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International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE)
Physical Implementation and Control of MultiAxis Motion Control System using LABVIEW
D. K. Krishna Kumari, Arvind Kumar, Sagar Narang
The basic architecture of a motion control system contains:
Abstract— Multi axis motion control system plays a major
role in the efficient use and cost effective applications of CNC
machine tools. In this paper, an attempt has been made to control
the axes motion by controlling the speed of both DC as well as
Stepper motors. A PC-to-Motor interface and driver circuit board
has been designed and developed for the present system. The
software of the system has been developed using LabVIEW-based
graphical programming language. LabVIEW provides the flexibility
of integration of
data acquisition software/hardware with the
motion control application software for automated test and
measurement applications. The control system proposed in this
paper has the capability to control four axis of motion using DC
motors or two axis of motion using stepper motors[1].
•
A motion controller to generate set of points (the desired
motion profile) and a closed loop for position or velocity
feedback.
•
A drive or amplifier to transform the control signal from
the motion controller into a higher power electrical current
or voltage that is presented to the actuator. Newer
"intelligent" drives can close the position and velocity
loops internally, resulting in much more accurate control.
•
An actuator such as a hydraulic pump, air cylinder, linear
actuator or electric motor for output motion.
Keywords— CNC machines, LabVIEW, DC and Stepper Motors
•
One or more feedback sensors such as optical encoders,
resolvers or Hall effect devices to return the position or
velocity of the actuator to the motion controller in order to
close the position or velocity control loops.
•
Mechanical components to transform the motion of the
actuator into the desired motion, including: gears, shafting,
ball screw, belts, linkages, and linear and rotational
bearings.
I. INTRODUCTION
M
OTION control is an important part of robotics and CNC
machine tools. In Personal Computer (PC)-based motion
control systems, the PC performs all the real-time motion
control operations including feedback loops and multi-axis
coordination. It also serves as a user-friendly graphical interface.
Figure 1 illustrates the block diagram of a basic PC-based motion
control system. The main components of the system includes a PC
to develop application software, a motion controller to create the
trajectories for the motors to follow but outputting a ±10 V signal
for DC motors, or a step and direction pulses for stepper motors,
Driver (amplifier) to take the commands from the controller and
generate the current required to drive the motor, a feedback device
to sense the motor position and reports the result to the
controller, thereby closing the loop to the motion controller[2].
A. Speed control of DC motor
In practice, the motor should rotate in a rated speed, if the speed is
more than rated speed then the motor will be damaged, in order to
control the speed of motor a rheostat should be connected to the field
side of motor. By varying the rheostat we can control the speed of
motor[3].
There are different methods of controlling the speed of the DC
motor. The methods are listed below:
1. Variation of Flux or Flux Control Method
Here, by decreasing the flux, the speed can be increased and vice
versa. With the help of a shunt field rheostat, the flux of a DC motor
can be changed by changing I sh . Since I sh is relatively small, shunt
field rheostat has to carry only a small current, which means I 2sh R
loss is small, so that rheostat is small in size.
Fig. 1. A basic PC-based Motion Control System
Motion control is widely used in the packaging, printing, textile,
semiconductor production, and manufacturing industries.
D.K. Krishna Kumari, Asst. Professor, Manipal Institute of Technology,
Manipal University, Manipal, Karnataka, India
([email protected])
Arvind Kumar, Manipal Institute of Technology, Manipal University,
Manipal, Karnataka, India,( [email protected])
Sagar Narang,, Manipal Institute of Technology, Manipal University,
Manipal, Karnataka, India,( [email protected])
Fig 2 Flux control method
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International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE)
2. Armature or Rheostat Control Method
A. Interface and Driver Circuit
It is a method of controlling the speed of electric motors that
involves varying the resistance or reactance in the armature or field
circuit, used in motors that drive elevators. This method is used
when speed below the no-load speed are required. Since the supply
voltage is normally constant, the voltage across the armature is
varied by inserting a variable rheostat in series with the armature
circuit. The armature speed is decreased when the controller
resistance is increased and voltage across the armature is decreased.
For a load constant torque, speed is approximately proportional to the
voltage across the armature. From the speed/armature current
characteristic, it is seen that greater the resistance in the armature
circuit, greater is the fall in the speed..
To implement the PC-based multi-axis motion control system,
an Interface and Driver Circuit (IDC) Board has been designed and
developed. The IDC board shown in figure 6, is used to connect and
interface motion control motors to a PC which has the capability to
drive/control four DC motors or two stepper motors using its eight
digital output lines.
3. Voltage Control Method:
Multiple Voltage Control: Here, the shunt field of the motor is
connected permanently to a fixed exciting voltage, but the armature
is supplied with different voltages by connecting it across one of the
several different voltages by means of suitable switchgear. The
armature speed will be approximately proportional to these different
voltages. The intermediate speeds can be obtained by adjusting the
shunt field regulator.
Fig. 6 Photograph of IDC board
B. Components used in the driver circuit
The following are the components used in the driver
circuit.
1.
2.
3.
4.
5.
6.
7.
Motor driver IC L293D
Optocoupler CNY17
Leds
Transformer
Capacitors
Diodes
Resistors
Fig 4 voltage control method
2. Motor Driver IC (L293B and L293D)
II. METHODOLOGY
The system presented here has been implemented using PC
Parallel-Port to Driver Circuit interface technique and LabVIEW
(Laboratory Virtual Instrumentation Engineering Workbench)
software which enhances the productivity and reduces the cost.
The motion control application software is developed using
LabVIEW on the PC and communicated to DC/stepper motors
through parallel port and the interface and driver circuit (IDC).
Figure 5 illustrates the block diagram of the proposed multi-axis
motion control system which include; Windows based PC, Parallel
Port Interface, Interface and Driver Circuit, Motors[4].
Fig 5 Block diagram of Multi-axis Motion Control System
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The L293B and L293D are quadruple high-current half-H drivers.
The L293B is designed to provide bidirectional drive currents of up
to 1 A at voltages from 4.5 V to 36 V. The L293D is designed to
provide bidirectional drive currents of up to 600-mA at voltages from
4.5 V to 36 V. Both devices are designed to drive inductive loads
such as relays, solenoids, DC and bipolar stepping motors, as well as
other high-current/high-voltage loads in positive-supply applications.
All inputs are TTL compatible. When the enable input is high, the
associated drivers are enabled and their outputs are active and inphase with their inputs. When the enable input is low, those drivers
are disabled and their outputs are off and in the high-impedance state.
With the proper data inputs, each pair of drivers forms a full-H (or
bridge) reversible drive suitable for solenoid or motor applications. A
VCC1 and VCC2 terminals are provided for the logic inputs to
minimize device power dissipation. The L293B and L293D are
characterized for operation from 0°C to 70°C[7].
International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE)
Fig 7 L293D Pin diagram
Fig 8 External Structure of a Geared DC Motor
1. Optocoupler CNY17
The CNY17 consists of a pair of gallium arsenide infrared emitting
diode optically coupled to a silicon NPN phototransistor. Signal
information, including a DC level, can be transmitted by the device
while maintaining a high degree of electrical isolation between input
and output. It can be used to replace relays and transformers in many
digital interface applications, as well as analog applications such as
CRT modulation. The input and output of the CNY17 is shown in
tables 1.[8]
IV. RESULTS
The speed of DC motors is controlled using variable speed motion
control application software. The front panel and the diagram of the
developed software for the system are shown in Figures 9 and 10
respectively[6].
TABLE 1 INPUT AND OUTPUT OF CNY17
Parameter
Test condition Symbol
Reverse voltage
Value
Unit
VR
6.0
V
IF
60
mA
FSM
2.5
A
100
mW
Forward current
Surge current
t ≤ 10 µs
I
P
Power dissipation
diss
70
Collector-emitter
breakdown Voltage
BV CEO
Emitter-base
breakdown Voltage
BV EBO
7.0
Collector current
t < 1.0 ms
Power dissipation
V
V
50
mA
IC
100
mA
P diss
150
mW
3. Geared DC Motor
In a geared motor, the energy output is used to turn a series of
gears in an integrated gear train. There are a number of
different types of gear motors, but the most common are AC
(alternating current) and DC (direct current). The speed of the motor
Fig 9 Front panel of 4-axis DC Motor speed control
is counted in terms of rotation of the shaft per minute (RPM). Simple
DC motors are restricted in terms of power and lack proper speed
control. They can even run at speeds approximately close to 3,000
RPM which may be beyond the desired requirements of the user.
However, using a geared motor can reduce down the RPM such as
150 and lower, hence providing more torque to the machine. Figure 8
shows details of the geared DC motor. A nut is placed near the shaft
to allow the motor to be mounted on chassis of a machine.
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International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE)
Fig 10. Block diagram of 4-axis DC Motor speed control
Fig 11 Block diagram of 2-axis stepper motor motion control
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International Conference on Innovations in Electrical and Electronics Engineering (ICIEE'2012) Oct. 6-7, 2012 Dubai (UAE)
The two and four axis motion control system has been successfully
developed and implemented using geared DC motors for each axis at
10RPM, 12V and 150mA. The front panel and block diagram of the
software is shown in Figures 9, 10 and 11 respectively. In all the
front panels of the developed motion control software, logic states
(signals) driving the motors are represented by LEDs shown as D0
to D7. The ‘Green Color’ LEDs represent logic state “1” (ON)
whereas ‘Dark Green Color’ LEDs represent logic state ‘0’ (OFF).
The motion control system has been successfully demonstrated for
controlling the axes positions for an angular range of 0º to 360º
within an accuracy of ±0.05º.
REFERENCES
[1]
E.Nesimi “Labview of electric circuits, machines,drives and
laboratories”, E.Nesimi, Prentice hall, New Jersey 2002.
[2] Remya ravindran, Arun kumar “A DC motor speed controller using
Labview”, Dept. of Electronics & Telecommunication, BIT, Durg, CG,
India
r
[3] D.P Kothari and I.J Nagrath, “Electric machines”, 3 edition, Tata McGraw
Hill, New Delhi, India.
[4] Saffet Ayasun, Gu¨ Ltekin Karbeyaz , DC Motor Speed Control Methods
Using MATLAB/Simulink and Their Integration into Undergraduate
Electric Machinery Courses” , March 2005
[5] P. Thepsatorn, A. Numsomran, V. Tipsuwanporn and T. Teanthong, “DC
Motor Speed Control using Fuzzy Logic based on LabVIEW”, SICEICASE, 2006
[6] Jianying Liu, Pengju Zhang, “Real-Time DC Servo Motor Position
Control
by
PID
Controller
Using
Labview”
Intelligent Human-Machine Systems and Cybernetics, 2009. IHMSC
'09,volume 1.
[6] National Instruments, “LabVIEW User Manual”, National Instruments,
Jan. 1998 Edition
[7] http://www.beyondlogic.org/spp/parallel.pdf.
[8] Optocoupler CNY17, Datasheet;
www.agilent.com/semiconductors.
[9] http://zone.ni.com/devzone/cda/tut/p/id/3367
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