ME6703-COMPUTER-INTEGRATED MANUFACTURING

SEVENTH SEMESTER-MECHANICAL ENGINEERING

UNIT-V (POSSIBLE Q&A)

INDUSTRIAL ROBOTICS PART-A

1. What is meant by Robot anatomy? Study of structure of robot is called robot anatomy. 2. Write the classification of robot. Coordinate Systems/Frames - Cartesian • Cylindrical • Spherical, SCARA Robot. 3. Name the different types of robot control system. Non-servo Control, Feedback Control Loop, Feed forward Control, Adaptive Control. 4. Define End effectors. (Nov/Dec 2012) End effector is a device that is attached to the end of the wrist arm to perform specific tasks. 5. What is meant by work volume and work envelope? The volume of the space swept by the robot arm is work volume. 6. What is meant by repeatability of robot? Repeatability refers to the ability to return to the programmed point when it is commanded to do so again and again. 7. What is meant by Accuracy of the robot? The ability of the robot to reach a reference point within the robot‘s full work volume is known as accuracy of the robot. 8. List the applications of robot in manufacturing area? Material transfer, Loading and unloading, processing operations, assembly and inspection. 9. What is a Sensor? Sensor is a device that is used to make the measurement of a physical variable of interest. 10. What are the methods of Robot programming? (May/June 2013) Lead through methods, Textual robot programming, and Mechanical Programming. 11. What is a teach pendant? (May/June 2012) The teach pendant is usually a small handheld control box with combinations of toggle switches, dials and buttons to regulate the robot‘s physical movements and program capabilities. 12. List some of the Robot programming languages. WAVE, AL, AML, MCL, VAL, PAL, RAIL, HELP 13. Differentiate between a transducer and a sensor. Transducer is a device that converts the one form of information in to another form without changing the information content. Sensor is a transducer that is used to make a measurement of a physical variable of interest. 14. What are the types of mechanical grippers? Linkage Actuation gripper, Gear and rack actuation gripper, Cam actuation gripper and screw actuated gripper.

PART – B

1. Briefly explain the different types of robots. An industrial robot commonly refers to a robot arm used in a factory environment for manufacturing applications. Traditional industrial robots can be classified according to different criteria such as type of movement (degrees of freedom), application(manufacturing process), architecture (serial or parallel) and brand. Then there is also a new qualifier for industrial robots that can be collaborative or not. This article presents the different classifications with some examples. Industrial robots with different types of movements

Cartesian robots Cartesian robots are robots that can do 3 translations using linear slides.

Scara robots Scara robots are robots that can do 3 translations plus a rotation around a vertical axis.

6-axis robots 6-axis robots are robots that can fully position their tool in a given position (3 translations) and orientation (3 orientations)

Redundant robots Redundant robots can also fully position their tool in a given position. But while 6-axis robots can only have one posture for one given tool position, redundant robots can accommodate a given tool position under different postures. This is just like the human arm that can hold a fixed handle while moving the shoulder and elbow joints.

Dual-arm robots Dual-arm robots are composed of two arms that can work together on a given work piece.

Industrial robots for different applications The application is the type of work that the robot is designed to do. Robot models are created with specific applications or processes in mind. Different applications will have different requirements. For instance, a painting robot will require a small payload but a large movement range and be explosion proof. On the other hand, an assembly robot will have a small workspace but will be very precise and fast. Depending on the target application, the industrial robot will have a specific type of movement, linkage dimension, control law, software and accessory packages. Below are some types of applications:

Welding robots

Material handling robots

Palletizing robot

Painting robot

Assembly robot

2. i) Write short notes on joint notation scheme.

Joint Notation Scheme

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.

The basic movements required for a desired motion of most industrial robots are:

Rotational movement: This enables the robot to place its arm in any direction on a horizontal plane.

Radial movement: This enables the robot to move its end-effector radially to reach distant points.

Vertical movement: This enables the robot to take its end-effector to different heights.

These degrees of freedom, independently or in combination with others, define the complete

motion of the end-effectors.

These motions are accomplished by movements of individual joints of the robot arm. The joint movements are

basically the same as relative motion of adjoining links. Depending on the nature of this relative motion, the joints are

classified as prismatic or revolute.

Prismatic joints are also known as sliding as well as linear joints. They are called prismatic because the

cross section of the joint is considered as a generalized prism. They permit links to move in a linear relationship.

Revolute joints permit only angular motion between links. Their variations include:

Rotational joint (R)

Twisting joint (T)

Revolving joint (V)

In a prismatic joint, also known as a sliding or linear joint (L), the links are generally parallel to one another. In some

cases, adjoining links are perpendicular but one link slides at the end of the other link.

The joint motion is defined by sliding or translational movements of the links. The orientation of the links remains the

same after the joint movement, but the lengths of the links are altered.

A rotational joint (R) is identified by its motion, rotation about an axis perpendicular to the adjoining links. Here, the

lengths of adjoining links do not change but the relative position of the links with respect to one another changes as

the rotation takes place.

A twisting joint (T) is also a rotational joint, where the rotation takes place about an axis that is parallel to both

adjoining links.

A revolving joint (V) is another rotational joint, where the rotation takes place about an axis that is parallel to one of

the adjoining links. Usually, the links are aligned perpendicular to one another at this kind of joint. The rotation

involves revolution of one link about another.

Types of joints used in robots

The Robot Joints is the important element in a robot which helps the links to travel in different kind of

movements. There are five major types of joints such as:

Rotational joint

Linear joint

Twisting joint

Orthogonal joint

Revolving joint

Rotational Joint:

Rotational joint can also be represented as R –Joint. This type will allow the joints to move in a

rotary motion along the axis, which is vertical to the arm axes.

Linear Joint:

Linear joint can be indicated by the letter L –Joint. This type of joints can perform both translational and sliding

movements. These motions will be attained by several ways such as telescoping mechanism and piston. The two

links should be in parallel axes for achieving the linear movement.

Twisting Joint:

Twisting joint will be referred as V –Joint. This joint makes twisting motion among the output and

input link. During this process, the output link axis will be vertical to the rotational axis. The output link

rotates in relation to the input link.

Orthogonal Joint:

The O –joint is a symbol that is denoted for the orthogonal joint. This joint is somewhat similar to the

linear joint. The only difference is that the output and input links will be moving at the right angles.

Revolving Joint:

Revolving joint is generally known as V –Joint. Here, the output link axis is perpendicular to the

rotational axis, and the input link is parallel to the rotational axes. As like twisting joint, the output link spins

about the input link.

ii) Write short notes on technical specification in Robotics.

Technical specification in Robotics Accuracy:

The robot's program instructs the robot to move to a specified point, it does not actually perform as per

specified. The accuracy measures such variance. That is, the distance between the specified position that

a robot is trying to achieve (programming point), and the actual X, Y and Z resultant position of the robot

end effector.

Repeatability:

The ability of a robot returns repeatedly to a given position. It is the ability of a robotic system or

mechanism to repeat the same motion or achieve the same position. Repeatability is is a measure of the

error or variability when repeatedly reaching for a single position. Repeatability is often smaller than

accuracy.

Degree of Freedom (DOF):

Each joint or axis on the robot introduces a degree of freedom. Each DOF can be a slider, rotary, or other

type of actuator. The number of DOF that a manipulator possesses thus is the number of independent

ways in which a robot arm can move. Industrial robots typically have 5 or 6 degrees of freedom.

Three of the degrees of freedom allow positioning in 3D space (X, Y, Z), while the other 2 or 3 are used for

orientation of the end effector (yaw, pitch and roll). 6 degrees of freedom are enough to allow the robot to

reach all positions and orientations in 3D space. 5 DOF requires a restriction to 2D space, or else it limits

orientations. 5 DOF robots are commonly used for handling tools such as arc welders.

Resolution:

The smallest increment of motion can be detected or controlled by the robotic control system. It is a

function of encoder pulses per revolution and drive (e.g. reduction gear) ratio. And it is dependent on the

distance between the tool center point and the joint axis.

Envelope:

A three-dimensional shape, that defines the boundaries that the robot manipulator can reach; also

known as reach envelope.

Reach:

The maximum horizontal distance between the center of the robot base to the end of its wrist.

Maximum Speed:

A robot simultaneously moving with all joints in complimentary directions at full speed with full

extension. The maximum speed is the theoretical values which does not consider under loading condition.

Payload:

The maximum payload is the amount of weight carried by the robot manipulator at reduced speed while

maintaining rated precision. Nominal payload is measured at maximum speed while maintaining rated precision.

These ratings are highly dependent on the size and shape of the payload due to variation in inertia.

Four types of robot control

1. Point-to-point (PTP) control robot

2. Continuous-path (CP) control robot

3. Controlled-path robot

4. Stop-to-Stop

Point to Point Control Robot (PTP):

The PTP robot is capable of moving from one point to another point. The locations are recorded in the

control memory.PTP robots do not control the path to get from one point to the next point. Common

applications include:

Component insertion

Spot welding

hole drilling

Machine loading and unloading

Assembly operations

Continuous-Path Control Robot (CP):

The CP robot is capable of performing movements along the controlled path. With CP from one

control, the robot can stop at any specified point along the controlled path.

All the points along the path must be stored explicitly in the robot's control memory. Applications

Straight-line motion is the simplest example for this type of robot.

Some continuous-path controlled robots also have the capability to follow a smooth curve path that

has been defined by the programmer.

In such cases the programmer manually moves the robot arm through the desired path and the

controller unit stores a large number of individual point locations along the path in memory (teach-in).

Typical applications include:

spray painting

finishing

gluing

Arc welding operations

Controlled-Path Robot:

In controlled-path robots, the control equipment can generate paths of different geometry such as

straight lines, circles, and interpolated curves with a high degree of accuracy.Good accuracy can be

obtained at any point along the specified path.

Only the start and finish points and the path definition function must be stored in the robot's control

memory. It is important to mention that all controlled-path robots have a servo capability to correct their

path.

Stop-to-Stop:

It is open loop system

Position and velocity unknown to controller

On/off commands stored as valve states

End travel set by mechanical 3. Explain robot parts and their functions with neat sketch

Robot Parts and Functions

The controller is the "brain" of the industrial robotic arm and allows the parts of the robot to

operate together. It works as a computer and allows the robot to also be connected to other systems.

The robotic arm controller runs a set of instructions written in code called a program. The program is

inputted with at each pendant. Many of today's industrial robot arms use an interface that resembles or is

built on the Windows operating system.

Industrial robot arms can vary in size and shape. The industrial robot arm is the part that positions the

end effector. With the robot arm, the shoulder, elbow, and wrist move and twist to position the end

effector in the exact right spot. Each of these joints gives the robot another degree of freedom. A simple

robot with three degrees of freedom can move in three ways: up & down, left & right, and forward &

backward. Many industrial robots in factories today are six axis robots.

The end effector connects to the robot's arm and functions as a hand. This part comes in direct

contact with the material the robot is manipulating. Some variations of an effector are a gripper, a

vacuum pump, magnets, and welding torches. Some robots are capable of changing end effectors and

can be programmed for different sets of tasks.

The drive is the engine or motor that moves the links into their designated positions. The links are the

sections between the joints. Industrial robot arms generally use one of the following types of drives:

hydraulic, electric, or pneumatic. Hydraulic drive systems give a robot great speed and strength. An

electric system provides a robot with less speed and strength. Pneumatic drive systems are used for

smaller robots that have fewer axes of movement. Drives should be periodically inspected for wear and

replaced if necessary.

Sensors allow the industrial robotic arm to receive feedback about its environment. Theycan give the

robot a limited sense of sight and sound. The sensor collects information and sends it electronically to

the robot controlled. One use of these sensors is to keep two robots that work closely together from

bumping into each other. Sensors can also assist end effectors by adjusting for part variances. Vision

sensors allow a pick and place robot to differentiate between items to choose and items to ignore.

Controller:

Every robot is connected to a computer, which keeps the pieces of the arm working together. This

computer is known as the controller.

The controller functions as the "brain"of the robot. The controller also allows the robot to be networked

to other systems, so that it may work together with other machines, processes, or robots.

Robots today have controllers that are run by programs - sets of instructions written in code. Almost all

robots of today are entirely pre-programmed by people; they can do only what they are programmed to

do at the time, and nothing else. In the future, controllers with artificial intelligence, or AI could allow

robots to think on their own, even program themselves. This could make robots more self-reliant and

independent.

Arm:

Robot arms come in all shapes and sizes. The arm is the part of the robot that 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. So, a simple robot arm with 3 degrees of freedom could move in 3 ways: up

and down, left and right, forward and backward.

Drive:

The drive is the "engine" that drives the links (the sections between the joints into their desired

position. Without a drive, a robot would just sit there, which is not often helpful. Most drives are powered

by air, water pressure, or electricity.

End-Effector:

The end-effector is the "hand" connected to the robot's arm. It is often different from a human hand

- it could be a tool such as a gripper, a vacuum pump, tweezers, scalpel, blowtorch - just about anything

that helps it do its job. Some robots can change end-effectors, and be reprogrammed for a different set

of tasks.

Sensor:

Most robots of today are nearly deaf and blind. Sensors can provide some limited feedback to the

robot so it can do its job. Compared to the senses and abilities of even the simplest living things, robots

have a very long way to go. The sensor sends information, in the form of electronic signals back to the

controller. Sensors also give the robot controller information about its surroundings and let it know the

exact position of the arm, or the state of the world around it.

4.Explain Various Industrial Applications of Robots. Applications:

Currently, robots perform a number of different jobs in numerous fields and the amount of tasks

delegated to robots is rising progressively. The best way to split robots into types is a partition by

their application.

1. Industrial robots – These robots bring into play in an industrialized manufacturing atmosphere.

Typically these are articulated arms particularly created for applications like- material handling,

painting, welding and others. If we evaluate merely by application then this sort of robots can also

consist of some automatically guided automobiles and other robots.

2. Domestic or household robots – Robots which are used at home. This sort of robots consists

of numerous different gears for example- robotic pool cleaners, robotic sweepers, robotic vacuum

cleaners, robotic sewer cleaners and other robots that can perform different household tasks. Also,

a number of scrutiny and tele-presence robots can also be considered as domestic robots if

brought into play in that sort of environment.

3. Medical robots – Robots employed in medicine and medicinal institutes. First & foremost

surgical treatment robots. Also, a number of robotic directed automobiles and perhaps lifting

supporters.

4. Service robots – Robots that cannot be classed into any other types by practice. These could

be various data collecting robots, robots prepared to exhibit technologies, robots employed for

research, etc.

5. Military robots – Robots brought into play in military & armed forces. This sort of robots consist

of bomb discarding robots, various shipping robots, exploration drones. Often robots at the start

produced for military and armed forces purposes can be employed in law enforcement, exploration

and salvage and other associated fields.

6. Entertainment robots – These types of robots are employed for entertainment. This is an

extremely wide-ranging category. It begins with model robots such as robosapien or the running

photo frames and concludes with real heavy weights like articulated robot arms employed as

movement simulators.

7. Space robots – I would like to distinct out robots employed in space as a split apart type. This

type of robots would consist of the robots employed on Canadarm that was brought into play in

space Shuttles, the International Space Station, together with Mars explorers and other robots

employed in space exploration & other activities.

8. Hobby and competition robots – Robots that is created by students. Sumo-bots, Line

followers, robots prepared merely for learning, fun and robots prepared for contests.

Now, as you can observe that there are a number of examples that fit well into one or more of

these types. For illustration, there can be a deep ocean discovery robot that can collect a number

of precious information that can be employed for military or armed forces purpose.

Robotics is a broad field and everyday there is a pioneering invention in the field. Robots were

invented by the humans just for fun but by now they are used for assisting humans in various

sectors. Human beings are better suitable for multifaceted, imaginative, adaptive jobs, and robots

are good for dreary, recurring tasks, permitting human beings to do the harder thinking

jobs, whereas a robot is employed for substituting humans for various recurring tasks or

entertainment to make living more expedient.

5.(i) Explain the robot and End effector interface functions.

In robotics, an end effector is the device at the end of a robotic arm, designed to interact with the environment. The exact nature of this device depends on the application of the robot.

In the strict definition, which originates from serial robotic manipulators, the end effector means the last link (or end) of the robot. At this endpoint the tools are attached. In a wider sense, an end effector can be seen as the part of a robot that interacts with the work environment. This does not refer to the wheels of a mobile robot or the feet of a humanoid robot which are also not end effectors—they are part of the robot's mobility.

End effectors may consist of a gripper or a tool. When referring to robotic prehension there are four general categories of robot grippers, these are:[1]

1. Impactive – jaws or claws which physically grasp by direct impact upon the object.

2. Ingressive – pins, needles or hackles which physically penetrate the surface of the object (used in textile, carbon and glass fibre handling).

3. Astrictive – suction[vague] forces applied to the objects surface (whether by vacuum, magneto- or electroadhesion).

4. Contigutive – requiring direct contact for adhesion to take place (such as glue, surface tension or freezing).

They are based on different physical effects used to guarantee a stable grasping between a gripper and the object to be grasped.[2] Industrial grippers can be mechanical, the most diffused in industry, but also based on suction or on the magnetic force. Vacuum cups and electromagnets dominate the automotive field and in particular metal sheet handling. Bernoulli grippers exploit the airflow between the gripper and the part that causes a lifting force which brings the gripper and part close each other (i.e. the Bernoulli's principle). Bernoulli grippers are a type of contactless grippers, namely the object remains confined in the force field generated by the gripper without coming into direct contact with it. Bernoulli grippers have been adopted in photovoltaic cell handling, silicon wafer handling, and also in the textile and leather industries. Other principles are less used at the macro scale (part size >5mm), but in the last ten years they demonstrated interesting applications in micro-handling. Some of them are ready of spreading out their original field. The other adopted principles are: Electrostatic grippers and van der Waals grippers based on electrostatic charges (i.e. van der Waals' force), capillary grippers and cryogenic grippers, based on liquid medium, and ultrasonic grippers and laser grippers, two contactless grasping principles. Electrostatic grippers are based on charge difference between the gripper and the part (i.e. electrostatic force) often activated by the gripper itself, while van der Waals grippers are based on the low force (still electrostatic) due to the atomic attraction between the molecules of the gripper and those of the object. Capillary grippers use the surface tension of a liquid meniscus between the gripper and the part to center, align and grasp the part, cryogenic grippers freeze a small amount of liquid and the resulting ice guarantees the necessary force to lift and

handle the object (this principle is used also in food handling and in textile grasping). Even more complex are ultrasonic based grippers, where pressure standing waves are used to lift up a part and trap it at a certain level (example of levitation are both at the micro level, in screw and gasket handling, and at the macro scale, in solar cell or silicon wafer handling), and laser source that produces a pressure able to trap and move microparts in a liquid medium (mainly cells). The laser gripper are known also as laser tweezers.

A particular category of friction/jaw gripper are the needle grippers: they are called intrusive grippers and exploits both friction and form closure as standard mechanical grippers.

The most known mechanical gripper can be of two, three or even five fingers.

The end effectors that can be used as tools serve various purposes, such as spot welding in an assembly, spray painting where uniformity of painting is necessary, and for other purposes where the working conditions are dangerous for human beings. Surgical robots have end effectors that are specifically manufactured for the purpose.

5.(ii)Discuss the factors that can be influenced in the selection of gripper. The industrial robots use grippers as an endeffector for picking up the raw and finished work parts. A robot can perform good grasping of objects only when it obtains a proper gripper selection and design. Therefore, Joseph F. Engelberger, who is referred as Father of Roboticshas described several factors that are required to be considered in gripper selection and design. The gripper must have the ability to reach the surface of a work part. The change in work part size must be accounted for providing accurate positioning. During machining operations, there will be a change in the work part size. As a result, the

gripper must be designed to hold a work part even when the size is varied. The gripper must not create any sort of distort and scratch in the fragile work parts. The gripper must hold the larger area of a work part if it has various dimensions, which will

certainly increase stability and control in positioning. The gripper can be designed with resilient pads to provide more grasping contacts in the work

part. The replaceable fingers can also be employed for holding different work part sizes by its interchangeability facility.

Moreover, it is difficult to find out the magnitude of gripping force that a gripper must apply to pick up a work part. The following significant factors must be considered to determine the necessary gripping force. Consideration must be taken to the weight of a work part. It must be capable of grasping the work parts constantly at its centre of mass. The speed of robot arm movement and the connection between the direction of movement and

gripper position on the work part should be considered. It must determine either friction or physical constriction helps to grip the work part. It must consider the co-efficient of friction between the gripper and work part.

gripper.

6.Describe the classifications of sensors and the factors to be considered for its selection.

Sensor Classification

Sensor classification schemes range from very simple to the complex. One good way to look at a sensor is to consider all of its properties, such as stimulus, specifications, physical phenomenon, conversion mechanism, material and application field.

For machine tools, sensor's conversion phenomena are mainly physical phenomena such as thermoelectric, photoelectric, photomagnetic, electromagnetic, magnetoelectric, thermoelastic, thermomagnetic, thermooptic, photoelastic, and so on. Stimulus is shown in Table 1.

Sensor Selection

Any sensor is based on a simple concept that physical property of a sensor must be altered by an

external stimulus to cause that property either to produce an electric signal or to modulate (to

modify) an external electric signal. Quite often, the same stimulus may be measured by using quite

different physical phenomena, and subsequently, by different sensors. Selection criteria depend on

many factors, such as availability, cost, power consumption, environmental conditions, etc. The

best choice can be done only after all variables are considered.

7.Explain the four common Robot configurations with neat sketch.

Articulated - This robot design features rotary joints and can range from simple two joint structures to 10 or more joints. The arm is connected to the base with a twisting joint. The links in the arm are connected by rotary joints. Each joint is called an axis and provides an additional degree of freedom, or range of motion. Industrial robots commonly have four or six axes. Cartesian - These are also called rectilinear or gantry robots. Cartesian robots have three linear joints that use the Cartesian coordinate system (X, Y, and Z). They also may have an attached wrist to allow for rotational movement. The three prismatic joints deliver a linear motion along the axis.

Cylindrical - The robot has at least one rotary joint at the base and at least one prismatic joint to connect the links. The rotary joint uses a rotational motion along the joint axis, while the prismatic joint moves in a linear motion. Cylindrical robots operate within a cylindrical-shaped work envelope. Polar - Also called spherical robots, in this configuration the arm is connected to the base with a twisting joint and a combination of two rotary joints and one linear joint. The axes form a polar coordinate system and create a spherical-shaped work envelope. SCARA - Commonly used in assembly applications, this selectively compliant arm for robotic assembly is primarily cylindrical in design. It features two parallel joints that provide compliance in one selected plane.

Delta - These spider-like robots are built from jointed parallelograms connected to a common base. The parallelograms move a single EOAT in a dome-shaped work area. Heavily used in the food, pharmaceutical, and electronic industries, this robot configuration is capable of delicate, precise movement. Typical industrial robots are articulated and feature six axes of motion (6 degrees of freedom). This design allows maximum flexibility. Six-axis robots are ideal for:

- Arc Welding - Spot Welding - Material Handling - Machine Tending - Other Applications

8.(i) Explain in detail the tactile and non tactile sensors.

A tactile sensor is a device that measures information arising from physical interaction with its environment. Tactile sensors are generally modeled after the biological sense of cutaneous touch which is capable of detecting stimuli resulting from mechanical stimulation, temperature, and pain (although pain sensing is not common in artificial tactile sensors). Tactile sensors are used in robotics, computerhardware and security systems. A common application of tactile sensors is in touchscreen devices on mobile phones and computing.

Tactile sensors may be of different types including piezoresistive, piezoelectric, capacitive and elastoresistive sensors.

Tactile sensors appear in everyday life such as elevator buttons and lamps which dim or brighten by touching the base. There are also innumerable applications for tactile sensors of which most people are never aware.

Sensors that measure very small changes must have very high sensitivities. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Tactile sensors can be used to test the performance of all types of applications. For example, these sensors have been used in the manufacturing of automobiles (brakes, clutches, door seals, gasket), battery lamination, bolted joints, fuel cells etc.

Tactile imaging, as a medical imaging modality, translating the sense of touch into a digital image is based on the tactile sensors. Tactile imaging closely mimics manual palpation, since the probe of the device with a pressure sensor array mounted on its face acts similar to human fingers during clinical examination, deforming soft tissue by the probe and detecting resulting changes in the pressure pattern.

Robots designed to interact with objects requiring handling involving precision, dexterity, or interaction with unusual objects, need sensory apparatus which is functionally equivalent to a human's tactile ability. Tactile sensors have been developed for use with robots. Tactile sensors can complement visual systems by providing added information when the robot begins to grip an object. At this time vision is no longer sufficient, as the mechanical properties of the object cannot be determined by vision alone. Determining weight, texture, stiffness, center of mass, coefficient of friction, and thermal conductivity require object interaction and some sort of tactile sensing.

Non-contacting sensors are also a very important type of sensor, which detect parametric information about the environment of the object. It is used to detect the existence, distance and features of the object. There are mainly six types of non-contacting sensor are as [8]: (1). Visual and optical sensor. (2). Magnetic and inductive sensor. (3). Capacitive sensor. (4). Resistive sensor. (5). Ultrasonic and sonar sensor. (6). Air pressure sensor. Visual and optical sensors operate by transforming light into an electrical signal. The photo detectors can be as simple as a single photo diode or as complex as a television camera. With stereo cameras, robotic vision systems are analogous to the human sense of sight

(ii) Briefly explain the working principle of Range sensors with neat sketch. An infrared sensor is an electronic device, that emits in order to sense some aspects of the surroundings. An IR sensor can measure the heat of an object as well as detects the motion.These types of sensors measures only infrared radiation, rather than emitting it that is called as a passive IR sensor. Usually in the infrared spectrum, all the objects radiate some form of thermal radiations. These types of radiations are invisible to our eyes, that can be detected by an infrared sensor.The emitter is simply an IR LED (Light Emitting Diode) and the detector is simply an IR photodiode which is sensitive to IR light of the same wavelength as that emitted by the IR LED. When IR light falls on the photodiode, The resistances and these output voltages, change in proportion to the magnitude of the IR light received.

IR Sensor Circuit Diagram and Working Principle

An infrared sensor circuit is one of the basic and popular sensor module in an electronic device.

This sensor is analogous to human‘s visionary senses, which can be used to detect obstacles and

it is one of the common applications in real time.This circuit comprises of the following components LM358 IC 2 IR transmitter and receiver pair Resistors of the range of kilo ohms. Variable resistors. LED (Light Emitting Diode).

9.Explain the different types of programming methods in detail.

Various Programming Techniques

This section is a short survey of programming techniques. There are various types of programming technique is available in the programming era. Here more focus has been given over OOP. List of Various Programming Technique: 1. Unstructured Programming 2. Procedural Programming 3.Modular Programming 4. Object-Oriented Programming (OOP) Unstructured Programming

Usually, people start learning programming by writing small and simple programs consisting only of one main program. Here "main program'' stands for a sequence of commands or statements which modify data which is global throughout the whole program. We can illustrate this as shown below: Unstructured programming. The main program directly operates on global data.

For example, if the same statement sequence is needed at different locations within the program, the sequence must be copied. This has lead to the idea to extract these sequences, name them and offering a technique to call and return from these procedures.

Procedural Programming

With procedural programming you are able to combine returning sequences of statements into one single place. A procedure call is used to invoke the procedure. After the sequence is processed, flow of control proceeds right after the position where the call was made. Execution of procedures. After processing flow of controls proceed where the call was made.

With introducing parameters as well as procedures of procedures (sub procedures) programs can now be written more structured and error free. For example, if a procedure is correct, every time it is used it produces correct results. Consequently, in cases of errors you can narrow your search to those places which are not proven to be correct. Now a program can be viewed as a sequence of procedure calls. The main program is responsible to pass data to the individual calls, the data is processed by the procedures and, once the program has finished, the resulting data is presented. Thus, the flow of data can be illustrated as a hierarchical graph, a tree, as shown below for a program with no sub procedures:

In the Procedural programming technique main program coordinates calls to procedures and hands over appropriate data as parameters

Now we have a single program which is divided into small pieces called procedures. To enable usage of general procedures or groups of procedures also in other programs, they must be separately available. For that reason, modular programming allows grouping of procedures into modules.

Modular Programming

With modular programming procedures of a common functionality are grouped together into separate modules. A program therefore no longer consists of only one single part. It is now divided into several smaller parts which interactthroughprocedurecallsandwhichformthewholeprogram.Modular programming. The main program coordinates calls to procedures in separate modules and hands over appropriate data as parameters.

Each module can have its own data. This allows each module to manage an internal state which is modified by calls to procedures of this module. However, there is only one state per module and each module exists at most once in the whole program.

Object-Oriented Programming

Today's large scale software systems are typically designed and implemented using the concepts of the object-oriented model. However, there is still a need for the existing OO languages and architectures to continuously adapt in response to demands for new features and paradigms. These new features include topics such asdynamicsoftwareevolution,security,safety,distributionandexpressiveness.Object programming is an approach that provides a way of modularizing programs by creating partitioned memory area for both data and functions that can be used as templates for creating copies of such modules on demand.That is, an object is considered to be a partitioned area of computer memory that stores data and set of operations that can access data. Since the memory partitions are independent, the objects can be used in a variety of different program without modifications.In Object-oriented programming technique the Objects of the program interact by sending messages to each other as shown be

10.Briefly explain the generations of Robot Programming Languages in detail. OFF-LINE PROGRAMMING Introduction

• WAVE • Val(Victor‘s Assembly Language) • VAL_2

Generations of languages First generation Second generation

ROBOT PROGRAMMING LANGUAGES FIRST GENERATION LANGUAGE

Use a combination of command statements & teach pedants

Motion level language Advanced teach pedant method Abilities to define manipulators motion, straight line interpolation & elementary binary

signals. E.g. VAL

SECOND GENERATION LANGUAGE Structured programming languages Improved languages More capabilities to make therobot more intelligent E.g.. AML, RAIL, MCL & val-2 e

Features of second generation programming

Motion control Advanced sensor capabilities Limited intelligence Communication and data processing

ROBOT LANGUAGE STRUCTURE Operating System Robot language elements and functions

• Constants , variables and other data objects • Motion commands

Motion Commands MOVE & Related statements MOVE P1 MOVES P1 MOVE A1 VIA A2 DMOVE(4, 125) APPRO P1, 40 MM DEPART 40 MM

Speed control statements SPEED 60 IPS SPEED 75 Definition of point in workspace

HERE A1 DEFINE A1=POINT(50.123 ,236.342 ,344.456,25.75,125.755)

SIMULATION & OFF-LINE PROGRAMMING Program is prepared at a remote computer terminal and downloaded to robot controller

for execution without need for lead through methods. Just as if operator is at one location and he writes the program for the robot located at

some remote location. 11.(i) Explain the teach pendant for Robot system

Teach pendant for Robot system

The teach pendant has the following primary functions:

Serve as the primary point of control for initiating and monitoring operations.

Guide the robot or motion device, while teaching locations. Support application programs.

The Teach Pendant is used with a robot or motion device primarily to teach. Robot locations for

use: in application programs. The Teach Pendant is also used with c routine's that pause execution

at specified points and allow an Operator to teach * re-teach the robot locations used by the

program.

There are two styles of Teach Pendants: the programmer‗s pendant, for use while an application is

being pendant, which is designed for use during normal system operation.

The operator‗s –activatedpendantswitch, whichhasisconnectedapalmtotheremote emergency stop

circuitry of the controller. Whenever this switch is released, arm power is removed from the motion

device.

To operate the Teach Pendant left hand is put through the opening on the left-hand side of the

pendant and the left thumb is used to operate the pendant speed bars. The right hand is used for

all the other function buttons.

The major areas of the Teach Pendant are:

1. Data Entry Buttons:

The data entry buttons are used to input data, normally in response to prompts that appear on the

pendant display

The data entry buttons include YES/NO, DEL, the numeric buttons, the decimal point and the

REC/DONE button, which behaves like the Return or Enter key on a normal keyboard. In many

cases, application programs have users press the REC/DONE button to signal that they have

completed a task.

2. Emergency Stop Switch:

The emergency stop switch on the Teach Pendant immediately halts program execution and turns

off arm power.

3. User LED:

The pendant is in background mode when the user LED is in not lit and none of the predefined

functions are being used. The user LED is lit whenever an application program is making use of the

Teach Pendant.

4. Mode Control Buttons:

The mode control buttons change the state being used to move the robot, switch control between

the Teach Pendant and the application programs and enable arm power when necessary.

5. Manual Control Buttons:

When the Teach Pendant is in manual mode, these buttons select which robot joint will move, or

the coordinate axis along which the robot will move.

6. Manual State LEDs:

The manual state LEDs indicates the type of manual motion that has been selected.

7. Speed Bars:

The speed bars are used totion. Pressing control the speed barthe rob near the outer ends will

move the robot faster, while pressing the speed bar near the centerwill move the robot slower.

8. Slow Button:

The slow button selects between the two different speed ranges of the speed bars.

9. Predefined Function Buttons:

The predefined function buttons have specific, system- wide functions assigned to them, like

display of coordinates, clear error, etc.

10. Programmable Function Buttons:

The programmable function buttons are used in custom application programs, and their functions

will vary depending upon the program being run.

11. Soft Buttons:

The soft buttons have different function or the selection made from the predefined function

buttons. (ii) Explain Lead through methods

Capabilities and limitations of Lead through methods

During this programming method, the traveling of robots is based on the desired movements,

and it is stored in the external controller memory. There are two modes of a control system in this

method such as a run mode and teach mode. The program is taught in the teach mode, and it is

executed in the run mode. The leadthrough programming method can be done by two methods

namely: Powered Lead through Method

Manual Lead through Method

Powered Lead through Method:

The powered lead through is the common programming method in the industries. A teach pendant

is incorporated in this method for controlling the motors available in the joints. It is also used to

operate the robot wrist and arm through a sequence of points. The playback of an operation is

done by recording these points. The control of complex geometric moves is difficult to perform in

the teach pendant. As a result, this method is good for point to point movements. Some of the key

applications are spot welding, machine loading & unloading, and part transfer process.

Manual Lead through Method:

In this method, the robot‗s end effectors desired movements. Sometimes, it may be difficult to

move large robot arm manually. To get rid of it a teach button is implemented in the wrist for

special programming. The manual lead through method is also known as Walk Through method. It

is mainly used to perform continuous path movements. This method is best for spray painting and

arc welding operations. 12.Explain the different commands used in VAL programming language.

Variable Assembly Language (VAL) is a computer-based control system and language designed specifically for use with Unimation Inc. industrial robots.The VAL robot language is permanently stored as a part of the VAL system. This includes the programming language used to direct the system for individual applications. The VAL language has an easy to understand syntax. It uses a clear, concise, and generally self-explanatory instruction set. All commands and communications with the robot consist of easy to understand word and number sequences. Control programs are written on the same computer that controls the robot. As a real-time system, VAL's continuous trajectory computation permits complex motions to be executed quickly, with efficient use of system memory and reduction in overall system complexity. The VAL system continuously

generates robot control commands, and can simultaneously interact with a human operator, permitting on-line program generation and modification.

A convenient feature or VAL is the ability to use libraries or manipulation routines. Thus, complex operations may be easily and quickly programmed by combining predefined subtasks.

The VAL language consists of monitor commands and program instructions. The monitor commands are used to prepare the system for execution of user-written programs. Program instructions provide the repertoire necessary to create VAL programs for controlling robot actions.

The following terms are frequently used in VAL related operations.

Monitor

The VAL monitor is an administrative computer program that oversees operation of a system. It accepts user input and initiates the appropriate response; follows instructions from user-written programs to direct the robot; and performs the computations necessary to control the robot.

Editor

The VAL editor is an aid for entering information into a computer system, and modifying existing text. It is used to enter and modify robot control programs. It has a list of instructions telling a computer how to do something. VAL programs are written by system users to describe tasks the robot is to perform.

Location

Location is a position of an object in space, and the orientation of the object. Locations are used to define the positions and orientations the robot tool is to assume during program execution.

Several conventions apply to numerical values to be supplied to VAL commands and instructions. Preceding each monitor-command description are two symbols indicating when the command can be typed by the user. A dot (.) signifies the command can be performed when VAL is in its top-level monitor mode and no user program being executed (that is, when the system prompt is a dot). An asterisk (*) indicates the command can be performed at the same time VAL is executing the program (that is, when the system prompt is an asterisk). If both symbols are present the command can be executed in either case. Most monitor commands and program instructions can be abbreviated. When entering any monitor command or program instruction, the function name can be abbreviated to as many characters as are necessary to make the name unique.

For commands and instructions, angle brackets, <>, are used to enclose an item which describes the actual argument to appear. Thus the programmer can supply the appropriate item in that position when entering the command or instruction. Note that these brackets used here are for clarification, and are never to be included as part of a command or instruction.

Many VAL commands and instructions have optional arguments. For notations, optional arguments are enclosed in square brackets, [ ]. If there is a comma following such an argument, the comma must be retained if the argument is omitted, unless nothing follows. For example, the monitor BASE command has the form:

BASE [<dx>] , [<dy>] , [<dz>] , [<rotation>]

To specify only a 300-millimeter change in the Z direction, the command could be entered in any of the following ways:

BASE 0,0,300,0

BASE ,,300,

BASE ,,300

Note that the commas preceding the number 300 must be present to correctly to relate the number with a Z-direction change. Like angle brackets, square brackets are never entered as part of a command or instruction.

Several types of numerical arguments can appear in commands and instructions. For each type there are restrictions on the values that are accepted by VAL. The following rules should be observed:

1. Distances are entered to define locations to which the robot is to move. The unit of measure for distances is millimeter, although units are never explicitly entered for any value. Values entered for distances can be positive or negative, with their magnitudes limited by a number representative of the maximum reach of the robot (for example, 1024 mm and 700 mm for the PUMA 500 and PUMA 250 robots, respectively). Within the resultant range, distance values can be specified in increments of 0.01 mm. Note, however, that some values cannot be represented internally, and are stored as the nearest representable value.

2. Angles in degrees are entered to define and modify orientations the robot is to assume at named locations, and to describe angular positions of robot joints. Angle values can be positive or negative, with their magnitudes limited by 1800 or 3600 depending on the usage. Within the range, angle values can be specified in increments of 0.01°. Values cannot be represented internally, however they are stored asnearest representable value.

The function of VAL is to regulate and control a robot system by following user commands or instructions. In addition to being a compact stand-alone system, VAL has been designed to be highly interactive to minimize programing time, and to provide as many programming aids as possible.

External communication

The standard VAL system uses an operator's console terminal and manual control box to input commands and data from the user. The operator console serves as the primary communication device and can be either a direct play terminal or a printing terminal. Interaction with other devices in an automated cell is typically handled by monitoring input channels and switching outputs. By this means the robot can control a modest cell without the need for other programmable devices.

VAL Operating System

The controller has two levels or operation:

the top level is called the VAL operating system, or monitor, because it administers operations of the system, including interaction with the user;

the second level is used for diagnostic work on the controller hardware. The system monitor is a computer program stored VAL programmable read-only memory (PROM) in the Computer/Controller.

PROM memory retains its contents finitely, and thus VAL is immediately available when the controller is switched on. The monitor is responsible for control of the robot, and its commands come from the manual control unit, the system terminal, or from programs. To increase its versatility and flexibility, the VAL monitor can perform of its commands even while a user program is being executed. Commands that can be processed in this way include those for controlling the status the system, defining robot locations, storing and retrieving information the floppy disk, and creating and editing robot control programs.

13.Discuss various programming languages used in computer controlled robots Non computer controlled robots do not require programming language. They are programmed by the walk through or lead through methods while the simpler robots are programmed by manual methods. With the introduction of computer control for robots came the opportunity and the need to develop a computer oriented robot programming language.

The VALTM Language • The VAL language was developed for PUMA robot

• VAL stands for Victors Assembly Language

• It is basically off-line language in which program defining the motion sequence is can be developed off-line but various point location used in the work cycle are defined by lead through.

• VAL statements are divided into two categories a) Monitoring command b) Programming instructions.

• Monitor command are set of administrative instructions that direct the operation of the robot system. Some of the functions of Monitor commands are Preparing the system for the user to write programs for PUMA Defining points in space Commanding the PUMA to execute a program Listing program on the CRT

• Examples for monitor commands are: EDIT, EXECUTE, SPEED, HERE etc.

• Program instructions are a set of statements used to write robot programs. One statement usually corresponds to one movement of the robots arm or wrist.

• Example for program instructions are Move to point, move to a point in a straight line motion, open gripper, close gripper. (MOVE, MOVES, APPRO, APPROS, DEPART, OPENI, CLOSEI, AND EXIT) The MCL Language

• MCL stands for Machine Control Language developed by Douglas.

• The language is based on the APT and NC language. Designed control complete manufacturing cell.

• MCL is enhancement of APT which possesses additional options and features needed to do off-line programming of robotic work cell.

• Additional vocabulary words were developed to provide the supplementary capabilities intended to be covered by the MCL. These capability include Vision, Inspection and Control of signals

• MCL also permits the user to define MACROS like statement that would be convenient to use for specialized applications. • MCL program is needed to compile to produce CLFILE.

• Some commands of MCL programming languages are DEVICE, SEND, RECEIV, WORKPT, ABORT, TASK, REGION, LOCATE etc.

Textual Statements

Language statements taken from commercially available robot languages 1 The basic motion statement is: MOVE P1 Commands the robot to move from its current position to a position and orientation defined by the variable name P1.The point p1 must be defined. The most convenient method way to define P1 is to use either powered lead through or manual leads through to place the robot at the desired point and record that point into the memory. HERE P1 OR LEARN P1

Are used in the lead through procedure to indicate the variable name for the point What is recorded into the robot‘s control memory is the set of joint positions or coordinates used by the controller to define the point. For ex, (236,157,63,0,0,0) The first values give joint positions of the body and arm and the last three values(0,0,0) define the wrist joint positions. MOVES P1 Denotes a move that is to be made using straight line interpolation. The suffix‗s‘ designates a straight line motion. DMOVE (4,125)

Suppose the robot is presently at a point defined by joint coordinates(236,157,63,0,0,0) and it is desired to move joint 4from 0 to 125. The above statement can be used to accomplish this move. DMOVE represents a delta move. Approach and depart statements are useful in material handling operations. APPROACH P1, 40 MM MOVE P1 (Command to actuate the gripper) DEPART 40 MM

The destination is point p1 but the approach command moves the gripper to a safe distance(40mm) above the point. Move statement permits the gripper to be moved directly to the part for grasping. A path in a robot program is a series of points connected together in a single move. A path is given a variable name DEFINE PATH123=PATH(P1,P2,P3) A move statement is used to drive the robot through the path.

MOVE PATH123 SPEED 75 the manipulator should operate at 75% of the initially commanded velocity. The initial speed is given in a command that precedes the execution of the robot program. For example, SPEED 0.5 MPS EXECUTE PROGRAM1 Indicates that the program named PROGRAM1 is to be executed by the robot at a speed of 0.5m/sec.

Interlock And Sensor Statements The two basic interlock commands used for industrial robots are WAIT and SIGNAL. The wait command is used to implement an input interlock. For example, WAIT 20,ON Would cause program execution to stop at this statement until the input signal coming into the robot controller at port 20 was in ―ON‖ condition.this might be used in a situation where the robot needed to wait for the completion of an automatic machine cycle in a loading and unloading application.

The SIGNAL statement is used to implement an output interlock. This is used to communicate to some external piece of equipment. For example, SIGNAL 20, ON Would switch on the signal at output port 20, perhaps to actuate the start of of an automatic machine cycle.

The above interlock commands represent situations where the execution of the statement appears. There are other situations where it is desirable for an external device to be continuously monitored for any change that might occur in the device. For example,in safety monitoring where a sensor is setup to detect the presence of humans who might wander into the robot‘s work volume.the sensor reacts to the presence of humans by signaling the robot controller. REACT 25, SAFESTOP

This command would be written to continuously monitor input port 25 for any changes in the incoming signal. If and when a change in the signal occurs, regular program execution is interrupted and the control is transferred to a subroutine called SAFESTOP.This subroutine would stop the robot from further motion and/or cause some other safety action to be taken. Commands for controlling the end-effectors

Although end effectors are attached to to the wrist of the manipulator,they are very much like external devices. Special command are written for controlling the end effector. Basic commands are OPEN (fully open) and CLOSE (fully close)

For grippers with force sensors that can be regulated through the robot controller, a command such as , CLOSE 2.0 N

Controls the closing of the gripper until a 20.N force is encountered by the grippers. A similar command would be used to close the gripper to a given opening width is, CLOSE 25 MM

A special set of statements is often required to control the operation of tool type end effectors (such as spot welding guns, arc welding tools, spray painting guns and powered spindles ). End Effectors

In the terminology of robotics, end effectors can be defined as a device which is attached to the robots wrist to perform a specific task. The task might be work part handling, spot welding, spray painting, or any of a great variety of other functions. The possibilities are limited only by the imagination and ingenuity of the application engineers who design robot systems. The end effectors are the special purpose tooling which enables the robot to perform a particular job. It is usually custom engineered for that job, either by the company that owns the robot or company that sold the robots. Most robot manufacturer has engineered groups which design and fabricate end effectors or provide advice to their customers on end effectors design.

14.Explain about any three types of Robot Control Systems.( Nov/Dec 2016) A robot must have a control system to operate its drivesystem, which is used to move the arm, wrist, and body of a robot at various paths. When different industrial robots are compared with their control system, they can be divided into four major types. They are:

Limited Sequence Robots Playback Robots with Point – Point Control Playback Robots with Continuous Path Control Intelligent Robots

Limited Sequence Robots:

The limited sequence robots are incorporated with the mechanical stops and limit switches for determining the finishing points of its joints. These robots do not require any sort of programming, and just uses the manipulator to perform the operation. As a result, every joint can only travel to the intense limits. It is considered as the smallest level of controlling, and it will be best for simple operations like pick & place process. This type of robots is generally equipped with the pneumatic drive system. Playback Robots:

The playback robots are capable of performing a task by teaching the position. These positions are stored in the memory, and done frequently by the robot. Generally, these playback robots are employed with a complicated control system. It can be divided into two important types, namely:

Point to Point control robots Continuous Path control robots

Playback Robots with Point to Point Control:

The point to point robots are shortly called as PTP. It has got the capability to travel from one position to another. The desired paths are taught and stored in the control unit memory. These robots do not

move from the desired location for controlling its path. It can be moved in a small distance only with the help of programming. This type of robots can be used for spot welding, loading & unloading, and drilling operations. Playback Robots with Continuous Path Control:

The continuous path control is also known as CP control. This type of robots can control the path, and can end on any specified position. These robots commonly move in the straight line. The initial and final point is first described by the programmer, and the control unit defines the individual joints. This helps the robot to travel in a straight line. Likewise, it can also move in a curved path by moving its arm at the desired points. In these robots, the microprocessor is used as a controller. Some of the applications are arc welding, spray painting, and gluing operations.

Intelligent Robots:

The intelligent robots can play back the defined motion, and can also work according to their environment. It uses digital computer as a controller. The sensor is incorporated in these robots for receiving the information during the process. The programming language will be based on high level language. This kind of robots is capable of communicating with the programmers in the work volume. It will be best for arc welding, and assembly purposes.