Introductiom to Robotic Systems

7/29/2019 Introductiom to Robotic Systems

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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 humanintelligence”

2. Robot Institute of America

“A robot is a re-programmable, multifunctionalmanipulator 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

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. Payloadii. 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 mayhave 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




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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




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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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(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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(cont)

Disadvantages

•Robots replace human workers creating economic

problems. E.g. lost salaries, social problems (dissatisfactionand 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 donot injured operators and machine working with them



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(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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(cont)

Disadvantages

•Robots have limited capabilities in

•Degree of freedom

•Dexterity

•Sensors

•Vision systems

•Real time response



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(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 elementswhich are integrated together to form a whole:

i. Manipulator (or rover)

ii. End effectorsiii. 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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• 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)




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Multiplication factor

E.g

Left piston = 2 inches in diameter (1-inch radius)

Right piston = 6 inches in diameter (3-inch radius)

Area = r 2

Answer

Area of the left piston = (1)2 = 3.14

Area 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 rightpiston 1 inch.

Actuators (cont)




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• 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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• 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 buteasy 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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• 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 thesurrounding.

Classification of Robot (cont)



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• 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 totelerobotics

• 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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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 asfollows:

• 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 writingequations 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 Robot

Arm 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)

Documents

Introductiom to Robotic Systems