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ROBOTICS

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INTRODUCTION TO ROBOTICS

ROBOTICS

Robotics is the engineering science and technology of robots, and their design, manufacture, application, and structural disposition. Robotics requires a working knowledge of electronics, mechanics, and software.

A person working in this field is known as a roboticist.

HISTORY TIMELINE OF ROBOTICS1921 - Czechoslovakian playwright

Karel Capek introduces the word robot in the play R.U.R. – Rossum’s Universal Robots. The word comes from the Czech robota, which means tedious labor.

1942 - Isaac Asimov publishes Runaround, in which he defines the Three Laws of Robotics.

1954 – George Devol designs the first programmable robot and coins the term Universal Automation, planting the seed for the name of his future company – Unimation.

1959 – Marvin Minsky and John McCarthy establish the Artificial Intelligence Laboratory in MIT.

1960 – Unimation is purchased by Condec Corporation and development of Unimate Robot Systems begins.

1960 – American Machine and Foundry, later known as AMF Corporation, markets the first cylindrical robot, called the Versatran, designed by Harry Johnson and Veljko Milenkovic.

1962 – General Motors purchases the first individual robot from Unimation and installs it on a production line. This manipulator is the first of many Unimates to be deployed.

1965 – Carnegle Mellon University establishes the Robotics Institute.

1965 – Homogeneous transformations applied to robot kinematics – this remains the foundation of robotics theory today.

1968 – Kawasaki licenses hydraulic robot design from Unimation and starts production in Japan.

1973 – Cincinnati Milacron releases the T3, the first commercially available minicomputer.

1978 –Unimation develops the PUMA (Programmable Universal Machine for Assembly). The PUMA can still be found in many research labs today.

1982 – Fanuc of Japan and General Motors from joint venture in GM Fanuc to market robots in North America

1986 – With Uninamation license terminated, Kawasaki develops and produces its own line of electric robots.

1988 – Staubli Group purchases Unimation from Westinghouse.

1995 – Intuitive Surgical formed by Fred Moll, Rob Younge, and John Freud to design and market surgical robot systems. Founding technology based on the work at SRI, IBM and MIT.

2000 – Honda showcases Asimo, the next generation of its series of humanoid robots.

2000 – Sony unveils humanoid robots, dubbed Sony Dream Robots (SDR), at Robodex.

2001 – Sony releases second generation of its Alto robot dog

2001 – Built by MD Robotics of Canada, the Space Station Remote Manipulator System (SSRMS) is successfully launched into orbit and begins operations to complete assembly of International Space Station

Robotics Terminology

Industrial robot:The Robotics Industries Association (RIA) defines robot in the following way:

“An industrial robot is a programmable, multi-functional manipulator designed to move materials, parts, tools, or

special devices through variable programmed motions for the performance of a variety of tasks”

DOF degrees-of-freedom: the number of independent motions a device can make. (Also called mobility)

five degrees of freedom


arms

Robot arms come in all shapes and sizes.

Positions the end-effector and sensors to do their pre-programmed business.

Many (but not all) resemble human arms, and have shoulders, elbows, wrists, even

fingers. This gives the robot a lot of ways to position itself in its environment.

Each joint is said to give the robot 1 degree of freedom.

1st Degree of Freedom

Left and right rotation

of the base of the arm.

2nd Degree of Freedom

Forward and backward movement of the base of the arm

3rd Degree of Freedom

Forward and backward movement of the elbow joint.

4th Degree of Freedom

Up and down movement of the wrist.

5th Degree of FreedomLeft and right movement of the wrist.

6th Degree of Freedom

Rotation of the wrist

End-effector: The tool, gripper, or other device mounted at the end of a manipulator, for accomplishing useful tasks.


Workspace: The volume in space that a robot’s end-effector can reach, both in position and orientation.

A cylindrical robots’ half workspace


Link: A rigid piece of material connecting joints in a robot.

Joint: The device which allows relative motion between two links in a robot.

A robot joint


Kinematics: The study of motion without regard to forces.

Dynamics: The study of motion with regard to forces.

Actuator: Provides force for robot motion.

Sensor: Reads variables in robot motion for use in control.


Laws of Robotics

Asimov's Laws of Robotics:1. A robot may not injure a human being, or, through inaction, allow a

human being to come to harm.2. A robot must obey the orders given it by human beings except where such

orders would conflict with the First Law.

3. A robot must protect its own existence as long as such protection does not conflict with the First or

Second Law.

Robotics and automation

1.Fixed automation2.Programmable automation3.Flexible automation

Robot Anatomy

Robot Anatomy Manipulator consists of joints and links

Joints provide relative motionLinks are rigid members between jointsVarious joint types: linear and rotaryEach joint provides a “degree-of-

freedom”Most robots possess five or six degrees-

of-freedom Robot manipulator consists of two

sections:Body-and-arm – for positioning of

objects in the robot's work volumeWrist assembly – for orientation of

objectsBase

Link0

Joint1

Link2

Link3Joint3

End of Arm

Link1

Joint2

Component of robot


The Robotic Joints

A robot joint is a mechanism that permits relative movement between parts of a robot arm. The joints of a robot are designed to enable the robot to move its end-effector along a path from one position to another as desired.

Manipulator Joints

Translational motionLinear joint (type L)

Rotary motionRotational joint (type R) Twisting joint (type T)Revolving joint (type V)

The Robotic Joints

CLASSIFICATION: CLASSIFIED INTO SIX CATEGORIES

– ARM GEOMETRY: RECTANGULAR;CYLINDIRICAL;SPHERICAL; JOINTED-ARM(VERTICAL);JOINED-ARM(HORIZONTAL).

– DEGREES OF FREEDOM: ROBOT ARM; ROBOT WRIST.

– POWER SOURCES: ELECTRICAL;PNEUMATIC;HYDRAULIC;ANY COMBINATION.

– TYPE OF MOTION: STRAIGHT-LINE INTERPOLATION; CIRCULAR INTERPOLATION.

– PATH CONTROL: LIMITED SEQUENCE; POINT-TO-POINT; CONTINOUS PATH; CONTROLLED PATH.

– INTELLLIGENCE LEVEL: LOW-TECHNOLOGY(NONSERVO); HIGH-TECHONOLOGY(SERVO).

Based on Physical Configuration

CartesianCylindricalPolarJointed arm

Polar Configuration

Polar Configuration:• Polar robots have a

work space of spherical shape. Generally, the arm is connected to the base with a twisting (T) joint and rotatory (R) and linear (L) joints follow.

Cylindrical RobotsA robot with 2 prismatic joints and a rotary joint – the axes consistent with a cylindrical coordinate system.

Commonly used for:•handling at die-casting machines•assembly operations•handling machine tools•spot welding

Cartesian RobotsA robot with 3 prismatic joints – the axes consistent with a Cartesian coordinate system.

Commonly used for:•pick and place work•assembly operations•handling machine tools•arc welding

ROBOT CLASSIFICATION

Joint-arm Configuration:• The jointed-arm is a combination of cylindrical and

articulated configurations. The arm of the robot is connected to the base with a twisting joint. The links in the arm are connected by rotatory joints. Many commercially available robots have this configuration.

SCARA (Selective Compliance Articulated Robot Arm) Robots

A robot with at least 2 parallel rotary joints.Similar to jointed-arm robot except that vertical axes are used for shoulder and elbow joints

Commonly used for:•pick and place work•assembly operations

Wrist Configurations• Wrist assembly is attached to end-of-arm• End effector is attached to wrist assembly • Function of wrist assembly is to orient end effector

– Body-and-arm determines global position of end effector

• Two or three degrees of freedom:– Roll – Pitch– Yaw

Mind Map


Work Volume of Robots

Work volume is the term that refers to the space within which the robot can manipulate its wrist end

Robot reach, also known as the work envelope or work volume, is the space of all points in the surrounding space that can be reached by the robot arm. Reach is one of the most important characteristics to be considered in selecting a suitable robot because the application space should not fall out of the selected robot's reach.

Depends on

• Physical configuration

• The size of body,arm,wrist

• The limit of joint movement

Robot Reach:

• For a Cartesian configuration the reach is a rectangular-type space.

• For a cylindrical configuration the reach is a hollow cylindrical space.

• For a polar configuration the reach is part of a hollow spherical shape.

• Robot reach for a jointed-arm configuration does not have a specific shape.

Configurations And Work Volumes

Polar Cylindrical Cartesian

Jointed Arm

Power Sources for Robots

• An important element of a robot is the drive system. The drive system supplies the power, which enable the robot to move.

• The dynamic performance of a robot mainly depends on the type of power source.

Drive Systems

• Hydraulic drive• Pneumatic drive• Electric drive

Joint Drive Systems

• Electric– Uses electric motors to actuate individual joints– Preferred drive system in today's robots

• Hydraulic– Uses hydraulic pistons and rotary vane actuators– Noted for their high power and lift capacity

• Pneumatic– Typically limited to smaller robots and simple

material transfer applications

There are basically three types of power sources for robots:

1. Hydraulic drive

• Provide fast movements

• Preferred for moving heavy parts

• Preferred to be used in explosive environments

• Occupy large space area

• There is a danger of oil leak to the shop floor

2. Electric drive• Slower movement compare to the

hydraulic robots• Good for small and medium size robots• Better positioning accuracy and

repeatability• stepper motor drive: open loop control• DC motor drive: closed loop control• Cleaner environment• The most used type of drive in industry

3. Pneumatic drive

• Preferred for smaller robots

• Less expensive than electric or hydraulic robots

• Suitable for relatively less degrees of freedom design

• Suitable for simple pick and place application

• Relatively cheaper

• Speed range about 1.7m/s

• Determine by how quickly accomplish cycle

• Speed depends on accuracy of wrist position, weight of the object, distance to be moved.

Speed of motion

Speed of motion

• It shows robot capable of traveling long distance in less time than sequence of short distance.

• Reason acceleration and deceleration problem

Load carrying capacity

• Size, configuration ,construction and drive system determine the load carrying capacity.

• Load capacity specified in arm weakest position.

• For example human lifting capacity with arm.

• Modern robot rated load capacity 2000lb• MAKER 110 capacity of 5lb

Control system

• 1.Limited sequence robot

• 2.Play back robot with point to point control

• 3.Play back with continuous path control

• 4.Intelligent robot

Precision of movement

• 1.Spatial resolution

Smallest increment movement into which robot can divide its work volume

Control resolution

Mechanical inaccuracy

• 2.Accuracy

• 3.Repeatability

END EFFECTORSEND EFFECTORS

End effectorsEnd effectorsThese enable the robot to perform These enable the robot to perform

specific tasks and are attached to the specific tasks and are attached to the wrist of robot. There are two types-wrist of robot. There are two types-

1) Grippers1) GrippersAre the end effectors used to Are the end effectors used to

grasp and manipulate objects during grasp and manipulate objects during work cycle. The objects are usually work cycle. The objects are usually work parts that are moved from one work parts that are moved from one place to another. place to another.

GrippersGrippers


There are different types of There are different types of grippers according to the shapes, sizes grippers according to the shapes, sizes and weights of parts to be held. For ex- and weights of parts to be held. For ex- mechanical grippers, vacuum grippers, mechanical grippers, vacuum grippers, magnetized grippers, dual, sensory magnetized grippers, dual, sensory multiple fingered grippers are used multiple fingered grippers are used according to the application.according to the application.


2) 2) ToolsToolsAre used in applications where the Are used in applications where the

robot must perform some processing robot must perform some processing operation on the work part. Therefore operation on the work part. Therefore the robot manipulates the tool relative the robot manipulates the tool relative to stationery or slowly moving objects: to stationery or slowly moving objects: Spot welding gun, arc welding tool, Spot welding gun, arc welding tool, spray painting gun, assembly tool, spray painting gun, assembly tool, water jet cutting tool, heating torch. water jet cutting tool, heating torch.


In each case, the robot not only In each case, the robot not only controls the relative position of tool controls the relative position of tool with respect to work piece but also with respect to work piece but also controls the operation of tool. In some controls the operation of tool. In some applications, multiple tools are also applications, multiple tools are also used by the robots during the work used by the robots during the work cycle. For ex- Several sizes of drilling cycle. For ex- Several sizes of drilling bits applied to the work part.bits applied to the work part.

ToolsTools

Mechanical Gripper

Mechanical Gripper

Actuation.

1.Linkage actuation

2.Gear and rack actuation

3.Cam actuation

4.Screw actuation

Linkage actuation&Gear and rack actuation

Cam and Screw actuation

Vacuum Gripper

Magnetic Gripper

Mind map(Drives)

Mind map(Gripper)

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