Robotics (CAD-CAM).pptx .

Industrial Robotics
• An industrial robot is defined as an automatically controlled,
reprogrammable, multipurpose manipulator which can be
programmable in three or more axes and designed to move
materials, parts, tools or special devices through variable
programmed motions for the performance of a variety of
tasks.
• A machine capable of carrying out a complex series of actions
automatically, especially one programmable by a computer.
• As a reprogrammable, multifunctional manipulator, Industrial
robotics may be more practically defined as the study, design
and use of robot systems for manufacturing.

Some of the key benefits of robots in industry in general are:
 Robots can perform many tasks more quickly, safely, accurately
and cheaply than human workers.
 Robots can work continuously for long periods of time without
fatigue or boredom.
 A robot can use sensors to gather information about its
environment that is not detectable using the human senses.
 Robots can be equipped with expert capabilities beyond those of
humans, in terms of speed, force and / or accuracy.
 Robots can work in hazardous or uncomfortable environments.

Some potential issues associated with robotic systems are :
 Robots are typically less able to respond effectively to unforeseen
circumstances than humans, either because they lack the
required intelligence or the mechanical adaptibility or both.
 The initial investment required to automate a process using
robotics can be very substantial.
 Robots can pose a safety hazard when their work environment is
shared with humans. Sudden robot movements do strike or crush
a human.
 As robotic systems become more advanced, more and more low-
skilled human jobs will simply disappear.

Robot anatomy and robot motions:
Robot anatomy deals with the study of body of a robot and
how the different parts are arranged.
Main parts of an industrial robot are:
 Manipulators
 End effectors
 Actuators
 Sensors
 Controller/processor
 Software

Manipulator:
• This is the main body of a robot, typically comprising a
series of rigid sections (links) connected by joints. The
manipulator often resembles an arm.
• A robot manipulator comprises a series of segments (rigid
sections), connected in a kinematic chain. Each segment is
called a kinematic link. The two connected segments meet
at a joint (which is a mechanism) that allows one segment
to move relative to the other, usually in some constrained
way (e.g. 1-dimensional rotation or 1-dimensional
translation).

End effector:
• This is the tool that is located at the end of the manipulator.
• End effectors may consist of a gripper or a tool. The gripper
can be of two fingers, three fingers or even five fingers.
• End effectors depend on the application, but examples of
end effectors include grippers, welding guns, spray nozzles,
scalpels, etc.

Actuator:
• This is an element that is designed to convert some kind of
energy into mechanical force or movement. Robotic
actuators are typically electrical, hydraulic or pneumatic.
• Common examples include DC motors, stepper motors,
servo motors, pneumatic cylinders and hydraulic cylinders.

Sensor:
• Sensors provide a robot with information about its own internal
state and about its environment.
• Used for the measurement of a data or
to sense some element in the robot
environment
• Sensors used in robotics are – position, proximity, distance,
angular displacement, tilt, movement, acceleration, force,
temperature, color, light, non-visible light, sound, ultrasound. The
measured property may be translated into an analog or digital
output voltage signal.

Processor:
• At run-time (i.e. when the robot is in operation), all decisions
regarding the desired state of the actuators is done by the
processor which receives input from the robot’s sensors.

• Software: A critical component of most modern robotics
systems is the software that runs on the processor since it is
this which defines the behavior of the robot.

Basic Robot Linear and Rotational movements

Robot physical configuration and basic robot motions
Manipulator Joints
• Translational motion
– Linear joint (type L)
– Orthogonal joint (type O)
• Rotary motion
– Rotational joint (type R)
– Twisting joint (type T)
– Revolving joint (type V)
Type L
Type O
Type R
Type T
Type V

Robot Configuration 1:
Cartesian Coordinate Body-and-Arm Assembly
• Notation LOO:
• Consists of three sliding joints,
two of which are orthogonal
• Other names include rectilinear
robot and x-y-z robot

Cylindrical Body-and-Arm Assembly
• Notation TLO:
• Consists of a vertical column,
relative to which an arm
assembly is moved up or
down
• The arm can be moved in or
out relative to the column

Polar Coordinate Body-and-Arm Assembly:
• Notation TRL:
• Consists of a sliding arm (L joint) actuated relative to
the body, which can rotate about both vertical axis (T
joint) and horizontal axis (R joint)

Jointed-Arm Robot Assembly
• Notation TRR:
• The actuated arm can be
rotated about two
Horizontal axes (R and R’)
and can be revolved about
the vertical axis (T)

SCARA Robot
• Notation VRO
• SCARA stands for Selectively
Compliant Assembly Robot Arm
• Similar to jointed-arm robot
except that vertical axes are
used for shoulder and elbow
joints to be compliant in
horizontal direction for vertical
insertion tasks

Wrist Configuration
• Notation :RRT
• Wrist assembly is attached to end-of-arm
• End effector is attached to wrist assembly
• Function of wrist assembly is to orient end effector
– Body-and-arm determines global position of end
effector
• Two or three degrees of freedom:
– Roll
– Pitch
– Yaw

Robot Specifications:
1. Workspace(work volume):
• A robot’s workspace (or workspace envelope) is the set of all
points the robot can reach. The dexterous workspace is the
subset of these points at which the end effector can be
positioned with any desired orientation.
• Determined by its physical configuration, size and the limits of its
arm and joint manipulations.

1. Cartesian Robot.
• This has three linear motions in x, y, and z direction.
• The work space covered is cuboidal type.

2. Cylindrical Robot.
• This has two linear motions in z and radial direction and a rotary
motion about z-axis forming a cylindrical work envelope.

3. Polar Robot:
• This has one linear motion and two rotary joints moving about z
and y axis. The work space generated is spherical in shape.

4. Combined Type (Revolute Robot).
• This has all the three joints revolute which produce rotary
movements in x, y and z direction giving a irregular-shaped work
envelope.

2. Precision of movement:
• This describes how precisely the end effector can be positioned at
a specified point.
• The precision of a robot depends on several factors including
gearing, the resolution of its actuators, and the resolution of its
position feedback sensors.
3. Repeatability:
• Ability of the robot to position the tool tip in the same place
repeatedly.

4. Accuracy:
• Accuracy is the measure of the robot's ability to orient and locate
the tool tip at a desired target location in the prescribed work
volume or envelope.
• Accuracy is related to resolution because as the resolution value
is less, the accuracy is more. So higher resolution gives better
accuracy, the ability to achieve the prescribed target location.

5. Resolution:
It is the least count of the movement into which the robot's work envelope can be
divided to represent the incremental or decremental steps. The spatial resolution can
be contributed by two components.
• The control resolution.
• The mechanical resolution.
• This component depends upon the type of position control system and its feed
back control elements.
6. Speed of motion:
• The speed with which the robot can manipulate the end effector.
• Ranges up to 1.5 m/s.
• Speed depends on weight of the object, distance moved and the precision with
which the object must be positioned during the work cycle.

7. Type of drive system in a Robot:
Hydraulic
– used for large robots
- high strength and high speed
- requires more floor space
Electric
- good accuracy and repeatability
- requires less floor space
Pneumatic
- smaller in size
- less sophisticated
- suitable for simple pick and place activities

8. Load carrying capacity:
• The size, configuration, construction, and drive system determine the
load carrying capacity of the robot.
• This load capacity 'should be specified under the condition that the
robot's arm is in its weakest position. In the case of a polar, cylindrical,
or jointed-arm configuration, this would mean that the robot arm is at
maximum extension.
• The manufacturer's specification of this feature is the gross weight
capacity. To use this specification, the user must also consider the
weight of the end effector.
• An example is the Prab Versatran Model FC which has a rated load
capacity of 2000 lb. The small assembly robots, such as the MAKER 110,
have weight-carrying capabilities in the vicinity of 5 lb.

9. Speed of Response and Stability:
• The speed of response refers to the capability of the robot to
move to the next position in a short amount of time.
• In robotics, stability is generally defined as a measure of the
oscillations which occur in the arm during movement from one
position to the next.
• A robot with good stability will exhibit little or no oscillations
either during or at the termination of the arm movement. Poor
stability would be indicated by a large amount of oscillation.
• The stability of a robot can be controlled to a certain extent by
incorporating damping elements into the robot's design.

Grippers / End effectors:
General aspects:
• End effectors range from commercial devices like grippers to special tool applications like welding.
• Due to diverse applications of robotics, the end effectors are usually customized for a particular
applications. Sometimes they may be multifunctional.
• While making the end effectors, the weight and moment of inertia must be considered.
• The end effectors must interface only with the robot and not with the other peripheral devices.
• End effectors must be reliable in its design and functions.
• End effectors may include a sensor attached to it to make it an intelligent device.
Apart from the basic classification, the grippers are associated with following:
• Mechanical fingers or special devices (on the basis of way of grasping)
• Single or multiple grippers (on the basis of gripper numbers mounted)
• Internal or external (mode of gripping)
• Single or multiple degree of freedom
• Pneumatic, electric or hydraulic (on the basis of source of power)

Types of End effectors / Grippers:
• The end effectors are broadly classified into two types and they
are grippers and tools.
• Grippers are special devices made to hold either the work part or
the tools. These are further classified as follows:
• Mechanical grippers
• Non mechanical grippers
Non mechanical grippers may be further classified into
• Suction or vacuum cups
• Magnetized grippers
• Adhesive or electrostatic grippers

Mechanical gripper:
• these grippers have finger like structures known as jaws to grasp
the work parts.
• These are further classified as mechanical grippers with two and
three fingers.
• Mechanical grippers with two fingers are used extensively in
industrial robotics and are mostly used to hold cylindrical
components.
• The primary aim of using a three finger gripper is to attain a
tighter grip and make it possible to hold variety of geometrical
shapes.
• The fingers may be attached or fixed type.
• The rubber pads are attached to end of an end effector gripper
helping it to hold the component with safer way.
• Two methods of holding here are physical construction method
and friction method.
• Gripper mechanisms may be linear or pivoted.

Mechanical grippers:
Figure 1: Fixed and pivot flat
type grippers
Figure 2: Fixed and pivot V
type grippers
Figure 3: Fixed and pivot
circular type grippers

Non Mechanical grippers:
Vacuum cup type:
• The objects have to be flat smooth and clean
• Cups are made of elastic materials round in shape
• Vacuum is created between cup and the object (eg. glass)

Adhesive type gripper :
• Used to handle fabrics and light weight materials.
• Gripping ability diminishes with successive operations

Magnetic gripper:
• Fast pickup time
• Variety of part sizes can be handled
• Metal parts with holes can be easily handled
• Requires only one surface for gripping

Grippers may also be classified as
• Part handling devices: these are used to grasp the work piece that are required to be
transported from one place to other and finds its practical application in machine loading
and unloading.
• Tool handling devices: These are used to hold the tools like welding gun or spray painting.
Robot deburring is yet another practical example of such a gripper.
• Specialized grippers: Specialized devices like remote centered compliances to insert external
mating component into an internal member.
• Tools: Tools are fastened directly to the robot wrist, where the robot is required to
manipulate a tool to perform an operation on the work piece. The common tools used are
• Spot welding gun
• Arc welding tools
• Spray painting gun
• Drilling spindle
• Routers, grinders
• Heating torches

Gripper(end effector mechanisms):
1.Linear actuation:
Many design possibility using linkages.
Higher gripping force at less actuating force due to leverage.
Opening width and the speed of gripping depends on the linkage
configuration.

1.Rack pinion actuation:
A rack actuated by a hydraulic/pneumatic cylinder operates two
pivoted pinions.
Pinions oscillate to move the racks.
The fingers attached to the racks open and close to grab and release
the object.

1.Cam actuation:
A cam attached to a cylinder moves to and fro.
Spring loaded followers moves on the cam profile.
The finger pads are attached to the pivoted liver connected to the
followers open and close to release and grab the object.

1.screw actuation:
A threaded block engages with a screw moves forward and
backward, the fingers attached to levers connected to the threaded
block by a hinged joint open and close providing releasing and
gripping action.
The screw is rotated by a motor through reduction box.

Robot programming methods:
1. Manual method
2. Walk Through method
3. Lead through methods
4. Offline programming procedure
1. Manual Method:
• Not really programming in the conventional sense of the word.
• Involves setting up of the machine rather than programming
• For these low technology, robots are used for shorter cycles.
• Mnual programming method is adequate.
• Involves the procedure used for setting mechanical stops, cams, switches
or relays in the robots control unit

2. Walk through method (Manual lead through method):
• In manual lead through method, the programmer physically grasps the robot
arm (and end effector) and manually moves it to the desired motion cycle.
• Each movement is recorded in the robots control memory for subsequent
playback during production cycle.
• Speed of movement are controlled independently and the programmer need
not worry about the cycle time.
• More readily used for continuous path programming where motion cycle
involves smooth, complex curvilinear movements of the robot arm.
• Continuous movement robotic manipulators include spray painting robots, in
which the robot wrist with spray painting gun attached as end effector must
execute a smooth, regular motion pattern in order to apply paint evenly over
the entire surface to be coated.
• Continuous arc welding is another example in which continuous path
programming is required.

3. Lead through (powered) method :
• Makes use of teaching pendant to power drive the robot arm and wrist
through a series of points in space.
• Teach pendant is usually a hand held control box with combinations of
toggle switches, dials and buttons to regulate robot’s physical movements
and programming capabilities.
• Each motion is recorded in the robots control memory for future playback
during the work cycle.
• Powered lead through method is probably the most common method of
programming today.
• It is largely limited to point by point motions rather than continuous
movement because of difficulty in using teaching pendant to regulate
complex geometric motions in space.
• Point to point movement robotic manipulators include machine loading and
unloading, part transfer tasks and spot welding.

4. Offline robot programming :
• Programming with textual programming method is similar to Computer
programming.
• Generally this method is used along with the lead through method to effectively
program a robot to teach locations of points defined in work space.
• The prepared program is entered into robots memory for use during the work
cycle.
• Production time of the robot is not lost due to delays in teaching the robot a new
task.
Different textual languages:
WAVE:
Developed in 1973 at Stanford university for a research involving a robot interfaced
to a machine vision system. Research demonstrated the feasibility of hand - eye co
ordination.
AL:
It was again developed subsequently at Stanford in 1974 and was used to control
multiple arms in tasks requiring arm co ordination.

VICTOR’S ASSEMBLY LANGUAGE (VAL):
• It was the first commercially robot textual language which had many concepts of WAVE and AL.
• VAL I was introduced in 1979 by Unimation.Inc for its PUMA robot series. This was upgraded as
VAL II and released in 1984. The VAL language was an offline programming language.
Common Programming instructions in VAL:
MOVE: - Moves the robot to the location and orientation specified by the robot.
MOVES: - Moves the robot along a straight line trajectory.
APPRO: - Moves the end effector to the position defined by the symbol, but offsets it along the z
axis by the distance given in millimeters.
DEPART: - Moves the tool the distance given along the current z axis of the tool.
OPENI: - Open the gripper immediately.
CLOSEI: - Close the gripper immediately.
EXIT: - Causes exit from the program.
Some of the other languages include AUTOPASS , AML developed by IBM Corporation, MCL developed
under US Air force sponsorship.

WORK CELL CONTROL AND INTERLOCKS:
WORK CELL CONTROL:
• Industrial robots usually work with other processing equipment,
work parts, conveyors, tools and human operators.
• A work cell controller is used to coordinate the various activities in a
sequence.
• The work cell controller usually resides within the robot controller.
Example:
A work station consists of a robot, the machine tool and two conveyors,
one for incoming raw work parts and other for outgoing finished work
pieces.

1. Incoming conveyor delivers raw work part to fixed position.
2. Robot picks up part from conveyor and loads it into machine.
3. Machine processes work part.
4. Robot unloads finished part from machine and places it on outgoing conveyor.
5. Outgoing conveyor delivers part out of work cell and robot returns to ready position near
incoming conveyor.
The work cell controller would have to make sure that certain steps are completed before
subsequent steps are initiated.
The work cycle consists of the following activitites.

The functions of the work cell controller include:
1. Controlling the sequence of activities in the work cycle.
2. Controlling simultaneous activities.
3. Making decisions to proceed based on incoming signals.
4. Making logical decisions.
5. Performing computations.
6. The work cell controller must receive signals from other devices in the
work cell, and it must communicate signals to the various components of
the work cell. The signals are accomplished by interlock and sensors.

INTERLOCKS:
Interlock is the feature of work cell control which prevents the work cycle sequence from
continuing until a certain condition or set of conditions has been satisfied. In a robotic work
cell there are two types of interlocks.
- Outgoing Interlock:
This is a signal sent from the work station controller to some external machine or
device that will cause it to operate or not operate. Ex: this would be used to
prevent a machine from initiating its process until it was commanded to proceed by the
work cell controller.
- Incoming Interlock:
This is a signal from some external machine to the work controller which determines
whether or not the programmed work cycle sequence will proceed. Ex: this would be
used to prevent the work cycle program from continuing until the machine
signaled that it had completed its processing of the work piece.
Use of interlocks:
- It prevents actions from happening when they should not.
- It causes actions to occur when they should.

ROBOTIC SENSORS:
• For certain robotic applications, the type of workstation control using interlocks is not
adequate.
• The robot must take humanlike senses and capabilities in order to perform a task
efficiently.
• These senses are done by the sensors with vision, hand – eye coordination, touch and
hearing which will improve the capability of robots.
TYPES OF SENSORS:
1)VISION SENSORS:
Consist of a video camera, a light source and a computer programmed to process image
data. The software enables the vision system to sense the presence of an object and its
position and orientation. Vision sensors enable the robot to carry out the following kinds of
operations.
- Retrieve parts which are randomly oriented on a conveyor.
- Recognize particular parts which are intermixed with other objects.
- Perform visual inspection tasks.
- Perform assembly operations which require alignment.

2) TACTILE AND PROXIMITY SENSORS:
TACTILE SENSORS:
• provide the robot with the capability to respond to contact forces between itself and
other objects within its work volume.
They are of two types.
a)Touch sensors: - Used to indicate whether contact has been made with an
object. Ex: Micro switch
b) Stress sensors:- Used to measure the magnitude of the contact force. Ex: Strain
gauge devices.
Application of tactile sensors: - In assembly, the robot could
perform delicate part alignment and joining operations.
In inspection, touch sensing would be useful in gauging
operations and dimensional measuring activities.
PROXIMITY SENSORS:
• are used to sense when one object is close to another object. They are used to indicate
the presence or absence of a work part or other object.

3) VOICE SENSORS:
• Voice programming is the oral communication of commands to the robot.
• The robot controller is equipped with a speech recognition system which analyses the
voice input and compares it with a set of stored word patterns.
• When a match is found between the input and stored vocabulary word, the robot
performs some action which corresponds to that word.
Application: Useful in hazardous working environments for performing maintenance and
repair work.

ROBOT APPLICATIONS
General Application Characteristics:
- Hazardous or uncomfortable working conditions
- Repeatitive Tasks
- Difficult Handling
- Multishift Operation
Application areas for industrial robots:
1) Material transfer:
- Simple pick and place operations
- Transfer of workparts from one conveyor to another conveyor
- Palletizing operations
- Stacking operations
- Depalletizing operations

2. Machine Loading:
Robot is required to supply a production machine with raw work parts and/or to unload
finished parts from the machine.
- Die casting
- Injection molding
- Hot forging
- Upset forging
- Stamping
- Machine operations such as turning and milling
3. Welding:
Spot welding:
- Position the welding gun in the desired location against two pieces
- Squeezing the electrodes against the mating pieces and release the tool

Arc welding:
A robotic arc welding station consist of the following components.
- Robot capable of continuous path control
- Welding unit, consisting of welding tool, power source and wire feed system
- Work part manipulator which fixtures the components and positions them for welding.
Advantage of robotic welding:
- Higher productivity
- Improved safety
- More consistent welds
4. Spray Coating:
Advantages of using robots for spray coating:
- Safety
- Coating consistency
- Lower material usage
- Reduced energy used
- Greater productivity

5. Assembly:
• For mass production assembly, fixed automation method is used.
• Robots are suitable for batch type assembly operations.
• Adaptable – programmable assembly system (APAS) is used in the robotic
assembly system.
• Adaptability is required in the sense that the assembly system would have to
compensate for the changes in the environment such as
 Variations in the position and orientation of assembly components
 Out of tolerance and defective parts
 Detection of human beings or objects intruding on the robot’s work volume
6. Inspection:
- Robots are used when 100% inspection is required.
- Robots equipped with mechanical probes, optical sensing capabilities, electronic
probes

Robotics (CAD-CAM).pptx .

Robotics (CAD-CAM).pptx .

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