Industrial automation uses control devices like PLCs and DCS to automatically control industrial operations without significant human intervention. It aims to reduce costs, improve quality and productivity, and increase flexibility and safety. An industrial automation system has three layers - a sensor level that collects process data, a control level that uses devices like PLCs to control processes, and a supervisory level that stores data and provides human-machine interfaces. Closed-loop control systems use feedback to accurately control outputs by comparing actual outputs to desired outputs and adjusting inputs accordingly.

1. • Industrial automation is the use of various control devices like
PC’s/PLC’s/DCS, used to have control on various operations of an
industry without significant intervention from humans and to provide
automatic control performance.
• In industries, control strategies use a set of technologies which
are implemented to get the desired performance or output, making the
automation system most essential for industries.
Industrial automation

2. • Industrial automation involves usage of advanced control strategies
like cascade controls, modern control hardware devices as PLC,
sensors and other instruments for sensing the control variables, signal
conditioning devices to connect the signals to the control devices,
drives and other significant final control devices, standalone
computing systems, communication systems, alarming and HMI
(Human Machine Interface) systems.

3. Need of automated industry

4. • To reduce Periodic or Manual checking
• To increase the Productivity
• Reduce the Production Cost
• To improve Product Quality
• To increase the Flexibility
• Operator Friendly and Improves the Safety

5. Structure of Industrial Automation

6. • Sensor level is also called as process layer. It uses the sensors and actuators to get the
values of the process variables in continuous or periodical manner. This act as eyes and
arms of the industrial processes.
• Automation control level or control layer uses industrial control devices like
PC’s/PLC’s/DCS, etc. This level utilizes the various embedded processors, PID algorithms
to control the process.
• Supervising level or SCADA layer gets lots of channel information and stores the data in the
system database. It acquires data from various control devices and displays them on HMI’s
(Human Machine Interface). It also gives alarm to indicate the levels of the process and
control variables. It uses special software to get the data and communication protocols to
interact with the field devices.
• Enterprise level performs the tasks like scheduling, orders and sales, product planning, etc.

7. What is a Control System?
 The Control system can be defined as, the output of a system
that can be controlled by changing its input.
 The system behaviour can be expressed with the help of
differential equations. So the desired output can be achieved in a
control system through managing, directing, or commanding the
behavior of the system.
 Open loop control systems and closed-loop control systems.

8. What is Open-Loop Control System?
The input can be given to the control system so that the required output can
be obtained.

9. • In OLCS, includes controller as well as the controlled process.
• Generally, the input is given to the system mainly depends on the required
output.
• Based on the input, the control signal can be generated through the controller.
• This signal can be given to the processing unit.
• Therefore, based on the control signal, appropriate processing can be
performed so that output can be attained.

10. • In the open-loop control system, there is no feedback path.
• The open-loop control system is independent of the output.
• It is notable here that this usually generates a fault within the system because
there is no chance of changing the input once the output illustrates the
difference from the estimated value.

11. Characteristics
The characteristics of the open-loop control system are,
•There is no contrast between real and preferred values.
•It has no control action on the value of output.
•Every input setting decides a set operating location for the controller.
•The changes within external conditions will affect to change the output directly.

12. • We can observe a traffic light controller at different road crossings. The signals which are
generated through the control system are time-dependent. At the designing time of the
controller, an internal timing can be given to the controller.
Thus, once the controller of a traffic signal is fixed at the crossing after that every signal
can be displayed through the controller.
• Here the control system has nothing to perform using the produced output because it
cannot change its input based on the traffic there at any side. After some fixed time gap,
based on the primarily generated input, the control system generates the output.

13. Advantages
•Very simple & easy to design these types of control systems.
•Low cost as compared with other systems
•Less maintenance
•The output is stable
•Very suitable to use
•Convenient operation
Disadvantages
•Inaccurate
•The non-feedback system is not dependable when their output is influenced through some outside
disturbances.
•The output differences cannot correct automatically.
•It needs timely recalibration.

14. What is a Closed-Loop Control System?
 A closed-loop control system can be defined as, a system that has a feedback loop
(or) a control system that uses a feedback signal to generate the output.
 The stability of this system can be controlled by a feedback system. So by providing a
feedback system, any open-loop control system can be changed into a closed loop.
 The desired output can be achieved and maintained by evaluating the actual
condition & generated output.
 If the generated output is moved away from the actual output, then this control
system produces a faulty signal which is fed to the i/p of the signal. Once the error
signal is added to the input signal, then the next loop output can be corrected which
is known as automatic control systems.

15. The block diagram of the closed-loop system is shown below. The basic elements of the
closed-loop control system include error detector, controller, feedback elements & power plant .

16.  When the control system includes a feedback loop, then the systems are known as feedback
control systems. So the output can be controlled accurately by providing feedback to the input.
This type of control system can include more than one feedback.
 In the above diagram, the error detector generates an error signal, so this is the variation of the
input as well as the feedback signal. This feedback signal can be obtained from the elements of
feedback in the control system by considering the system output as an input. As an alternative of
the input, this error signal can be given as an input of a controller.
 The controller generates an actuating signal to control the plant. In this arrangement, the control
system output can be corrected automatically to get the preferred output. Therefore, these
systems are also named as automatic control systems. The best example of a closed-loop control
system is a traffic light control system including a sensor at the input.

17. Types of Closed Loop Control System
Closed-loop control systems are classified into two types depending on the feedback
signal nature such as positive feedback signal and the negative feedback signal.

18. Positive Feedback Signal
• The closed-loop system including a positive feedback signal can be connected
to the input of the system is known as a positive feedback system. This system
is also named as regenerative feedback.
• The best example of this positive feedback in electronic circuits is an
operational amplifier.
• Because this loop can be achieved by connecting some portion of the output
voltage to the input of the non-inverting terminal through a feedback loop using
a resistor.

19. Negative Feedback Signal
• The closed-loop system including a negative feedback signal can be
connected to the input of the system is named as a negative
feedback system. This kind of system is also named as degenerative
feedback. These types of systems are very stable and also enhance
strength.
• These systems are used to control the electronic machines like
current generators, voltage generators, and also control the
machinery speed.

21. The closed-loop control system example is shown below.
For the above system,
C(S) = E(S) * G(S)
E(S) = R(S) – H(S) * C(S)
Substitute this E(S) value in C(S), then we can get
C(S) = [R(S) – H(S) * C(S)]* G(S)
C(S) = R(S) G(S) – H(S) * C(S) * G(S)
From the above equation
R(S) G(S) = C(S) + H(S) * C(S) * G(S)
R(S) G(S) = C(S) [1 + H(S) * G(S)]
C(S)/ R(S) = G(S)/ [1 + H(S) * G(S)]
This is the transfer function of this system with negative feedback.
For the positive feedback, the transfer function equation can be written as
C(S)/ R(S) = G(S)/ [1 – H(S) * G(S)]

22. Closed-Loop Control System Examples
•In servo voltage stabilizer, the voltage stabilization can be attained by giving output voltage
feedback to the system
•In the water level controller, the level of water can be decided by the input water.
•The temperature in the AC can be adjusted depending on the temperature of the room.
•The motor speed can be controlled using a tachometer or current sensor, where the sensor
detects the motor speed and sends feedback to the control system to change its speed.
•Some more examples of these systems include thermostat heater, solar system, missile launcher,
auto engine, automatic toaster, water control system using a turbine.

23. Advantages
•These systems are very precise & less error.
•Errors can be corrected through the feedback signal
•It supports automation
•They cannot affect by means of noise.
Disadvantages
•The designing of this system is complicated
•They are very complex & Expensive
•Huge maintenance is needed
•The control system oscillates sometimes due to feedback signals.
•More efforts, as well as time, are required while designing the system.