Low cost Real Time Centralized Speed Control of DC Motor Using Lab View -NI USB 6008

International Journal of Power Electronics and Drive System (IJPEDS)
Vol. 7, No. 3, September 2016, pp. 656~664
ISSN: 2088-8694, DOI: 10.11591/ijpeds.v7i3.10478  656
Journal homepage: http://iaesjournal.com/online/index.php/IJPEDS
Low cost Real Time Centralized Speed Control of DC Motor
Using Lab View -NI USB 6008
C. Bharatiraja*, JL Munda**, Ishan Vaghasia**, Rajesh Valiveti**, P Manasa**
*Department of Electrical and Electronics Engineering, E&T, SRM University, Kattankulathur Campus, India
**Centre for Energy and Electric Power Tshwane University of Technology, South Africa
Article Info ABSTRACT
Article history:
Received Nov 12, 2015
Revised Mar 9, 2016
Accepted Apr 10, 2016
DC motors are an outstanding portion of apparatus used in automotive and
automation industrial applications requiring variable speed and load
characteristics, due to its ease of controllability. Creating an interface control
system for multi DC motor drive operations with centralized speed control,
from small-scale models to large industrial applications is in much demand.
By using Lab VIEW (laboratory virtual instrument engineering workbench)
as the motor controller, we can control a DC motor for multiple purposes
using single software environment. The aim of this paper is to propose the
centralized speed control of DC motor using Lab VIEW. Here, Lab VIEW is
used for simulating the motor, whereas the input armature voltage of the DC
motor is controlled using a virtual Knob in Lab VIEW software. The
hardware part of the system (DC motor) and the software (in personal
computer) are interfaced using a data acquisition card (DAQ) -Model PCI-
6024E. The voltage and Speed response is obtained using LABVIEW
software. Using this software, the speed of a group of motors can be
controlled from different locations using remote telemetry. The proposed
work also focuses on controlling the speed of the individual DC motor using
PWM scheme (Duty cycle based Square wave generation) and DAQ. With
the help of the DAQ along with Lab VIEW front panel window, the DC
motor speed and directions can be changed easily in remote way. In order to
test the proposed system the laboratory model for an80W DC motor group
(multi drive) is developed for different angular displacements and directions
of the motor. The simulation model and experimental results conforms the
advantages and robustness of the proposed centralized speed control.
Keyword:
Data acquisition card
Lab VIEW
Virtual Instrument
Copyright © 2016 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Dr. C. Bharatiraja,
Department of Electrical and Electronics Engineering,
Faculty of Engineering and Technology, SRM University - Kattankulathur Campus,
Kattankulathur, Chennai, India - 603203.
Email: bharatiraja@gmail.com
1. INTRODUCTION
The DC motors were invented in mid-nineteenth century, its impressive characteristics like speed
control over wide range, high starting torque, quick starting, stopping, reversing and acceleration, etc. have
helped this motor to exist in today‟s generation. Because of its various good characteristics, it finds
application in various automotive industries, agricultural industries, in electric vehicles etc. Since it is used in
various industries, it becomes very important to keep a check on performance, efficiency and running status.
[1] Using traditional methods lowers the productionand increases the possibility of errors, so it is eventually
eliminated. Although there were many significant attempts made to make things easier there are still many
limitations [2]. In order to make things automated, the use of virtual instrument and computer technology can
be of great help [3].

 ISSN: 2088-8694
IJPEDS Vol. 7, No. 3, September 2016 : 656 – 664
657
Virtual instrumentation is basically a combination of software and hardware setup system. This
system works on a specific design which is given or already designed by the user. Virtual instrumentation has
significantly grown since its inception in 1970s. In recent years, commonly used simulation software‟s are
Pspice, Protel and Matlab. Lab VIEW, compared with other computer software is created based upon the
language along the text lines of code, Lab VIEW graphical programming language – G language. The
resulting program is shown in block diagram form [4]. Lab VIEW is also a perfect simulation, debugging
tool such as setting breakpoints, single step and so on. With Lab View‟s dynamic continuous tracking mode,
the process of data and changes can continuously and dynamically be observed, hence it is more convenient
and effective than any other language development environment. The actual motor parameters can be
measured, controlled and modified directly, which will greatly facilitate simulation [5]. The better response
of the system can be obtainedTo control the speed of motor and display the changes of rotational speed of
motor. The NI USB-6008 [6] data acquisition (DAQ) card scratches the data of D/A converter to transmit the
signal in real time to PC to be the speed response of DC motor real-time supervision. Because the DAQ card
has the capability of data storage and calculating, analysis and A/D, D/A conversion matches with the Lab
VIEW virtual instrument characteristic applying to detect the revolution of DC motor. This mode can
substitute the traditional instruments, for instance, oscilloscope, signal generator, power etc. and the test
operation is convenient [7]. However, National Instruments increases the productivity of engineers and
scientists in developing test, control, and design systems by providing software products for a wide range of
functionality [8-10]. NI Lab VIEW is a graphical development environment for creating flexible and scalable
test, measurements, and control applications rapidly and at minimal cost. Based on the above discussion, the
VI platform givesenhanced performance to control a motor in real time. Very few research papers are
available to test the VI based real time DC-motor control, particularly low cost DAQ based DC-motor real
time control.
Hence, this paperdeals with the speed of a DC motorinLab VIEW real time platformance using low
cost hardware structure including virtual Knob in Lab VIEW software a DAQ -Model PCI- 6024E. The
proposed work also focuses on controlling the speed of the individual DC motor using PWM scheme (Duty
cycle based Square wave generation) and DAQ. With the help of the DAQ and Lab VIEW front panel
window, the DC motor speed and directions can be change easily in remote way. In order to test the proposed
system the laboratory model for a 15W DC motor group (multi drive) is developed for different angular
displacements and directions of the motor. The simulation model and experimental results conformthe
advantages and robustness of the proposed centralized speed control.
2. DC MOTOR SPEED CONTROL FUNCTIONAL BLOCK DIAGRAM
2.1. Speed Control of DC Motors
This work usesa separately excited DC motor, which is often used for the velocity tuning and the
position adjustment. The proposed DC motor control is by using the armature voltage control method, where
the field voltage maintaining constant. The equivalent circuit of the DC motor using the armature voltage
control method is shown in Figure 1.
Figure 1. DC motor equivalent circuit
Armature resistance (Ω)
Armature inductance (H)
Armature current (A)
Field current (A)

IJPEDS ISSN: 2088-8694 
Low cost Real Time Centralized Speed Control of DC Motor Using Lab View -NI USB 6008 (C. Bharatiraja)
658
Input voltage (V)
Back electromotive force (EMF) (V)
Motor torque (Nm) ω
Rotor inertia (kgm) B
Friction constant (Nms/rad)
Torque constant (Nm/A) W
EMF constant (Vs/rad)
The equivalent armature voltage control functional block diagram of a DC motor armature voltage
control system is shown in Figure 2, in which control parameter is supply voltage (given through DC to DC
converter)
Figure 2. DC motor armature control system block diagram.
3. PROPOSED DC MOTOR SPEED CONTROL IN LABVIEW ENVIRONMENT
The first step to scheming a closed-loop controller is to discover a mathematical illustration of the
system to create a model. Many types of systems canbemodeled, including mechanical systems, electronic
circuits, analog and digital filters, and load system (mechanical load). For this trial, we have created a model
for a DC motor through VI, based on the transfer function (Figure 2). The DC motor can be best represented
by a transfer function. A transfer function provides a mathematical description for how the inputs and outputs
of a system are related. In our case, the input to the system is voltage (Vm) and the output from the system is
angular velocity (Ωm). We can use the equation below to represent the model of our DC Motor, where:
km = Motor back-EMF constant (V/ (rad/s))
Rm = Motor armature resistance (Ohms)
Jeq = Equivalent moment of inertia (kg*m2
) (Assume that Jeq=Jm (Motor armature moment of inertia))
Figure 3. Model of the DC Motor represented in the Lab VIEWMath Script Node
The next step is to choose a control method and design a controller. When designing a controller it
is best to fully understand the plant, in our case, the DC Motor. This understanding comes from the analysis
of specialized graphs, such as Bode, and root-locus, which build perception of how the plant will perform.
Graphs in the time domain, such as the step response, offerinstantaneous feedback on the perfectperformance
of the system, such as rise time, overshoot, settling time, and steady-state error. (Due to the page constraint
the behaviors of the motor is not given).

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Figure 4. Model of the DC Motor represented in Schematic of a Closed-Loop Control System
For this experimentation, awelldesigned PI controller is usedfor the DC motor using the Lab VIEW
Control Design and Simulation module. The Simulation Loop, which includes a built-in ODE solver for
handling integrals and derivative terms, can be found in the Control Design and Simulation palette under
Simulation. To control parameters of PI controller the following steps to tune is worn: Begin with gains set
at: Kp = 1 and Ki = 0 Increase Proportional Gain (Kp) to get preferred rise time to increase integral gain (Ki)
to decrease steady-state error if necessary. While the rise time looks good with our proportional gain, kp set to
1, the plot shows a small amount of stead-state error, which is represented by the gap between the desired
speed data and the estimated speed data. It can reduce this steady-state error by increasing our integral gain,
ki. Onincreasing the integral gain, ki, to 10, the system response goes much better.
Figure 5. Closed-Loop PI Controller performance
For the tuning and verification simulate both our controller and the response of the DC motor, it
follows an iterative process to optimize designed controller. It will tune the controller parameters from the
Lab VIEW front panel while verifying the system routine. The block diagram of start-stop VI is shown in
Figure 8.
Figure 6. Iterative Process Controller

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Figure 7. Closed-Loop PI Controller with DC Motor TF
Figure 8. Sub-VI for DC motor armature control
Figure 9. Desiged LABVIEW front panel

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4. HARDWARE SYSTEM AND RESULT DISCUSSION
4.1 Structure of Hardware System
One of the main instruments that are used is national instrument USB6008. It is a low cost
multifunction data acquisition device (DAQ) that provides the data acquisition for some applications of
portable measurement. It is compatible with software‟s like Lab view, .NET, Mat lab etc. With recent
bandwidth improvements and new innovations from National Instruments, USB has evolved into a core bus
of choice for measurement applications. The NIUSB-6008 and USB-6009 are low-cost data acquisition
(DAQ) devices with easy screw connectivity and a small form factor [17-19]. With plug-and-play USB
connectivity, these devices are simple enough for quick measurements but versatile enough for more
complex measurement applications. DAQ software is needed for the DAQ hardware to work with a PC. The
device driver performs low-level register writes and reads on the hardware, while exposing a standard API
for developing user applications. A standard API such as COMEDI allows the same user applications to run
on different operating systems, e.g. a user application that runs on Windows will also run on Linux [20-21].
Figure 10 illustrates the experimental setup of Opamp- V and I amplifier.
Figure 10. Experimental setup-Opamp- V and I amplifier
Figure 11. NI USB 6008Figure 12.A class „C‟ 80 WDC motor
Figure 15 (a) shown below depicts low speed of 1840 rpm, high current of 0.86 A and voltage of
7.56 V where two parameters go out of specification. All failure modes can be preloaded into the
programming and can be prompted to the testing person to intimate the production line as a quality alert.
Figure 16 shown below depicts the no load performance characteristics of a particular DC Motor. The no
load speed of the motor is 2370 rpm, current is 0.21 A, and voltage is 5.29 V which highlights it is working
under normal condition.All relevant parameters are monitored in terms of numerical values and graphical
representation. One of the advantages of the Graphical Programming is to visualize all the parameters online.
As the numerical values keep on changing, one cannot track the changes if the sampling speed is higher.
Figure 17, shown depicts the load performance characteristics of a particular DC Motor. The curve obtained,
for torque, current, voltage, power and speed, when the motor is under load condition, is also shown. All
relevant parameters are monitored in terms of numerical values and graphical representation. Advantage and
flexibility of Lab VIEW is exploited here and load profile is clearly monitored online. Calibration of the DC
motor can also be done with the help of Lab VIEW software.

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Figure 14. DAQ and NI USB 6008 interface Sub-VI
(a) (b)
Figure 15. LABVIEW front panel (a) Low speed and low current, (b) Low speed and high current
Figure 16. No load performance Figure 17. Load performance characteristics
Table 1 shows the different experimental results for various conditions of DC motor. The
performance of the motor was also tested in different load conditions from no-load to full load as shown in
Figure 18. Based on that, it could beunderstood that, the proposed Lab view based low cost platform also

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proves the performance in steady state and transient condition. During the transient condition the PI
controller tuning their constants and performing the motor in close to the desired speed input.
Table 1. Experimental Results for various conditions of DC motor
Parameter/performance Speed (rpm) Current (A) Voltage (V)
Over speed condition 3440 0.22 7.56
Low speed high current 1840 0.86 5.27
No load condition 2370 0.21 5.29
Load condition 2090 0.58 5.27
(a) (b) (c)
Figure 18. Steady state response (a) Supply Voltage, (b) Armature Current, (c) Speed response
(a) (b) (c)
Figure 19. Transient state response (motor loaded condition) (a) Supply Voltage, (b) Armature Current,
(c) Speed response
5. CONCLUSION
This paper proposes the speed control of DC motor using LabVIEW software program and displays
the real-time speed of the motor in order to obtain the system response. The real-time monitoring application
can not only act as a substitute for traditional instruments, but can also monitor if the machine operation is
normal. This programming system is based on a structure of the PC, and combines the DC motor supervision
needed instrument, and then replaces other hardware equipments with the cheaper and more efficient method
to provide operators with the graphical interface of an easy and kind operation. The development system can
be set up to supervise and control the outdoor factory from the indoor office. We can supervise and control
all motors in the factory or instrument equipment indoors, and also monitor the factory operational condition
from the outside. In other words, this system can monitor the motor currently, and also can join all
equipmentsthat are desired to supervise and control to perform a whole supervision system in early future.
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