Port Said University ﺟﺎﻣﻌـــﺔ ﺑـﻮرﺳــﻌﯿـﺪ
Faculty of Engineering ﻛﻠــﯿﺔ اﻟﮭــــﻨﺪﺳﺔ
Mechanical Power Eng. Dept. ﻗﺴﻢ ھﻨﺪﺳﺔ اﻟﻘﻮى اﻟﻤﯿﻜﺎﻧﯿﻜﯿﺔ
3rd Year Mechanical Power
Dr. Mohamed Hammam
2022
Course Grades
Attendance and sections 5
Mid-Term 10
Simulations and sheets 5
Tests 10
Final 70
Total 100
Course Contents
Lecture Number Topic
1 Introduction
2 System Modelling
3 Transfer functions and Laplace transforms
4 Time response
5 Block Diagram reduction
6 System stability
7 Steady state errors
8 Root locus technique 1
9 Root locus technique 2
10 Frequency response 1
11 Frequency response 2
12 Applications
Control System Response
• A control system consists of processes assembled for the purpose of obtaining a desired output with desired
performance, given a specified input.
Figure 1 Simplified description of a control system.
• System Response:
Figure 2 shows the response of an elevator that move up from first to fourth floor.
Figure 2 Elevator response.
Control System Configurations
• Open-Loop Systems
A generic open-loop system is shown in Fig. 3(a). It contains a subsystem called an input transducer, a controller and a plant.
Other signals, such as disturbances can exist. For example, the plant can be a furnace or air conditioning system, where the
output variable is temperature. The controller in a heating system consists of fuel valves and the electrical system that operates
the valves.
• Closed-Loop (Feedback Control) Systems
The disadvantages of open-loop systems, namely sensitivity to disturbances and inability to correct for these disturbances, may
be overcome in closed-loop systems. The generic architecture of a closed-loop system is shown in Fig. 3(b). It contains a
feedback from the output that is compared to the input. The difference between both is called the errors.
FIGURE 3 A control systems: a. open-loop system;
b. closed-loop system.
Example of a closed loop control system
• Temperature Control of a Chamber :
• This system is designed so that the temperature of the chamber, which is the system’s output, remains constant. The
temperature of the chamber is being controlled by a thermometer. The operation of the system is regulated via a temperature
measurement device. This device compares the room temperature with the desired temperature and transforms the error signal
into a pressure signal. This pressure acts on the control valve, which accordingly closes or opens, thus controlling the supply
of the liquid fuel. The amount of the liquid fuel which enters the burner, essentially, controls the temperature of the hot air.
Figure 4 Temperature Control of a Chamber.
Analysis and Design Objectives of a
Control System
• Control systems analysis and design focuses on three primary objectives:
• Transient Response: Producing the desired transient response. Ex: Comfort and Fast motion of the elevator.
• Steady-State Response: Reducing steady-state errors. Ex. The elevator reach a position close to the required floor.
• Stability: Achieving stability. Ex: the elevator approaches the floor with time.
The Design Process of A control System
Case study : Antenna Azimuth: Position Control System.
• Step 1: Transform Requirements Into a Physical System:
• For example, in the antenna azimuth position control system, the
requirements would state the desire to position the antenna from a
remote location and describe such features as weight and physical
dimensions of the antenna.
Figure 5 Antenna azimuth position control system: system concept.
• Step 2: Draw a Functional Block Diagram
The designer translates a qualitative description of the system into a functional block diagram that describes the component parts
of the system (that is, function and/or hardware) and shows their interconnection. It indicates functions such as input transducer
and controller, as well as possible hardware descriptions such as amplifiers and motors as shown in Fig. 6.
Figure 6 Functional block diagram
• Step 3: Create a Schematic
The schematic contains a simplified description of the internal components of each control system parts as shown in Fig.7. When
we draw the potentiometers, we make our first simplifying assumption by neglecting their friction A differential amplifier and a
power amplifier are used as the controller to yield gain and power amplification, respectively, to drive the motor. Again, we
assume that the dynamics of the amplifiers are rapid compared to the response time of the motor; thus, we model them as a pure
gain, K. A dc motor and equivalent load produce the output angular displacement. The speed of the motor is proportional to the
voltage applied to the motor’s armature circuit. Both inductance and resistance are part of the armature circuit. We assume the
effect of the armature inductance is negligible for a dc motor.
Figure 7 Antenna azimuth position control
system: a schematic.
• Step 4: Develop a Mathematical Model (Block Diagram)
• Once the schematic is drawn, the designer uses physical laws, such as Kirchhoff’s laws for electrical networks and Newton’s
law for mechanical systems, along with simplifying assumptions, to model the system mathematically.
• mathematical models are that describe the relationship between the input and output of dynamic systems. One such model is
the linear, time-invariant differential equation.
• Many systems can be approximately described by this equation, which relates the output, c(t), to the input, r(t),
by way of the system parameters, a and bj.
i
• In addition to the differential equation, the transfer function is another way of mathematically modeling a system. The
model is derived from the linear, time-invariant differential equation using the Laplace transform.
Step 5: Create and Reduce the Block Diagram
• The Functional Block Diagram is transformed into a mathematical block diagrams that describe the mathematical relation
between the input and the output of each block.
Figure 8 Mathematical block diagram for the antenna azimuth position control system.
• The mathematical block diagram is reduced to one block diagram describing the relation between the input of the angular
position and the actual output of the angular position
Figure 9 Equivalent block diagram for the antenna azimuth position control system.
• Step 6: Analyze and Design
• The next phase of the process, following block diagram reduction, is analysis and design. In this phase, the engineer analyzes
the system to see if the response specifications and performance requirements can be met by simple adjustments of system
parameters.
• Test input signals are used to verify the design. The types of common test signals are shown in Table 1.
• The response of the system to a step input is shown in Fig.10 for cases of low and high controller constant ( amplifier gain).
Table 1 Test waveforms used in control systems.
Figure 10 Response of a position control system, showing effect of high
and low controller gain on the output response.
Software
• Two software will be used in the course
• MATLAB
• LabVIEW
References
Norman S. Nise “CONTROL SYSTEMS ENGINEERING”, 7th ed, John Wiley & Sons, 2015.
Student Resources
https://bcs.wiley.com/he-bcs/Books?action=index&itemId=1118170512&bcsId=9295
