Assignment 02– Control System & PLC

 

Assignment – Control System & PLC 

Course: Electrical Engineering Semester: 4 Subject: Control System & PLC **Assignment No.: 02 Maximum Marks: 20 Submission Date: 22/04/2026

Instructions

• Answer all questions neatly with proper diagrams wherever required.

• Use standard notation and units.

• Each question carries equal marks unless specified.

• Show all steps in derivations and numerical problems.

Part A – Short Answer Questions (Any five) (2 Marks Each)

1. Explain the difference between open‑loop and closed‑loop control systems with examples.

2. Define transfer function and explain its importance in system analysis.

3. State the advantages of frequency response analysis over time domain analysis.

4. What is the significance of block diagram reduction in control systems?

5. List the advantages of PLCs compared to conventional relay logic.

6. Explain the role of timers and counters in PLC programming.

7. Write a simple ladder logic program for a lamp controlled by a switch.

Part B – Long Answer Questions (Any two) (5 Marks Each)

1. Derive the transfer function of a control system using block diagram reduction and signal flow graph.

2. Explain the Routh–Hurwitz stability criterion. Discuss how it determines system stability.

3. Draw and explain the construction and working of a PLC. Mention its industrial applications.

4. Write and explain a ladder diagram program for motor control with start/stop push buttons and overload protection.

5. Describe the advanced PLC instructions (Timers, Counters, Shift Registers, Sequencers) with examples.

                                         OR

Numerical Problems (5 Marks Each)

1. Routh–Hurwitz Criterion: For the characteristic equation:

$$s^4+2s^3+3s^2+4s+5=0$$

Construct the Routh array and determine the stability of the system.

2. Bode Plot: Draw the Bode plot for the transfer function:

$$G(s)=\frac{10}{s(1+0.1s)}$$

Determine the gain margin and phase margin from the plot.

Submission Guidelines

• Attach the assignment sheets with a cover page (Name, Roll No., Semester, Subject).

• Use proper diagrams, equations, and references.

• Late submission will result in deduction of marks.