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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 27
Jurnal Teknologi, 42(A) Jun. 2005: 27–48
© Universiti Teknologi Malaysia
1&2 Department of Electrical and Electronic Engineering,
3Department of Computer and Communication System Engineering,
4Department of Mechanical and Manufacturing Engineering,
Faculty of Engineering, Universiti Putra Malaysia, Serdang, 43400 Selangor, Malaysia
*Corresponding author. Email: ishak@eng.upm.edu.my
DESIGN AND DEVELOPMENT OF A PROGRAMMABLE
PAINTING ROBOT FOR HOUSES AND BUILDINGS
I. ARIS1*, A. K. M. PARVEZ IQBAL2, A. R. RAMLI3 & S. SHAMSUDDIN4
Abstract. Nowadays robots are widely used in many applications such as military, medical
application, factories, entertainment, automobile industries etc. However, the application of robot
is still not widely implemented in construction industry. In construction industry, robots are designed
to increase speed and improve the accuracy of construction field operations. It can also be used to
do hazardous and dangerous jobs in construction. For example, currently house painting is done
manually. This process can be simplified using a special dedicated robot. It is very difficult and
troublesome for human being to work in an upright position, especially for painting, cleaning and
screwing in the ceiling for a long time. Painting in an upright position is also very dangerous for the
eyes. To overcome this difficulty, a programmable painter robotic system is proposed, designed
and developed. This paper describes all the processes that are involved in designing and constructing
the proposed painter robot. The system is divided into two main parts namely hardware and
software. In hardware part, mechanical design, fabrication, electrical and electronics system are
described and in software part, control algorithm is explained. The testing results indicate that the
performance of the painter robot is better compared with that of using manual painting technique.
Keywords: Painting machine, cartesian robotic system, PLC (Programmable logic controller), electro-
pneumatic system, motor controlling, construction robotics
1.0 INTRODUCTION
The term robot implies different meaning to different people. Construction robots
are ingenious machines that use intelligent control but vary in sophistication. Generally,
they are designed to increase speed and improve accuracy of construction field
operations. Construction robots are especially helpful where the constructions are
done under dirty and dangerous conditions. According to Steward [1] and Stein [2],
the Japanese have a liberal interpretation of the term “robot”. Their definition includes
advanced automation and remote control devices used on the construction site and
prefabrication shop. However, there is no consensus on a clear definition of
construction robotics [1-5].
The construction industry uses different kind of robot. Generally in the
manufacturing field, robots are stationary and the product moves along the assembly
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN28
line. However, construction robots must move inside and outside the buildings,
which are stationary and of a large size. The operating parameters of the robot keep
changing and it needs to be reprogrammed with each new condition. That is why
digital control with manipulators using coordinate systems to control three-dimensional
motion is required for construction robots. Construction robots often handle large
loads with components of variable sizes. They must be also able to function under
adverse weather conditions including variation in humidity and temperature.
Designing construction robots are more challenging compared with those conventional
industrial robots. There are now 89 different kinds of single task robots that are used
on Japanese construction sites [6]. Single task robots perform a specific job and
imitate construction labor. Although single task robots have been successful but
these devices are limited because they are not capable of identifying and fixing the
problem in real time. Workers are still needed to set up, monitor, and clean the
machine. Because of these limitations, the Japanese have been exploring the use of
fully automated construction site. According to Moore, contractors using this approach
report time savings of 30% and labor cost reductions of 50% [7]. The computerised
information management system keeps a running inventory of materials, drawings,
schedules and volume of completed working real time [8]. Some previous works
related to painting machine are described as follows.
The University of Texas has developed a prototype-automated surfaces finishing
system for use on large diameter tanks. This system uses a computer-controlled
motion module to refinish the vertical exterior walls of a tank. The module is
configurable for both blasting and painting and utilises the conventional surface
finishing equipment for these processes [9]. This system consists of an aluminum
motion module, which rolls on the surface of the tank. The module attaches to the
wind girt of a tank via two steel cables. The position and velocity of the module are
determined by the amount and speed of the cable splayed through two hoist located
at the rear of the module. Squirrel cage assemblies mounted beneath the motion
module retain the excess cable from the hoist [10-11]. Another robot for painting the
exterior wall was developed by Terauchi [12]. This robot is mounted on equipment,
which permits it to move up and down, left and right along the exterior walls of the
building. It is computer controlled and activated simply by the operator pressing a
switch on the control panel located on the ground. The robot is capable of
painting a four square meter wall surface at one time. It is also equipped with
sensors, which measure indentations and protrusions in the wall surface, making it
possible for it to paint exterior walls with windows, pillars or other indentations or
protrusions.
Another painting machine for applying the coatings to elongated thin shaft such
as golf club shafts was invented by Bauerle [13]. This specially designed machine
can apply precise, uniform coatings to elongated shafts. The conventional painting
techniques are not effective in painting the thin elongated shaft. Painting with brushes
and rollers requires considerable skill, is time consuming and likely to result in
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 29
uneven coatings with streaks, brush marks, runs, and other irregularities. Spraying
also requires considerable skill to produce even coating without runs or uneven
areas. In addition, where the shaft is quite narrow, much of the coating material is
wasted as over spray passes by the object being painted. In order to solve the coating
problem, this machine was developed. Shafts are held by a gripper in a downwardly
hanging array. A paint head assembly is moved upwardly over each shaft in sequence
to apply a paint coating to a selected portion of the shaft length. The paint head
assembly includes a flexible container including a central hole, a vertically moveable
edge frame and an expander for changing the area of the hole. Raising the frame
forms the container into a bowl like configuration, so that the paint will contact a
shaft extending through, and in contact with the hole.
According to Warszawaski and Rosenfeld’s [14] economic analysis of performance
of multi-purpose interior finishing robot, it can be concluded that the employment
of a robot for interior finishing works has considerable potential for productivity
improvement on the building site. It appears that economic savings can be also
realised from robots employment. Other non-quantifiable benefits which can be
also obtained include increased safety, reduction of strenuous and unpleasant tasks,
and improved quality of building. Realisation of these benefits depends, however,
on very high precision of the building shell and a very high level of materials packaging
and handling, and work organization on site.
A painting machine for painting the surgical tubes was invented by Flood [15].
This painting machine includes a chain driven track assembly, which moves the
tube pieces held on paint fixtures into a paint chamber for painting and into an oven
to dry the paint to the tube.
From the discussion mentioned above, it is clear that the automatic spray painting
is feasible for various finishing tasks. In the construction industry, different painting
machines, robots and techniques are used for painting the external and internal
walls of the buildings and houses. It is also very difficult and troublesome for human
to work in an upright position, especially for painting, cleaning and screwing in the
ceiling for a long time. Painting in an upright position is also very dangerous for the
eyes. To overcome this difficulty, a robotic system which is capable of painting the
houses and buildings is proposed and developed. The proposed painter robot has
three degrees of freedom (DOF). For X direction, a single-phase induction motor
and a chain-sprocket mechanism are used. Two limit switches and two electronic
sensors are used to limit the movement in X direction. Another sensor is used to
position the robotic arm along the X direction. For Y direction, two limit switches
are used to limit the movement in Y direction. Two sensors are used to protect the
robotic arm along the Y direction. The single-phase motor with an inverter is utilized
to control the speed of the robot in Y direction. For Z direction, a parallelogram
structure and a ball-screw mechanism are used in this project. A single-phase brake
motor and a photoelectric sensor are used to control the position in Z direction.
Two limit switches are used to limit the movement in Z direction. The proposed
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN30
robot is used to paint the ceiling of houses. The paint is automatically sprayed by the
robot using pneumatic system.
The software part involves the design and development of the system control
software. The system control software is created using FP WIN GR PLC programming
software. This software can run on windows. It has its own graphics interface. It is
more user friendly compared with a hand-held programmer. This software provides
three programming styles: Ladder symbol mode, Boolean, Ladder Mode and Boolean
Non-ladder mode [16]. In this system, the ladder symbol mode is used to create the
control program of the proposed robot. The Programmable Logic Controller (PLC)
is used to control the overall operation of the robot.
2.0 SYSTEM DESIGN
The proposed robotic system consists of a personal computer, a controller, input
and output devices, actuators and the mechanical structure. A personal computer is
needed to develop the program and then download this program into the controller.
The PLC is used as the main controller of the robotic system. The input signals from
the input devices will be processed in this controller and the resulting output signals
will activate the output devices. The actuators are utilised to drive the mechanical
robotic structures. Figure 1 shows the processes that are involved in developing this
robotic system.
3.0 MECHANICAL DESIGN
The mechanical design consists of a positioning module and an end-effector
module.
3.1 Positioning Module
The design of the positioning module of this painter robot is based on the Cartesian
coordinate concept and it is also known as the X-Y-Z coordinate. It is the combination
of individual joints where the action must be controlled in order to perform the
robotic manipulator in the desired motion cycle. For X and Y modules movement,
the chain-sprocket mechanism is used. For Z module movement, the ball-screw
mechanism is utilised. Thirty-six aluminium plates are used as links to make the Z-
axis as parallelogram structures. Two parallelogram structures are connected to each
other by the iron rod connector.
3.1.1 X-axis Module
The X-axis module is the first step of this project to be fabricated according to the
proposed design. Figure 2 shows the X-axis module of the system. The description
of the X-axis module includes the following:
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 31
The X-axis module is fabricated to provide the motion of the robotic system in the
X direction. The base frame, which is included in the X-axis module, is fabricated
using a hollow iron bar. The hollow bar is selected for its low weight and adequate
strength. Four wheels are attached at the four bottom corners of the frame. Two of
the four wheels are caster wheels and the remainings are unidirectional wheels. The
objective of providing the wheels is to give mobility to the whole system. Two slider
guide ways and four runner blocks are mounted along the X-axis at the top of the
frame. These are the main parts of the X-axis module. Specially designed mountings
are attached to the two opposite side runner blocks. These mountings are designed
to hold the Y-axis module. The mild-steel made mountings are attached to the driving
chain and are designed to hold the shafts, bearings and the motor of the Y-axis
module and to attach the driving chain of the X-axis module. Four pillow bearings
are attached with the frame to hold the two shafts of the X-axis module. Each shaft
consists of two sprockets at its opposite end. The sprockets are provided to drive the
Figure 1 The process that are involved in developing the robotic system
Start
Painter robot
Electrical &
electronic
system
Position
module
Software
Mechanical
design
Hardware
Problem statement
End effector
module
2
1
3
X-axis
module
Test
Y-axis
module
Test
Z-axis
module
Test
No
NoNo
Yes Yes Yes
Test
Yes
No
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN32
Software
development
Main
program
Test
No
Yes
Yes
Yes
Yes
2
1
Yes
Hardware integration
Overall
integration
Test
No
Yes
End
Yes
Test
3
Power supply
module
Test
No
Control
panel
Test
No
PLC
Test
No
Electro pneumatic
system
Test
No
Motor
driving
module
Test
No
Sensing
module
Test
No
Yes Ye s
Figure 1 The process that are involved in developing the robotic system (cont.)
chains. Two chains are used to drive the X-axis module. Four tensioners are attached
in the frame to adjust the chains of the X-axis module. The sprocket bearing attachment
is mounted at the end of each tensioner. This sprocket can freely rotate and mesh
with the chain. The tensioners are mounted in the frame so that they can adjust their
angle by loosening the screws. After adjusting the angle, they can be fixed by screwing.
The angle adjustment is necessary for adjusting the chain. A single-phase AC induction
motor is mounted with a frame to drive the X-axis module. The motor is coupled
with the shaft by the flexible coupling. To select a proper motor, it is very important
to know the amount of torque, which can drive the X-axis module. The motor,
which is used for the X-axis module, will have to carry the total systems. Two limit
switches, three inductive proximity sensors and one photoelectric sensor are used to
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 33
control the X-axis movement. In order to determine the suitable motor size, it is
important to calculate the torque of the X-axis module. The process of calculating
the torque is described as follows:
()
w
=+ + + +
=+++ +
1
Total load sprocket Chain Motor Friction
Load sprocket Chain Motor Friction
TTT TTT
JJ J J T
gt
(1)
=2
Load L
JWR (2)
=
2
2
S
sprocket
WR
J(3)
=2
Chain c
JWR (4)
=
Friction
TFR (5)
w=V
R(6)
Motor
Control panel
Paint tank
Bearing
X direction
Chain
Figure 2 X-axis module of the painter robot
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN34
The above formulae are taken from Parker motion and control catalog [17]. Using
the above equations and considering all design factors, the total torque for the
X- axis module is found as:
()
−
=+×+++
=
4
10 298 2 66 10 0 0254 0 0647 0 1608
981
0 608 N-m
Total
T.....
.
.
After getting the value of the torque, the motor for X-axis module was determined.
A 0.95 Amp, 240 V single phase AC induction motor was selected for this application.
The general velocity profile and torque-speed curve are shown in Figures 3 and 4.
The two limit switches are used to provide the maximum limit and the inductive
proximity sensors are used to control the positioning of the X-axis module. The
photoelectric sensor is used to protect the total system from obstacles in the work
place when painting process is in progress.
Velocity
V
S/3
ad
Time S
2S/3
Figure 3 General velocity profile of motor
Figure 4 Torque-speed curve of the motor
Torque (N-m)
Power (HP)
Speed (rps)
Torque
Horsepower
0
0
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 35
Figure 5 Y-axis module the painter robot
Y-direction
3.1.2 Y- axis Module
The Y-axis module is depicted in Figure 5. The chain sprocket mechanism and
motor are used to carry the Z-axis module and the end-effector module in the Y
direction. To make the Y direction movement smooth and frictionless, hardened
guide rods and linear bushings are provided. The design of the Y-axis module can
be divided into two parts, namely the hardened guide rod selection and the motor
torque calculation. By analysing the bending stress, it is possible to select a proper
hardened guide rod. The process for selecting the hardened guide rod is as follows:
d=
d
MY
J(7)
22
LL
ll
MW m g=×=×× (8)
=Y2
d(9)
p
=
2
42
d
J(10)
dd
d=uy
d
or
FS (11)
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN36
After using the above formulae and considering all design factors, the diameter of
the guide rod was calculated to be of 24.5 mm. The system uses two hardened guide
rods as a guide for smooth running of the Y-axis module, the Z-axis module and the
end-effector module. Therefore, the diameter of each guide rod is at least half of the
calculated value. Figure 6 shows the free body diagram and cross sectional area of
the guide rod.
The Y-axis module is fabricated to provide the motion in the Y direction. Two
stainless steel guide rods and two linear bushings are provided in the Y-axis module.
These are the main parts required to provide the motion in the Y direction. The
stainless steel guide rods are attached to the mountings, which are mounted to the
two opposite side runner blocks in the X-axis module. To avoid the sliding of the
guide rod during operation, slots and circular locks are provided at both ends of the
guide rods. When the guide rods are adjusted to the mountings of the X-axis, these
slots and circular locks fix the guide rods to the mountings. Two flange bushings are
used in the Y-axis module. The flanges are used with bushings to attach the bushing
with other body. These two flange bushings are inserted to the two fixed stainless
steel guide rods and provide the Y-axis motion. A specially designed mounting is
attached to the flange bushing. This mounting is designed to hold the Z-axis module.
It can also be attached to the roller chain of the Y-axis module. Four pillow bearings
and two shafts are used to carry the mountings along the Y-axis direction. The roller
chain and sprocket are used for this movement. An AC induction motor, which has
similar rating as that one used for the X direction, is mounted with a frame to drive
the Y-axis module. The motor is coupled with the shaft by a flexible coupling. The
motor for the Y-axis module is selected using the process, which is mentioned in the
X-axis module. Two limit switches are used to control the maximum limit of movement
of the Y-axis module in both forward and reverse directions. Two photoelectric
sensors are used to protect the system during the operation, especially when the
robot runs in both forward and reverse movements in the Y direction.
Figure 6 Free body diagram and cross sectional area of the guide rod
WL
l/2
d
Y
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 37
3.1.3 Z-axis Module
Figure 7 shows the Z-axis module that is used in the painter robot. The Z-axis
module is fabricated to provide the motion in Z direction for the robot. Thirty-six
aluminium plates are used to make this module. The dimensions of each plate are
the same. The plates are linked to each other in such a way that they can form a
zigzag ladder. There are two zigzag ladder structures in the Z-axis module, which
are parallel to each other. These structures are linked to each other by mild-steel
pins attached at the joints. The gap between each parallel structure is 20.5 cm. These
parallelogram structures are made in this way to avoid inclination. The bottom end
of the parallelogram structures is hinged to a mounting, which is attached to the Y-
axis module. One part of the bottom end is hinged to the mounting but this part is
not movable. The other part of the bottom end is hinged and this part can move
back and forth. When this movable part moves forward, the structures go up and
when the movable parts moves backward, the structures go down. Four deep-grooved
ball bearings are used to make the rotation of the bottom part of the parallelogram
structure smooth. These four bearings are fixed to the ends of four bottom plates
which ends are used for making hinges. Two linear bushings and two stainless steel
guide rods are used to provide linear motion of the movable bottom part of the
parallelogram structures. The ball-screw mechanism is used to drive the movable
bottom part of the structure. The special arrangement is provided to hold a ball-
screw nut to the movable bottom part of the structure. The ball-screw is mounted to
the two flange bearings, which are attached to the mounting of the Y-axis module.
When the ball-screw rotates clockwise or counter clockwise, the nut and the movable
bottom part move forward or backward. An induction reversible brake motor is
used to drive the ball-screw. This motor is coupled with the ball screw by a flexible
Figure 7 Z-axis module of the painter robot
Connector
Parallelegram structure
Motor for Z direction
movement
Z-direction
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN38
coupling. To select a motor for the Z-axis module, it is important to know the amount
of torque required to drive the ball-screw. The process to calculate the torque is as
follows:
=+
Total Friction Acceleration
TT T (12)
=2
Friction
F
Tpe (13)
w=2pV (14)
()
w
=++
-
1
Acceleration Load ball screw motor
TJJJ
gt
By using the above equations and considering the design factors, the torque of the
motor of the Z-axis module was determined as 0.069 N-m. After getting the value of
the torque, it is clear that the torque of the Z-axis motor must be higher than the
calculated value to ensure a smooth movement. One photoelectric sensor and two-
limit switches are used to control the movement of the Z-axis module. The
photoelectric sensor is used to detect the ceiling position and two limit switches are
used to control the maximum movement along the Z-axis.
3.2 End-Effector Module
The end-effector module is designed in such a way that it can hold a spray gun and
operate the spray gun during the operation. A single acting pneumatic cylinder is
attached to the lever. The lever can move up and down by the actuation of a cylinder.
Figure 8 shows the proposed design of the end-effector module. Two hosepipes are
attached to the spray gun. One of them is directly connected to a paint tank and the
other is connected to an air compressor. The paint tank is a pressure vessel and is
directly connected to the air compressor. The paint is moved through the hosepipe
by air pressure. The air pressure that is used by the robotic system to perform the
painting activity is 10 bar. This air pressure is kept constant throughout the operation
to achieve the standard quality paint.
4.0 ELECTRICAL AND ELECTRONIC SYSTEM
There are six main parts in the electrical and electronic system of a painter robot.
They are a power supply module, a main controller PLC, a sensor module, an
electro-pneumatic system, an AC induction motor drive system and a control panel.
A proper distribution of power supply is required to activate the components of
the system. The AC and DC voltages are supplied and distributed to the robotic
system as depicted in Figure 9. A supply of 24V DC voltage is required for most of
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 39
the electrical and electronic components such as PLC, sensors, pneumatic valve,
limit switches etc. In this system, a commercial switching power supply unit is used
to convert the AC voltage from the main source to 24 DC voltage. The input of
240 AC voltage is reduced to 36V AC and then rectified and regulated to 24V DC.
The output 24V DC is distributed to activate the main controller, optical sensors,
pressure sensors, inductive proximity sensors, limit switches, start/stop button,
indication light and motor driven relay. The AC induction motors are connected
directly to the main supply. Figure 10 depicts the inside of the control panel of a
painter robot.
4.1 System Protection
Four photoelectric sensors, three inductive proximity sensors and six limit switches
are used to protect a painter robotic system from obstacles in the work environment.
For the X direction, inductive proximity sensors are used to change the position of
the robotic system along the X-axis and provide the maximum running length within
the X-axis. To ensure the protection of the system in the X-direction, one photoelectric
sensor and two limit switches are provided in the X-axis module. When the system
changes its position along the X-direction, during this time, if the sensor detects any
obstacle, it will stop the total system. The total system can be stopped again if the
system touches the limit switches. The system can be initialised to return to its home
position by using the reset button. For the Y-direction, two photoelectric sensors and
two limit switches are used to protect the system and limit the movement of the
Figure 8 End-effector module (paint spray gun holder) of the painter robot
Pneumatic cylinder holder
Spray gun holder
Photoelectric sensors
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN40
Figure 9 Power distribution system of the painter robot
Main power
supply 240 V
AC
Power supply
24 V DC
Pneumatic
cylinder
Pneumatic
valve
AC induction
motor
Programmable
Logic Controller
(PLC)
Relays
Reset
Start
Inductive
proximity sensors
Motor drive
system
Capacitor
AC induction
motor
Indicator
Limit switches
Photoelectric
sensors
Figure 10 The inside of a control panel of a painter robot
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 41
system along the Y-direction. Painting operation will be performed in this direction.
During this operation, if the sensors detect any obstacle in forward or reverse direction,
the painting process will be stopped and the system will be changing its position
along the X-direction. After changing the position, the painting process will start
again automatically. For the Z-direction, one photoelectric sensor and two limit
switches are used to detect the ceiling and limit the movement in the Z-direction.
The maximum range of movement of the robotic system along the Z-direction is
1.83 m. If the system crosses the maximum limit, the limit switch will stop the total
system. In the reverse direction, along the Z-axis, when the system reaches its initial
position, another limit switch is used to stop the movement of the system. Within this
range of movement, the proposed robotic system is capable in performing the painting
operation. An AC induction brake motor is used to keep the robotic system in an
up-right condition along the Z-direction. Figure 11 illustrates the sensor detection
system.
Figure 11 The detection system of sensor
Sensing distance
To PLC
Object
Sensor (inductive/
photo-electric)
+ –
24 V DC
5.0 SOFTWARE DEVELOPMENT
The PLC is used to control the operation of the proposed robot. A new program to
control the PLC was written. After the program is loaded, it will go into a run mode.
At that time, it can check the input COM ports and solve the user program ladder
logic instructions. Figure 12 shows the programming environment and ladder diagram
of FP WIN GR software. According to the input instruction, it can control the output
COM ports and their associated devices. Table 1 shows the input and output mapping
of the system. A personal computer and PLC programming software are used to
develop the program. The program is downloaded to the PLC via the communication
cable through the RS232 port. The software which is used in this project is called the
FPWIN GR. Before starting the project, it is important to do the planning for the
user program. The planning is needed to create a workable, reliable, and efficient
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN42
Table 1 Input and output mapping of the Programmable Logic Controller of the proposed painter
robot
Input port Device Output port Device
X0Start button Y0Motor brake
X1Reset button Y1Motor for Z axis
X2Upper sensor Y2Motor for Z axis
X3Forward sensor Y3Pneumatic Valve
X4Side sensor Y4Motor for Y axis
X5Backward sensor Y5Motor For Y axis
X6X axis positioning sensor 1 Y20 Motor for X axis
X7Pressure sensor Y21 Motor for X axis
X20 Sensor for home position Y22 Indicating light
X21 X axis positioning sensor 2
X22 Limit switch 1
X23 Limit switch 2
X24 Limit switch 3
X25 Limit switch 4
X26 Limit switch 5
X27 Limit switch 6
Figure 12 Programming environment and ladder diagram of FP WIN GR software
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 43
PLC program. The following sequences are used to develop the program as illustrated
in Figure 13.
•Turn on the air compressor.
•Turn the start button on.
•From the home position, the Z-axis motor turns on.
•The robotic arm moves up until the upper sensor detects the ceiling.
•The upper sensor detects the ceiling and stops the Z-axis motor.
Figure 13 Partial flowchart of sequence of operations
Total system is in
home position
No
Allow Y0 and Y2 to
turn on
Start X0 turn on
Sensor
X2 on?
Allow Y0 and Y2 to
turn on
Touch the limit
switch X24
Total system will
be halted
Indicator Y22
turn on
Go to home
position
Sensor
X3 on?
Allow motor Y4 and
valve Y3 to turn on
Touch the
limit switch
X23
Motor Y4 and valve
Y3 turn off
End
Yes
No
Yes
No
Yes
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN44
•The pneumatic valve and the Y-axis motor turn on and painting will start
until the forward sensor detects or the limit switch touches the robotic
arm.
•The forward sensor detects and turns off the pneumatic valve and the
Y-axis motor.
•The limit switch touches the robotic arm and stops the pneumatic valve
and the Y-axis motor.
•The X-axis motor turns on and moves the system along the axis until the
side sensor and the sensor along the X-axis detect it.
•The sensor along the X-axis detects the position and stops the X-axis motor.
•The pneumatic valve and the Y-axis motor turn on and painting will start
again until the back sensor detects or the robotic arm touches the limit
switch.
•The back sensor detects and stops the pneumatic valve and the Y-axis
motor.
•The limit switch touches and stops the pneumatic valve and the Y-axis
motor.
•The X-axis motor turns on and moves the system along the X-axis from
the previous position to forward position until the sensor along the X-axis
and the side sensor detects it.
•The sensor along the X-axis detects the position and stops the X-axis motor.
•The side sensor detects the beam or other unwanted element, and stops
the total system. In that case, it is necessary to initialise the system.
The above sequences are repeated to complete one position. After completing
the painting process, the robotic arm returns to its home position by maintaining the
following sequences:
•After touching the limit switch, the Y-axis motor and the pneumatic valve
will be stopped.
•The Z-axis motor turns on and moves the Z-axis to its initial position.
•The Y-axis motor turns on and moves the robotic arm in a backward
position.
•The X-axis motor turns on in the reverse direction and moves the total
system to its home position.
6.0 SYSTEM INTEGRATION
The painter robot is created for painting houses and buildings. The fully automatic
painter robot has a 3 DOF Cartesian movements and a PLC is used to control the
painter robot. The summary of the specifications of the completed painter robotic
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 45
system is illustrated in Table 2. To make the robot more intelligent, four photoelectric
sensors and two inductive proximity sensors are used in this system. The degrees of
freedom involve the X-axis, the Y-axis, the Z-axis and the end effector lever
movements. The system has the ability to work in a rectangular envelope. The area
of the working envelope depends on the length of the slider guide, ball-screw and
the positions of the limit switches and the limit sensors. These limit switches and
sensors limit the movement of the motors for safety purpose. The linear motion of
the X-axis and the Y-axis depends on the trigger signals that drive the induction
motors, the chain and the sprocket drive. The motion of the Z-axis depends on the
trigger signal and also the pitch of the ball-screw. The X-axis and Z-axis modules are
able to handle a speed of 30 mm/sec, while the Y-axis module is capable of handling
the speed ranging from 1 mm/sec to 35 mm/sec. The speed of the Y-axis module can
be adjusted depending on the quality of paint. Figures 14 and 15 show a 3-D view of
the robotic system and a prototype of the painter robot respectively.
7.0 PAINTING PERFORMANCE TEST
After integrating the total system, the painting test was performed. By observation, it
can be seen that the painting quality depends on the air pressure, the paint and air
ratio, and the speed of the Y-axis motor. The paint and air ratio can be adjusted by
the adjusting screw of the spray gun. The air pressure, which was used to perform
the painting was 10 bars. The speed of the Y-axis motor can be adjusted by an
inverter. During the painting operation, 46 m2 wall surface was painted by the painter
robot. To paint this area, this painter robot took 3.5 hours. The painting quality was
smooth and consistent. To manually paint the same area of the wall surface, it takes
1.5 more time than the robotic system and the painting quality is not so smooth. The
total costs for painting manually and using robot are US$139.5 and US$94.25,
Table 2 Specification of the proposed painter robot
Type of robot Cartesian
Robotic control Automatic
Degrees of freedom 3
Working envelope (84 × 72 × 122) cm3
Linear X-axis speed 30 mm/sec
Linear Y-axis speed 35 mm/sec
Linear Z-speed 30 mm/sec
End effector actuation Pneumatic
Type of controller Programmable logic controller
Software PF WIN GR
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I. ARIS, A. K. M. PARVEZ IQBAL, A. R. RAMLI & S. SHAMSUDDIN46
Figure 14 A 3-D view of the painter robot
X-axis module
End-effector module
Z-axis module
Y-axis module
Figure 15 The painter robot demonstrates its capability
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DESIGN AND DEVELOPMENT OF A PROGRAMMABLE PAINTING ROBOT 47
respectively for 46 m2 area. From this comparison, it can be seen that the use of
painting robot is more convenient than manual painting.
8.0 CONCLUSION
The painter robotic system has achieved optimum benefits with regard to reliability,
safety appearance, and ease of use. All the objectives set up for this system have
been achieved successfully.
In terms of mechanical design, the X-axis, the Y-axis, the Z-axis module and the
end-effector module were designed and fabricated properly. All motor mountings
and couplings were properly adjusted. All the prismatic joints were developed
successfully.
In terms of electrical and electronic systems, the power distribution module, the
sensor module, the electro-pneumatic system, the AC induction motor driving system
and the control panel were developed successfully.
In terms of software development, the author had written a control program for
the painter robot. This was indicated by the performance of the painter robot. Each
movement of the painter robot was successfully controlled by the control program.
It can be reprogrammed easily to cope with any changes in the process.
A conclusion can be made that the painter robotic system had been successfully
created to solve the problem of working in an upright position, which is very
troublesome, boring, unhealthy and harmful to a human being if the working period
is long.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the Institute of Advanced Technology (ITMA)
and the Faculty of Engineering of Universiti Putra Malaysia for providing some
financial assistance. The authors would also like to thank the staffs of Engineering
Faculty of University Putra Malaysia for providing the equipments to carry out the
project.
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