PANGASINAN STATE UNIVERSITY
ASINGAN CAMPUS
Asingan, Pangasinan
Bachelor of Industrial Technology
Major in Electronics and Computer Technology
INDUSTRIAL AUTOMATION AND CONTROL
ELECTRONICS
Prepared by:
MR. JERRY C. ACLERA
Assistant Professor 1V
Introduction to Automation, Systems Overview
Course Objectives
In this course, we shall learn about the different aspects of factory automation and
its components. At the lowest level, we study sensors and actuators that control the
physical process, and how they work with simple electrical or mechanical stimulus.
We study how systems containing a large number of sensors and actuators that
follow pre-defined logic can be controlled automatically using Logic Controllers.
Finally, in more complex systems, the logic that governs actions of the actuators is
based not only on inputs from sensors, but also from other sources such as data
stored by humans etc. Such automation requires connection between hardware
(sensors, actuators) and computer(s) linked together on networks. We will learn how
high level programming languages (e.g. C++ or Java) can be used to design
automation control in such complex systems. The most significant element of
automation in modern industry is the growing use of computers and electronic
controls. In keeping with this, the course shall concentrate on computers and
computer applications.
History of Automation:
The concept of automated factories is not old historically. The first organized
automation is believed to have sprung out of the industrial revolution in England
in the latter half of the 18th century. Some of the landmark events in these 200
years of rapid industrialization include:
• Outburst of mechanization due to the Industrial revolution, 1770.
• Henry Ford and the development of hard automation and transfer lines, 1900.
• Machine tools with automatic controls; e.g. copying machines with a stylus to
traverse the master copy in order to generate an electrical signal for the servomotor
drive.
• Numerically Controlled (NC) machine tools, 1952 (US Air Force, MIT).
• Rapid development of microchip computers, late 1960's.
• CNC (computer numerical controlled) machine tools.
• Industrial Robots (1970's).
• Computer networks (1970's).
• Fully automated, Flexible Manufacturing Systems (FMS) for high flexibility,
1990's.
Why Automate?
• Improved quality: Interchangeability, increased life
• Precise control with shorter response time
• Shorter processing time: low lead-time, lower work-in-progress time, lower
inventory
• Safer work-place: hazardous substance handling, chemicals handling,
heavy/unwieldy materials handling Less waste: repeatability Computers
Communication network A/D converter Analog Signals Digital Signals Sensors
and Actuators Network Interface Physical Process Analog controls D/A converter
Microprocessor PLC
Figure 1.1. Basic Structure of Automatic Control System
Open Loop Vs Closed Loop Systems
Control structures can basically be looked upon as open loop or closed-loop
(feedback) systems. In open loop systems, the actuator is given a command to take
an action for a fixed amount of time, or of fixed magnitude. No sensors are used;
the user must know, for example, by calibration
of the actuator behavior, how much work (or magnitude of effect) will be done by
the actuator for that value of the signal. Such systems are cheaper, and usually
lighter (since there is no sensor to be mounted on the operated device). Closed loop
systems typically use a sensor to measure the actual effect being caused by the
actuator. If the device is far from the target, the actuator is given a signal to keep
working; when the device reaches the target, the sensor signals the actuator to stop
its action (thus the signal from the sensor is called a feedback). Usually, feedback
systems also accelerate the device when the target is far away, and decelerate the
device when it is near the target to account for inertia.
Actuator Device Signal - Sensor feedback
Examples of Automation:
1a. Kowloon Motor Bus
To request the bus to stop, you press a button. A bell rings (once), and a Light bulb
near the driver’s seat turns on.
- identify the sensor(s) and actuator(s) in this system.
- do you think this is an analog signal or digital?
- do you think this is a closed loop or open loop control?
1b. Kowloon Motor Bus
To request a stop, you press on the black/yellow strip. Bell rings, and light bulb
turn on.
- what type of sensor do you think is being used in this system?
2a. Automatic doors
When you walk in front of the door of some buildings, the door automatically opens.
After a fixed amount of time, it shuts.
- Identify the sensor, and the actuators in this case.
- Give examples of two types of sensors that such a system may be using.
- Give examples of two types of actuators that such systems may be using.
2b. Automatic doors
Sometimes the door starts to close as you are walking through it. In such cases, a
sensor automatically detects your presence and re-opens the door.
- Lift doors often use this type of system; what type of sensor is used?
- Lift doors additionally use a system where the closing door re-opens if it hits the
person standing in the doorway. What sensor is used for this?
- Let sensor-1 be “person-in-door”, sensor-2 be “door-hit-person” and actuator
control be “open-the-door”. What is the logical statement for the control of the
actuator?
3. HMV (or other CD selling shop)
If a person walks out of the CD shop, carrying a CD for which they did not pay, an
alarm rings out, and a light bulb flashes.
- What are the sensors and actuators in this case?
4. Fridge
The fridge in your home cools the food you keep inside it. You can set the intensity
of the cooling by setting a slider or dial.
- What are the sensor and actuator in this case?
- Give an example of how such a control system can be made using analog devices.
- Give an example of how such a control system can be made using digital devices.
5. Automatic rice cooker
I have a very nice rice cooker. I can put the rice and water in it in the morning, and
set it to start cooking at, say 6pm in the evening. It turns on automatically, and
when the rice is cooked, it switches to “keep warm” mode. - How does it control
when to turn on?
-
What type of sensor(s) and actuators do you think are inside this machine?
How would you sense when the rice is cooked?
How can the rice be kept warm for up to 12 hours?
Such cookers can also be set to cook different food types (rice, congee, fish…).
How is the logic for so many functions controlled?
5. Park and Shop
When you buy something from Park and Shop, the sales clerk ‘swipes’ it across a
glass sheet on top of the counter. The price (and name) of the item are automatically
printed on the receipt. The receipt also calculates the total price of all items you
have bought.
-
Identify the sensors and actuators in this example.
Is this an example of digital or analog control?
How does the system know what item was swiped?
How does the system know the price and name of the item?
If the system “knows” which item is being purchased, can this information be
usedby the inventory manager of Park and Shop to improve customer service?
How?
All of the above are examples of automation that we encounter every day of our
lives. The same technology is used in the control of automatic machines in all
types of factories and companies. In this course, we will learn, to some extent,
how such control systems work.
LEARNING ACTIVITY.
Answer the following:
1. Why do we need to Automate?
2. Differentiate Open Loop to Closed Loop.
3. In the Automatic Doors, give what sensor and actuator used and give
their functions.
4. In the Fridge, give 1 sensor and 1 actuator being used and give their
functions.
5. In the Park and Shop, what kind of sensor and actuator being used?