1 What is a Robot? Definition of Robot 1.Webster: “An automatic apparatus or device that performs functions ordinarily ascribed to human beings or operates.

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What is a Robot?Definition of Robot

1. Webster:

“An automatic apparatus or device that performs functions ordinarily ascribed to human beings or operates with what appears to be almost human intelligence”

2. Robot Institute of America

“A robot is a re-programmable, multifunctional manipulator designed to move material, parts, tools or specialized devices through variable programmed motions for the performance of variety of tasks”

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• Mechanical Engineering

•Design of the mechanism.Understanding of the kinematics and

dynamics of the system.

• Electronic Engineering

•Design of the actuator and sensor systems.

• Systems Engineering

•Analysis and integration of the overall system. Signal conditioning and Control.

• Computer Science

•Design of the logic, intelligence or adaptability, networking and

interface.

Technologies that go to make up a robot

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Robot Characteristics

1. The following definition are used to characterized robot specification

i. Payload

ii. Reach

iii. Precession

iv. Repeatability

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•Payload is the weight a robot can carry and still remain within its other specifications

•E.g. A robot maximum load capacity may be much larger than its specified payload, but at maximum level it may become less accurate, may not follow its intended path accurately, or may have excessive deflections

Payload

Robot Characteristics (cont)

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Reach

•Maximum distance a robot can reach within its work envelope

Precision (validity)

•Defined as how accurately a specified point can be reached.

•Most industrial robot can have precision of 0.001 inch or better

Robot Characteristics (cont)

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Repeatability (variability)

•Repeatability is how accurate the same position can be reached of the motion repeated many times.

•Repeatability is more important than precision

•If a robot is not precise, it will generally show a consistent error, which can be predicted and thus corrected using programming.

•If the error is random, it cannot be predicted and thus cannot be eliminated.

•Most industrial robots have repeatability in the 0.001 inch range

Robot Characteristics (cont)

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Advantages & Disadvantages of Robots

Advantages

•Robotics and automation can, in many situations increase productivity, safety,efficiency, quality and consistency of product

•Robot can work in hazardous environments without the need of life support, comfort or concern about safety

•Robot needs no environmental comfort, such as lightning, air conditioning, ventilation and noise protection

•Robots work continuously without experiencing fatigue or boredom, do not get mad, do not have hangovers and need medical insurance or vacation

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Advantages & Disadvantages of Robots (cont)

Advantages

•Robots have repeatable precision at all times, unless something happens to them or unless wear out

•Robots can be much more accurate than human. E.g. New wafer handling robots have micro inch accuracies

•Accessories and sensor can have capabilities beyond humans

•Can process multiple stimuli or tasks simultaneously.

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Advantages & Disadvantages of Robots (cont)

Disadvantages

•Robots replace human workers creating economic problems. E.g. lost salaries, social problems (dissatisfaction and resentment among workers)

•Robots lack capability to respond in emergencies, unless the situation is predicted and the response is included in the system. Safety measures are needed to ensure that they do not injured operators and machine working with them

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Advantages & Disadvantages of Robots (cont)

Disadvantages

•This includes:

•Inappropriate or wring responses

•A lack of decision making power

•A loss of power

•Damage to the robot and other devices

•Human injuries

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Advantages & Disadvantages of Robots (cont)

Disadvantages

•Robots have limited capabilities in

•Degree of freedom

•Dexterity

•Sensors

•Vision systems

•Real time response

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Advantages & Disadvantages of Robots (cont)

Disadvantages

•Robots are costly due to

•Initial cost of equipment

•Installation cost

•Need of peripherals

•Need for training

•Need for programming

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Robot Components

• A Robot as a system consists of the following elements which are integrated together to form a whole:

i. Manipulator (or rover)

ii. End effectors

iii. Actuators

iv. Sensors

v. Controller

vi. Processor

vii. Software

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Robot Components (cont)

• Is the main body of the robot and consists of links, the joints and other structural elements

Manipulator

• The part that is connected to the last joint (hand) of a manipulator.

• In most cases the action of the end effector is either controlled by the robot’s controller or the controller communicates with the end effector’s controlling device such as (e.g. PLC)

End Effectors

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Robot Components (cont)

• 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.

Actuators

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Actuators (cont)

Robot Components (cont)

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Multiplication factorE.g Left piston = 2 inches in diameter (1-inch radius) Right piston = 6 inches in diameter (3-inch radius) Area = r2

AnswerArea of the left piston = (1)2 = 3.14Area of the right piston = 28.26.

The piston on the right is 9 times larger than the piston on the left. What that means is that any force applied to the left-hand piston will appear 9 times greater on the right-hand piston. So if you apply a 100-pound downward force to the left piston, a 900-pound upward force will appear on the right. The only catch is that you will have to depress the left piston 9 inches to raise the right piston 1 inch.

Actuators (cont)

Robot Components (cont)

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Robot Components (cont)

• Sensors are used to collect information about the internal state if the robot to communicate with outside environment

• E.g. Vision system, speech, and touch/tactile

Sensors

• Similar to cerebellum (controls motions)

• Receive data from computer, control actuators motions and coordinates the motions with the sensory feedback information

• E.g. Controls angle, velocity, force

Controller

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Robot Components (cont)

• The brain

• Generally a computer but dedicated to a single purpose

• E.g. Calculates motions, how much/fast joint must move

Processor

• 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)

Software

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Types of Robot – Function & Application

• Japanese Industrial Robot Association (JIRA)

• Class 1: Manual Handling Device: A device with multiple DOF that is actuated by an operator

• Class 2: Fixed-Sequence Robot: A device that performs the successive stages if a task according to predetermined, unchanging method and is hard to modify

• Class 3: Variable–Sequence Robot: Same as 2 but easy to modify

• Class 4: Playback Robot: A human operator performs the task manually and records the motions for later playback. The robot repeats.

Classification of Robot

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Types of Robot – Function & Application

• Japanese Industrial Robot Association (JIRA)

• Class 5: Numerical Control Robot: The operator supplies the robot with a movement program rather than teaching them manually

• Class 6: Intelligent Robot: Robot with means to understand its environment and the ability to successfully complete a task despite changes in the surrounding.

Classification of Robot (cont)

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Types of Robot – Function & Application

• Robotics Institute of America (RIA) only consider class 3-6 as robots

• The Association Francaise de Robotique (AFR)

• Type A: Handling devices with manual control to telerobotics

• Type B: Automatic handling devices predetermined cycles

• Type C: Programmable, servo controlled robot with continuous point-to-point trajectories

• Type D: Same as type C, but with the capability to acquire information from its environment

Classification of Robot (cont)

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Types of Robot – Function & Application

Robot Application

•4D Application

•Dangerous

•Dirty

•Dull

•Difficult

•4A tasks

•Automation

•Augmentation

•Assistance

•Autonomous

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Degree of Freedom (DOF)

• Six degree of freedom is needed to fully place the object in space and also oriented it as desired (move & rotate along x-, y- and z-axes)

• If fewer than six, the robot’s capabilities are limited

• E.g.

• Robot with three DOF can only move along x-, y- and z-axes. No orientation can be specified (only parallel to axes)

• Robot with five DOF capable of rotating about three axes but only moving along x-, y-axes (not z-axes)

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Degree of Freedom (DOF) (cont)• A system with seven degrees of freedom does not have

unique solution. There are infinite number of ways it can position a part and orientate it at desired location. There must be additional decision making routine (for the controller) that allows it to pick the fastest or shortest path to the desired destination.

• Due to this which take much computing power and time no seven DOF is used in industry

• Human arms have seven DOF. (Shoulder – 3 DOF, Elbow – 1 DOF, wrist - 3 DOF)

• In robot end effectors never consider as on of DOF

• ½ DOF - if movement is not fully controlled (e.g only can fully extended or retracted, can only at 0, 30, 60 or 90 degrees)

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Robot Coordinates

• Robot configurations for positioning the hand are as follows:

• Cartesian/rectangular/gantry (3P)

• Cylindrical (R2P)

• Spherical (2RP)

• Articulated/anthropomorphic (3R)

• Selective Compliance Assembly Robot Arm (SCARA)

 P = Prismatic (linear), R = Revolute, S = Spherical

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Robot Coordinates (cont)

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Robot Workspace

• Robot workspace is the ability of a robot to reach a collection of points (workspace) which depends on the configuration and size of their links and wrist joint.

• The workspace may be found mathematically by writing equations that define the robot’s links and joints including their limitations, such as ranges of motions for each joint

• Alternatively can be found by subtracting all the space it can reach with what it cannot reach.

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Robot Workspace (cont)

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A Point for a Cartesian-coordinates RobotArm Configuration

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Arm Configuration (cont)A Point for a Cylindrical-coordinates Robot

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Arm Configuration (cont)A Point for a Cylindrical-coordinates Robot (cont)

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Arm Configuration (cont)A Point for a SCARA Robot

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Arm Configuration (cont)A Point for a SCARA Robot (cont)

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Arm Configuration (cont)A Point for a Polar-coordinates Robot

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Arm Configuration (cont)A Point for a Polar-coordinates Robot (cont)

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Arm Configuration (cont)A Point for a Jointed-arm Robot

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Arm Configuration (cont)A Point for a Jointed-arm Robot (cont)