ME-314 Introduction to Control Engineering is a course taught to Mechanical Engineering senior undergrads. The course is taught by Dr. Bilal Siddiqui at DHA Suffa University. This lecture is about block diagram reduction for finding closed loop transfer functions.

1. ME-314 Control Engineering
Dr. Bilal A. Siddiqui
Mechanical Engineering
DHA Suffa University

2. Block Diagrams and Their Utility
• With transfer functions, it is easy to represent interconnected
components of a system graphically.
• Each transfer function is represented as a block, with inputs
and outputs.
• Output of one subsystem may serve as the input of another
subsystem, and vice versa.

3. Summing, Branch Takeoff Points
• Summing points
• Takeoff points

4. Block Diagram of an Industrial Control
System (Ogata)

5. Block Diagram of a General Close
Loop System

6. Close Loop Transfer Function

7. Characteristic Equation of Close
Loop Transfer Function
Characteristic equation
is important since it
determines stability, as
we will see.

8. Block Diagram Reduction

11. Example

13. Another Example

15. Another Example
Hint: bottom loop does not have feedback. Why?

19. Superposition of Multiple Inputs

20. Multiple Input Single Output
Systems (MISO)

23. HW 3a

24. HW 3b
Obtain transfer function C(s)/R(s)

25. HW 3d
• Obtain expression for C(s) when both R(s) and
D(s) are present