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International Journal of Computer Application
(Special issue- Issue 5, Volume 2 (January 2015)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
DESIGN AND IMPLEMENTATION OF ROBOTIC
ARM WITH SIX DEGREES OF FREEDOM USING
FPGA
Ruchi Dwivedi#1, Preeti Kumari#2,Arvind Kumar#3,Munmun Ghosal#4
#1Umbergaon, Dist-Valsad, Gujarat (396165), 8446396767.
#2 Kundwapar, dist-nalanda, Bihar(801301), 8793301406.
#3 map 2/5,ballygunge, Kolkata(700019), 8983896443.
#4 GHRCEM Wagholi, 8007178659,.
ABSTRACT
The purpose of this paper is to make a multipurpose robotic arm which can perform
operations with higher accuracy with 6 degrees of freedom with the help of FPGA kit .The
arm will exhibit higher speed of operations and lower delay in processing due to the use of
FPGA for processing and control .This will improve speed of operation and reduce the latency
period of response when used for application such as bionic arm as compared to present
methods. This is so because FPGA uses parallel execution of PWM pulses.
Pulse Width Modulation (PWM) is used to control the speed of DC motor. The hardware
functional block is to be designed in software module with the help of VHDL coding. This
hardware and software co-design is for six axes arm robot model for the movement of robotic
arm for pick and place application. The interfacing of different hardware blocks with software
module for real time application is very challenging and demanding in every field to achieve
better command over control through software only without disturbing the hardware.
Key words: FPGA, Robotic Arm, Degrees of freedom, Sliding Mode Controller .
Corresponding Author: Munmun Ghosal
CONFERENCE PAPER
National level conference on
"Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)"
On 6-8 Jan 2015 organized by
" G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India."
Page 89
International Journal of Computer Application
(Special issue- Issue 5, Volume 2 (January 2015)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
INTRODUCTION
A robotic arm is a mechanical arm, which can be automatic or controlled manually, having
multipurpose manipulator programmable in three or more axes and can be used to perform a
variety of tasks with great accuracy and speed. The Robotic arm with six Degrees Of Freedom
(DOF) as that of a human arm can perform all tasks with ease and comparatively faster ,
simpler with fewer movements. In the present scenario, Robotic arm has fewer degrees of
freedom typically less than five, but for successful replication of a human arm we require six
DOF [1][2]. The replication of a human arm would be ideal to use it as a bionic arm and to
perform other industrial automations in a simpler manner.
In this paper Sliding Mode Controller (SMC) will be used to control the robotic arm. Use of
slider increases the stability and robustness of the robotic arm. Conversely, sliding mode
controller induces chattering phenomenon which affect the accuracy of the system output [3].
To solve the chattering in the system output, boundary layer method should be used in the
main controller in the control loop and also used for adjusting sliding surface to have best
performance [4-5].
In this paper, a Robotic arm with servo motor will be made. The selection of the servo motor
is due to their ability to move to a finer angle, it provides high torque during loaded and
unloaded conditions versus DC motors and stepper motors have low holding torque with less
precision. These features made the servo motor an effective choice for the construction of the
arm.
In this paper, a user interface (GUI) will be created using MATLAB which is used to control
the Arm. The MATLAB interface is responsible for sending the data to the FPGA via serial
port. Since microcontroller can generate limited number of PWM channel required for servo
motor, hence a Xilinx based SPARTAN3 FPGA will be used which can generate large
number of PWM channel. The decoded information is converted into digital data and is
updated along with the address. The FPGA reads the data and then generates the PWM and
updates the value to the corresponding joint motor. The robot offers the following two modes
of operation.
AUTOMATIC MODE:
In this mode the robotic arm will be pre-programmed to perform certain task or tasks in a
sequential manner without any human intervention.
MANUAL MODE:
In this mode the robotic arm will be operated manually [6].
MATERIALS AND METHODS:
Hardware Used: FPGA Spartan3 Kit
 Servo Motor
 DC Motor
 Robotic Arm (Hand-made)
 Computer
CONFERENCE PAPER
National level conference on
"Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)"
On 6-8 Jan 2015 organized by
" G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India."
Page 90
International Journal of Computer Application
(Special issue- Issue 5, Volume 2 (January 2015)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
Software Used: Xilinx (VHDL Coding)
 MATLAB
Methods:-
Fig.1: Program Flow
In this paper, robotic arm is controlled in two modes i.e automatic as well as manual. Both the
mode is controlled by GUI which is created using MATLAB software. For six degree of freedom
there are six sliders in the GUI, one for each movement. Firstly maximum and minimum value of
the slider is set in degrees. Now when the slider is moved upward and downward , there is a
change in the values (angle). With the help of MATLAB interface this data is send to the FPGA
using serial communication. FPGA is used to generate large number of PWM channel. FPGA
will generate PWM channel according to the value transmitted from GUI. The pulse is given to
the servo motor and hence corresponding rotation of the motor takes place. For movement of
robot from one place to another two DC motor is connected to the base of robot.
The robot and the arm can be pre-programmed to perform certain task in sequential manner
without any human intervention.
FPGA:In robotic application mostly non-linear controllers are used for the real time operation. In this
application FPGA based controller has been used because of its small size, high speed, low cost
and short time to market. The FPGA based controller has a short execution time because of its
parallel execution [7-10].
CONFERENCE PAPER
National level conference on
"Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)"
On 6-8 Jan 2015 organized by
" G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India."
Page 91
International Journal of Computer Application
(Special issue- Issue 5, Volume 2 (January 2015)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
PWM:PWM is a way of delivering the energy in the form of pulse rather than a continuous
varying(analog) signal. The controller regulates energy flow to the motor shaft by increasing or
decreasing pulse width. In our case the servo motor which will be made to rotate according to the
desired angle is controlled using PWM signal. PWM signal used for controlling servo motor has
constant pulse width of 20ms (50Hz) whose ON time is varied according to thr desired point. For
entire servo motors, PWM width is constant. We will first adjust the motor shaft to 90 degrees
and forward and reversed movement is controlled by slider application in the MATLAB[11].
The numerical value of 8 bit is from 0 to 255. This value will be mapped with the angle from 0 to
180 degrees. These angles from 0 to 180 degrees will be divided equally between 1ms to 2ms
which is the ON time of the servomotor. According to this ON time, FPGA will generate the
pulse of particular voltage which depends on the ON time and then this voltage will be sent to
the servomotor.
Fig.2 PWM waveform
CONCLUSION:
The paper presents the constructions of a Robotic Arm which is equivalent to a human arm.
The robotic arm is tested in different working conditions and terrains and its performance is
noted. It is noted that arm could lift an object of 3kg which should be within the diameter of
10cm. It provides various approaches for the data communication between the electronic
devices and also some precautions to be taken to avoid errors. The electronic circuit in arm is
affected by electromagnetic radiation due to electromagnetic devices used and surroundings.
This causes significant errors. The error is solved by the use of shielded twisted pair cable
which protects the circuit from EMI radiations.
There are many future scopes for the Robotic Arm in various fields: a) By the use of more
servo-motors its load as well as degree of freedom can be increased. b) Different types of
sensors can be used which will make the arm more advance. c) A voice control arm can be
made using voice sensors. d) By the use of web interface arm can be controlled from remote
place using web browser.
CONFERENCE PAPER
National level conference on
"Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)"
On 6-8 Jan 2015 organized by
" G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India."
Page 92
International Journal of Computer Application
(Special issue- Issue 5, Volume 2 (January 2015)
Available online on http://www.rspublication.com/ijca/ijca_index.htm
ISSN: 2250-1797
REFERENCE:
[1] P. Bande, U. Meshram, R.R. Harkare, “Hardware and Software Co-design for Robot Arm
Position Control using VHDL and FPGA”,International Conference on Multimedia, Signal
Processing and Communication Technologies,IMPACT’09,pp.8-11,2009.
[2] Hao, W.Guan, Leck, Y.Lee,Hun,L.Chot “6-DOF PC-based Robotic Arm (ROBOARM)
with efficient trajectory planning and speed control”,4th International conference on
Mechatronics(ICOM),pp. 1-7,2011.
[3] T.R. Kurfess, Robotics and automation handbook: CRC,2005.
[4] B. Siciliano and O. Khatib, Springer handbook of robotics: Springer-Verlag New York
Inc, 2008.
[5] O. Kaynak ,”Guest editorial special section on computationally intelligent methodologies
and sliding-mode control,”IEEE Transactions on Industrial Electronics, vol. 48, pp.2-3, 2001.
[6] J. Losansky, M.Rentzsch, H. Gulder, “Intelligent measurement and control platform using
SPARTAN3 FPGA”,In Proc. of European Conference on Power electronics and application,
August, 2005.
[7] N. Sulaiman, et al., “Design and Implementation of FPGA-Based System-A Review.”
Australian Journal of Basic and Applied Sciences, vol. 3,pp.3575-3596,2009.
[8] U. Meshram, et al., “Robot arm controller using FPGA,” 2009,pp. 8-11.
[9] U.D. Meshram and R. Harkare,”FPGA Based Five Axis Robot Arm Controller.”
[10] F.J. Lin, et al., “FPGA-based fuzzy sliding-mode control for a linear induction motor
drive,” 2005, pp. 1137-1148.
[11] V. Ramakrishnan, N.S.Gopal, R.Ashok,S.Moorthi,”FPGA based DC servo motor
control for remote application of movements for a surgical arm”, 10th Regional IEEE
conference, (TENCON),pp.671-675,Nov.2011
CONFERENCE PAPER
National level conference on
"Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)"
On 6-8 Jan 2015 organized by
" G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India."
Page 93