Control Systems Second Edition
Dr. N.C. Jagan B.E., ME., Ph.D., MlSTE, FIE
Retd. Professor in Electrical Engineering University College of Engineering Osmania University, Hyderabad.
BSP BS Publications 4-4-309, Giriraj Lane, Sultan Bazar, Hyderabad - 500 095 - A.P. Phone: 040-23445605,23445688
Copyright © 2008 by Publisher
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Published by :
SSP BS Publications 4-4-309, Giriraj Lane, Sultan Bazar, Hyderabad - 500 095 - A.P. Phone: 040-23445605,23445688
e-mail:
[email protected] www.bspublications.net
Printed at Adithya Art Printers Hyderabad
ISBN: 978-81-7800-177-2 (HB)
Contents 1 Introduction
1
1. 1 1.2
Why Automatic Control ? .................................................................... 1 Open Loop and Closed Loop Control Systems ................................ 2
1.3
Open Loop Vs Closed Loop Control Systems ................................... 3
1.4
Feedback Control Systems ................................................................ 4
1.5
Classification of Control Systems ...................................................... 4 1.5.1 Continuous Time Feedback Control Systems ..................... 5 1.5.2 Discrete Data Feedback Control Systems .......................... 5 1.5.3 Linear Control Systems ........................................................ 6 1.5.4 Non-Linear Control Systems ................................................ 6
2 Mathematical Modelling of Physical Systems
8
2.1
Introduction ............................................................., ........................... 8
2.2
Mathematical Models of Physical Systems ........................................ 8 2.2.1 Electrical Systems ................................................................. 9 2.2.2 Dual Networks ..................................................................... 14 2.2.3 Mechanical Systems ........................................................... 15 2.2.4 Analogous Systems ............................................................ 18 2.2.5 Gears ................................................................................... 24 2.2.6 Thermal Systems ................................................................ 27 2.2.7 Fluid Systems ...................................................................... 29
Contents 2.3
Block Diagrams of Closed Loop Syst~ms ........................................ 34 2.3.1 Block Diagram Reduction Techniques ............................... 35
2.4
Signal Flow Graph Representation of Control Systems ................. 42 2.4.1 Construction of a Signal Flow Graph for a System ........... 43 2.4.2 Mason's Gain Formula ....................................................... 44
2.5
Effects 2.5.1 2.5.2 2.5.3 2.5.4
2.6
Modelling of Elements of Control Systems ...................................... 59 2.6.1 DC Servo Motor .................................................................. 59 2.6.2 AC Servo Motors ................................................................. 63 2.6.3 Synchros ............................................................................. 65 2.6.4 AC Tacho Generator ........................................................... 68 2.6.5 DC Tacho Generator ....................