BE FINAL PROJECT

Design & Analysis Of Detachable Mechanical Scoop Grippers For Collection Of Solid, Liquid & Semi-Solid
Sample With Ingress Protection Design.
MES College of Engineering, Pune-01 B.E.(Mechanical)
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1. INTRODUCTION
A gripper is an end-of-arm tooling used in a robot for grasping, holding, lifting, moving and
controlling of materials. Human hands have been the most common, versatile, effective and
delicate form of material handling. But, for repetitive cycles, heavy loads and under extreme
environments, grippers had to be developed as a substitute to human hands.
In 1960s, after the emergence of modern robots, grippers replaced human hands on numerous
occasions. Robot-gripper systems are found to be effective for repetitive material handling
functions in spite of their initial capital and ongoing maintenance expenses because of their
reliability, endurance and productivity. However, the cost of grippers may be as high as 20% of
the cost of a robot, depending on the application and part complexity. For manufacturing
systems where flexibility is desired, the cost of a suitable gripper may even go higher since they
require additional controls, sensors and design needs with regards to being able to handle
different parts.
In the 21st century, under the influence of globalization, manufacturing companies are required
to meet continuously changing demands in terms of product volume, variety and rapid response.
Flexible and reconfigurable manufacturing systems (FMS and RMS) have emerged as a science
and industrial practice to bring about solutions for unpredictable and frequently changing
market conditions.
Several research projects exist among these industrial gripping systems. Researchers are
working on the imitation of the flexibility of the human hand. Examples are the Karlsruher
Hand, the IFASH developed at RWTH Aachen and the DLR-Hand. They stated high-end
technology not suitable for general industrial use.
There are some applications where adaptive industrial gripper solutions could be helpful to
decrease setup times of handling systems and achieve a high flexibility of the whole automation
system. One example deals with the handling of car reflectors. Automobile suppliers have to
produce different kinds of car reflectors, sometimes hundreds of versions for current car types
and for the accessories market .

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Degrees of Freedom:-
Grippers also differ in their degree of freedom. Basically there are 6 degrees of freedom: 3
translations and 3 rotations.
But generally, unless you're building an arm, you wouldn't need all 6 degrees of freedom
(DOF). You get one DOF for free on a mobile robot: it can already move forwards and
backwards on its own. Although adding gripper movement along this direction will increase
your robot's accuracy, it's not really necessary.
How many DOF you need depends on how complicated the movement of your robot has to be.
If it only needs to pick up a glass and move towards a goal and put it down again, it would be
sufficient to make a gripper that can tilt back (towards the robot).
If you intend that your robot will have to be able to pick up Lego blocks and build a structure
with them, you'll need more DOF.
Types of Artificial Gripper Mechanisms:-
Gripper Mechanisms can be classified into following major categories:
1) Mechanical finger Grippers- sub-classification is based on method of actuation.
2) Vacuum and Magnetic Grippers- sub-classification is based on type of the force-
exerting elements.
3) Universal Grippers- sub-classification is inflatable fingers, soft fingers & three
fingered grippers.
Scoops:-
Raised Scoop Flat scoop

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Scoops are very simple 'grippers'. These can be flat, flat with raised edges or more
complicated shapes. These 'grippers' are easily to control as they can be build with
minimal moving parts: being able to move up and down is sufficient for many purposes.
Forward Tilting is common too and may be necessary to 'unload' the scoop.

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1.1 Problem statement
Robotic gripper should handle samples like solid, liquid, semi-solid with the payload of
200g.Robotic gripper should be electrically actuated.It should be protected from environmental
factors with the use of ingress protection .
1.2 Objective
The main objective of this project is to design and perform analysis on a detachable
electromechanical scoop for collection of solid, liquid, semi-solid sample with ingress
protection. This robot gripper will be handling sample like solid, liquid, semi-solid with the
load of 200 g.
Objectives of project:
• To conduct research on the topic that is related to this project.
• To implement the knowledge gained from the research to design a detachable robot
gripper that is able to pick and place the sample in any form of 200 g load.
• Design of scoop for collecting solid, semi-solid , liquid sample with ingress protection.
• To make Sample container with insulation so as to avoid contamination.
• To conduct full finite element analysis of the design using software.
• To produce complete assembly drawing of the robot gripper.
• To run simulation on the gripper’s working condition.
• Features-
• Payload = 200g
• Sample Form:- Solid/semisolid/liquid
Dimensions:- 40x50x60 (L x W x H)mm.
• Gripper opening:- 50mm
• Ingress protection

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1.3 Scope of Present Work
Since designing a robot gripper is a vast and wide title, the scope for this project has been
scaled down so that the project’s objectives can be achieved. First and foremost, this project
will cover:
a) Design of a robot gripper that is able to pick and place 200 gm payload for sample collection.
b) Finite element analysis of the design such as movement analysis and material stress for the
load that the gripper will handle. This is done with the help of design software such as CATIA,
PROE and ANSYS.
c) Producing a complete engineering drawing for the final assembly of the robot gripper.
d) Simulate the Gripper in its working condition.
Stated above are the scopes that are covered in this project. As for the robot gripper, there are
certain requirements that this gripper needs to meet. They are:
a) The gripper must be able to pick and place .
b) The gripper should be dust resistant and waterproof.
c) The gripper should be IP 67 protected.
1.4 Methodology
1. Study of different grippers.
2. Selection of mechanism- Type of Gripper.
3. Conceptual designs of scoop arm.
4. Calculation of components.
5. Selection of Motor & other components.
6. Analysis of designed gripper .
7. Simulation of robotic gripper.

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2. LITERATURE REVIEW
Paper No. 1
Nobuaki Nakazawaa[et al ]- “Force Control Of A Robot Gripper Based On Human Grasping
Schemes”.
The Grasping Process:The complexity of the grasping process is often underestimated since it
looks very familiar for human beings. However the automation of this process creates many
problems. In fact the design of a gripper does not depend only on the object characteristics but it
is also affected by previous phases as feeding and the following phases such as handling,
positioning and releasing. In general correctly fed parts require less versatile grippers with
respect to a bin picking situation where the gripper has to face problems such as pieces with
different orientation, part tangling, etc. Similarly, handling needs such as high acceleration,
reorientation, high precision releasing generate constraints in the gripper design or choice.
Neglecting the further requirements due to feeding and handling, the grasping process can be
generally described as follows (Fig. 1): -Approaching the object: the gripper is positioned
nearby the object. Coming into contact: the contact is achieved. In case of contactless handling,
the object is in the range of the force field generated by the gripper: Increasing the force within
certain limits.
Securing the object: the force stops increasing when the desired degrees of freedom of the
object are removed and the object stops moving independently from the gripper. Moving the
object. In such conditions the gripper and the object are joined and the object can be moved.
Sometimes the process can be carried out by the gripper itself. Releasing the object. Usually at
the macro scale it is caused by gravity when the grasping force is deactivated. At the micro
scale the problem is more complex since surface forces overcome gravity, therefore other
releasing strategies are needed. Monitoring the grasping: force and torque sensors, stick slip
sensors, contact sensors, etc. can be used to detect and monitor all the process and particularly
the effectiveness of grasping.

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Fig.1. Typical phases of the grasping process
The Grasping principles:
The design of an industrial gripper must ensure a secure, robust and reliable grasping. Several
grasping principles (Fig. 2) have been proposed in the last decades, some of them mimicking
the human fingers or animals’ claws or jaws, or exploiting different physical effects. Some
principles can be applied only at the micro scale (e.g. acoustic levitation or laser tweezers),
while others proposed for micro-handling are now expanding beyond that field (e.g. van der
Waals forces). The grasping principle can be defined as ‘‘the physical principle which causes
the force effect necessary to get and maintain the part in a relative position with respect to the
gripping device’’. Mechanical grippers are the most widespread: they are based on friction or on
form closure, but also intrusive grippers belong to that class. Suction based grippers and
magnetic grippers dominate the automotive field and in particular metal sheet handling.
Bernoulli grippers work on the basis of airflow between the gripper and the part that causes a
force which brings the gripper and part close together. This is now receiving more attention
since it acts as a vacuum system, but without coming into contact with the handled part. Other
principles are less used in the macro domain, but in the last ten years they have led to interesting
applications in micro-handling so that now research teams are trying to exploit them to grasp
standard objects. Electrostatic grippers are based on charge difference (some-times induced by
the gripper itself) between the gripper and the part, while van der Waals grippers are based on

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the low force (electrostatic forces) due to the atomic attraction between the molecules of the
gripper and those of the object. While capillary grippers use the surface tension of a liquid
meniscus between the gripper and the part, cryogenic grippers freeze a small amount of liquid
and the resulting ice produces the required force. Other grippers are even more complex: for
example the ultrasonic based grippers generate standing pressure waves used to lift up a part,
while laser sources can produce an optical pressure able to trap and move microparts in a liquid
medium (optical tweezers ).
Fig.2. Grasping principles

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Smart sensing
An emerging smart solution in the monitoring of gripping is the integration of sensors in
fingertips. This solution may provide high performance but requires miniaturized devices. The
fingertips of the DLR Hand II contain tiny force-torque sensors (20 mmØ, 16 mm in height) .
The sensors consist of a mechanical structure with applied foil strain gauge bridges and internal
electronics for signal conditioning and digital conversion. Thereby, the sensors deliver digital
force and torque values at very high bandwidth and with very low noise. A three-finger
dexterous hand with tactile sensors on the finger surface is presented in. The fingers are covered
(Fig. 3) with a novel low-cost and low-noise artificial skin. The skin of the gripper consists of
132 normal-pressure-sensing taxels (tactile pixels) and can measure forces up to 100N.
Fig.3.Sensor suite on Robotic Adaptive Gripper.

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Paper No. 2
MinzhouLuo A [et al ]
“Analysis And Design For Changing Finger Posture In A Robotic Hand”
Grasp modes:-
The human hand is a very good example of how proper grasp modes can be achieved in
versatile tasks by using a combination of fingertips, joints, and phalanges. That is why many
researchers pay great attention to grasp configurations of human hand to design grasp planning
and finger distribution. A power grasp is characterized by having multiple contact points among
grasped object, finger, and hand palm. It can maximize load capabilities and show a high
stability, which is due to the large number of contact points that are distributed on the surface of
grasped object. Heavy wrap configurations are the most powerful grasps, but they cannot be
achieved with dextrous features.A precision grasp is characterized by pinching the object with a
combination of thumb, index, and middle finger. Contact points are located at the fingertips of
the fingers. The thumb is opposite to the other fingers. In generally, the goal of a precision grasp
can be recognized in grasping and manipulating an object with dextrous features. Thus,
precision requires small grasp forces, full manipulability, and isotropy. Furthermore, location of
contact points can be a critical issue since a limited number of contacts.

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Fig.4 Grasp Modes
There are two different grasp modes, the first one is called parallel-grasp mode since all other
fingers are lined up except the thumb. A parallel-grasp mode can be identified by a
configuration in which the thumb and other finger, together grasp an object by acting in parallel
to each other. This grasp mode includes two-finger parallel pinching, three-finger parallel
pinching, three-finger cylinder enveloping as shown in the examples in Fig.4. The other mode is
called centripetal- grasp mode since in the grasping configuration all the fingers including the
thumb are located around the object surface. This grasp mode includes three-finger centripetal
pinching and three-finger sphere enveloping .
Needfor moving and rotating fingers
In this section, experiment tests are discussed to illustrate the stability of the two basic grasp
modes for human hand in order to motivate the need of moving and rotating fingers in robotic
hands. In order to acquire accurately information of grasp force in each grasp mode, four
contact force sensors have been attached respectively to each finger of a human hand. Three of
them have been installed in the surface of the thumb finger, index finger and little finger. These
fingers have been used to grasp an object with a three-finger parallel pinching grasp and with a

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three finger centripetal pinching grasp. The thumb of other hand has been equipped with
another force sensor and has been used to push the object as an external force in each grasp
mode.
Fig.5Need for moving and rotating fingers
When the external force by the is directed along the direction of the axis of the cylinder like in
the case of , the resultant force vectors that are exerted by the other three fingers cannot resist
the external force (wrench). Thus, the object slips out from the hand. This experiment indicates
that this grasp mode is not easy to reach stable grasp state because there are d.o.f (degree of
freedom) of the grasped object which cannot be constrained. In second case, the fingers 1, 2 and
3 are distributed around the boundary of a circular object. When the external force is directed
along the radial directions of a circle shaped object, the three fingers can adjust their forces and
direction to resist an external force and achieve equilibrium grasp quickly. The circular object
cannot easily slip out from hand in this grasp mode and the grasp can be in an equilibrium state
all the time.
Designand operation of a new mechanism:
A solution for the problem of changing the finger location in the hand can be proposed by using
the above-mentioned FRM which is able to move and rotate one or two fingers. The novel
mechanism is shown with a mechanical design that is based on the concept of rotating and
translating two fingers simultaneously in a three-fingered robotic hand with simple and compact
assembly.

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Fig.6 Design and operation of a new mechanism
Two inner gears are symmetrically fixed on the edge of the palm. Two small planetary gears can
be driven from an initial position to a final position within a slot having circular shape. Two
fingers are connected to the above-mentioned planetary gears. Then, the planetary gears are
driven by a fan-shaped gear and the inner gears. The fan-shaped gears can rotate about the
centre of the palm since they are connected to the links of the folding linkage. The fan-shaped
gears are part of the link bodies. The folding linkage is a four-bar mechanism that is driven by
one actuator acting on point B.The mechanical configuration of the actuator. Therefore, this
solution makes possible to actuate both fingers simultaneously and to move them
symmetrically.

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Paper No. 3
Deeptam Tudu Saha[et al] “Design And Implementation Of A 4-Bar Linkage Gripper”.
Gripper Design And Configuration-Comparison of grippers with human grasping systems.
They classified grasping systems considering design requirements of grippers into three
categories as under.
• Compatibility with a robot arm and controller
• Secure grasping and holding of an object
• Accurate completion of handling task.
Many industrial applications of grippers were described, and guidelines for gripper design were
summarized the strategies for design and selection of grippers to suit different applications. In
their study, variables affecting the selection of a gripper were listed as:
• component type,
• task to do,
• environmental condition within the work volume,
• type of robot arm, and
• control conditions.
Guidelines Of Gripper Design
There are different guidelines for respective typical gripper designs. Sometimes, one guideline
may indicate one design direction, while some other may suggest the opposite. So, it is not
possible to apply all the guidelines to any one design. Each particular situation needs be
examined carefully, and a decision is to be made to change the appropriate guidelines. The
design guidelines are as follows: -
• Minimization of gripper weight: This allows quick acceleration of a robot for performing the
required task.
• To grasp objects securely: This allows a robot to move at a high speed thereby reducing the
cycle time.
• To grip multiple objects with a single gripper: This can avoid tool change.
• Encompassing fully the object with the gripper: This holds the part securely.
• Not to deform an object during grasping: Some objects are easily deformed and care needs be
taken to grasp these objects.

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• To minimize finger length: This is done for the fact that longer the fingers of a gripper, more
they are going to deflect when grasping an object.
• To design for proper gripper-object interaction: If a flat surface is used at a finger, then a high
friction interface is desired, else the part would not be aligned properly and high friction
increases secured grasping.
Selection Of Four Bar Linkage Gripper
Incorporating 4-bar linkage in the gripper provides some advantages over normal gripping
systems, such as
• The total workspace of the gripper gets reduced, resulting in less space required for the
working of the gripper. Figure 7 compares the workspace of two different grippers.
• The pressure is applied gradually on the gripped object rather than somewhat abruptly in case
of normal grippers, reducing the chances of deformation of the object.
Figure 7.(a) Workspace of 2-bar linkage gripper , (b) Workspace of 4-bar linkage
gripper

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Paper No. 4
Ho Choi, MuammerKoc [et al]“Design And Feasibility Tests Of A Flexible Gripper Based On
Inflatable Rubber Pockets”
The component variables include geometry, shape, size, weight, surface quality and
temperature of objects to be handled. For reconfigurable systems, they divided these
components into part families according to their shape and size. For the task variables, type of
gripper, number of different parts, accuracy, and cycle were considered in addition to major
handling operations such as pick, hold, move and place. For the right gripper design at the right
place, all aspects should be considered, and multiple validation tests should be conducted.
Gripper types and classification by driving force
Grippers could be also classified with respect to their purpose, size, load, and driving
force. Typically, gripper mechanisms and major features are defined by their driving forces. The
driving forces for robot grippers are usually electric, pneumatic, hydraulic; or in some cases,
vacuum, magneto-rheological fluid and shape memory, etc. Grippers with electric motors have
been used since 1960, abreast with robot technology. Many other grippers adopted motor driven
mechanisms.
Basically, this type of systems included step motors, ball screws, encoders, sensors and
controllers. As the arms approach the object, distance, force, weight and slip are detected by
sensors. At the same time, a controller regulates the force, speed, position and motion, and stop
to better analyze grasping of parts. Another way of actuating the robot gripper is through
pneumatic (or hydraulic) systems. Pneumatic systems have been developed because of their
simplicity, cleanliness and cost-effectiveness. a soft pneumatic gripper which can handle soft
materials such as eggs. grasp-force control in two-finger grippers with pneumatic actuation.
They proposed force control in a two-finger gripper with a sensing system using commercial
force sensors. A suitable model of the control scheme has been designed to control the grasping
force. Experiments showed the practical feasibility of two-finger grippers with force controlled
pneumatic actuation. They offered natural passive compliance to correct for inevitable
positioning inaccuracy with simple design and minimum moving parts. The gripper finger relied
on the elastic deformation of cylindrical metal bellows with thin convoluted walls. The
convolution ensured that the assemblywas significantly stiffer in the radial direction than the
longitudinal one. Therefore longitudinal extension was much greater than radial expansion

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when subjected to internal hydraulic pressure. The modular finger tip contained a variety of
sensors and interfaces. The finger tip contact zone contains both a strain gage and a
piezoelectric vibration sensor. Closed-loop position control was used. It was driven by hydraulic
pressure measured from sensors within each tube . Grippers based on vacuum forces are
designed and used mainly for deformable and lightweight part handling. For example, used
suction-based control for handling limp material without distortion, deformation or damage.
They developed a fixed-sized gripper and also a reconfigurable gripper system with suction
units. A sensor-based control system based on the hierarchical control architecture controlled
the operation of the robotic gripper system. Fixed dimension grippers were developed for
stacking dissimilar-sized panels of clothes. A fuzzy controller computes the needed suction and
control depending on material porosity, weight, robot speed, and travel distance.

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Paper No. 5
Spadafora, [et al] “Design And Construction Of A Robot Hand Prototype For Underwater
Applications”
HAND DESIGN
For the articulation of the first phalanx, the architecture of the specific finger was built inside
the palm of the hand, featuring a driving gear (A) connected to the servomotor (B) that transfers
the motion to a driven gear (C) by means of a belt (D); the drive torque, suitably amplified by a
gearing (E), is transmitted to the articulation of the finger (see Figure 8).
Fig.8. Layout of the hand
For the actuation system, the choice fell on programmable servomotors hitec hs5646, not
specific to underwater applications, but capable of expressing a maximum torque of 12.5 kg*cm
at 7V; this value can ensure a good tightening for each finger, and also a good speed of opening
and closing (equal to 0.2 sec/60°). The chosen servomotors work in a range that varies
approximately of ± 60°. Belts are used to couple servo motors and drive shafts for the
transmission of power. They are made with elastomer reinforced by glass fibers and they are
particularly suitable to ensure a correct kinematics and the flexibility of the fingers. The
filaments have been designed to pass through two ducts, located in the front part and in the back
of the finger itself . In this way, each tendon, while appropriately balancing the pulling forces, is
able to open or close the phalanges.

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Gearing design
A belt transmission with toothed pulleys, aimed to amplify the motion (see Figure 8), was
designed for transmitting the motion from the servomotor (1) to the shaft (5). In order to make
the finger - the first phalanx in particular - complete a rotation of 120°, the gearing was sized by
fixing the distance between (1) and (4) to 40.12 mm, the diameter of the driving gear located
downstream of the servomotor to 24.5 mm, and the diameter of the driven gear to 16mm. The
transmission ratio τ1 amounts to 1.53, so it is capable of amplifying the motion of the
servomotor, whose effective rotation is ± 60°. Fig. 8
Fig.9 Transmission system of hand
The size of the belt chosen for actuating the mechanism has a pitch length of 144mm. Table 1
summarizes the data of the first kinematic mechanism.
With respect to the tendon transmission for handling and gripping the objects via the three
fingers, the main problem has been the identification of the actual values of the force to be
applied. Though the use of Nylon wires for the transmission of motion inside the finger can

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improve the easiness of assembly of the fingers on the palm, it can't ensure an optimum
tightening of the three phalange because of its elasticity. we used a "hybrid" solution in order to
make the mechanism suitable for flexing the fingers on the palm. So the choice fell on a tendon
actuation for the motion of the two last phalanges, and on a gear actuation for the first phalanx.
This hybrid solution allowed for ensuring the desired flexibility and, at the same time, for
gripping objects of different size and shapes. A series of experimental measurements was
conducted to define the actual length of the Nylon wires during opening and closing. The
obtained results are shown in Table 2.
Fig.10 Actual prototype

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Paper No. 6
GujjarlapudiKrishnavamsi[et al ] ,“Design And Analysis Of Pneumatic Gripper With Two
Jaw Actuavation”
Conventional System
A mechanical gripper is end effectors that use mechanical fingers actuated by a mechanism to
grasp an object. The fingers, sometimes called the jaws, are the appendages of the gripper that
actually make contact with the object either by physically constraining the object with the
fingers or by retaining the object with the help of friction between the fingers. For a Two jaw
cam actuated rotary gripper there is a cam and follower arrangement, often using a spring-
loaded follower which can provide for the opening and closing of the gripper. The movement of
cam in one direction would force the gripper to open, while the movement of the cam in
opposite direction
Fig.11 Two Jaw Cam Actuated Rotor Gripper.
causes the spring to force the gripper to close. The advantage of this arrangement is that the
spring action would accommodate different sized parts. Most mechanical drives used in
grippers are based on cam and followers or rack and pinion gears as force convertors. Cam

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driven gripper jaws normally enjoy a relatively large stroke not normally achievable with other
gear types as shown in Fig.11. As a prime mover almost any form of electrically commutated
DC servo motor is suitable
Angular Gripper:
Angular gripper jaws swing in an arc that can be adjusted to reduce the opening swing; usually
they are dedicated to picking up one size part. They are useful where vertical space is limited
and fail safe part handling is needed as shown in Fig.12. Once the jaws are two degrees past
parallel the jaws are toggled locked so even if air pressure is lost the part is held firmly.
Fig.12Angular GripperFig.13.Parallel grippers.
Parallel Grippers:
Parallel grippers are the most common, due to the ease of tooling, their adaptability to various
part sizes without the need to change the tooling finger as shown in Fig.13. Their also suited for
synchronous where both jaws move at the same time or non-synchronous use, which allows the
jaws to comply and shift to the work piece centreline. Specialized grippers that do not fit the
traditional two jaw parallel and angular gripper categories include O-ring grippers, single jaw,
three jaw parallel or angular, bladder grippers that inflate against the part O.D or I.D, and
magnetic grippers. Adaptive grippers “blind to shape” or “dexterous manipulation” are the
newest being developed.

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Paper No. 7
Ashish Singh, [et al],“ Design And Fabrication Of A Gripper For Grasping Irregular Objects” ,
DESIGN OF THE GRIPPER
It is well known that minimum three points are required to hold any object. In this work, a
three-fingered gripper each with two limbs have been designed and fabricated to hold irregular
objects as this can be used for both force and form closure purpose. In comparison to gripper
with single limb (Figure 14 a) where it may fail if the friction force is not sufficient, here the
presence of the second limb (Figure 14 b) will augment the friction force and will help in firmly
gripping the object
Figure 14 (a) Fingers with single limb (b) Fingers with two limbs; Fr : frictional force, N:
normal reaction force, W: weight of object
Figure 15: (a) Back side of the horizontal base with pulley and belt arrangement.
(b) Front side of the horizontal base with three fingers.
The gripper consists of a base, three fingers with two limbs each and two motors placed
centrally. In order to control the two limbs of each finger, two independent actuators are
required. Hence, in this case with three fingers one may require six actuators. Synchronizing the
motion of three fingers, only two motors have been used to grasp the object. This design can be

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modified with six motors for independent motion of three fingers. Here belt drive is used to
connect the motors with the pulleys of the fingers (Figure 15). This arrangement is made on the
top of the horizontal base, by employing six pulleys (two for each finger) Pa, Pc, Pe connected
to center motor Ma with three belts and Pb, Pd, Pf connected to the center motor Mb with three
different belts. Each pulley in turn rotates six different worm gears of three fingers (two in each
finger).
DESCRIPTION OF THE FINGER
Fig.16 DESCRIPTION OF THE FINGER
Each finger is a simple parallelogram four bar mechanism with link A as the first limb and the
extension of the link B as the second limb. At a particular position of link A if link D is rotated
about Iad (the instantaneous center of rotation between link A and link D) as an input then
rotation of link B about Iab(the instantaneous center of rotation between link A and link B) is
obtained as an output of the four bar mechanism. At any instant the angular velocity ωb of the
link B will besame as the angular velocity ωd of the link D, since links A, B, C and D constitute
a parallelogram. Second limb being an extension of link B will have same angular velocity ωb of
link B
ω(limb2) = ω b = ω d for all time (t).
Now at any instant θab= θad
θabis the angle between link A and link B. θad is the angle between link A and link D.

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So at any instant the angle between the second limb and the horizontal ψ(limb 2) can be known by
simply subtracting α from the angle that link D makes with the horizontal, i.e., ψd.
ψ(limb2) = ψd – α
If the angle between Link D and the horizontal is fixed say θ then the angle of link B with the
horizontal is simply θ and it do not depend on the orientation of link A (figure4)
Figure 17: Different orientations of link A when the inclination of link D (θ) is fixed
andtherefore the inclination of the second limb (ψ) is fixed
To drive first limb (link A) and the second limb (link B) of the finger, a pair of worm gears have
been used. The first worm gear is directly attached to link A (Worm gear wheel being an
integrated part of link A), and the second is attached to link D (Worm gear wheel being an
integrated part of link D). Link D in turn operates the second limb i.e. link B of four bar
mechanism. For such an arrangement in this design, two independent actuators have been used
to control the two links of the four bars. In order to give mobility to a four bar mechanism one
actuator is sufficient, but in this case one has to change the orientation of the four bar
mechanism, therefore additional actuator is required for each finger. With this actuator user can
change the orientation of the first limb i.e. link A.

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Selectionofmechanism: Type of gripper
Mechanism selected: Lead screw mechanism.
1) One of the main advantage , mechanism is self locking.
2) Due to lead screw mechanism, there is greater accuracy control in positioning
of linkages.
3) The overall dimensions of the lead screw are small, resulting in compact construction.
4) A power screw is simple to design.
5) The manufacturing of lead screw is easy without requiring specialised machinery.
6) A power screw provides large mechanical advantage.
7) A power screw provides precisely controlled and highly accurate linear motion.
8) A power screw gives smooth and noiseless service without much maintenance.
9) There are few parts in power screw. This reduces cost and increases reliability.
10) There is less backlash problem. Hence operation is smooth.
11) There is no need of sensors for closing and full opening position because it can be
controlled by length of threading.

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Conceptual Designs ofscooparm:
Model1
Disadvantages
1. Complex design : Links are occupied in scoop bucket.
2. Inside opening due to which collecting spaceis reduced.
3. More power is required for closing flap because flap is closing against
gravity.
4. Not properly insulated.

Page 28
Model2;
Features
1. Hinge point is shifted outside of the scoop.
2. Less power is required because flap is closing along with gravity force.
3. Complex design : Links are occupied in scoop bucket.
4. Not properly insulated

Page 29
Model3
Features
1. Hinge point is shifted outside of the scoop.
2. Less power is required because flap is closing along with gravity force.
3. Simple design, all linkages are outside the scoop bucket.
4. Properly insulated, lead screw and bearing both are enclosed in separate
casing.
5. Outside opening due to which collecting spaceis increased.

Page 30
3.1 CACULATIONS:
3.1.1 DESIGNOF FLAP:
SELECTION OF MATERIAL:
Material Ultimate Strength(N/mm2) Yield strength(N/mm2)
Al6061 T6 300 241
Table No. Material selection for FLAP
FOS=2 Load=5 Kg = 5*10 = 50N
Fig.: Force on Flap
Moment @ point A,
M =50*18.5 =925 N mm
𝜎𝑎𝑙𝑙=
𝑆𝑦𝑡
𝐹𝑂𝑆
=
241
2
120.5 Mpa
According to flexural formula,
𝑀
𝐼
=
𝜎 𝑎𝑙𝑙
𝑌

Page 31
b =15d
925
𝑏𝑑3
12
= 120 .5
𝑑
2
d= 1.45 mm
d≈2.5 mm , b=15d =15*2.5=37.5mm ,b ≈ 38mm
3.1.2 DesignofLINK 1:
Al6061 T6 300 241
Fig.: Forces on link1
b=38mm d=2.5mm

Page 32
Assuming FOS=2
50
cos(68)
=133.47 N
Buckling of link1:
Assuming FOS=2
P=133.473*2 =266.946 N
I=
𝑏.(2𝑏)3
12
=0.66 b4
K=√
𝐼
𝐴
=√
0.66𝑏4
2 𝑏2 =0.574 b mm
Where,
I= Moment of inertia of cross- section (mm4)
According to Rankine formula ,
𝑃 =
𝑆𝑦𝑐 ∗ 𝐴
1 + 𝛼 (
𝑙𝑒2
𝐾2 )
Both ends are hinged Le=l=31 mm
Where,
P =Crippling load on link 1
A=area of c/s (mm2)
𝑙e= Equivalent unsupported length (mm)
K=radius of gyration
Syc =yield stress in compression(N/mm2)
α =Rankine’s constant =(1/5000)
266.94=
120×2𝑏2
1+
1
5000
(
312
0.288𝑏2 )

Page 33
b= 2.5 mm≈ 4mm
d= 2b=8 mm
3.1.3 Designof LINK 2:
Al6061 T6 300 241
Fig.: Forces on link2
Assuming FOS=2
Bending of link2:
Moment @ point A,
M=133.79*25.5 =3411.645 N mm
b=4mm d=8mm

Page 34
𝜎𝑎𝑙𝑙=
𝑆𝑦𝑡
𝐹𝑂𝑆
=
241
2
According to flexural formula,
𝑀
𝐼
=
𝜎 𝑎𝑙𝑙
𝑌
3411.645
0.66𝑏4
=
120.5
𝑏
b =2.5mm ≈ 4mm
d=2b=8 mm
Buckling of Link2:
One end fixed and other end hinged, n=2
According to Johnson’s equation,
Pc r= Syt A {1-
𝑆 𝑦𝑡
4𝑛𝐸𝜋2 × (
𝑙2
𝐾2)}
Where,
Pcr= critical load (N)
n=end fixity coefficient
E=modulus of elasticity (N/mm2)
A=area of the cross-section(mm2)
K=√
𝐼
𝐴
=√
170 .66
32
=2.3093 mm
𝑙 = 25.5 mm
I=
𝑏.(𝑑)3
12
=170.66 mm4
b=4mm d=8mm

Page 35
Pcr = 241 × 4 × 8 {1 -
241
4×2×69×103 𝜋2 × 121.92}
=7670.407 N > 133.8 N
As, The critical load causing buckling is high as compared to actual load of 133.8N the link 2 is
safe in buckling.
3.1.4 DESIGN OF NUT AND SCREW:
En19 T 800 650
Table No. Design of Nut and Screw
Type of thread : Trapezoidalthread
A trapezoidal thread has more thickness at the core diameter than asquare
thread. Therefore, a screw with trapezoidal threads is stronger. Such ascrew has
a large load carrying capacity
Type of thread : Trapezoidalthread

Page 36
A trapezoidal thread has more thickness at the core diameter than asquare thread. Therefore, a
screw with trapezoidal threads is stronger. Such ascrew has a large load carrying capacity
Pitch , p =1.5mm Nominal diameter, d =8 mm
Pitch, P= 1.5mm Nominal dia.=8 mm
Core dia.=6.5mm Pitch dia.=7.25 mm
Core diameter , dc =d-p =8-1.5 =6.5 mm
Pitch diameter, dm =d-0.5 p =8- 0.5*1.5 =7.25 mm
Single start Thread.
tan 𝛼 =
𝑙
𝜋× 𝑑 𝑚
=
1.5
𝜋×7.25
α =40
2β= 300 β=150
µ1 =
µ
cos 𝛽
=
0.16
cos 15
=0.1657
µ1=tanØ Ø = 9.405
Torque required to raise the load ,
Tt =
w dm
2
tan(∅1 + 𝛼)

Page 37
Tt =
133.79×7.25
2
tan(9.405 + 7.5)
=115.5853 N mm
Stressesin screw Body:
𝜏all =
0.5∗𝑆𝑦𝑡
2
=
0.5∗650
2
=162.5 N/mm2
Direct compressive stress :
𝜎𝑐 =
𝑊×4
𝜋𝑑 𝑐
2 =
133.79×4
𝜋6.52 =4.03 N/mm2
Torsional Shear Stress:
𝜏=
16×𝑇
𝜋𝑑 𝑐
3 =
16×115.58
𝜋 ∗6.53 =2.143 N mm
The principal shear stress is given by ,
𝜏max =√(
𝜎
2
)2 + 𝜏2
= √(
4.03
2
)2 + 2.1432
= 2.945 N/mm2
Buckling of Screw:
l= 57mm
l =
𝜋𝑑 𝑐
4
64
=
𝜋6.54
64
= 87.62
A =
𝜋𝑑 𝑐
2
4
=
𝜋6.52
4
= 33.18
K =√
𝐼
𝐴
=√
87.62
33.18
=1.624

Page 38
Slenderness Ratio (ƛ):
𝑙
𝑘
=
57
1.624
=35.077
The boundary line between Johnson’s and Euler’s equation is given by,
One end is fixed, n =0.25
𝑆 𝑦𝑡
2
=
𝑛𝐸 𝜋2
(
𝑙
𝑘
) 𝑐𝑟
2
400
2
=
0.25×2.1×105
𝜋2
(
𝑙
𝑘
) 𝑐𝑟
2
(
𝑙
𝑘
) 𝑐𝑟= 50.9
ƛcr=51 ƛ=35<ƛcr
Since the slenderness ratio of screw (35) is less than 50.9,the screw treated as short column and
Johnson’s equation is applicable,
Pcr= Syt A {1 -
𝑆 𝑦𝑡
4𝑛𝐸𝜋2 × (
𝑙2
𝐾2 )}
= 400 ×
𝜋
4
6.52
{1 -
400
4×0.25×2.1×105 𝜋2 × 35.0772
}
= 10121.39 N > 133.79N
As, The critical load causing buckling is high as compared to actual load of 133.79N the screw
is safe in buckling.

Page 39
Stresses in screw threads :
Velocity of nut
I C R method
Tp= Time required for closing flap,
Tp =
𝜋
2×𝜔
ω=
𝜋
2×5
ω = 0.3141 rad/sec
Velocity of nut,
V4 =r × ω= ω( I12I24)
= 0.3141 ×14
= 4.4 mm/s≈ 5mm/sec
Bearing Pressure :
Pb =
𝑤
𝜋
4
𝑍{𝑑2 −𝑑𝑐2 }
Where, Pb = bearing pressure, N/mm2
Z = number of threads

Page 40
h = height of nut, mm
Low speed application,
Pb = 18 N/mm2
18 =
133.79
𝜋
4
𝑍{82−6.52}
Z= 0.45
Z≈ 4 𝑡ℎ𝑟𝑒𝑎𝑑𝑠
h= 4 ×1.5 = 6 mm
Direct shear stress in screw threads :
Thickness of the thread at the root, t =
𝑝
2
𝜏s =
𝑊
𝜋×𝑡×𝑧×𝑑 𝑐
=
133 .79×2
𝜋×6.5×1.5×4
=2.18
Direct shear stress in nut threads:
𝜏normal=
𝑊
𝜋𝑑×𝑡×𝑧
=
133.79×2
𝜋8×1.5×4
=1.77
3.1.5 Selectionofmotor :
V= 𝑙 * N (Assume V=5 mm/s)
( mm/min) V=1.5* N rpm
5*60= 1.5 *n
N= 200 rpm

Page 41
3.1.6 Powerrequired :
P= 2π N T/60 =
2π∗200∗115.58 ∗10^3
60
P=2.42 W
Therefore,
3.1.6 Bearing Selection:
Mass of lead shaft = 0.063 kg
Mass of nut =0.007 kg
Mass of link 2 =0.009 kg
Total mass=0.079 kg
Forces :
Radial Load, Fcr = 0.079*10/2=0.395N
Axial Load, Fa =133.79 N
Bearing Selection: Single Row DeepGroove Ball Bearing
Bearing No.- 6000
d=10 mm D= 26 mm
B= 8 mm Max speed -200000 rpm
Static load capacity, Co=190 Kg f =190*10=1900 N
Dynamic load capacity, C= 360 Kg f =360*10=3600 N
Fcr=0.395 N
(Fa/Co)=(133.79/1900)=0.07041
P= 3 W & N= 200 rpm

Page 42
(Fa/Fr)=(133.79/0.395)=338.7088
(Fa/Fr)>e
X=0.56 Y=1.6
Pe=(X*Fr +Y*Fa)Ka
=0.56*0.395 + 1.6*133.79
Pe=214.2852 N
3.1.7 Life of bearing:
Once in 1 Hr for 10 years
Life in hours, Lh10=1*1*24*365*10
=87600 Hrs
Life in million revolutions,
L10=
𝐿ℎ10∗60∗𝑁
10 ^6
=
87600 ∗60∗200
10^6
L10 =1051.2 mill / rev
L10 =(C/Pe)^3
1051.2 =(C/214.2852)^3
C=2178.8163 N < 3600 N.

Page 43
3.2 Modelling-
3.2.1 What is solid modelling?
Solid modelling is the most advanced method of geometric modelling in three dimensions. It
is the representation of the solid parts of the object on your computer. The typical geometric
model is made up of wire frames that shows the object in the form of wires. This wire
frame structure can be two dimensional, two & half dimensional or three dimensional.
Providing surface representation to the wire three dimensional views of geometric models
makes the object appear solid on the computer screen & this is what is called as solid
modelling.
3.2.2 Advantages of solid modelling
Solid modelling is one of the most important application of the CAD software & it has been
becoming increasingly popular of late. The solid modelling CAD software helps the
designer to see the designed object as if it were the real manufactured product. It can be seen
from various direction & in various views. This help the designer to be sure that the object
looks exactly as they wanted it to be. It also gives additional vision to the designer as to what
changes can be done in the object.
3.2.3.Process of making the solid models
To make the solid models you have to first make the wire frames model of the object &
convert it into 3D view. Thereafter the surface are added to the 3D model to convert it int 3D
solid model. For creating the solid model you need to have special CAD software that can
create solid models. One of the most popular CAD software for solid modelling is CATIA
V5 R15.A number of other CAD software like AUTOCAD &other also have feature of
creating the solid models
CATIA V5 R14 is the world’s leading 3Dproduct development solution .This solution
enables designers & engineers to bring better products to make market faster. It takes care of
the entire product definition to serviceability .CATIA delivers measureable value to
manufacturing companies of all sizes & in all industries.

Page 44
3.2.4 Create a solid model:Modelling provides the design engineer with intuitive &
comfortable modelling techniques such as sketching, feature based modelling & dimension
driven editing .An excellent way to begin a design concept is with a sketch. When you see a
sketch , a rough idea of the part becomes represented & constrained ,based on the fit &
function requirements of your design . In this way , your design intent is captured . This
ensures that when the design is passed down to the next level of engineering, the basic
requirements are not lost when design is edited. The strategy you use to create & edit your
model to form the desired object on the form & the complexity of the object. You will likely
use different method during work session . The next several fig explain examples of the
design process, starting with a sketch & ending with a finished model.
Parts of models
Scoop bucket Flap
Bearing cover pipe Lead screw cover pipe

Page 45
Link 2 Link 1
Nut Bearing
Lead screw shaft Scoop blade

Page 46
Back plate Stopper
Assembly

Page 47
3.3 Finite element analysis
The basic concept in FEA is that the body or structure may be divided into smaller elements
of finite dimensions called “Finite Elements”. The original body or structure is then
considered as an assemblage of these elements connected at a finite number of joints called
“Nodes or Nodal points”. Simple function are chosen to approx the displacements over each
finite elements . Such assumed functions are called “shape functions”. This will represent the
displacement with in he element in the terms of the displacement ata the nodes of the
element.
The FEM is a mathematical tool for solving ordinary & partial differential equation . Because
it is a numerical tool, it has the ability to solve the complex problem that can be represented
in differential equations form .The applications of FEM are limitless as regarding the solution
of practical design problem. Due to high cost of computing power of year gone by, FEA has
a history of being used to solve complex & cost critical problems. Classical method alone
usually cannot provide adequate information to determine the safe working limit of a major
civil engineering construction or an automobile or an aircraft. In the recent years, FEA has
been used to solve structure engineering problems. The departments, which are heavily relied
on this technology, are the automotive & aerospace industry. Due to the need to meet the
extreme demands for faster , stronger ,efficient & lightweight automobile & aircraft ,
manufactures have to reply on this technique to stay competitive.
FEA has been used routinely in high volume production & manufacturing industries for many
years, as to get a product design wrong would be detrimental. For eq, if a large manufacturer
had to recall one model alone due to hand brake design fault, they would end up having to
replace up to few millions of hand brakes . This will cause a heavier loss to the company.
3.3.1 Basic step in FEA
Mathematically , the structure to be analysed is subdivided into a mesh of finite sized
elements of simple shape. Within each element , the variation of displacement is assumed to
be determined by simple polynomial shape polynomial shape functions & nodal
displacements. Equation for the strains & stress are developed in terma of the unknown nodal
displacements. From this, the equation of equilibrium are assembled in a matrix from which
can be easily be programmed & solved on a computer After applying the appropriate

Page 48
boundary conditions, the nodal displacements are found by solving the matrix stiffness
equation. Once the nodal displacements are known , element stresses & straina can be
calculated .
1. Discretization of the domain
2. Application of boundary conditions
3. Assembling the system equations
4. Solution for system equations
5. Post processing the results.
Discretizition the domain: The task is to divide the continuum under the study into a
number of subdivision called element. Based on the continuum it can be divided into line or
area or volume elements.
Application of boundary conditions: From the physics of the problem we have to apply the
field condition i.e loads & constraints, which will help us in solving for the unknowns
Assembling systemequations: This involves the formulation of respective characteristics
equation of matrices & assembly.
Solution for system equations: Solving the equation to know the unknowns. This is
basically the system of matrices which are nothing but a set of simultaneous equation are
solved.
Result: After the completion of the solution we have to review the required results, The first
two steps of the above said process is known as pre-processing stage, third & fourth is the
processing stage & final step is known as post –processing stage.
What is elements?

Page 49
Elements is an entity into which a system under study can be divided. An element definition
can be specified by nodes. The shape (area, length & volume) of the element depends upon
the nodes which it is made of.
What is nodes?
Nodes are the corner points of the element. Nodes are independent entities in the space. These
are similar to point in geometry. By moving node in space an element shape can be changed.
Types of finite elements:
0-D Elements:
This has the shape of the point , it requires only one node to define it.
1-D Elements:
This has the shape of the line/curve , it requires only two node to define it.
2-D Elements:
This is an n area elements , which has the shape of a quadrilateral/triangle & hence requires
minimum four/three nodes to define it.3 D Elements: This is a volume element, can take the
shape of a hexahedron or a Wedge or a Tetrahedron. Hexahedron element requires 8 nodes to
define its shape . A pent element requires 6 nodes to define its shape.
3.3.2 Methodology for FEA:The following flowchart shows the procedure for FEA which
includes selection of materials & defining material properties. After that CATIA model is
prepared & import in ANSYS. In ANSYS meshing is the key process which define the
accuracy of solution. Suitable loads & boundary condition are applied to the model, which
leads to the solution. This solution is then validated with theoretical results.
Selection Of Materials
Defining Material Properties

Page 50
Importing Model From CATIA
Meshing
Defining Loads & Boundary Conditions
Solution
Validation
Fig Design & FEA Process
3.3.3 Analysis using ANSYS WORKBENCH
The procedure for performing structural analysis is as follow:-
1. Pre-processing.
2. Solution.
3. Post processing.
(i) Pre-processing:
It involves the description of the geometry or model, the physical characteristics of the
model. Definition of type of analysis, material properties , element type ,loads &
boundary conditions.

Page 51
(ii) Solution :
It involves the application of the finite element analysis. Run analysis to obtain
solution(stresses).
(iii) Post Processing:
It includes the visualization & interpretation of the result of the solution & graphical
representation of stresses & interpretation of results.
The steps which are carried out are given below:
Analysis of link1:
1. Import model: The model of parts is drafted in different software for this we have used as
mention earlier CATIA V5. The file is imported by converting it into step form .
2. Define analysis type : ANSYS is a software having vast application such as thermal analysis,
fluid flow analysis, structural analysis for obtaining stress result on the part. We have
selected structural analysis for obtaining the result on the part.

Page 52
3. Define the engineering data: In this we provide the properties of material so that it can
calculate the result .Also it has large database of material properties with standard value from
which we can select the material.
4. Apply constrains & boundary condition: It is one of the most important step as in this step
we actually need to interpret the mechanism of the system in the virtual system.
5. Define the type of meshing: The objective in building a solid model is to mesh that
model with nodes & elements. Once the creation of solid model completed, set element
attributes & establishing meshing controls, which turn the ANSYS pro-grams to generate the
finite element mesh. For defining the elements attribute, the user has to select the correct
elements type . This is most important task in finite element analysis because it decide the
accuracy & computational time of analysis . In this work , meshing elements is tetrahedral,
number of nodes is 103804, Number of elements are 71187.

Page 53
6. Solve using solver & obtain the results:

Page 54
Total deformation of link1
Equivalent stress of link1

Page 55
Analysis of Link 2:
Total Deformation of link 1 Equivalent stress of link1
Analysis of Flap:
Total Deformation of flap Equivalent stress of flap

Page 56
Analysis of Lead Screw Shaft
Total Deformation of Lead Screw Shaft Equivalent stress of Lead Screw Shaft

Page 57

Page 58

Page 59

Page 60
REFERENCES :
[1] Nobuaki Nakazawaa, Hwan Kimb, Hikaruinooka C, RyojunIkeurad , “Force Control Of A
Robot Gripper Based On Human Grasping Schemes”, Science Direct ,Control Engineering
Practice 9 (2001) 735–742.
[2] MinzhouLuo A, Giuseppe Carbone B, Marco Ceccarelli B, Xianxiang Zhao A,
“Analysis And Design For Changing Finger Posture In A Robotic Hand”, Sciencedirect,
Mechanism And Machine Theory 45 (2010) 828–843
[3] DeeptamTuduSaha, SubhajitSanfui, RajatKabiraj, Dr.Santanu Das, “Design And
Implementation Of A 4-Bar Linkage Gripper”, Iosr Journal Of Mechanical And Civil
Engineering (Iosr-Jmce) E-Issn: 2278-1684,P-Issn: 2320-334x, Volume 11, Issue 5 Ver. Iv
(Sep- Oct. 2014), Pp 61-66.
[4] Ho Choi, MuammerKoc, “Design And Feasibility Tests Of A Flexible Gripper Based On
Inflatable Rubber Pockets”, Sciencedirect, International Journal Of Machine Tools &
Manufacture 46 (2006) 1350–1361
[5] Spadafora, F. Muzzupappa , M. Bruno, F., Ribas , Ridao, P. , “Design And Construction Of
A Robot Hand Prototype For Underwater Applications” , SciencedirectIfac-Papersonline 48-2
(2015) 294–299
[6] GujjarlapudiKrishnavamsi, G.AdiNarayana , “Design And Analysis Of Pneumatic Gripper
With Two Jaw Actuavation” , ijsetrIssn 2319-8885 Vol.04, Issue.01 January-2015,
Pages:0020- 0023.
[7] Ashish Singh, Deep Singh And S.K. Dwivedy ,“ Design And Fabrication Of A Gripper For
Grasping Irregular Objects” ,Department Of Mechanical Engineering, Indian Institute Of
Technology ,Guwahati-781039, India.

Page 61

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