Components%20of%20a%20Robotic%20System

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Components of a Robotic System
Control
Robot Articulated Mechanical System with
Actuators
Computer
Internal sensed Information e.g. force
Language (Program)
Interaction
External sensed Information e.g. camera, sonar
Task
Environment
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Components of a Robotic System

• Robotic System is Task specific
• Sensory information (internal and External)
  provides intelligence to the system but generates
  many challenging research topics
• The Mechanical System with Actuators INTERACT
  with the Environment
• The Computer System CONTROLS the Robot

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Classification of Robot Arms by Drive Technology

• Hydraulic System
• made up of an electric motor that pumps a
  non-compressible fluid into a system consisting
  of a reserve tank, control valves and actuators
  to transmit energy.
• generally associated with larger robots
• Advantages
• greater power, i.e. can handle heavy load
• greater speed
• Disadvantages
• occupies large floor space
• tendency to leak oil gt dirty
• noisy
• Applications for heavy dirty task, e.g.
  welding in automobile and aircraft industries

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Classification of Robot Arms by Drive Technology

• Hydraulic System
• Electric System
• AC motor, DC servo or stepper motor
• for small robots
• Advantages
• high accuracy
• high repeatability
• clean
• Disadvantages
• less power, i.e. less payload
• slower
• Applications assembly tasks that requires
  precision, e.g. circuit board.

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Classification of Robot Arms by Drive Technology

• Hydraulic System
• Electric System
• Pneumatic System
• Uses compressed air
• for smaller robots with fewer degrees of freedom
• Advantages
• readily installed since compressed air is readily
  available in factory floors and laboratories
• Disadvantages
• difficult to provide good precision due to the
  fact that air is compressible , easily affected
  by temp., humidity, etc.
• Applicationscontrol of grippers to provide
  compliance in grasping objects, e.g. SONY robots
  in the lab.

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Classification of Robot Arms by Drive Technology
Hydraulic Power Supply
Pneumatic Power Supply
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Classification of Robot ArmsWork Envelope
Geometry

• Kinematics of Robot Arms is defined as the
  Relationship between arm (link) parameters and
  the configuration (position and orientation) of
  the end-effector with respect to a reference
  point
• Arm parameters motion of joints
• Prismatic (P) - Linear motion ALONG an axis
• Revolute (R) - Rotary motion ABOUT an axis

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Classification of Robot Armsby Work Envelope
Geometry

• Definition The Gross Work Envelope of a robot is
  defined as the LOCUS of points in the 3D space
  that can be reached by the wrist (end
  effector).
• Considering 3 major axes only (5 types)
• Axis 1 Axis 2 Axis 3
• Cartesian P P P
• Cylindrical R P P
• Spherical R R P
• SCARA R R P
• Articulated R R R
  
  

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Cartesian

• Rectangular-coordinates Robot
• 3 linear axes (P,P,P)
• Advantages
• Easy to visualize
• Rigid structure
• Easy to program off-line
• Good repeatability and accuracy
• Disadvantages
• Requires large floor space for the large
  structure
• Can only reach in front of itself
• Restriction on the compatibility with other types
  of arms in a common work space

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Examples of Cartesian Robots
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Cylindrical

• Work space is the space between 2 concentric
  cylinders of the same height
• 2 Prismatic (linear) axes (P,P) and 1 Rotational
  axis (R)
• Advantages
• Rigid structure
• Easy to program off-line
• Good repeatability and accuracy
• Disadvantages
• Horizontal motion is circular only
• Restriction on the compatibility with other types
  of arms in a common work space

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Example of Cylindrical Robots
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Spherical

• Polar-coordinates Robot
• 1 linear axis (P), 2 rotational axes (R)
• Work envelope is the volume of concentric spheres
  but truncated from above, below and behind (where
  the arm cannot reach)
• Advantages
• can be light in weight
• Easy to program
• Good precision
• Disadvantages
• Large and variable torques on joints 2,3 gt the
  counter balance problem
• Positional error is proportional to the radius at
  which the arm is operating

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Example of Spherical Robots
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Examples of Spherical Robots and the work
envelope
General View
Working Volume
Range of motion of the 5 axes
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SCARA

• Selected Compliance Assembly Robot Arm
• 1 linear axis (P) and 2 rotational (R) axes
• Work envelope similar to the cylindrical one
• Advantages
• Relatively inexpensive
• Height axis is rigid gt good for insertion type
  of tasks
• Good repeatability
• Disadvantages
• Difficult to program off-line

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Example of SCARA Robots
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Articulated

• Closely resembles a human arm
• 3 rotational axes (R,R,R)
• Advantages
• Most flexible
• Most anthropomorphic
• Compatible with other robots working in common
  work space
• Disadvantages
• Most difficult to control
• Accuracy can be poor

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Example of Articulated Robots
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References

• Diagrams and figures are from the following
  references
• James L. Fuller, Robotics - Introduction,
  Programming, and Projects, Prentice Hall, 2nd
  edition, 1999. (ISBN 0-13-095543-4)
• Robert J. Schilling, Fundamentals of Robotics -
  Analysis Control, Prentice Hall, 1990. (ISBN
  0-13-344433-3)