IRJET - Controlling 4 DOF Robotic ARM with 3-Axis Accelerometer and Flex Sensor

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 07 Issue: 04 | Apr 2020 www.irjet.net p-ISSN: 2395-0072
© 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 939
Controlling 4 DOF Robotic ARM with 3-Axis Accelerometer and Flex
Sensor
Mehmet Gül
Assistant Professor, Computer Engineering, Şırnak University, Şırnak Turkey
---------------------------------------------------------------------***----------------------------------------------------------------------
Abstract - Nowadays there are many robotic systems
performed different tasks in many areas, especially in the
industry. The usage of the robotic system is at most 5% in all
over the world. According to the International Federation of
Robotics (IRF), this usage will be much more inthenearfuture
compared to now. The robotic system gathers information
about surrounds with sensors. Sensors play an important role
for robots. Besides, in conventional robotic systems, joints
feedback is usually by calculating the angular measuring
device such as rotary encoders orpotentiometers. Theserotary
encoders or potentiometers are fixed to the joints to obtained
angular data. In advanced systems, an optical measuring
device such as an IR sensor or color sensor is used for the
position of robots in the working space.
Versatile solutions are developed inroboticsystems. Oneof the
offered solutions in this study is that control robotic system
with human hands autonomously. This solution can be used in
a critical situation. In this study, two differentsensorsareused
for controlling the robotic arm. These two sensors are an
acceleration sensor and a flex sensor. Within the acceleration
sensor, the human can control a robotic arm with axes data
obtained from an acceleration sensor and within the flex
sensor, the gripper can be controlled.
Key Words: Robotic Arm, Acceleration sensor, Flex Sensor,
Autonomous Control
1. INTRODUCTION
Nowadays, there are robotic systems that perform different
tasks in the different application areas, especially in the
factories producing industrial production.Theuseofrobotic
systems is becomingmorecomplex, especiallyintheaviation
and automotive industries. The usage rate of robots in
industrial production is at most 5% in all over the world [1].
According to the International Federation of Robotics (IFR)
data, this rate will be more than 2 million robots in the
industry field between 2018 and 2021 [2]. The fact that
robots can be operated versatileandthedesiredtaskscanbe
fulfilled completely is the most important factor in the
widespread use of the industry. In robotic systems, whether
the robot performs simple or complex tasks, it is possible to
control and monitor the movement in robot working space.
Many collaborative works on robotic systems are on
kinematics and control policy. It is extremely important to
know the positions and power of the robot arms to establish
and design an effective system. In conventional systems,
feedback is usually made by calculating the angular values
obtained from rotary encoders or potentiometers fixed to
the joints. In advanced systems, an optical measuring device
such as an IR sensor or color sensor is used for direct
feedback calculation to determine the position of robots in
the working space. To select any object whose position is
known in the working space, the robotic arm can then be
directed so that the position of theobjectcanbedisplaced[3,
4].
2. SYSTEM ARCHITECTURE
In the study, an open-source model robot arm with4degrees
of freedom (DoF) [5] was printed with a 3D printer and
mounted. The model interface and system architectureofthe
robot arm are shown in figure 1 below. The robot arm andits
components are listed below in the study.
2.1 Power Supply
The power supply converts the power obtained from the
battery or ACsource into thecurrentandvoltagerequiredfor
the movement of the robot. The used power supply converts
220V AC to 24V voltage and 12.5A current required by the
system. Since the movementof theaxesintherobotarmused
different features and different power requirements stepper
motor, all requirementsofthesystemmustbemetthispower
supply.
2.2 Motherboard
MKS Gen V1.4 motherboard is used for the movement of the
robot arm. The motherboard has an 8-bit AVR RISC-based
Atmega2560 microchip, which stands out with its advanced
RISC architecture and low power consumption.
Atmega2560's self-programmable flash memory for the
256KB system offers very high performance for the
microcontroller. The microchip has also 8KB Ram and 4KB
internal SRAM. The Microchip also features 8KB Ram and
4KB internal SRAM. The microprocessor with 16MHz
operating speed allows storing long character strings with
the 4KB EEPROM and hundreds of settings data of an
advanced system. It has a total of 100 pins, 86 of the pins are
used for I / O data input, while 16 channels accommodate 4
USART and Master / Slave SPI serial interfaces for 10 bit-
ADC converters.
MKS Gen 1.4 has a high-performance microprocessor and
also integrated Ramps and Ramps compatible firmware.
These features stand out a developer-friendly advantageous
motherboard with access to Ramps. While it can be
controlled with display and LCD board ports on it as well as
allows a smart controllerwithanSDcardconnector.Besides,
there are three AUX ports and servo motor control ports.

There are 5V and 12V voltage output opportunities on the
motherboard powered by 12V-24V voltage. There is a
recoverable fuse for short-circuit protection on the
motherboard. At least 10 stepper/DC motors and 3 servo
motors can be controlled with this motherboard. The
motherboard is also capable of withstanding up 24V voltage
[6, 8].
2.3 Robot Arm
The robot arm was obtained from an open-source software
library with a 3D printer. The robot arm has 4 axes and
fingers. Stepper motors have been used to provide the 2-
dimensional horizontal and vertical movement of the robot
arm. The manipulator task in the robot arm is achieved with
a stepper motor and TB6560 driver.Theused TB6560motor
driver is provided with high performance in the robotic arm
system that can withstand up to 35V / 3A, it sends the
current required by motors of different properties used in
different joints of the system.
(a) (b)
(c) (d)
Fig-1: 4 DoF Robotic Arm Working Space
The motherboard used in the project is Arduino AVR based
MKS Gen 1.4. With this motherboard, only single operations
can be performed and therefore the movement of the axes is
carried out sequentially. The base of the BCN3D Moveo has
approximately 270 degreesrotational angleinthehorizontal
plane, the 1st joint has a maximum 220 degrees rotational
angle in the vertical plane, the 2nd joint has a maximum 250
degrees rotational angle in the vertical plane, the 3rd joint
has a maximum 210 degrees rotational angle in the vertical
plane, and the gripper can clutch a maximum 8cm width
object. Within the scope of the project,thebaseoftheBCN3D
Moveo robot has 270 degrees and the 1st joint has 220
degrees, even if the robot arm base is programmed 180
degrees the robot can reach any object in the 360 degrees in
working space. It is shown in figure 1.a-d.
2.4 Motor driver
The TB6560 motor driver is a driver made of Toshiba
TB6560AHQ chip and used especially for operating two-
phase bipolar stepper motors. It is effective in controlling
even large stepper motors such as Nema 23 with its
continuous maximum 3A current. The chip on the drive
incorporates various safety functions such as overcurrent,
low voltage shutdown, and overheat protection. The driver
does not have reverse-voltage protection. The voltage can
withstand between 10-35V voltage and 3.5A current
however the optimum voltage for the driver is 24V and the
working current is 3A. The sensitivity of the driver is 1, 1/2,
1/8, 1/16 micro step degree, the user can also interferewith
the step control of the motor. The current on the driver is
controllable with 100%, 75%, 50%, and 25% rates, this also
helps prevent overheating of the used motors [7, 11, 12].
2.5 Stepper motor
Stepper motors respond to a very important need among
known motors. There are many common uses of stepper
motors used especially in measurement and control
applications, robot applications, CNC applications, etc. [9].
2.6 Sensor
Within the scope of the study, 2 different sensors were used
for the movement of the robot arm system. One of the
sensors used is the acceleration sensor and the other is the
flex sensor. Each joint of the robot arm is moved by the axis
values obtained with the acceleration sensor. Each joints
movement is obtained by these values and microprocessor
moves step by step each joint. The gripper is controlled by
the flex sensor which is located at the head of the 4th joint.
2.6.1 ADXL345 sensor
ADXL345 acceleration sensorusedtoprovidethemovement
of the joints of the robot arm. The acceleration sensor gives
positive and negative axis values of X, Y and Z axes. The
single acceleration sensor gives just only 3 axis values and it
is not enough for the movement of 4 manipulators. Because
of that, two acceleration sensors used for 4 manipulators.
Two-axis of each acceleration sensor was used to determine
the movement of 4 DoF joints. Each acceleration sensor was
located on two gloves, and 4 manipulators were controlled
with 2 axis values obtained from these sensors.
The accelerometer gives positive and negative data on X, Y,
and Z axes that provide data transmission using I2C serial
communication protocol or SPI digital interface. It is a high-
resolution 13bit sensor that can be up to ± 2g, ± 4g, ± 8g or ±
16g. Digital output data is formatted by completing 16 bits,
and data is obtained via SPI or I2C digital interface. The low
range gives more resolution for slow movements, on the
other hand, the high range gives a good resolution for high-
speed monitoring. It can be fed with an input voltage 3-5V
since the sensor has an internal voltage regulator.

Measurement of slope changes less than 1.0 degrees is
ensured by the high resolution of the sensor (4mg / LSB).
There are several special detection functions on the sensor
(Figure 2). Detection of activity and inactivity, the presence
or lack of motion, and whether any accelerationinanyaxisis
exceeded by a user-adjusted level can be determined. Step
detection helps single and double level detection. Freefall
detection gives information on whether the device falls or
not. These functions are achieved by mapping oneofthetwo
cutting output pins. Low power modes, threshold detection
and active acceleration measurement due to extremely low
power loss allow intelligent motion-based power
management [10].
Fig 2: Functional Block Diagram [8]
2.6.2 Flex sensor
The flex sensor is a variable resistor that helps achieve
resistance change as it bends. When it is not bending, it has
~25KΩ resistance value, while this value increases to
~100KΩ during bending. Its structure is very similar to
force-sensitive resistors (FSR). Angle displacement is
obtained by bending, one of the most important areas of use
is robot technology.
2.7 Block Diagram
The movement of the robot arm depends on the two
acceleration sensors and the gripper movement of the robot
arm depends on the flex sensor. The flow diagram of the
robot arm is shown below (Figure 3).
Fig-3: Block Diagram of Robotic Arm
3. APPLICATION
With the applied prototype study, the joint movement of the
robot arm was provided depending on the axis values
coming from the acceleration sensor on the gloves.Thus, the
robot arm, which is controlled by humans, can be developed
as a prototype that can be used in hazardous areas that
people cannot enter. It can especiallybeusedintheindustry,
it is necessary to work in fast decision-making processes
without waiting for autonomous programming function, in
first aid rescue works, etc. There may be vibrations on the
robot arm, depending on the hand sensitivity of the human
who use the robot arm. In the next phase of this study, a
system will be developed to be able to tolerate the hand
vibration of the user.
In the prototype study, the movementsoftherobotjoints are
controlled with an Arduino compatible ATmega2560
processor and the use of MKS Gen 1.4, which performs a
step-by-step operation, makes it imperative that the motion
of each joint is performed sequentially.Withtheuseofmulti-
processing motherboards, multiple joints can be moved
simultaneously and more effective results can be achieved.

4. CONCLUSIONS
A robot arm was successfully designed which can rotate360
degrees around its axis and executed all the necessary tasks
sequentially. It can grasp any object in the working space
with autonomous control. The system has an autonomous
controllable feature. Using powerful ATmega2560
microprocessor stands out with many features for the
control of the system, a robot arm prototype quickly detects
axis movements due to acceleration changes obtained and
gives early reflexes.
REFERENCES
[1] U. Schneider, J.R.D. Posada and A.W. Verl. "Automatic
pose optimization for robotic processes." IEEE
International Conference on Robotics and Automation,
May. 2015
[2] “Robots and the Workplace of the Future.” A positioning
paper by the International Federation of Robotics
[Online]. Available:
https://ifr.org/downloads/papers/IFR_Robots_and_the_
Workplace_of_the_Future_Positioning_Paper.pdf
[3] E. Abele, S. Rothenbücher and M. Weigold. "Cartesian
compliance model for industrial robots using virtual
joints." ProductionEngineering2(3):339-343.Sep.2008
[4] R. Gautam, A. Gedam, A. Zade, A. Mahawadiwar.“Review
on Development of Industrial Robotic Arm”,
International Research Journal of Engineering and
Technology (IRJET), Volume: 04 Issue: 03 | Mar -2017
[5] “BCN3D Technologies.” [Online]. Available:
https://github.com/BCN3D
[6] “ATmega2560.” [Online]. Available:
https://www.microchip.com/wwwproducts/en/ATmeg
a2560
[7] “Tb6560 stepping motor driver.” [Online]. Available:
http://www.ribu.at/PDF/Tb6560.pdf
[8] “MKS GEN V1.4 Board Technical Specifications.”
[Online].Available:http://evrodekor34.ru/en/mks-gen-
v-1-4-opisanie-podklyuchenie-elektroniki-k-plate-mks-
gen-v1-4-podklyuchenie.html
[9] “Stepping Motors Fundamentals.” [Online]. Available:
http://www.t-es-t.hu/download/microchip/an907a.pdf
[10] “Digital Accelerometer ADXL345.” [Online]. Available:
https://www.sparkfun.com/datasheets/Sensors/Accele
rometer/ADXL345.pdf
[11] “3-Axis TB6560 CNC Driver Board Users Manual.”
http://www.cncbotto.com/controller.pdf
[12] “TB6560 Stepper Motor Driver with Arduino Tutorial.”
https://www.makerguides.com/tb6560-stepper-motor-
driver-arduino-tutorial/

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