Lecture # 11
Automation Fundamentals
Hardware Components for Automation
Computer Numerical Control
Industrial Robotics
Manufacturing Systems
A manufacturing system can be defined as a collection of
integrated equipment and human resources that
performs one or more processing and/or assembly
operations on a starting work material, part, or set of
 The integrated equipment consists of production
machines, material handling and positioning devices,
and computer systems
 The manufacturing systems accomplish the valueadded work on the part or product
Automation Fundamentals
Automation can be defined as the technology by which
a process or procedure is performed without human
 Humans may be present, but the process itself
operates under is own self-direction
 Three components of an automated system:
1. Power
2. A program of instructions
3. A control system to carry out the instructions
Three Basic Types of Automation
 Fixed automation - the processing or assembly steps
and their sequence are fixed by the equipment
 Programmable automation - equipment is designed
with the capability to change the program of
instructions to allow production of different parts or
 Flexible automation - an extension of programmable
automation in which there is virtually no lost
production time for setup changes or reprogramming
Features of
Fixed Automation
 High initial investment for specialized equipment
 High production rates
 The program of instructions cannot be easily changed
because it is fixed by the equipment configuration
 Thus, little or no flexibility to accommodate product
Features of
Programmable Automation
 High investment in general purpose equipment that
can be reprogrammed
 Ability to cope with product variety by reprogramming
the equipment
 Suited to batch production of different product and
part styles
 Lost production time to reprogram and change the
physical setup
 Lower production rates than fixed automation
Features of
Flexible Automation
 High investment cost for custom-engineered
 Capable of producing a mixture of different parts or
products without lost production time for changeovers
and reprogramming
 Thus, continuous production of different part or
product styles
 Medium production rates
 Between fixed and programmable automation types
Hardware Components for
Interface devices
Process controllers - usually computer-based devices
such as a programmable logic controller
A sensor is a device that converts a physical stimulus or
variable of interest (e.g., force, temperature) into a
more convenient physical form (e.g., electrical voltage)
for purpose of measuring the variable
 Two types
 An analog sensor measures a continuous analog
variable and converts it into a continuous signal
 A discrete sensor produces a signal that can have
only a limited number of values
An actuator is a device that converts a control signal
into a physical action, usually a change in a process
input parameter
 The action is typically mechanical, such as a change
in position of a worktable or speed of a motor
 The control signal is usually low level, and an
amplifier may be required to increase the power of
the signal to drive the actuator
 Amplifiers are electrical, hydraulic, or pneumatic
Interface Devices
 Interface devices allow the process to be connected
to the controller and vice versa
 Sensor signals form the process are fed into the
 Command signals from the controller are sent to
the process
Process Controllers
 Most process control systems use some type of
digital computer as the controller
 Requirements for real-time computer control:
 Respond to incoming signals from process
 Transmit commands to the process
 Execute certain actions at specific points in time
 Communicate with other computers that may be
connected to the process
 Accept inputs from operating personnel
Programmable Logic Controllers
A PLC is a microcomputer-based controller that uses
stored instructions in programmable memory to
implement logic, sequencing, timing, counting, and
arithmetic control functions, through digital or analog
input/output modules, for controlling machines and
 PLCs are widely used process controllers that satisfy
the preceding real-time controller requirements
Major Components of a
Programmable Logic Controller
Computer Numerical Control
A form of programmable automation in which the
mechanical actions of a piece of equipment are
controlled by a computer program which generates
coded alphanumeric data
 The data represent relative positions between a
workhead (e.g., a cutting tool) and a workpart
 CNC operating principle is to control the motion of the
workhead relative to the workpart and to control the
sequence of motions
Components of a CNC System
1. Part program - detailed set of commands to be
followed by the processing equipment
2. Machine control unit (MCU) - microcomputer that
stores and executes the program by converting each
command into actions by the processing equipment,
one command at a time
3. Processing equipment - accomplishes the sequence
of processing steps to transform the starting
workpart into completed part
CNC Coordinate System
 Consists of three linear axes (x, y, z) of Cartesian
coordinate system, plus three rotational axes (a, b, c)
 Rotational axes are used to orient workpart or
workhead to access different surfaces for
 Most CNC systems do not require all six axes
CNC Coordinate Systems
 Coordinate systems used in CNC control: (a) for flat
and prismatic work and (b) for rotational work
Two Types of Positioning
 Absolute positioning
 Locations are always
defined with respect
to origin of axis
 Incremental positioning
 Next location is
defined relative to
present location
CNC Positioning System
 Motor and leadscrew arrangement in a Computer
numerical control positioning system
CNC Positioning System
Converts the coordinates specified in the CNC part
program into relative positions and velocities between
tool and workpart
 Leadscrew pitch p - table is moved a distance equal
to the pitch for each revolution
 Table velocity (e.g., feed rate in machining) is set by
the RPM of leadscrew
 To provide x-y capability, a single-axis system is
piggybacked on top of a second perpendicular axis
Two Basic Types of Control in
Computer Numerical Control
 Open loop system
 Operates without verifying that the actual position
is equal to the specified position
 Closed loop control system
 Uses feedback measurement to verify that the
actual position is equal to the specified location
Two Types of Control System
 (a) Closed loop and (b) open loop
Two Basic Types of Control in
Computer Numerical Control
Operation of an Optical Encoder
Precision in Positioning
Three critical measures of precision in positioning:
1. Control resolution
2. Accuracy
3. Repeatability
Control Resolution (CR)
Defined as the distance between two adjacent control
points in the axis movement
 Control points are locations along the axis to which
the worktable can be directed to go
 CR depends on:
 Electromechanical components of positioning
 Number of bits used by controller to define axis
coordinate location
Statistical Distribution of
Mechanical Errors
 When a positioning system is directed to move to a
given control point, the movement to that point is
limited by mechanical errors
 Errors are due to various inaccuracies and
imperfections, such as gear backlash, play between
leadscrew and worktable, and machine deflection
 Errors are assumed to form a normal distribution
with mean = 0 and constant standard deviation
over axis range
Accuracy in a Positioning
Maximum possible error that can occur between desired
target point and actual position taken by system
 For one axis:
Accuracy = 0.5 CR + 3
where CR = control resolution; and  = standard
deviation of the error distribution
Capability of a positioning system to return to a given
control point that has been previously programmed
 Repeatability of any given axis of a positioning
system can be defined as the range of mechanical
errors associated with the axis
Repeatability = 3
CNC Part Programming
Manual part programming
Computer-assisted part programming
CAD/CAM-assisted part programming
Manual data input
Common features:
 Points, lines, and surfaces of workpart must be
defined relative to CNC axis system
 Movement of cutting tool must be defined
relative to these part features
Applications of Computer
Numerical Control
Operating principle of CNC applies to many
 Many industrial operations require the position of
a workhead to be controlled relative to the part or
product being processed
Two categories of CNC applications:
1. Machine tool applications
2. Non-machine tool applications
Machine Tool Applications
 CNC widely used for machining operations such as
turning, drilling, and milling
 CNC has motivated development of machining
centers, which change their own cutting tools to
perform a variety of machining operations
 Other CNC machine tools:
 Grinding machines
 Sheet metal pressworking machines
 Thermal cutting processes
Non-Machine Tool Applications
 Tape laying machines and filament winding machines
for composites
 Welding machines, both arc welding and resistance
 Component insertion machines in electronics
 Drafting machines (x-y plotters)
 Coordinate measuring machines for inspection
Benefits of CNC
 Reduced non-productive time
 Results in shorter cycle times
 Lower manufacturing lead times
 Simpler fixtures
 Greater manufacturing flexibility
 Improved accuracy
 Reduced human error
Industrial Robotics
An industrial robot is a general purpose programmable
machine that possesses certain anthropomorphic
 The most apparent anthropomorphic feature is the
robot’s mechanical arm, or manipulator
 Robots can perform a variety of tasks such as loading
and unloading machine tools, spot welding
automobile bodies, and spray painting
 Robots are typically used as substitutes for human
workers in these tasks
Robot Anatomy
An industrial robot consists of
 Mechanical manipulator
 A set of joints and links to position and orient the
end of the manipulator relative to its base
 Controller
 Operates the joints in a coordinated fashion to
execute a programmed work cycle
 Manipulator of
an industrial
robot (photo
courtesy of
Manipulator Joints and Links
 A robot joint is similar to a human body joint
 It provides relative movement between two parts
of the body
 Typical industrial robots have five or six joints
 Manipulator joints - classified as linear or rotating
 Each joint moves its output link relative to its input
 Coordinated movement of joints enables robot to
move, position, and orient objects
Manipulator Design
Robot manipulators can usually be divided into two
 Arm-and-body assembly - function is to position an
object or tool
 Three joints are typical for arm-and-body
 Wrist assembly - function is to properly orient the
object or tool
 Two or three joints are associated with wrist
Five Basic Arm-and-Body
Cartesian coordinate
SCARA (Selectively Compliant Assembly Robot
Basic Arm-and-Body
 (a) Polar, (b) cylindrical, and (c) Cartesian coordinate
Basic Arm-and-Body
(d) Jointed-arm and (e) SCARA (Selectively Compliant
Assembly Robot Arm)
Manipulator Wrist
 The wrist is assembled to the last link of the
 The SCARA is sometimes an exception because it is
almost always used for simple handling and
assembly tasks involving vertical motions
 A wrist is not usually present at the end of its
 Substituting for the wrist on the SCARA is
usually a gripper to grasp components for
movement and/or assembly
End Effectors
Special tooling that connects to the robot's wrist to
perform the specific task
1. Tools - used for a processing operation
 Applications: spot welding guns, spray painting
nozzles, rotating spindles, heating torches,
assembly tools
2. Grippers - designed to grasp and move objects
(usually parts)
 Applications: part placement, machine loading
and unloading, and palletizing
Gripper End Effector
 A robot gripper: (a) open and (b) closed to grasp a
Robot Programming
 Robots execute a stored program of instructions that
define the sequence of motions and positions in the
work cycle
 Much like a part program in CNC
 In addition to motion instructions, the program may
include commands for other functions:
 Interacting with external equipment
 Responding to sensors
 Processing data
Two Basic Robot Programming
1. Leadthrough programming
 Teaching-by-showing - manipulator is moved
through sequence of positions in the work cycle
and the controller records each position in
memory for subsequent playback
2. Computer programming languages
 Robot program is prepared at least partially offline for subsequent downloading to robot
Where Should Robots be Used?
Work environment is hazardous for humans
Work cycle is repetitive
The work is performed at a stationary location
Part or tool handling is difficult for humans
Multi-shift operation
Long production runs and infrequent changeovers
Part positioning and orientation are established at the
beginning of work cycle, since most robots cannot
Applications of Industrial Robots
Three basic categories:
1. Material handling
 Moving materials or parts (e.g., machine
loading and unloading)
2. Processing operations
 Manipulating a tool (e.g., spot welding, spray
3. Assembly and inspection
 May involve moving parts or tools