Experiment No: 01
Name of the Experiment: Design of open loop system and investigate the performance
Objectives:
1. To design an open-loop control system for a specified process.
2. To investigate the performance of the designed system under various conditions.
3. To understand the principles behind open-loop control systems and their application in
real-world scenarios.
Theory:
Open Loop Control System :
An open loop control system is a type of control system in which the system’s output does
not have any effect on its input and, therefore, does not have any feedback. Open loop
system is also known as non feedback control system because it does not depend on the
any previous output or any continuous output of the system. In this type of system input is
provided to the system and the output is generated without taking any feedback from the
output.
Fig 1.1: Block diagram of open loop control system.
Transfer Function :
The transfer function of a system is defined as the ratio of Laplace transform of output to
the Laplace transform of input where all the initial conditions are zero.
1.T(S) = Transfer function of the system.
2.C(S) = output.
3.R(S) = Reference output.
4.G(S) = Gain.
2
Required apparatus:
MATLAB software
System model :
R L
Fig 1.2: Circuit Diagram of system model 1 .
𝑘
Transfer function for the system 1 : TF = ((𝐽∗𝑠+𝑏)∗(𝐿∗𝑠+𝑅)+𝑘2 )
K1
D f
m
K2
Fig 1.3: Circuit Diagram of system model 2 .
1
Transfer function for the system 2 : TF = (m∗s2 +D∗s+K)
2
R1 R2
V C
L
Fig 1.4: Circuit Diagram of system model 3 .
s∗L
Transfer function for the system 3 : TF = (s2 ∗C∗L∗(R1+R2)+s∗(R1+R2∗C+L)+R1)
Matlab code :
System 01 System 02 System 03
clc; clc; clc;
% close all; % close all; % close all;
clear all clear all clear all
J=0.01; m=0.01; C = 0.01;
b=0.1; D=0.5; R1= 0.1;
k=0.1138; K=1; R2 = 3;
R=1; s=tf('s'); L=20;
L=0.5; TF =1/(m*s^2+D*s+K); s=tf('s');
s=tf('s'); sys= ss(TF) TF=s*L / ((s^2*C*L*(R1+R2) +
TF = k/((J*s+b)*(L*s+R)+k^2) step(TF) s*(R1+R2*C+L) + R1))
sys= ss(TF) sys= ss(TF)
step(TF) step(TF)
3
Results :
Fig 1.5: Step response of system 01
Fig 1.6: Step response of system 02
4
Fig 1.7: Step response of system 03
Performance analysis :
For System 01:
Rise time Peak time Settling time Peak Value
0.9860 2.9456 1.7917 1.0062
For System 02:
Rise time Peak time Settling time Peak Value
1.0536 3.5083 1.8957 0.9993
For System 03:
Rise time Peak time Settling time Peak Value
0 0.2595 0.9923 0.9923
4
Discussion :
In this experiment, we investigate the step response of three open loop systems. Our aim
is to get the step response of the systems near 1 . We get the step response of the system
model one and two near one and get the values of peak time, settling time, rise time etc.
But for the system model 3 , the step response is not desirable. Overall, the lab provided
valuable insights into the design and operation of open-loop control systems and the
factors that influence their performance. Further experimentation and analysis could focus
on comparing the performance of open-loop and closed-loop systems under different
conditions to better understand their relative advantages and limitations.
Conclusion:
The open-loop control system designed in this lab demonstrates the fundamental
principles of control systems. While open-loop systems are simple and easy to implement,
they lack the ability to adapt to changes in the system or external disturbances. As a
result, their performance may be limited compared to closed-loop systems. However,
open-loop systems can still be useful in applications where precise control is not required
or where the system dynamics are well-understood and predictable.
References:
[1]“Open Loop Control System,” GeeksforGeeks, Nov. 15, 2023.
https://www.geeksforgeeks.org/open-loop-control-system/
[2]Electronics Tutorials, “Open-loop System and Open-loop Control Systems,” Basic
Electronics Tutorials, Aug. 30, 2013. https://www.electronics-
tutorials.ws/systems/open-loop-system.html
[3]“Control System Transfer Function - javatpoint,” www.javatpoint.com.
https://www.javatpoint.com/control-system-transfer-function
