Periodicals Inc.
1
examples on web-based laboratory can be found
in literature. Some examples area applied for
remote laboratories are chemical engineering [1],
numerically controlled machining [2], torsion
laboratory [3], a greenhouse scale model [4], a virtual
instrument detecting spatial saliencies in induction
machines [5], the automatic control of interconnected
tanks [6] and a virtual laboratory for neuro-fuzzy
control of induction motors [7]. In addition, recently,
several architectures and several techniques have been
presented to develop a remote laboratory for electrical
engineering education [8]. In Ref. [9], a distance
programmable logic controller (PLC) programming
course employing a remote laboratory is introduced.
The system is based on a flexible manufacturing cell
and the problem proposed for the students is the
automation of such a cell with commercial PLCs.
Similarly, another remote laboratory facility is also
presented in Ref. [10] in which PLCs and oscillo-
scopes are fully integrated into the same industrial
network combined with a supervisory control and data
acquisition (SCADA) supervision system. The first
computer works as a system supporter and the other
one works as a system controller. In Ref. [11], an
extending network communication module is applied
to the traditional electrical machine control unit
and J2EE Platform technology is used in electrical
machine control. A subminiature permanent direct
current (DC) motor is connected to the server via
RS232 serial port and is also used as an object for
remote control. In Ref. [12], development and
experimental evaluation of an e-laboratory platform
in the field of robotics are presented. In the study, the
results of a pilot experimental study are also presented
providing a comparative evaluation for three training
modalities, which are real, remote, and virtual training
on robot manipulator programming. Similarly, remote
robotic laboratories are also studied in Ref. [13]
presenting control of a web-based semi-autonomous
mobile robot, in Ref. [14] introducing virtual
control of an industrial robot, in Ref. [15] showing
mobile robotics virtual laboratory, and in Ref. [16]
describing Internet-based telerobotic system. A dif-
ferent approach for remote laboratories is presented in
Ref. [17]. The article proposes different, low-cost
solutions for integrating a remote laboratory in a
hypertext of electrical measurement and shows how
they have been implemented in the realization of a
remote experiment on a three-phase three-terminal
load. A virtual laboratory is also presented in Ref.
[18] that gives the possibility of study on the grid
connection of a synchronous generator. In Ref. [19],
the development of an Internet-based remote-access
control system is presented and a DC motor control
experiment is given as an example to illustrate the
design presented. The system is composed of an
internal distributed system and an application system
linked by a data acquisition interface card. Similarly,
remote DC motor experiments operated over the
Internet are also presented in Refs. [20�22]. Several
remote laboratory applications for electrical machines
experiments can also be found in Ref. [23] presenting
two laboratory experiments as an AC motor control
application and a web-based temperature measure-
ment, in Ref. [24] introducing digital signal processor
(DSP)-based control schemes for motor drive appli-
cations and control system for 3-phase brushless
DC motor, in Ref. [25] describing a distance learning
system which includes theories and operation
experiences of electric machinery experiments, and
in Ref. [26] performing a prototype client-server
system for remotely conducting experiments on
brushless DC motors.
In this article, development of the system
architecture to perform laboratory experiments over
the Internet for electrical engineering education is
presented. Since DC motors are widely used as an
actuator in industrial applications because of their
wide adjustability range and understanding the
DC motor behaviors is a useful study for analysis
and control of many industrial applications as well,
four-quadrant speed control experiment for a DC
motor is given as a sample remote experimental study
for the purpose of illustrating the system designed.
Although, several remote laboratory applications
about the DC motors have been presented in the
literature recently, web-based four-quadrant control
operation with real-time experiments has not been
studied in detail. Another difference of the system
presented in this study is usage of the MATLAB with
its powerful numeric computation capabilities, highly
sophisticated visualization and graphic tools for
analyzing operations. Although MATLAB has been
already used for the virtual and remote laboratory
applications recently [27�34], an Internet-based
remote electrical machines laboratory based on
MATLAB and its web server toolbox has not been
studied. Authors have tested the system architecture
developed for different applications recently and the
results obtained from the tests have also been reported
in Refs. [35�37]. As a difference from the other
studies achieved by the authors, a more detailed and
more complex architecture including remote experi-
mentation is described in this article.
The system developed accelerates the learning
period with its interactive frame as well as instructive
structure, increases the concentration on the experi-
ment due to visual feedbacks, decreases the faults
2 IRMAK ET AL.
because of using quite powerful and flexible hardware
units, and finally provides a safe experimental
environment on account of its secure structure isolated
from dangerous conditions such as high voltage
and rotating equipments. Consequently, a web-based
real-time and open laboratory has been presented
that offers to researchers and students not only
learning and using latest technologies and concepts
but also realizing, controlling, monitoring, recording,
discussing, and testing remote applications.
SYSTEM ARCHITECTURE
Since the main objective of this study is to perform
laboratory experiments over the Internet, a common
client/server architecture is constituted. A simplified
block diagram of the system is given in Figure 1.
Thanks to the system architecture designed, all
operation steps are executed from the server while
the experiment is being operated remotely, so
clients do not need to install any additional software.
This is important for clients. Because, most of the
Internet users are accustomed to use web pages by
simply clicking their mouse on the links, and they do
not want to download any software due to possibility
of virus infections. In this regard, the system
developed in this study can be accepted by most
people.
Four-quadrant speed control experiment for a
separately excited DC motor is prepared in this
article as a sample remote experimental study to
illustrate the system developed. DC motors, as
components of electromechanical systems, are widely
used as actuating elements in industrial applications
for their advantages of easy speed and position control
and wide adjustability range [38,39]. Consequently,
examination of DC motor behavior constitutes a
useful effort for analysis and control of many practical
applications [39�41]. Speed control of DC motors
can be implemented easily by changing armature
voltage. In this study, a four-quadrant motor control
unit is designed firstly to achieve the speed control
operation of the DC motor. The control unit designed
consists of a control circuit given in Figure 2, a
PIC18F4520 microcontroller used for generating
PWM signals, an LCD used for local monitoring, a
full bridge converter used for removing dead time
delay, and other necessary circuits and equipments.
Figure 3 depicts the control unit developed. It has
been tested with various experiments and results
obtained from the tests have been reported by the
authors recently, so more detailed information about
the control circuit can be found in Ref. [42].
Data transferring operations between the server
and the experimental set are achieved via a powerful
data acquisition (DAQ) board. The DAQ board is
placed on the PCI bus of the server. Control
commands required for operation are produced and
data obtained from the experimental set are measured
by the DAQ board in real time. MATLAB software
and its MWS toolbox are used for processing data on
the server and to communicate the server and client
in order. Additionally, a web camera and a network
camera transferring the frames captured to the Internet
directly with high-speed and high-resolution are used
for remote monitoring during the experiment is being
operated. A detailed block diagram of the system
architecture designed is given in Figure 4.
IMPLEMENTATION OF THE SYSTEM
The primary goal of this study is to develop an
advanced platform applicable to e-learning environ-
ments that allows students to perform laboratory
experiments from remote locations. In the study, a
remote laboratory experiment for four-quadrant speed
control of a DC motor is selected as a pilot study. The
system developed has been implemented at Gazi
University in Turkey. Figure 5 illustrates the complete
appearance of the experimental set which can be
accessed and performed over the Internet.
Figure 1 A simplified block diagram of the system
designed. [Color figure can be viewed in the online issue,
which is available at www.interscience.wiley.com.]
A REMOTE LABORATORY EXPERIMENT 3
The operational treatment of the system can be
investigated in four separate units as the client, the
server, the DAQ board and the DC motor control
unit. Although each unit executes different tasks,
all of them interact with each other continuously.
Figure 6 shows a simplified flowchart for remote
experimentation and tasks performed from each unit.
Tasks performed from each unit can be summarized as
following:
Client connects to the server firstly. Since web
pages about the experiment can be visited only by the
registered users, one who wants to use the system on a
client PC must register the system using the member
entrance system. Once the user successfully logins the
system as a client, he/she can open either the remote
experimentation page directly or the theoretical
information pages to obtain some information about
the experiment before performing it. On the remote
experimentation page, the user sets the operational
parameters and sends them to the server. Results
obtained are shown on the user’s screen as graphical
format automatically after finishing the experiment.
The user can repeat the experiment again and again if
he/she desires.
Server responses the remote connection requests
sent from clients and checks users who want to
enter the system as registered or not. It serves either
the theoretical information pages or the remote
experimentation page according to the preferences
of users. When a user wants to perform experiment
remotely, server receives operational parameters
set from the user on the remote experimentation
page. Then it transfers data just received into the
MATLAB m-file written previously via the MWS.
The m-file is the main application software and
includes application routines. Analog input (AI)
object for reading data on the experimental set
and digital input/output (DIO) objects are created
automatically by means of DAQ toolbox. The
experimental set is controlled from the DIO object
and data measured are read from the AI object
continuously as long as the experiment is being
operated. When the experiment is finished, the
server plots figures using data received from the set,
Figure 2 Speed control circuit for four-quadrant DC motor.
Figure 3 Control unit designed. [Color figure can be viewed in the online issue, which is available
at www.interscience.wiley.com.]
4 IRMAK ET AL.
converts them into the JPEG format and sends them to
the client respectively.
The DAQ board is activated and controlled from
the server according to the commands into the m-file.
A connection is established between the server and the
experimental set via the DAQ board after the DIO
object starts to run. DIO subsystem of the board sends
signals to the experimental set and the set starts to
operation instantly. Once the operation is started, AI
subsystem of the DAQ board is activated and receives
data from the experimental set. Both subsystems of
the board are deactivated from the server after the
experiment is completed.
The Experimental Set is self-controlled by the
PIC18F4520 microcontroller with 4 pulse width
modulation (PWM) outputs as described in System
Architecture Section. Recently, PIC series micro-
controllers have been used for motor control applica-
tions as well as industrial applications in several
studies and it has been reported that the results
obtained were quite satisfactory [43�46]. In the
system developed, when a signal is received from
the DAQ board that declares starting of operation,
PIC18F4520 starts to produce PWM signals and
applies them to the driver circuit. Thus, DC motor
starts to run. Thanks to the PWM signals produced
from the PIC for speed control as well as the direction
signals produced from the PIC similarly for changing
Figure 4 A detailed block diagram of the system
architecture designed. [Color figure can be viewed in the
online issue, which is available at www.interscience.wiley.
com.]
Figure 5 Complete appearance of the experimental set.
[Color figure can be viewed in the online issue, which is
available at www.interscience.wiley.com.]
A REMOTE LABORATORY EXPERIMENT 5
the direction of the motor, the motor runs in the four
quadrants respectively. The PWM signals, the motor
current, the voltage, and the speed values are
measured and then collected in PIC during operation
of the motor. A current transformer, a voltage
transformer, and an encoder are used for these
measurements. These values measured are transferred
to the server via the AI subsystem of the DAQ board.
When a signal is received that declares finishing
of operation, PIC resets all signals to the initial
conditions to get ready for next operation.
The experimental set also includes a special
measurement device. This device is connected to the
DC motor and it measures the speed and the torque of
the motor in real time. The measured values are
displayed on LCD screens of the device. One of the
cameras used in the system developed in this study
monitors the screen of the measurement device
continuously. Thus, the remote users can see the
real-time operation values of the motor.
EXPERIMENTAL RESULTS
Web-based operation of the four-quadrant speed
control experiment of a separately excited DC motor
Figure 6 A simplified flowchart for remote experimentation.
6 IRMAK ET AL.
is given in this part. Parameters of the DC motor
used in this study are 2 kW, 110 V armature voltages,
5 A armature current, 170 V excitation voltage, 1.5 A
excitation current, and 1,200 rpm speed.
Firstly, an online course is prepared for DC
motors including not only remote experimentation,
but also theoretical presentations, animations, and
simulations. Figure 7 shows a sample theoretical
presentation page designed.
Thanks to the e-course platform developed,
students can learn important and critical information
about the DC motors and they can do preliminary
studies before performing the experiment. Basic
HTML commands and PHP techniques as well as
several animation and graphic programs are used
in the theoretical information pages. Additionally, a
simple and reliable member management system is
designed. Thus, usage of the system is only allowed to
the registered users.
Once a user is ready for performing the experi-
ment, he/she can open the HTML input page designed
for remote experimentation. This page is designed as
quite simple and comprehensible for facilitating the
learning.
If the user desires, he/she can monitor the real
laboratory environment as well as the experimental
set from two different points remotely. For this aim,
the user should simply click on the Camera1 and
Camera2 links on the page. One of these cameras is a
standard web camera. The other one is a network
camera, so it operates independently from the server
and transfers captures to the Internet directly with
high speed and high resolution. The first camera
(web camera) monitors the general appearance of the
experimental set and the DC motor. Thus, users can
easily comprehend whether the motor is rotating or
not while the remote experiment is being operated
over the Internet. The second camera (network
camera) monitors the measurement devices. Thus,
the real-time operating values of the motor such as the
speed and the torque can be seen on the window
belonging to the second camera.
Figure 8 shows the HTML input page designed
for the remote experimentation. The user determines
and inputs parameters for operation on this page
and clicks on the Submit button. A connection is
established between the client computer and the
server after the Submit button is clicked on. Then,
Figure 7 A sample theoretical presentation page from the e-course. [Color figure can be viewed in
the online issue, which is available at www.interscience.wiley.com.]
A REMOTE LABORATORY EXPERIMENT 7
all operation steps as described in previous section are
executed from the server respectively. The HTML
input page also includes some useful hints as well as
the experiment procedure about the remote experi-
ment. Thus, the user can get information about the
operation before starting it.
Figure 9 shows the appearance of the web page
while the experiment is being operated from the
server. As shown on this figure, the experimental
operation executed from the server can be monitored
from the cameras. In the web page, a message box is
also appeared that is named as ‘‘Server Message.’’
Some information is given in this message box
including goings-on about the online operation. For
instance, if the experiment is being used from another
user at the same time, a warning message is appeared
in the message box automatically. Likewise, if the
experimental set is out of order due to a hardware
problem, the message box is used to inform the users
about the problem.
When the operation is completed, the HTML
result page is appeared on the monitor of the remote
user’s screen immediately. This result page includes
graphics which are plotted from the server using real
data measured from the experimental set. Several
graphics are generated and sent to the client related to
the experimental study such as the motor current, the
voltage, and the PWM signal generated for speed
control. These graphics are converted to the JPEG
format before they are sent to the client using
wsprintjpeg function of the MWS. Since the graphics
are as picture format, users can easily save them into
their PCs.
Figures 10�12 illustrate sample HTML result
pages including graphics plotted and sent to user after
a sample remote experimentation session. For this
session, the experimental set is activated over the
Internet along 5 s. According to choice of the user,
three different graphics are plotted by the server and
sent to user after the experimental session is finished.
These graphics are belonging to motor voltage, motor
current, and speed.
As seen in the Figures 10 and 11, the DC motor
operates in four quadrants. Namely, the motor
operates in Quadrant I (forward motoring) between
approximately 0.9 and 1.9 s where the motor voltage
and the motor current are in positive region. The
supply voltage is about 170 V and the motor current
drawn from supply is about 1 A during the steady-
state operation between 1.2 and 1.9 s. If the supply
voltage is cut off while the field current is still
available, the motor operates in Quadrant II (forward
Figure 8 HTML input page for remote experimentation. [Color figure can be viewed in the online
issue, which is available at www.interscience.wiley.com.]
8 IRMAK ET AL.
Figure 10 HTML result page including current graphic. [Color figure can be viewed in the online
issue, which is available at www.interscience.wiley.com.]
Figure 9 Appearance of the web page while the experiment is being operated. [Color figure can be
viewed in the online issue, which is available at www.interscience.wiley.com.]
A REMOTE LABORATORY EXPERIMENT 9
regenerating) between approximately 1.9 and 2.1 s
where the current is in negative region. Due to the
kinetic energy stored in the rotating mass, the motor
operates as a generator and feeds the loads. But, the
voltage produced during the Quadrant II decreases to
zero due to friction and windage losses of the motor.
In Quadrant III (reverse motoring) between about
3.1 and 4.2 s, the motor voltage and the motor
current are in negative region. Absolute values of
supply voltage and current in Quadrant III are
same as in Quadrant I. Finally, the motor operates
in Quadrant IV (reverse regenerating) between about
4.2 and 4.4 s in where the current is in positive region.
Similar to Quadrant II, the generated voltage reduces
to zero in Quadrant IV due to mechanical losses as
well as friction and windage losses of the motor.
The experimental set developed offers not only
four quadrant operation experiment but also speed
control experiment. For this aim, a PIC18F4520
microcontroller is used for generating PWM signals
that adjust the voltage value applied to the motor, so
the speed is controlled. The speed control operation
can be achieved at both no-load and loaded working
conditions. The interface used for this operation is
presented in the Figure 12. As seen in the figure
clearly, users should sign the relevant check-box
Figure 11 HTML result page including voltage graphic. [Color figure can be viewed in the online
issue, which is available at www.interscience.wiley.com.]
Figure 12 An extended appearance of the HTML input page. [Color figure can be viewed in the
online issue, which is available at www.interscience.wiley.com.]
10 IRMAK ET AL.
according to their own request about achieving loaded
or no-load experiment. Figure 13 presents HTML
output page and speed graphics for sample operational
sessions. It must be considered that, these graphics
are acquired from different sessions according to
Figures 10 and 11. As seen on the graphics given in
the Figure 13, when the motor is operated as loaded,
duration of the quadrant 2 and quadrant 4 are quite
short (approximately 0.05 s). On the other hand, when
the motor is operated as unloaded, duration of the
quadrant 2 and quadrant 4 are longer (approximately
0.4 s).
CONCLUSIONS
Design, development, and implementation of remote
laboratory application for electrical engineering
education are presented in this article. Four-quadrant
speed control experiment for a separately excited DC
motor is selected and realized as a sample laboratory
session to illustrate the functional process of the
system architecture.
Since most of the Internet users refrain from
downloading any special software on web pages,
workload on the client has been minimized by means
of authentic system architecture designed. Thanks to
the system developed, all operations are executed
from the server. Conversely, most of the remote
laboratory applications presented in the literature use
special software such as LabVIEW, Java applets, and
ActiveX. Usage of these software units requires
downloading and installing some special programs
or plug-ins. Disadvantage of using such applications is
not only hesitations felt by the users as just mentioned,
but also the slow response time occurred when the
experiment is being operated in real time according to
network conditions as well as hardware specifications
of the remote PC used for operation.
Furthermore, MATLAB is used for computing,
analyzing, and plotting the data obtained from the
experiment. As compared with the other software
such as Java, LabVIEW, and ActiveX used for such
applications in the literature, MATLAB is more
accomplished than others with its powerful numeric