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Ch4

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Part II AUTOMATION AND
CONTROL TECHNOLOGIES
Chapters:
4. Introduction to Automation
5. Industrial Control Systems
6. Hardware Components for Automation and
Process Control
7. Numerical Control
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
1/20
Ch 4 Introduction to Automation
Sections:
1. Basic Elements of an Automated System
2. Advanced Automation Functions
3. Levels of Automation
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
2/20
Automation and Control Technologies
in the Production System
Figure 4.1
Automation
and control
technologies
in the
production
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system.
No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
3/20
Automation Defined

Automation is the technology by which a process or
procedure is accomplished without human
assistance.
Basic elements of an automated system:
1. Power - to accomplish the process and operate
the automated system
2. Program of instructions – to direct the process
3. Control system – to actuate the instructions
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
4/20
Elements of an Automated System
Fig. 4-2
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5/20
Electricity The Principal Power Source
 Widely available at moderate cost
 Can be readily converted to alternative forms, e.g.,
mechanical, thermal, light, etc.
 Low level power can be used for signal transmission, data
processing, and communication
 Can be stored in long-life batteries
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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6/20
Power to Accomplish the
Automated Process
 Power for the process
 To drive the process itself
 To load and unload the work unit
 Transport between operations
 Power for automation
 Controller unit-based on digital computers to read the program of
instructions, perform the control calculations, and execute the
instructions by transmitting the proper commands to actuating devices.
 Power to actuate the control signals: The commands sent by the
controller unit are carried out by means of electromechanical devices,
such as switches and motors, called actuators. The commands are
generally transmitted by means of low-voltage control signals.
 Data acquisition and information processing
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
7/20
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
8/20
Program of Instructions





Set of commands that specify the sequence of steps in the work cycle
and the details of each step. the set point is the value of the process
parameter or desired value of the controlled variable in the process.
process parameter : is an input to the process, such as the temperature
dial setting.
process variable: is the corresponding output of the process, which is the
actual temperature of the furnace
Example: CNC part program
During each step, there are one or more activities involving changes in one
or more process parameters
 Examples:
 Temperature setting of a furnace
 Axis position in a positioning system
 ©2008
Motor
on or off
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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Five Categories Of Work Cycle
Programs
 Set-point control, in which the process parameter value is
constant during the work cycle (as in the furnace example).
 Logic control, in which the process parameter value depends on
the values of other variables in the process.
 Sequence control, in which the value of the process parameter
changes as a function of time. The process parameter values
can be either discrete (a sequence of step values) or
continuously variable.
 Interactive program, in which interaction occurs between a
human operator and the control system during the work cycle.
 Intelligent program, in which the control system exhibits aspects
of human intelligence (e.g., logic, decision making, cognition,
learning) as a result of the work cycle program.
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
10/20
Example 4.1 An Automated Turning
Operation
Consider an automated turning operation that generates a cone-shaped
product The system is automated and a robot loads and unloads the work
units. The work cycle consists of the following steps: (1) load starting
workpiece, (2) position cutting tool prior to turning, (3) turn, (4) reposition
tool to a safe location at end of turning, and (5) unload finished workpiece.
Identify the activities and process parameters for each step of the
operation.
Solution: In step (1), the activities consist of the robot manipulator
reaching for the raw work part, lifting and positioning the part into the
chuck jaws of the lathe, then retreating to a safe position to await
unloading. The process parameters for these activities are the axis values
of the robot manipulator (which change continuously), the gripper value
(open or closed), and the chuck jaw value (open or closed).
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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11/20
Example 4.1 An Automated Turning
Operation
 In step (2), the activity is the movement of the cutting tool to a “ready”
position. The process parameters associated with this activity are the x- and
z-axis position of the tool.
 Step (3) is the turning operation. It requires the simultaneous control of three
process parameters: rotational speed of the workpiece (rev/min), feed
(mm/rev), and radial distance of the cutting tool from the axis of rotation. To
cut the conical shape, radial distance must be changed continuously at a
constant rate for each revolution of the workpiece. For a consistent finish on
the surface, the rotational speed must be continuously adjusted to maintain a
constant surface speed (m/min); and for equal feed marks on the surface, the
feed must be set at a constant value. Depending on the angle of the cone,
multiple turning passes may be required to gradually generate the desired
contour.
 Each pass represents an additional step in the sequence.
 Steps (4) and (5) are the reverse of steps (2) and (1), respectively, and the
©2008parameters
Pearson Education, Inc., Upper
Saddle
River, same.
NJ. All rights reserved. This material is protected under all copyright laws as they currently exist.
process
are
the
No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
12/20
Decision-Making in a
Programmed Work Cycle
 In Example 4.1, the only two features of the work cycle were
(1) the number and sequence of processing steps and (2)
the process parameter changes in each step. The following
are examples of automated work cycles in which decision
making is required:
 Operator interaction (input data)
 Automated teller machine
 Different part or product styles processed by the system
 Robot welding cycle for two-door vs. four door car
models
 Variations in the starting work units
 Additional machining pass for oversized sand casting
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
13/20
Features of a Work Cycle Program
 Number of steps in the work cycle
 Manual participation in the work cycle (e.g., loading
and unloading workparts)
 Process parameters - how many must be controlled?
 Operator interaction - does the operator enter
processing data?
 Variations in part or product styles
 Variations in starting work units - some adjustments in
process parameters may be required to compensate
for differences in starting units
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
14/20
Control System – Two Types
1. Closed-loop (feedback) control system – a system in
which the output variable is compared with an input
parameter, and any difference between the two is used
to drive the output into agreement with the input
2. Open-loop control system – operates without the
feedback loop
 Simpler and less expensive
 Risk that the actuator will not have the intended
effect
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
15/20
(a) Feedback Control System and
(b) Open-Loop Control System
(a)
(b)
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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Positioning System Using
Feedback Control
A one-axis position control system consisting of a leadscrew driven by
a servomotor and using an optical encoder as the feedback sensor.
For the open-loop case, the diagram for the positioning system would be similar to the
preceding, except that no feedback loop is present and a stepper motor would be used in place
of the dc servomotor. A stepper motor is designed to rotate a precise fraction of a turn for each
pulse received from the controller. Since the motor shaft is connected to the leadscrew, and the
leadscrew drives the worktable, each pulse converts into a small constant linear movement of
the table. To move the table a desired distance, the number of pulses corresponding to that
distance is sent to the motor. Given the proper application, whose characteristics match the
preceding list
operating
anAllopen-loop
system
works
with
high
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Pearson
Education, Inc.,conditions,
Upper Saddle River, NJ.
rights reserved. Thispositioning
material is protected under
all copyright
laws as they
currently
exist. reliability.
No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
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When to Use an
Open-Loop Control System
 Actions performed by the control system are simple
 Actuating function is very reliable
 Any reaction forces opposing the actuation are small
enough as to have no effect on the actuation
 If these conditions do not apply, then a closed-loop control
system should be used
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
18/20
Advanced Automation Functions
1. Safety monitoring
2. Maintenance and repair diagnostics
3. Error detection and recovery
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
19/20
Safety Monitoring
Use of sensors to track the system's operation and
identify conditions that are unsafe or potentially unsafe
 Reasons for safety monitoring
 To protect workers and equipment
 Possible responses to hazards:
 Complete stoppage of the system
 Sounding an alarm
 Reducing operating speed of process
 Taking corrective action to recover from the safety
violation
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
20/20
Maintenance and Repair Diagnostics
 Status monitoring
 Monitors and records status of key sensors and
parameters during system operation
 Failure diagnostics
 Invoked when a malfunction occurs
 Purpose: analyze recorded values so the cause of
the malfunction can be identified
 Recommendation of repair procedure
 Provides recommended procedure for the repair crew
to effect repairs
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
21/20
Error Detection and Recovery
1. Error detection – functions:
Use the system’s available sensors to determine
when a deviation or malfunction has occurred
 Correctly interpret the sensor signal
 Classify the error
2. Error recovery – possible strategies:
 Make adjustments at end of work cycle
 Make adjustments during current work cycle
 Stop the process to invoke corrective action
 Stop the process and call for help

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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
22/20
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist.
No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
23/20
©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist.
No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
24/20
Levels of Automation
1. Device level – actuators, sensors, and other hardware
2.
3.
4.
5.
components to form individual control loops for the next
level
Machine level – CNC machine tools and similar
production equipment, industrial robots, material
handling equipment
Cell or system level – manufacturing cell or system
Plant level – factory or production systems level
Enterprise level – corporate information system
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover.
25/20
Levels of Automation
Fig. 4.6
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No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book
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