5+2 degree of freedom robot with mobile base

VISVESVARAYA TECHNOLOGICAL UNIVERSITY

Project Report On

PICK AND PLACE ROBOT Submitted in partial fulfillment of requirements for the award of degree in

BACHELOR OF ENGINEERING IN MECHANICAL ENGINEERING VISVESVARAYA TECHNOLOGICAL UNIVERSITY BELGAUM Submitted by RAMA CHANDRA

:1MV05ME085

LAKSHMAN R. RAJU

:1MV05ME050

GIRISH H.N.

:1MV05ME029

CHIRAG D.SONI

:1MV05ME021

Under the guidance of Internal guide

External Guide

Mr.GANESH PRASAD ASSISTANT PROFFESSOR Dept of Mechanical Sir.M.V.I.T, Bangalore

RAVI CHANDRA.V HARDWARE ENGINEER BOSCH Bangalore

DEPARTMENT OF MECHANICAL ENGINEERING SIR.M.VISVESVARAYA INSTITUTE OF TECHNOLOGY

SIR.M.VISVESVARAYA INSTITUTE OF TECHNLOGY BANGALORE – 562157 Department of Mechanical Engineering

CERTIFICATE This is to certify that the project work entitled “PICK AND PLACE ROBOT” been submitted by RAMA CHANDRA (1MV05ME085), LAKSHMAN R RAJU (1MV05ME50),GIRISH

H.N.

partial

(1MV05ME029)

(1MV05ME021)

in

fulfillment

MECHANICAL

ENGINEERING

by

for

the

AND

CHIRAG

award

of

VISVESVARAYA

D.

SONI

BACHELORS

IN

TECHNOLOGICAL

UNIVERSITY , Belgaum, during the year 2008-2009.It is certified that all corrections/suggestions indicated for internal assessment have been incorporated in the report deposited in the department library. The project report has been approved as it satisfies the academic requirements in respect to the project work prescribed for the Bachelor of Engineering Degree.

Mr.GANESH PRASAD

DR.D.N.DRAKSHAYANI

Dr.M.S.INDIRA

ASSISTANT PROFFESSOR

Head Of the Department of ME

Principal

Dept of Mechanical

Sir.M.V.I.T, Bangalore

SIR MVIT, Bangalore

Sir.M.V.I.T, Bangalore

Signature of External Examiners Name of Examiners 1)___________________ 2)___________________

Signature

ACKNOWLEDGEMENT The satisfaction that accompanies the successful completion of any task would be incomplete without the mention of people who made it possible. It is their constant guidance and encouragement that crowns all our effort with success.

We are extremely grateful to Sri. M. S. GANESH PRASAD, Asst.professor, Department of Mechanical Engineering, SirMVIT,Bangalore,who was the architect in bringing the project through and inspired through his knowledge and humbleness. He is the man behind the success of the project.

We would like to thank Dr. M.S.INDIRA , Principal, Sir SMVIT,Bangalore and DR.D.N.DRAKSHAYANI, Head, Departmant of Mechanical Engineering, Sir MVIT, Bangalore for providing all facilities, guidance and encouragement to carry out this project.

We would like to thank RAVI CHANDRA.V, Hardware Engineer, BOSCH, Bangalore. for the facility and infrastructure support from the organization.

We would like to mention our special thanks to all the teaching and technical staff members of department of Mechanical Engineering, Sir MVIT, who helped us directly or indirectly during the project work.

The project team

SYNOPSIS The field of robotics and control is both interdisciplinary and multidisciplinary as robots are amazingly complex systems comprising mechanical, electrical and electronics hardware and software systems and issues germane to all these. This project team is intended to introduce the subject of industrial robotics. Robotics is a prominent component of manufacturing automation which will affect human labor at all levels, from unskilled workers to professional engineers and managers of production.

With a pressing need for increased productivity and the delivery of end products of uniform quality, industry is turning more and more towards computer-based automation. The industrial applications and atmospheres are diverse in nature, frequent, complex, non-reachable or harmful to human beings. In all these cases the robot can be an alternative to human hands. The project is aimed to build a Pick and place robot, which can lift a payload of 200 grams to a maximum of 1 kilogram. It’s a third generation robot that provides fast, efficient sample handling. Robot is a fully programmable robot with a mobile base.

Pick and Place Robot

INDEX TITLE/CONTENT 1.

2.

PAGE NO.

INTRODUCTION

1

1.1 What is a Robot?

2

1.2 Asimov’s Laws of Robotics

2

1.3 Robotics in science fiction

3

1.4 History

4

Fundamentals of Robot Technology

5

2.1 Robot anatomy

6

2.2 Classification of Robots

7

2.3 Robot Configuration

8

2.4 Components of a Robot

10

2.41 Manipulator

10

2.42 Actuators and drive

11

2.43 End effecter

12

2.44 Sensors

12

2.45 Controllers

13

2.46 Software

13

2.5 Some Terminologies

14

2.6 Specifications

15

3. DESIGN 3.1 Requirements

16 17

3.11 The ROBOT must be as LIGHT as possible

19

3.12 Determination of section thickness

20

3.2 Design a simple mechanism Department of mechanical engineering, sir MVIT

21

Pick and Place Robot 3.3 Preliminary design

22

3.4 Revision of design

23

3.5 Final drawings

25

3.6 Gripper design: Different End Effectors Mechanisms

26

3.7 Mobile base design

30

4. Manufacturing

33

4.1 Machined Components

34

4.2 Machining for minor base

35

4.3 Casings/chest

36

4.4 Machining of arm1(tapered)

37

4.5 Arm 2( I-shaped)

38

4.6 Machining for shafts and bushes

39

4.7 Spacers

41

4.8 Mobile base

42

4.81 Machining of mobile base 4.9 Other components 5. Controllers

42 43 44

5.1 INTRODUCTION

45

5.2 Key Components used in controller

46

5.21 Transistors

46

5.22 16*2 LCD display

47

5.23 Relays

47

5.24 Push button switches

48

5.25 Voltage regulator

48

5.26 MICRO CONTROLLER

49

5.3 Features of ATMEGA16 microcontroller

49

5.4 Pin Configurations

51

Department of mechanical engineering, sir MVIT

Pick and Place Robot 5.5 Block diagram of microcontroller 5.51 Motor circuit 6. Robot Applications

52 53 54

6.1Robot Applications

55

6.2 Advantages

55

7. Conclusion 7.1 Further Scope and Development

8. References 8.1References


56 57

59 60


List of figures TITLE

PAGE NO.

Chapter 2 Robot manipulator Fig (2.1)

6

Robot configurations Cartesian fig (2.2)

8

Cylindrical fig (2.3)

8

Spherical fig (2.4)

9

Articulated fig (2.5)

9

SCARA fig (2.6)

9

Revolute joints Fig (2.7)

11

Fig (2.8)

11

Fig (2.9)

11

Servo motor fig (2.10

11

Power window motor fig (2.11)

11

Wiper motor fig (2.12)

11

End effectors Fig (2.13)

12

Fig (2.14)

12

Fig (2.15)

12


Pick and Place Robot Chapter3 Free body diagram fig (3.1)

19

Gripper in vertical position Fig (3.2)

20

Fig (3.3)

20

Gripper in horizontal position Fig (3.4)

21

Driving system fig (3.5)

22

Inventor part drawing fig (3.6)

25

Gripper mechanisms fig (3.7)

26

Gripper photo fig (3.8)

27

Gripper illustration fig (3.9)

28

Mobile base photo fig (3.10)

32

Chapter 4 Inventor model of minor base Fig (4.1)

35

Inventor model of casings Fig (4.2)

36

Inventor model of arm 1 fig (4.3)

37

Inventor model of arm 2 fig (4.4)

38

Inventor model of shafts fig (4.5)

39

Inventor model of bushes Fig (4.6) Department of mechanical engineering, sir MVIT

39

Pick and Place Robot Fig (4.7)

39

Chapter 5 Controller diagram fig (5.1)

45

MOFSET symbol fig (5.2)

46

16*2 LCD display fig (5.3)

47

Voltage regulator circuit diagram fig (5.4)

48

Pin config of Atmega 16 controller fig (5.5)

51

Motor circuit diagram fig (5.6)

53

Final picture of pick and place robot

61



INTRODUCTION


Page 1


Chapter 1

INTRODUCTION 1.1 What is a Robot? The term robot derives from the Czech word robota, meaning forced work or compulsory service, or robotnik, meaning serf. First used to describe fabricated workers in a fictional 1920s play called Rossum’s Universal Robots by Czech author Karel Capek.

Definitions “A reprogrammable, multifunctional manipulator designed to move material, parts, tools, or specialized devices through various programmed motions for the performance of a variety of tasks."

- Robot Institute of America, 1979 “An automatic device that performs functions normally ascribed to humans or a machine in the form of a human.”

-Webster’s Dictionary 1.2 Asimov’s Laws of Robotics

A robot may not injure a human being, or, through inaction, allow a human being to come to harm

A robot must obey orders given it by human beings, except where such orders would conflict with the First Law.


Page 2


A robot must protect its own existence as long as such protection does not conflict with the First or Second Law.

1.3 Robotics in science fiction

Following the early instances of robots in plays and science fiction stories , robots then started to appear on television shows, like Lost in Space and then in Hollywood movies.

In Lost in Space the robot demonstrated human characteristics such as feelings and emotions.

Scientists today are still a long way off from programming robots which can think and act like humans.

1.4 History Science fiction has no doubt contributed to the developments of robotics, by planting ideas in minds of young people who might embark on careers in robotics, and by creating awareness among the public about this technology. We should also identify certain technological developments over the years that have contributed to the substance of robotics.

The below table presents a chronological listing which summarizes the historical developments in the technology of robotics.


Page 3


YEAR

SCIENTIST/

Robot/Type

Organisation 1801

J.Jacquard

Jacquard loom

1805

H. Maillardet

Mechanical doll

1951

U.S patents

Development work on teleoperators

1952

Massachusetts institute of

Prototype numerical control machine

technology 1954

C. W Kenward

Robot design

1959

Planet corporation

First commercial robot

1960

---------------------

Unimate robot

1961

Ford motor company

Unimate robot used for tending a die casting machine

1966

Trallfa

Spray painting machine

1968

Stanford research institute

Shakey- mobile robot

1971

Stanford university

Stanford arm

1973

S.R.I

Computer type robot

1974

A.S.E.A

All electric drive IRB6 robot

1975

Olivitti

Sigma

1976

Stark Drapper labs

Remote center compliance device

1978

General motors

PUMA

1979

Yamanashi university

SCARA

1980

University of Rhode Island Bin-picking robotic system

1981

Carnegie-mellon university Direct drive robot

1982

IBM

1983

National science foundation Adaptable programmable assembly


1984

----------------------

RS-1

system Offline programming system

Page 4


Fundamentals of Robot Technology


Page 5


Chapter 2

Fundamentals of Robot Technology 2.1 Robot anatomy

Robot anatomy is concerned with the physical contraction of the body, arm, and wrist of the machine. The body is attached to the base and the arm assembly is attached to the body. At the end of the arm is the wrist. The wrist consists of a number of components that allow it to be oriented in a series of joints. The body, arm and wrist assembly is sometimes called the manipulator.

Robot manipulator (fig 2.1)


Page 6


2.2 Classification of Robots The robots are classified based on following categories 1. Degrees of freedom 2. Kinematic structure –

Serial (open kinematic chain)

–

Parallel (closed)

–

Hybrid

3. Drive technology 4. Workspace geometry and mechanical configuration 5. Motion characteristics –

Planar

–

Spherical

–

Spatial

6. Control method –

Point-to-point

– Continuous path


Page 7


2.3 Robot Configuration Industrial robots are categorized by the first three joint types Prismatic (P) Revolute (R) Spherical (S) Robot configurations: – Cartesian/rectangular/gantry (PPP) – Cylindrical (RPP) – Spherical (RRP) –

Articulated/anthropomorphic (RRR)–

–

Selective Compliance Assembly Robot Arm (SCARA)

– Fig (2.2)


Fig(2.3)

Page 8


Fig(2.4)

Fig(2.5)

Fig (2.6)


Page 9


2.4 Components of a Robot Manipulator (arm) Actuators and drive – Servo and stepper motors – Hydraulics – Pneumatics – Gearbox End effecter (gripper) Sensors and transducers Controllers (power conversion) Software Base - Wheeled, tracked, legged - Fixed

2.41 Manipulator Is the main body of the robot and consists of links, the joints and other structural elements. Relative motion permitted by a joint is governed by form of contact surfaces between the members Typical manipulators allow for: Prismatic motion (linear movement) Rotary motion (around a fixed hub)


Page 10


Fig (2.7)

Fig (2.8)

Fig (2.9)

Revolute joints 2.42 Actuators and drive Are the “muscles” of the manipulator that move or create mechanical action Common types •

Servomotors – power driven mechanism that help main controller operates using low force

Stepper motors – a rotating motor in a small step and not continuous Pneumatic cylinders – relating to air or other gases Hydraulic cylinders – moved by, or operated by a fluid, especially water, under pressure.

Fig (2.10) Servo motor

Fig (2.11) power window motor


Fig (2.12) Wiper motor

Page 11


2.43 End effectors The part that is connected to the last joint (hand) of a manipulator. In most cases the action of the end effecter is either controlled by the robot’s controller or the controller communicates with the end effectors controlling device The end effectors may be: a Gripper, Suction/Vacuum, Glue, Hooks, Rack and Pinion, Screw and Fastener Devices

Fig(2.13)

Fig (2.14)

Fig (2.15)

2.44 Sensors Sensors are used to collect information about the internal state if the robot to communicate with outside environment. Sensors that tell the robot position/change of joints: odometers, speedometers, etc.Force sensing. Enables compliant motion—robot just maintains contact with object. Sensors used in robotics are tactile sensors or nontactile sensors; proximity or range sensors; contact or non contact sensors, or a vision system. For manipulator motion control, joint-link positions, velocities, torques, or forces are required to be sensed.


Page 12


Visual

Video cameras Range sensors

Auditory

Microwave

Olfactory

Gas sensor

Taste

(Under study)

Tactual

Pressure, temperature, humidity, touch

Table 2 2.45 Controllers The brain generally a computer but dedicated to a single purpose Like Calculates motions, how much/fast joint must move. It receive data from computer, control actuators motions and coordinates the motions with the sensory feedback information E.g. Controls angle, velocity, force.

2.46 Software Three group of software • Operating system • Robotic software: calculates necessary motions of each joint based on kinematics equations • Collection of routines and application programs – to use peripheral devices E.g. vision routines, specific task


Page 13


2.5 Some Terminologies:

Work volume: It is the term that refers to the space with in which the robot can manipulate its wrist end. The convection of using the wrist end to define the robots work volume is adopted to avoid the complication of different sizes of end effectors that might be attached to the robot wrist. The work volume is determined by the following physical characteristics of the robot: •

The robot’s physical configuration.

•

The sizes of the body, arm and wrist components.

•

The limits of the robot joint movements.

Load carrying capacity: The size, configuration, construction and drive system determine the load carrying capacity of the robot. This load capacity should be specified under the condition that the robot’s arm is its weakest position.

Speed of response: It refers to the capability of the control system to move to the next position in a short amount of time.

Stability: It is defined as a measure of the oscillations which occur in the arm during movement from one position to the next.

Spatial resolution: The special resolution of a robot is the smallest increment of movements into which the robot can divide its work volume.


Page 14


Accuracy: It is the robots ability to position its wrist end at a desired target point within the work volume.

Repeatability: The ability to position its wrist or an end effectors attached to its wrist at a point in space that had previously been taught to the robot.

2.6 Specifications Robot arm configuration: Jointed- arm configuration. Arm

: 500mm.

Base

: 410mm.

Weight

: 15kgs.

Degrees of freedom

: 5+2

: Wiper motor driven

Axis positioning

Lifting capacity

: 500grams.

Workspace

: shelled semi-sphere

Gripper type

: power screw mechanism

Material

: aluminum.


Page 15


DESIGN


Page 16


Chapter 3

DESIGN The robot design is the most important part in the process of constructing the robot. Here we develop new ideas for the construction of the robot and express these ideas in the form of plans and drawings. The robot arm design procedure involves: Material selection Design of mechanism Preliminary design Revision of design Final drawings

3.1 REQUIREMENTS The robot must be as light as possible The arm must be rigid enough to withstand forces generated due to •

Own body weight

•

Weight of the object to be lifted

•

Inertia forces due to changes in velocity

•

Centrifugal forces due to changes in velocity

The mechanism must be simple such that the manufacturing process is simplified. The cost of the producing the robot must be reduced


Page 17


3.2 ARM DESIGN

3.21 MATERIAL SELECTION Since we want the robotic arm to be as light as possible we have chosen aluminum as material for this robot.

PROPERTIES OF ALUMINIUM DENSITY Light weight is perhaps aluminum’s best known characteristic and with a density of 2.7 x 103 kg/m3 is approximately 35% that of steel. This feature together with other characteristics such as corrosion resistance and tensile strength has led to it replacing steel in many applications.

TENSILE STRENGTH Commercially pure aluminum has a tensile strength of approximately 90MPa and can be improved to around 180MPa by cold working. The heat treatable grades can develop a tensile strength of around 570MPa and even higher in some alloys (7001). This figure compares favorably with mild steel which has a tensile strength of approximately 260MPa.

CORROSION RESISTANCE Aluminum has a good resistance to corrosion. This is attributable to a thin oxide film which forms and protects the metal from further oxidation: unless exposed to some substance or condition which destroys this protective coating the metal remains protected from corrosion.


Page 18


3.22 RIGIDITY OF THE ARM. The arm is designed to withstand forces generated due to own body weight, object weight, forces due to velocity and centrifugal forces.

Fig 3.1

Free body diagram Here ‘W’ indicates weight of the link ‘M’ indicates weight of the motor ‘L’ indicates the length (point to point) of the link After making the preliminary drawings of each link, the weight of the link is calculated by ρ=M/V Where ρ is density in kg/m3 M is the mass in kg V is the volume in m3


Page 19


Determination of section thickness 1st case: Gripper in vertical position

200

200

60 200

200 P

Fig (3.2)

Fig (3.3) Gripper with end effecter

Mb = F*e = 29.4*200 = 5880N-mm I = (b*d^3)/12 = (b*60^3)/12 Where c = distance from NA (Neutral axis) = 60/2 = 30 mm Working stress = F/A + (M*b*c)/I = 29.4/(60*b) + (5880*30)/((b*60^3)/12) Total stress/FOS= 90/5 = 18 = 0.49/b+9.8/b b = .571mm


Page 20


Case 2: When gripper is in horizontal position 200

200

Payload = 2*9.81

200 100 Motor weight = 2.50kg Fig (3.4) Bending moment Mb = 19.62*400 + 2.45 * 300 + 2.45*200 = 9195.5 N-mm Total tensile stress

= F/A = F1/A + F2/A + F3/A = (19.62 + 2.45 * 2)/A = 24.52/A

Combined stress

= F/A + Mbc/I = 24.52/ (60*b) + (9195.5 * 30*12)/ (b*60^3) = 15.47/b.

Working stress

= Total stress/FOS (Where FOS stands for factor of safety)

Therefore working stress = 90/5 = 18 = 15.74/b b = 0.874 ~ 0.9mm


Page 21


Conclusion = aluminum plate of 1mm is sufficient to withstand load of 0.9 kg. But the plate is to be thicker if it has to withstand other forces. To reduce the design procedure for calculating inertia forces and forces due to change in velocity we use spacers. Spacers not only help in withstanding these forces, but also provide rigidity for the robotic arm.

3.23 DESIGN A SIMPLE MECHANISM. To reduce the manufacturing work we are fixing the arm to the shaft by means of fastening, otherwise we have to use keys and slots to fix the shaft to the arm which consumes lot of time in designing the keys and slots. We designed the robot to work using simple chain drives. The chain drives are from automobile engines. Using these chains also reduces the cost of the chain drive and also these chains operate silently.

Driving systems of pick and place robot.

Fig (3.5)

Driving system


Page 22


3.24 PRELIMINARY DESIGN Preliminary drawings of all the parts are made. An inventor model of the robot with all the links is prepared, which gives insight of how the arm is to be assembled and how the arm looks after the assembly. These drawings are subject to changes in manufacturing process depending on the availability of the materials.

3.25 REVISION OF DESIGN The entire design is reviewed for defects; suitable corrections are made to suit the requirement. The design can be changed as per the torque requirement. Referring to the fig 1 the torque required is calculated as shown below

Torque required at the 3rd joint (wrist) T3=W7*L3+ (W6*L3)/2+M3*L4+M2*L5 =9.81*0.2+ (0.4*0.2)/2+0.2*0.1+0.2*.05 =2.005 N-m

Torque required at 2nd joint (elbow) T2= (L2+L3) W7+ (L2+ L3/2)*W6+ (W4*L2)/2+M2*(L2+L4)+M1*(L2+L5) =(0.2+0.2)*9.81+(0.2+0.1)0.4+(.4*.2)/2+0.2(0.2+0.1)+0.2*(0.2+0.05) = 4.194 N-m


Page 23


Torque required at 1st joint (shoulder) T1= (L1+L2+L3) W7+ (L1+L2+L3/2)*W6+ (L1+L2/2) W4+ (L1+L2+L4)*M2+ (L1+L2+L5)*M1+ (W2*L1)/2 = (0.2+0.2+0.1)*9.81+(0.2+0.2+0.1)*0.4+(0.2+0.1)0.4+(0.2+0.2+.1)*0.2+ (0.2+0.2+0.05)*0.2+ (0.4*0.2)/2 =5.455 N-m By referring the above equations we can see that the torque required is a function of weight of the links, weight of the motor, length of the link. The design can be altered if torque requirement is very high, the length can be minimized to reduce the torque requirement.


Page 24


3.26 FINAL DRAWINGS As per the requirements the design is changed and final drawing is made. These drawings are taken to the workshop to manufacture various parts which are then assembled as per the inventor model. Final drawings of few parts. :-

Fig (3.6) Inventor part drawings


Page 25


3.3 Gripper design 3.31Different End Effectors Mechanisms

Fig (3.7) Gripper mechanisms Department of mechanical engineering, sir MVIT

Page 26

Pick and Place Robot From all the above gripper mechanisms we are adopting power screw mechanisms because of its strong holding property, simple mechanism hence easy to construct and it is cost efficient.

Fig (3.8) Gripper photo


Page 27


3.32 Gripper force The force required to grip an object is to be calculated. Here a small illustration is shown, where the robot is supposed to grip an object and that object is a human neck in this case.

Fig (3.9) Gripper illustration The condition that is to be satisfied in order to hold the object is (FORCE APPLIED)*(COEFFICENT_OF _FRICTION) > WEIGHT OF THE OBJECT There are two kinds of friction coefficients that are to be taken into consideration they are 1) Static friction 2) Kinetic friction The static coefficient of friction is when the materials are stationary. The kinetic coefficient of friction is when the materials are already in motion Since our robot is used to move only stationary objects, we are considering only static friction.


Page 28


The following table shows coefficient of friction of some common materials.

Material 1

Material 2

Friction coefficient

Aluminum

Aluminum

1.05 - 1.35

Aluminum

Steel

0.61

Plexiglass

Plexiglass

0.8

Plexiglass

Steel

0.4 - 0.5

Polystyrene

Polystyrene

0.5

Polystyrene

Steel

0.3 - 0.35

Polystyrene

Steel

0.2

Rubber

Asphalt (dry)

0.5 - 0.8

Rubber

Asphalt (wet)

0.25 - 0.75

Rubber

Concrete (dry)

0.6 - 0.85

Rubber

Concrete (wet)

0.45 - 0.75

Teflon

Steel

0.04

Table 3


Page 29


3.4 Mobile base design The robotic arm is placed over the mobile base. The mobile base gives additional two more degrees of freedom to the arm. The base is made up of aluminum to reduce the weight of the robot. The base consists of the following parts 1) Aluminum frame 2) Aluminum plates( casing) 3) Aluminum shaft 4) Aluminum pulleys 5) Drive motors 6) Chain drive

3.41 Frame The frame of the robot is the basic structure to which we attach everything else. It is probably the largest part of the robot, so we make sure it is made of a light weight rigid material such as aluminum.

3.42 Aluminum plates Aluminum plates are attached to the frame, which forms the body of the mobile base. The plates must house the bearings in which the shafts are housed and also it houses the motor, which drives the shafts.


Page 30


3.43 Shafts and pulleys We wanted to mobile base to appear like a tanker, so we have used belt drives to give the tank look. We have used teethed belt for this purpose. This belt has better traction capacity as compared to normal flat belts. The shaft and pulleys are made up of aluminum to reduce the weight. The pulleys are given toothed profile to grip the belt properly and prevent it from slipping. Wheel diameter: When making the wheels we want to put our motor into consideration. For a start, there is torque and velocity. Large diameter wheels give the robot low torque but high velocity. Since we already have a very strong motor, we can use wheels with larger diameters. Lower diameter wheels have low velocity but high torque. While selecting the diameter of the pulley we also had to check frame width and the ground clearance.


Page 31


Fig (3.10) Mobile base photo


Page 32


Manufacturing


Page 33


Chapter 4

Manufacturing Some of the important factors to be considered are: 1. Shape to be produced 2. Type of material 3. Quality and property requirements 4. Technical viability of the process 5. Desired surface finish 6. Dimensional tolerance 7. Economic considerations

4.1 Machined Components 1. Major base. 2. Minor base. 3. Chest/casing. 4. Arm1 (Tapered). 5. Arm2 (I-shape) 6. Long Shaft. 7. Moderate shaft. 8. Short shaft.

9. H-type bush. 10. Step bush. Department of mechanical engineering, sir MVIT

Page 34

Pick and Place Robot 11. Normal bush.

12. Spacers.

4.2 Machining for minor base

Fig (4.1) inventor model of minor base After selecting an aluminum slab of required thickness as per design the following operations were carried out •

Metal cutting

Using Hack-saw the slab was cut to the required dimension.

Surface finish was obtained by filing.

Slot creation

Using the vertical milling machine and the end milling cutter the hole was made .

A slot of exact dimension was obtained by using slot milling cutter.

Drilling and tapping of holes

To fix both casings/chest as per the design center punch was marked at the required dimensions and using 5.1mm drill bit holes were drilled as shown in the previous slide.

Using hand tap of 6 mm, holes were threaded.


Page 35


4.3 Casings/chest

Fig (4.2) inventor model of casings Using hand shear, aluminum plate was cut for required size of casings. •

After obtaining the size for casing the aluminum plate was subjected to bench press to obtain “L”-shape as shown in previous slides

•

To fix both casings/chest as per the design center punch was marked at the required dimensions and using 6 mm drill bit holes were drilled as shown in the previous slide

•

According to the dimension of the shaft of the motor marking was made on the casing plate and hole for shaft diameter was drilled and using the round file the finishing was obtained.

•

With respect to center of the thus drilled hole the PCD hole marking were made and was drilled accordingly.

•

To connect the casings using shaft and bearing arrangement a hole was drilled to diameter of step bearing.

•

The ends were chamfered to give aesthetic mechanical design.


Page 36


4.4 Machining of arm1 (tapered)

Fig (4.3) inventor model of arm 1 •

As per the design markings were made on the aluminum plate and using hand shear the plate was cut on the marking.

•

To obtain the proper finishing on the cut surface grinding was done using the portable hand grinding machine.

•

To connect this arm to casing via bearing and shaft, holes were drilled as per the dimension of the bearing and to fix the bush to the arm through fasteners countersunk holes were created at the surface as shown in the previous slides.

•

To connect this tapered arm to arm2 (I-shape) one more hole is drilled at the other end of the arm which is according to the dimensions of the arrangement of “moderate sized shaft and step bearing”.


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4.5 Arm 2( I-shaped)

Fig(4.4) Inventor model of Arm 2 •

As per the design markings were made on the aluminum plate and using hand shear the plate was cut ton the marking

•

Using the “JIGSAW CUTTER” the “I” shape was achieved

•

To connect this arm to arm1 (tapered) via bearing and shaft, holes were drilled as per the dimension of the bearing and to fix the bush to the arm through fasteners countersunk holes were created at the surface as shown in the previous slides.

•

After obtaining the “I” shape to connect both the arms through the “short shaft & bearing” arrangement, holes of the required size were drilled accordingly.

•

The holes were filed using the round file to obtain the smooth radial finish.

•

The arm was also filed for smooth finish.


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4.6 Machining for shafts and bushes

Fig (4.5) inventor model of shafts •

An aluminum rod of dimension greater than the requirement was obtained.

•

It was subjected to turning operation in lathe providing certain tolerance.

•

Later it was subjected to step turning according to the required dimension.

•

It was so finished such that it fits into the bearing, situated in the casing rigidly.

•

Similarly other two shafts “MODERATE SHAFT & SHORT SHAFT” of the required dimensions were machined to connect the arm1 & arm2 respectively. Step Bush

Fig (4.6)

Fig (4.7)

Inventor model of bushes


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Pick and Place Robot •

An aluminum rod of dimension greater than the requirement was obtained, and required length was cut to make the bushes

•


•

In the robot Shape of bush is h type so as to insert 2 bearings at both side of it which will allow free movement of sprockets on the shaft to complete sprocket chain mechanism.

•

Higher accuracy was required in the machining of this bush as otherwise lead to misalignment and would not support the bearing and sprocket properly.

•

PCD holes were then drilled to fix the driving sprocket to the bush and a radial hole was drilled to ground the bush on longest shaft.

•

An aluminum rod of dimension greater than the requirement was obtained, and required length was cut to make the bushes

•


•

In the robot Shape of bush is step type so as to fix the arm1 to casing and further to join arm1 to arm 2 and support them on the shaft

•

One more application of the step bush is to support the driven sprocket fixed on moderate shaft so as to drive the arm2.

•

Higher accuracy was required in the machining of even this bush as otherwise lead to misalignment and would not support the arms and casing on respective shafts.

•

PCD holes were then drilled to fix the driven sprocket to the one of the step bushes and also to attach them to end of arms and casings.

•

Radial holes were drilled to ground the bush on respective shafts.


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4.7 Spacers

Fig (4.8) Spacers photo An aluminum rod of square cross section and dimension greater than the requirement was obtained, and required length was cut to make the spacer •

Using Hacksaw the aluminum rod was cut to the required size providing certain tolerance on both the sides.

•

Since perfect flat surface is required at the ends the, spacers were machined using “universal milling machine”.

Drilling •

To fix spacers as per the design center punch was marked at the required dimensions and using 4 mm drill bit holes were drilled

•

Using hand tap of 5 mm, holes were threaded.

Need of spacers

Spacer is an element which is used to maintain uniform distance between two plates

Use of spacers in between two plates prevents from bending due to inertia forces generated due to movement of arm.

Hence the robot arm remains rigid.


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4.8 Mobile base: Mobile base is used for the movement of the robotic arm. For this robot we are using track configuration.

4.81 Machining of mobile base • First the frame of the mobile base is built using angle plates. • Then it’s fastened rigidly to the major base which consisting of robotic arm. • The casing is cut from aluminum sheet according to the design. • On this casing holes are drilled to support shaft-bearing arrangement. • Gear cutting operation is used for the manufacturing of pulley according to number of teeth and other considerations. • Depending on the number of teeth and centre distance the belt which rotates along the pulley is purchased • Care is taken to provide enough required belt tension. • Machining of the casing is done so that the motor can be attached to it.

• Sprocket and chain mechanism is used to transfer the power of motor to the shaft and rotating the pulley.


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4.9 Other components 1. Bearings Collar bearing Thrust bearing Stepped collar bearing 2. Sprockets 3. Timing chain 4. Pulley 5. Belt 6. Fasteners


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Controller


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Chapter 5

Controllers

Fig (5.1) controller diagram 5.1 INTRODUCTION A micro controller is a microcomputer on a single chip I.e., it is a integration micro process with memory and input/output interfaces (ports) and other peripherals such as timer etc on a single chip. They are programmable, cheap, small, can handle abuse, require almost zero power, and there are so many varieties to suit every need. This is what makes them so useful for robotics - they are like tiny affordable computers that you can put right onto the robot. The considerations in robot programming are: •

The three dimensional objects with different physical properties are to be manipulated.

•

The environments of robot operations can be complex.

•

Visualization of the object can be discrete.

•

The processing and the analysis of the digital data from sensors and vision system have to be done in real time.


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5.2 Key Components used in controller 1. 2. 3. 4. 5.

Transistors 16*2 LCD display Relays Push button switches 7805 voltage regulator 6. microcontroller

5.21 Transistors A transistor is a semiconductor device commonly used to amplify or switch electronic signals. A transistor is made of a solid piece of a semiconductor material, with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals.

There is variety of transistors available in the market, but the transistor we have selected for our microcontroller is a MOFSET transistor. The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a device used to amplify or switch electronic signals.

N-channel

Fig (5.2)

p-channel

MOSFET dep


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5.22 16*2 LCD display

Fig (5.3) 16*2 LCD A liquid crystal display (LCD) is an electronically-modulated optical device shaped into a thin, flat panel made up of any number of color or monochrome pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector. It is often utilized in batterypowered electronic devices because it uses very small amounts of electric power.

5.23 Relays A simple electromagnetic relay, is an adaptation of an electromagnet. It consists of a coil of wire surrounding a soft iron core, an iron yoke, which provides a low reluctance path for magnetic flux. Relays are used to control the motor speed.

Working principle When an electric current is passed through the coil, the resulting magnetic field attracts the armature, and the consequent movement of the movable contact or contacts either makes or breaks a connection with a fixed contact. The type relay used in our microcontroller is Pole and throw type relay.

DPDT - Double Pole Double Throw. These have two rows of change-over terminals. Equivalent to two SPDT switches or relays actuated by a single coil. Such a relay has eight terminals, including the coil.


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Application in our robot. In this robot the relays are used to control the speed of the motor.

5.24 Push button switches A push-button (also spelled pushbutton) or simply button is a simple switch mechanism for controlling some aspect of a machine or a process. Buttons are typically made out of hard material, usually plastic or metal. The surface is usually flat or shaped to accommodate the human finger or hand, so as to be easily depressed or pushed. Buttons are most often biased switches, though even many un-biased buttons (due to their physical nature) require a spring to return to their un-pushed state. The push button switches are the means by which we control the robot motion. By pressing a particular switch a motor is activated and the motion is provided to the respective part of the robot. The motion can be provided to a joint or a wheel of the robot.

5.25 Voltage regulator A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. It may use an electromechanical mechanism, or passive or active electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages. 7085 voltage regulator

Fig (5.4) Voltage regulator circuit diagram


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5.26 MICRO CONTROLLER A microcontroller (also microcontroller unit, MCU or µC) is a small computer on a single integrated circuit consisting of a relatively simple CPU combined with support functions such as a crystal oscillator, timers, watchdog, serial and analog I/O etc. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a, typically small, read/write memory. We are using ATMEGA16 micro controller

Features of ATMEGA16 microcontroller

High-performance, Low-power AVR 8-bit Microcontroller Advanced RISC Architecture o 131 Powerful Instructions – Most Single-clock Cycle Execution o 32 x 8 General Purpose Working Registers o Fully Static Operation o Up to 16 MIPS Throughput at 16 MHz o On-chip 2-cycle Multiplier High Endurance Non-volatile Memory segments o 16K Bytes of In-System Self-programmable Flash program memory o 512 Bytes EEPROM o 1K Byte Internal SRAM o Write/Erase Cycles: 10,000 Flash/100,000 EEPROM o Data retention: 20 years at 85°C/100 years at 25°C(1) o Optional Boot Code Section with Independent Lock Bits In-System Programming by On-chip Boot Program True Read-While-Write Operation o Programming Lock for Software Security JTAG (IEEE std. 1149.1 Compliant) Interface o Boundary-scan Capabilities According to the JTAG Standard Department of mechanical engineering, sir MVIT

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Pick and Place Robot o Extensive On-chip Debug Support o Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface Peripheral Features o Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes o One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode o Real Time Counter with Separate Oscillator o Four PWM Channels o 8-channel, 10-bit ADC 7 Differential Channels in TQFP Package Only 2 Differential Channels with Programmable Gain at 1x, 10x, or 200x o Byte-oriented Two-wire Serial Interface o Programmable Serial USART o Master/Slave SPI Serial Interface o Programmable Watchdog Timer with Separate On-chip Oscillator o On-chip Analog Comparator Special Microcontroller Features o Power-on Reset and Programmable Brown-out Detection o Internal Calibrated RC Oscillator o External and Internal Interrupt Sources o Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby I/O and Packages o 32 Programmable I/O Lines o 40-pin PDIP, 44-lead TQFP, and 44-pad QFN/MLF Operating Voltages o 2.7 - 5.5V for ATmega16L o 4.5 - 5.5V for ATmega16 Speed Grades o 0 - 8 MHz for ATmega16L Department of mechanical engineering, sir MVIT

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Pick and Place Robot o 0 - 16 MHz for ATmega16 Power Consumption @ 1 MHz, 3V, and 25°C for ATmega16L o Active: 1.1 mA o Idle Mode: 0.35 mA o Power-down Mode: < 1 µA o

Pin Configurations

Fig 5.5 Pin config of Atmega 16 controller

The device is manufactured using Atmel’s high density nonvolatile memory technology. The Onchip ISP Flash allows the program memory to be reprogrammed in-system through an SPI serial interface, by a conventional nonvolatile memory programmer, or by an On-chip Boot program running on the AVR core. The boot program can use any interface to download the application


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5.3 CIRCUIT DIAGRAM


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MOTOR CIRCUIT DIAGRAM

Motor circuit

Fig (5.7) motor circuit diagram


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Robot Applications and advantages


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Chapter 6

APPLICATIONS AND ADVANTAGES

6.1 Robot Applications Material Handling Machine Loading/Unloading Assembly Inspection/Testing

6.2 Advantages • Cost efficient because of the use wiper motor as actuator. • Flexibility is more. • Greater power to mass ratio is achieved. • Track mechanism of the mobile base provides simple steering system and can be used in various terrains.


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Conclusion and Further Scope and Development


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Chapter 7

CONCLUSION AND FUTURESCOPE AND DEVELOPMENT

CONCLUSION • Presently it is a prototype, but in future it has an opportunity for industrial utilization for picking and placing objects since it is cost efficient. The developed robot is a remote controlled robot, with a mobile base. The robot is able to lift a load of 5oog and is able to move along the floor easily because of the track configuration. • The developed robot is of reprogrammable type with mobility, therefore can be used any type of co-ordinate system. Therefore in machine milling operation and even in CNC systems.

FUTURE SCOPE Since our robot has majorly two applications such as “pick and place” and “moveable”. Therefore in future it may be used: For sample handling in bio and chemistry labs. It can be used in shop floor for material handling.

DEVELOPMENT By the use of different kinds of end effectors we can make the robot to perform variety of operation. Example drilling spray painting, fastening, spot welding etc.


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Pick and Place Robot By modifying the present program we can achieve flexible controlling of the robot. Since the robot uses track configuration for movement it can used in all types of terrains. Therefore it can be used for excavation. By adding camera to the robot manipulator we can achieve vision ability. This robot can be used as study equipment for students.


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REFRENCES


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CHAPTER 8

REFERENCES •

www.robotics.org

•

www.lynxmotion.com

•

www.societyofrobots.com

•

www.space.gc.ca

•

www.nasa.gov

•

http:robotz.org

•

www.fanucrobotics.com

•

http://asimo.honda.com

•

www.bbc.co.uk/science/robots/rooteers/index.shtml

•

Industrial Robotics by Groover, TATA Mc-GRAWHILL publications.


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Final photo of pick and place robot


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5+2 degree of freedom robot with mobile base

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