robotics

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.

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.

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.

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.

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

a. Inflatable bladder

b. Two-finger clamp

c. Vaccum cups

d. Three-fingers clamp

e. Magnet head

f. 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

– 0o for vertical motion– 90o 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:

a. The part weighs 20 pounds and is of a non-uniform shape.

b. The gripper's jaws are parallel to each other and are grasping the part by its vertical sides.

c. The part is grasped 24 inches from its center of gravity.

Sample Problem 1

d. The jaws' gripping surface is 4 inches wide.

e. The part is 2 inches thick at the point where it is being grasped.

f. The part is being lifted with a maximum acceleration of 2.5 Gs, including normal gravitational force.

g. The coefficient of friction between the part and the gripper is 0.85.

h. 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 D2 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 D2 x P – Ff

• Inward Stroke– F = 0.7854 x (D2 – Dr

2) x P – Ff

• Where– D: diameter of the piston– P: pressure of the fluid entering the cylinder

– Dr: 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 Rc) - Tf

• Where– T: torque developed by the actuator – P: fluid pressure– A: vane area

– Rc: 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

– Rc: 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 OPERATING METHODS OF ROBOT CONTROL UNITCONTROL UNIT

• Pick-and-Place Control units

• Point-to-Point Control Units

• Continuous-path Control Units

PICK & PLACE CONTROL UNITPICK & 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 UNITPICK & PLACE CONTROL UNIT• Typical sequence of operationsTypical 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 UNITCONTINOUS 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