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Robot Configurations
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Definitions of Robot
"A reprogrammable, multifunctional manipulator designed to move
material, parts, tools, or specialized devices through various
programmed motions or the performance of a variety of task."
- 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
"Robotics is that field concerned with the intelligent connection
of perception to action." - Mike Brady
Alternate definition:
An automatic device that performs functions normally
ascribed to humans or a machine in the form of a human. 1
Automation vs. Robots
• Automation –Machinery designed to carry out a specific task
• Bottling machine
• Dishwasher
• Paint sprayer
• Robots – machinery designed
to carry out a variety of tasks
• Pick and place arms
• Mobile robots
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How Robots Work
Human Robot
A body structure.
A muscle system.
A sensory system.
A power source.
A brain system.
A movable physical structure
A motor of some sort
A sensor system
A power supply
A computer "brain"
As human beings are made up of five major components , Robots are also
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Figure 1.1. An illustration of a humanlike robot and its ‘‘internal organs.’’
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All Have 5 Common Components
• Mobility: legs, arms, neck, wrists
• Platform, also called “effectors”
• Perception: eyes, ears, nose, smell, touch
• Sensors and sensing
• Control: central nervous system
• Inner loop and outer loop; layers of the brain
• Power: food and digestive system
• Communications: voice, gestures, hearing
• How does it communicate (I/O, wireless, expressions)
• What does it say?
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SPECIFICATIONS OF A ROBOT SYSTEM
1. Pay load / Load carrying Capacity
2. Repeatability – it is the ability of a manipulator to return to its position in
space where it has been previously.
3. Maximum tip speed – how fast the manipulator can move.
4. Coordinate system
5. Maximum movements
6. Type of Drive system
7. Control system – Servo /no-servo and PTP or CP motion
8. Memory Devices – internal memory types and mass storage capacity.
9. Programming Method – via keyboard, teach pendant, walk-through etc.
10.Memory Capacity – It gives an indication of the no. of program steps or
points that the robot controller can handle.
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Work Space Vs. Configuration Space
• Work space
• The space in which the object exists
• Dimensionality
• R3 for most things, R2 for planar arms
• Configuration space
• The space that defines the possible object configurations
• Degrees of Freedom
• The number of parameters that necessary and sufficient to define position in configuration
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Degrees of freedom
So, a simple robot arm with 3 degrees
of freedom could move in 3 ways: up
and down, left and right, forward and
backward. Most working robots today
have 6 degrees of freedom.
Humans have many more and some robots have 8, 12, or even 20
degrees of freedom, but these 6 are enough for most basic tasks.
As a result, most jointed-arm robots in use today have 6 degrees of
freedom
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ROBOT CONFIGURATIONS Ro
bot C
onfig
uratio
ns
• Rectangular / Cartesian / X, Y, Z Robot
• Cylindrical /Post-type Robot
• Spherical / Polar Robot
• Articulated / Joined-arm Robot
• SCARA Robot (Horizontal or Vertical)
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ROBOT CONGIOGURATIONS
Classification By Mechanical Structure
Cartesian Robot
Cartesian robot is form by 3 prismatic joints, whose axes are coincident with the X, Y and Z planes.
Application Areas
This structure is most often seen in machine tools and co-ordinate measuring because of its rigidity.
This robot is suited for pick and place applications where either there are no orientation requirements or the parts can be pre-oriented before the robot picks them up (such as surface mounted circuit board assembly).
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Gantry Robot
Cartesian coordinate robots with the horizontal member supported at both ends are sometimes called Gantry robots.
Application Areas:
It is used primarily to position a wide varietyof end-effectors such as: Automatic screwdrivers, Automatic drills, Dispensing heads, Welding heads, Water jet cutting heads and Grippers.
Gantry robots provide flexible and efficient solutions for a wide range of material handling applications such as pick and place, machine loading and unloading, stacking, unitizing, and palletizing
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Cylindrical RobotCylindrical robot is able to rotate along his main axes forming a cylindrical shape.
Application Areas
With different payload capability, reach and design, articulate robots are designed to employ in the following applications: Arc welding Spot welding Assembly cleaning/spraying Cutting Deburring Die casting
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Polar Robot
Polar robot is able torotate in two different
directions along it’smain axes and the third
joint moves in translation forming a hemisphere or polar coordinate system.
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Parallel RobotParallel robot constitutes two or more kinematics chains between the base and the platform where the end-effectors are located. Parallel robot is a complex mechanism which is constituted by two or more kinematics chains between, the base and the platform where the end-effectors are located. Good examples are the flying simulator and 4-D attractions at Univ. Studios.
Application Areas
Parallel robots are used to assemble automobiles, food products, surgical and many other applications. For instance, the Delta robot is mostly used as a pick-and-place robot. And, almost all flight simulators are based on the hexapod design. They are also used for machining operations where machine tool level tolerances are not required but greater flexibility is
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SCARA Robot
SCARA(Selective Compliance Articulated Robot
Arm) robot is built with 2 parallel rotary joints to provide
compliance in a plane.
Application Areas
The selective compliant feature of the SCARA robot which
provides substantial rigidity for the robot in the vertical
direction, but flexibility in the horizontal plane, makes it very
suitable for many types of assembly operations, e.g., inserting a
round pin in a round hole without binding.
SCARA robots reportedly offer the best price/performance ratio
as regarding speed. They are faster because they move less
mass due to its configuration. Their single pedestal mount
requires a small footprint and provides an easy, unhindered
form of mounting. Thus, besides assembly, Scara is ideal for a
variety of general-purpose applications requiring fast,
repeatable and articulate point to point movements such as
palletizing, de-palletizing, machine loading/unloading, pick-
and-place and packaging applications. The electronic printed
circuit board industry, in particular, use large numbers of
SCARAs for placing semiconductor IC.
Due to their ''elbow'' motions, SCARA robots are also used for
applications requiring constant acceleration through
circular motions like dispensing and in-place gasket
forming.15
It is still in the research laboratory, the Spherical robot is actually a spherical shape robot, which has an internal driving source.
Spherical Robot
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Articulated RobotArticulated robots are mechanic manipulator that looks like
an arm
with at least three rotary joints.
Application Areas
With different payload capability, reach and design, articulate
robots
are designed to employ in the following applications:
Arc welding,
Spot welding ,Assembly
,cleaning/spraying ,Cutting ,
Deburring
Die casting ,
Gluing/sealing
Grinding/polishing ,
Injection molding
Machine tending ,
Material handling ,
Packing
Palletizing ,
Picking ,
Pre-machining
Press brake tending17
Configuration Advantages Disadvantages
Cartesian / XYZ Robot /
Rectilinear Robot
3 linear axes, easy to
visualize, rigid
structure,easy to program
Can only reach front of
itself, requires large floor
space, axes hard to seal
Cylindrical Coordinates 2 linear axes +1 rotating,
can reach all around itself,
reach and height axes
rigid, rotational axis easy to
seal
Can’t reach above itself,
base rotation axis as less
rigid, linear axes is hard to
seal, won’t reach around
obstacles
SCARA Coordinates 1 linear + 2 rotating axes,
height axis is rigid, large
work area for floor space
2 ways to reach point,
difficult to program off-line,
highly complex arm
Spherical Coordinates 1 linear + 2 rotating axes,
long horizontal reach
Can’t reach around
obstacles, short vertical
reach
Revolute Coordinates 3 rotating axes can reach
above or below obstacles,
largest work area for least
floor space
Difficult to program off-line,
2 or 4 ways to reach a
point, most complex
manipulator
Comparison of various Configurations
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Comparison of various Configurations with their work volumes
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Ap
pli
ca
tio
ns
of
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us
Co
nfi
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Basic robot motions
Point to point control
Continuous path control.a. Straight line interpolation
b. Circular interpolation
c. Curvilinear interpolation
d. Parabolic interpolation
Basic
Rob
ot Mo
tions
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PONIT TO POINT CONTROL
• Moves items from one point to
another
• Does not need to follow a specific
path between points
• Uses include loading and
unloading machines, placing
components on circuit boards, and
moving parts off conveyor belts.
Basic
Rob
ot Mo
tions
22
CONTINUOUS PATH CONTROL
• Moves along a specific
path
• Uses include welding,
cutting, machining parts.
Basic
Rob
ot Mo
tions
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