Introduction to robotics

Introduction to Robotics

SUBJECT: MTS 417: Introduction to Robotics

CREDIT HOURS: 3-1

CONTACT HOURS: 6 Hours per Week

TEXT BOOKS: Introduction to Robotics by JJ Craig, Latest

Edition

REFERENCE BOOKS: A Mathematical Introduction to Robotic

Manipulation by R. M. Murray, Z. Li, S. S.Sastry

PREREQUISITE: ME-230: Engineering Dynamics

Course Instructor : Lec Aqeela Mir (MS Mechatronics, CEME, NUST) [email protected]

Lab Instructor: LE Adnan Shujah (BS Mechatronics, CEME, NUST) [email protected]

Mark Distribution

Sessionals 25%

Lab 25%

Quizzes 07%

Assignments 03%

Final 40%

S.No Topic Week/Lecture

1 Types of robots 1

2 Types of joints used in robots 2

3 Spatial descriptions 3-5

4 Manipulator Kinematics 6-8

5 Jacobians 9-11

6 Inverse kinematics 12

7 Dynamics of Robots 13-14

8 Path Planning and Trajectory Analysis 15

9 Control 16

Learning Outcomes

1. Analyze a serial manipulator and develop geometric descriptions of the position and orientation of the robots

linkages

2. Apply forward/inverse kinematics equations for serial mechanism

3. Apply force and velocity analysis/ transformations on mechanisms

4. Understand and able to solve basic robotic dynamics, path planning and control problems.

5. Use modern analytical tools, test equipment and computer aided design to assemble different types of robotic systems

and measure performance.

Course Targets

S.No Outcomes Level of Learning

PLO

1 Analyze a serial manipulator and develop geometric descriptions of the position and orientation of the

robots linkages

C4 2

2 Apply forward/inverse kinematics equations for serial mechanism

C3 2

3 Apply force and velocity analysis/ transformations on mechanisms

C3 2

4 Understand and able to solve basic robotic dynamics, path planning and control problems.

C2 2

5 Use modern analytical tools, test equipment and computer aided design to assemble different types of

robotic systems and measure performance.

P4 5

Lecture 1

What is a Robot ?

322 B.C If every tool, when ordered, or even of its own accord, could do the work that befits itthen there would be no need either of apprentices for the master workers or the slaves for the lords - Aristotle

1495 Leonard da Vinci designs a mechanical clockwork that sits up, waves its arms and moves its head

1738 Jacques de Vaucanson creates a mechanical duck that was able to eat, flap its wings and excrete

1769 Wolfgang von Kempelen builds The Turk, which gained fame as an automation capable of playing chess until the hidden human operator was discovered

1921 Karel Capek popularizes the term robot in a play called R.U.R. (Rossums Universal Robots) wherein robot workers take over the earth

1942 Issac Asimov publishes Runaround, which introduces the three Laws of Robotics

The term robotics was introduced by Asimov as the science devoted to the study of robots which was based on the three fundamental laws:

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 by the human beings, except when 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

1951 Raymond Goertz builds the first master/slave tele-operation system for handling radioactive

1961 Unimate, the first industrial robot, begins work on a General Motors assembly line

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 - The Robotics Institute of America

Arent robots more/different?

No single correct definition of robot, but a typical robot will have several or possibly all of the following properties:

It is artificially created

It can sense its environment and manipulate or interact with things in it

It has some ability to make choices based on the environment, often using automatic control or a preprogrammed sequence

It is programmable

It moves with one or more axes of rotation or translation

It makes dexterous coordinated movements

It moves without direct human intervention

Arent robots more/different?

Robot Examples

Robot Examples

Mars Rovers

Mobile Robots

RISE (the climbing robot)

Robot Examples

Rhex hexapod Robot Sony AIBO Robot

Robot Examples

Medical Application

Examples : Micro/Nano Robots

Flying insect robot Bacteria like Microbots to help in surgery

Examples: Remote Exploration

Planetary Exploration Underwater Exploration

Examples: Humanoid

Robot Necessity

Robots are needed for a variety of tasks, few are:

Tasks that humans cannot perform :

Examples are space or underwater exploration, moving in confined and restrained spaces such as narrow pipes and passageways are needed in earthquake rescue tasks, and moving objects that are too small or too big for humans to handle

Some tasks require performance beyond human capabilities such as a higher degree of repetitive precision, high-speed motion, or high levels of strength

Robot Necessity Task that human do not want to perform: Repetitive, boring, tedious work such as assembly line work,

ship cleaning and long shift security tasks Tasks that are dangerous for humans: Work in dangerous environments such as volcano craters,

space and underwater exploration missions, chemical spill clean-up, nuclear waste disposal, explosive material manipulation, and tasks that require prolonged exposure to cold, heat, pressure, lack of air, or other conditions harmful to humans

The amusement and entertainment of humans: Robotic toys for children and robots for the entertainment

industry

Robotics

Robotics is commonly defined as the science studying the intelligent connection between perception and action

A robotic system is in reality a complex system, functionally represented by multiple subsystems

Robotic System

The essential component of a robot is the mechanical system in general, with a locomotion apparatus (wheels, crawlers, mechanical legs) and manipulation apparatus (mechanical arms, end-effectors, artificial hands)

The realization of such a system refers to the context of design of articulated mechanical systems and choice of materials

The capability to exert as action, both locomotion and manipulation, is provided by an actuation system which animates(make alive) the mechanical components of the robot

The concept of such a system refers to the context of motion control, dealing with servomotors, drives and transmissions

Robotic System

Robotic System

The capability for perception is entrusted to a sensory system which can acquire data on the internal status of mechanical system(proprioceptive sensors, such as position transducers) and on the external status of the environment (exteroceptive sensors, such as force sensors and camera)

The realization of such a system refers to the context of materials properties, signal conditioning, data processing and information retrieval

Robotic System

The capability for connecting action to perception in an intelligent fashion is provided by a control system which can command the execution of the action in respect to the goals set by the task planning technique, as well as of the constraints imposed by the robot and the environment

Therefore, it can be said that robotics is an interdisciplinary subject concerning the areas of mechanics, control, computers and electronics

Degrees of Freedom

The number of independent movements that an object can perform in a 3-D space is called the number of degrees of freedom (DOF)

Thus the rigid body free in space has six degrees of freedom:

- Three for position

- Three for orientation

Degrees of Freedom

These six independent movements shown in figure are:

Three translations (T1,T2,T3)

representing linear motions along

three perpendicular axis, specify

the position of body in space

Three rotations(R1,R2,R3) which

represent angular motions about

the three axis, specify the

orientation of body in space

Z

X

Y

T3

T2 T1

R3

R1

R2 O

The key feature of a robot is its mechanical structure:

Robots can be classified as :

- Those with a fixed base, robot manipulators, and

- Those with a mobile base, mobile robots

Robot Mechanical Structure

Robot Manipulators

Labor is typically performed by human arms powered by muscles and augmented by the use of tools. It is therefore not a coincidence that the first widely commercialized industrial robots were robotic arms, also called robot manipulators

The mechanical structure of a robot manipulator consists of a sequence of rigid bodies(links) interconnected by means of articulations(joints)

A manipulator is characterized by an arm that ensures mobility, a wrist that confers dexterity(skill and grace in physical movement) and an end-effector that performs the task required of the robot

Robot Manipulators

Mitsubishi PA-10 robotic arm

Robot Manipulators

Robots like PA-10, as electromechanical devices, can easily far exceed the capabilities of the human arm in terms of strength, range of motions, speed of action, precision, repeatability and endurance

Today, robot manipulators constitute the largest portion of industrial robots in operation in the world

Robot Manipulators The fundamental structure of a

manipulator is the serial or open kinematic chain

From a topological viewpoint, a kinematic chain is termed open when there is only one sequence of links connecting the two ends of the chain

Alternatively, a manipulator contains a closed kinematic chain when a sequence of links forms a loop

Robot Manipulators A manipulators ability is ensured by

the presence of joints. The articulation between two consecutive links can be realized by means of either a prismatic or a revolute joint

In an open kinematic chain, each prismatic or revolute joint provides the structure with a single degree of freedom(DOF)

A prismatic joint creates a relative translational motion between the two links, whereas a revolute joint creates a relative rotational motion between the two links

Robot Manipulators(DOF)

B, C J2 joint

A J1 joint Ground

The degree of freedom should be properly distributed along the mechanical structure in order to have a sufficient number to execute a given task

Consider an open kinematic chain of two links with revolute joints at A and B(or C) as shown in figure

Here, the first link is connected to the ground by a joint at A


B, C J2 joint

A J1 joint Ground

Therefore, link 1 can only rotate about joint 1 (J1) with respect to ground and contributes one independent variable(an angle), or in other words, it contributes one degree of freedom

Link 2 can rotate about joint 2 (J2) with respect to link 1, contributing another independent variable and so another DOF


Thus, an open kinematic chain with one end connected to the ground by a joint and the farther end of the last link free, has as many degrees of freedom as the number of joints in the chain

It is assumed that each joint has only one DOF

The DOF is also equal to the number of links in the open kinematic chain


The variable defining the motion of a link at a joint is called a joint-link variable

Thus, for an n-DOF manipulator n independent joint-link variables are required to completely specify the location(position and orientation) of each link(and joint), specifying the location of the end-effector in space

Thus, for the two link, in turn 2-DOF manipulator, in figure two variables are required to define location of the end point

Required DOF in a Manipulator

It is concluded that to position and orient a body freely in a space, a manipulator with 6- DOF is required

Such a manipulator is called a spatial manipulator. It has three joints for positioning and three for orienting the end effector

A manipulator with less than 6-DOF has constrained motion in the 3-D space

There are many industrial manipulators that have five or fewer DOF that are useful for specific applications that do not require 6-DOF


Spatial manipulators with more than 6-DOF have surplus joints and are known as redundant manipulators

The extra DOF may enhance the performance by adding to its dexterity

Dexterity here implies that the manipulator can reach a sub-space which is obstructed by objects, by the capability of going around these

However, redundant manipulators present complexities in modeling and coordinate frame transformations and therefore in their programming and control


The DOF of a manipulator are distributed into sub-assemblies of arm and wrist

The arm is used for positioning the end effector in space and hence the three positional DOF

The remaining 3-DOF are provided in the wrist, whose task is to orient the end effector

The type and arrangement of joints in the arm and wrist can vary considerably

Introduction to robotics

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