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Robotics
 

Robotics

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  • Links are considered to be the rigid components of the robot. The purpose of the joint is to provide controlled relative movement between the input link and the output link. Links are considered to be the rigid components of the robot. The purpose of the joint is to provide controlled relative movement between the input link and the output link.
  • Roll . This d.o.f can be accomplished by a T-type joint to rotate the object about the arm axis Pitch . This involves the up-and-down rotation of the object, typically done by means of a type R joint Yaw . This involves right-to-left rotation of the object, also accomplished typically using an R-type joint
  • These are the devices that perform the actual task. End effectors are often designed for a particular task, but can also be made as all-purpose hands to do many types of tasks.
  • Torque - exists when a part is picked up at a place other than its center of gravity. Center of gravity - the point where its mass seems to be concentrated or the point where the part is balanced. Coefficient of friction - measures how efficiently the gripper holds the part. If the part and the grippers surface are both rough, the coefficient of friction may be greater than 1. For most gripping tasks, coefficient of friction is less then 1.
  • The first complex sensors used by robots used feedback information to ascertain the present conditions or position. This sense is known as haptic perception and is equivalent to the human sense of kinesthesia. Governor is a mechanical device that uses adjustable spinning weights to control the rotational speed of devices such as generators and motors. Some hydraulic cylinders are equipped with lead screws that can detect the position of the cylinder shaft by counting the revolutions of the screw as the shaft is extended or retracted. For rotational joints, a shaft-encoder can be used to detect very fine rotational movement. The expensive direct-readout encoders or absolute-readout encoders can give the degrees of rotation from 0.000 degrees to 359.999 degrees.
  • One of the earliest sensors for robots was a microswitch or pressure sensor that could detect when the robot had something in its gripper. A photoelectric device can also be used to detect something in a gripper.
  • For example, hydraulic pressure may have to reach some minimum level before hydraulic actuators are allowed to move.
  • Single-point detection can tell if a part is present or not. Simple edge detection can be use to determine how far an object is placed into a gripper. A multiple-point shape detector is a matrix of touch sensors that can determine the shape of one surface of an object. The term type of surface refers to such characteristics as hardness and smoothness or roughness.

Robotics Robotics Presentation Transcript

  • Artificial Intelligence and Robotics ROBOTICS BE – CIS
  • Reference Book
    • Robotics – Introduction, Programming and Projects
    • By: James L. Fuller
  • Robotics
    • Not a pure Computer Engineering subject
      • Combination e.g. Mechanical, Electrical and Computers
      • Mechatronics = Mechanical + Electronics.
    • The Study of Robots
  • What is a Robot?
    • A machine that looks and acts like a human being.
    • An efficient but insensitive person
    • An automatic apparatus.
    • Something guided by automatic controls.
      • E.g. remote control
    • a computer whose main function is to produce motion.
  • What is a Robot?
    • A robot is an automatic, general-purpose device whose primary function is to produce motion in order to accomplish some task.
  • Industrial Robots
    • “a robot is a reprogrammable, multifunctional manipulator designed to move materials, parts, tools, or specialized devices through variable programmed motions, for the performance of a variety of tasks”.
  • Where the names “ROBOT” & “ROBOTICS” come from
    • ROBOT:
      • First used by a Czechoslovakian dramatist, Karel Capek, in his 1921 play "Rossum's Universal Robots."
    • ROBOTICS:
      • Isaac Asimov in his science fiction stories about robots in the 1940's coined the term robotics as the science or study of robots.
  • Terms
    • Remote control
      • a form of human operation in which the human is not physically present at the site of operations.
    • Automation
      • involves using specialized machines to do a specific operation.
    • Numerical control
      • is one type of specialized machine operation used in automation.
  • The 4 Ds of robotics
    • Use a robot if a job is:
      • Dull
      • Dirty
      • Dangerous
      • Difficult
  • Laws of Robotics
    • By Isaac Asimov:
      • Robot may not harm a human, nor through inaction allow one to come to harm
      • A robot must always obey human beings, unless it is in conflict with the above law.
      • A robot must protect itself from harm, unless it is in conflict with the above two laws
  • Laws of Robotics
    • By Skokes:
      • A robot may take up a human’s job, but it should not leave a human jobless
  • Choosing Among Humans, Robots, and Automation
    • Rule 1:
      • Follow the 4Ds
    • Rule 2:
      • Follow Skoke’s law
    • Rule 3:
      • Can you find a human to do the job?
    • Rule 4:
      • Short-term and long-term economic sense
  • Nonindustrial Robots
    • Robot applications:
      • military,
      • show or promotional,
      • educational,
      • medical,
      • domestic or personal,
      • hobbyist robots.
  • Military Robots
    • Military engineers consider any machine that can be operated without a person being present a robot. This includes remote controlled tanks, airplanes and devices for detonating bombs.
    • Flight simulators are a form of military robot.
    • Military interest in atomic energy led to the development of mechanical remote-controlled devices known as teleoperators to handle dangerous radioactive materials.
  • cockpit of the F-4C Weapons System Trainer
  • Show (Promotional) Robots
    • The show robot (also known as play or promotional robots) are nonindustrial robots that might be better described as remote-control devices.
  • Educational Robots
    • Educational robots are devices that can be used to teach the principles of robotics.
    • Here is the SCORBOT-ER V plus robot from Eshed. It is a jointed-arm robot.
  • Medical Robots
    • Medical robots include a robotlike devices that either give medical aid or substitute for or restore functions that a disabled perosns lacks.
    • Here is the HelpMate hospital orderly.
  • Domestic (Personal) Robots
    • The domestic (or personal) robot has yet to get off the ground.
    • Here is a picture of "Roomba" a domestic robot vacuum cleaner.
  • Characteristic of a Robot
    • Repeatability
    • Manual control
    • Automatic control
    • Speed of operation
  • Components
    • Manipulator
    • Controller
    • Power supply
    • Vehicle
  • General Components
    • Manipulator
      • Configurations
        • Cartesian Coordinates
        • Cylindrical Coordinates
        • SCARA
        • Polar Coordinates
        • Jointed Arm
      • Wrist
      • Gripper
  • General Components
    • Power supply
      • Pneumatic
      • Electrical
      • Hydraulic
  • General Components
    • Controller
      • Servo Systems
        • Open Loop
        • Closed Loop
      • Operating Methods
        • Pick and Place
        • Point-to-point
        • Continuous path
    • Vehicle
      • Stationary
      • Mobile
  • Manipulator
  • Robotic Manipulator Vs Human Manipulator
  • Joints and Links
    • degree of freedom (d.o.f) of motion.
    • Connected to each joint are two links, one that we call the input link , the other called the output link.
  • The LERT Classification System
    • The LERT classification system uses the type of motion produced by each robot axis as a basis for classifying the robot.
    • LINEAR (L-Type)
    • Extensional (E-Type)
    • ROTATIONAL (R-Type)
    • TWISTING (T-Type)
  • LINEAR JOINT (L-type)
    • Here is the linear motion of the type that might be seen on a rack and pinion.
    • Linear movement is produced by a part moving along the outside of another part.
    Linear Movement
  • Extensional (E-Type)
    • Here is an extension motion such as that which occurs when one part of a robot arm slides inside another part of the arm.
    • Ext motion is produced by one part moving with another part , with a telescoping movement.
    Extensional motion
  • ROTATIONAL JOINT (R-type)
    • Here is a rotational motion such as that found when a part turns at something other than its center; something like the arm bending at the elbow.
    Rotational Motion
  • TWISTING Joint (T-Type)
    • Here is a twisting motion, which may be seen when a part turns about its center; something like the turning of a human neck joint .
    Twisting motion
  • Manipulator Configurations
    • Cartesian Coordinates
    • Cylindrical Coordinates
    • SCARA
    • Polar Coordinates
    • Jointed Arm
  • Cartesian/Rectangular Coordinates
    • straight, or linear motion along three axes:
      • in and out, (x)
      • back and forth, (y)
      • up and down (z)
  • Cylindrical Coordinates
    • Rotation about the base or shoulder. ( θ )
    • up and down (z)
    • in and out. (R)
  • SCARA Robot
    • Selective Compliance Assembly Robot Arm
      • the same work area as a cylindrical-coordinates robot.
      • the reach axis includes a rotational joint in a plane parallel to the floor.
  • Polar Coordinates
    • Also called spherical-coordinates
      • rotation about the base
      • Rotation about an axis in the vertical plane to raise and lower it.
      • reaches in and out.
  • Comparison of Manipulator Configurations
  • Wrist
  • Grippers (End-of-Arm Tooling ) Can make or break the robotic project
  • End-of-Arm-Tooling
    • This general class of devices is also called end-of-arm tooling (EOAT).
    • Robot end-of-arm tooling is not limited to various kinds of gripping devices.
    • Grippers not available by default in general-purpose robots
    • In some situations, a robot must change its gripper during its task. If so, the robot's wrist must be fitted with a quick-disconnect device.
  • The First Gripper Designed
    • The first gripper which was designed resembles more to the human hand.
    • Later it was realized to design grippers along to the requirement.
  • Robotic Hands versus Human Hands
    • Robot end effectors
      • heavy objects, corrosive substances, hot objects, or sharp and dangerous objects.
      • not good at handling complex shapes and fragile items.
      • do not have good tactile sensing capability,
  • How Grippers work?
    • Seven different methods to grip a part:
      • grasp it
      • hook it
      • scoop it
      • inflate around it
      • attract it magnetically
      • attract it by a vacuum
      • stick to it
  • Types of Robotic Grippers
    • Vacuum cups
    • Electromagnets
    • Clamps or mechanical grippers
    • Scoops, ladles, or cups
    • Hooks
    • Hands with three or more fingers
    • Adhesives or strips of sticky tape
  • Types of Robotic Grippers
  • Types of Robotic Grippers
    • Inflatable bladder
    • Two-finger clamp
    • Vaccum cups
    • Three-fingers clamp
    • Magnet head
    • Tubing pickup device
  • REQUIREMENTS FOR AN EFFECTIVE GRIPPER
    • 1. Parts or items must be grasped and held without damage
    • 2. Parts must be positioned firmly or rigidly while being operated on.
    • 3. Hands or grippers must accommodate parts of differing sizes or even of varying sizes
    • 4. Self-aligning jaws are required to ensure that the load stays centered in the jaws
    • 5. Grippers or end effectors must not damage the part being handled.
    • 6. Jaws or grippers must make contact at a minimum of two points to ensure that the part doesn’t rotate while being positioned.
  • Remote Center Compliance (RCC)
    • Useful for accurate positioning of objects.
    • Robots contains a built-in multiaxis floating joint to adjust for the misalignments.
  • Power for Grippers
    • Independent power supply required
    • Four types of power are used for grippers:
      • pneumatic
      • electrical
      • hydraulic
      • springs
  • Calculating Gripper Payload and Gripping Force
    • Payload handled by a manipulator
    • Payload handled by a gripper
    • Example:
      • Consider a manipulator that can handle 60 pounds, including a 10-pound wrist and a 6-pound gripper. Compute the total weight that can be handled.
  • Other factors to consider
    • Center of gravity
    • Angle of gripping
      • 0 o for vertical motion
      • 90 o for horizontal motion
    • Torque
      • Thickness of part
      • Width of gripper’s jaws
      • Distance from center of gravity
    • Coefficient of friction
      • 1 for rough surfaces
      • < 1 for most surfaces
  • Other factors to consider
    • Acceleration or deceleration
      • Measured in G’s.
        • Normal gravitational force is a 1-G acceleration.
        • Addition if part moves upward
        • Subtraction if part moves downward
    • Safety factor
      • typical safety factor is 2.
  • Sample Problem 1
    • How much force will the jaws of a gripper need to exert to hold a part in a vertical plane under the following conditions:
    • The part weighs 20 pounds and is of a non-uniform shape.
    • The gripper's jaws are parallel to each other and are grasping the part by its vertical sides.
    • The part is grasped 24 inches from its center of gravity.
  • Sample Problem 1
    • The jaws' gripping surface is 4 inches wide.
    • The part is 2 inches thick at the point where it is being grasped.
    • The part is being lifted with a maximum acceleration of 2.5 Gs, including normal gravitational force.
    • The coefficient of friction between the part and the gripper is 0.85.
    • A safety factor of 2 must be included.
  • Pictorial Representation
  • Sample Problem 2
    • What force is required if the gripper operates under the same conditions as in Sample Problem 1, but in a horizontal plane?
  • Sample Problem 3
    • What would be the required force if the jaws were 8 inches wide in Sample Problem 2?
  • Manipulator Power Supplies
    • Pneumatic
    • Electrical
    • Hydraulic
  • Pneumatic Power
    • Uses compressible fluid
    • Parts
      • compressor,
      • storage tank
      • motor or engine
    • Types:
      • Single-action
      • Double action
  • Single-Action Cylinder
    • Outward Stroke
    • Return Stroke
  • Single-Action Cylinder
    • Outward Stroke
      • F = (0.7854 x D 2 x P) – (S + Ff)
    • Return Stroke
      • F = S – Ff
    • Where
      • D: diameter of the piston
      • P: pressure of the fluid entering the cylinder
      • S: return spring pressure
      • Ff: friction force of the piston
  • Double-Action Cylinder
    • Outward stroke
    • Inward Stroke
    • Hold Position
  • Double-Action Cylinder
    • Outward Stroke
      • F = 0.7854 x D 2 x P – Ff
    • Inward Stroke
      • F = 0.7854 x (D 2 – D r 2 ) x P – Ff
    • Where
      • D: diameter of the piston
      • P: pressure of the fluid entering the cylinder
      • D r : diameter of piston rod
      • Ff: friction force of the piston
  • Electric Power
  • Hydraulic Power
    • Hydraulic power uses a non-compressible fluid to transmit energy.
  • Single-Action Rotary Actuator
    • T = (P x A x R c ) - Tf
    • Where
      • T: torque developed by the actuator
      • P: fluid pressure
      • A: vane area
      • R c : center radius of the vane,
      • Tf: friction torque.
  • Single- and Double- Action Rotary Actuator
    • T = (2 x P x A x Rc) – Tf
    • Where
      • T: torque developed by the actuator
      • P: fluid pressure
      • A: vane area
      • R c : center radius of the vane,
      • Tf: friction torque.
  • Sample Hydraulic Motors
  • Control Unit
  • Control Units
    • The brain of a robot
    • Servo Systems
      • Open Loop
      • Closed Loop
  • OPERATING METHODS OF ROBOT CONTROL UNIT
    • Pick-and-Place Control units
    • Point-to-Point Control Units
    • Continuous-path Control Units
  • PICK & PLACE CONTROL UNIT
    • Generally small and pneumatic-powered, with no position information feedback.
    • Open-loop servo-controlled robots.
    • Sometimes referred to as low-technology control units.
  • PICK & PLACE CONTROL UNIT
    • Typical sequence of operations
      • Move robot to starting position.
      • Grasp a part.
      • Remove the part from a machine.
      • Move to second position
      • Deposit part.
      • Prepare to start another cycle.
  • POINT TO POINT CONTROL UNIT
    • Can reach any point within its work envelope
    • Can have as many points in its work sequence
    • Medium-technology control units.
    • Can be programmed by a person moving the robot through the sequence of points that the robot will be required to repeat in performing the task.
  • POINT TO POINT CONTROL UNIT
    • The path between the points
      • Not predictable
    • Uses Stepper Motor
  • CONTINOUS PATH CONTROL UNIT
    • Can reach any point within its work envelope
    • Can have as many points in its sequence as a particular task may require
    • Most expensive of all control units .
    • High-technology control unit
    • Large memory capacity required
  • The Vehicle and the Robot's Base
    • Many industrial robots have fixed-position bases and thus do not have a vehicle.
    • Even with a fixed-base robot, stable mounting is essential.
    • Fixed-base robots could be used: a) overhead mounting, b a gantry mount, c) a wall mount, or d) a floor mount.
  • Mobile Robots
    • Wheel configuration
    • Center of Gravity
      • Should be Low
  • Wheel Configuration
  • Sensors
  • Sensors
    • Sensors changes a robot from dumb to intelligent.
      • The ability to adapt to particular surroundings is one definition of intelligence.
  • Classes of Sensors
    • Sensors for robots can be divided into three classes:
      • internal sensors,
      • external sensors,
      • interlocks
    • Most sensors are some type of transducer .
      • E.g. The ear converts sound energy into electrical signals.
  • Internal Sensors
    • Limit switches
    • Haptic perception
    • Governor
    • Lead screws
    • Shaft-encoder
    • Direct-readout encoders or absolute-readout encoders
  • External Sensors
    • Microswitch or pressure sensor
    • Photoelectric device
  • Interlocks
    • Interlocks are devices that do not allow an operation to be performed until certain conditions exists.
    • Can be internal or external.
  • Sensor Areas for Robots
    • Vision
    • Touch
    • Range and proximity detection
    • Navigation
    • Speech output
    • Speech input
    • Smell
  • Vision
    • Present-day industrial robots use vision to locate and orient parts.
  • Touch
    • Tactile sensing, the sense of touch for robots, is needed if a robot is to perform delicate assembly operations.
    • When a robot touches something, force is reflected back through each joint.
    • In screwing nut and bolt, touch is more imp then vision.
  • Types of Touch Detection
    • Single-point detection
    • Simple edge detection
    • A multiple-point shape detector
  • Range and Proximity Detectors
    • Range Detector detects objects situated at some distance from the robot.
      • Non-contact devices
        • Laser, radar, sonar, vision and infrared devices.
    • A proximity detector detects objects in the immediate vicinity of the robots.
      • can be contact or non-contact devices.
        • E.g. A magnetic detector