EC-404 RGPV B.Tech
Control System (CS)
Previous year papers and the official syllabus are free to read, no account needed.
Previous Year Papers
7 papers, latest Jun 2026
- EC-404 paper, Jun 2026
- EC-404 paper, Jun 2025
- EC-404 paper, Dec 2024
- EC-404 paper, Jun 2024
- EC-404 paper, Nov 2023
- EC-404 paper, Jun 2023
Syllabus, notes and important questions for EC-404
Syllabus units
Topics as the official RGPV syllabus lists them.
Unit 1 Introduction to Control system 11 topics
- Terminology and classification of control system
- Examples of control system
- Mathematical modeling of mechanical and electrical systems
- Differential equations
- Transfer function
- Block diagram representation and reduction
- Signal flow graph techniques
- Feedback characteristics of control systems: open loop and closed loop systems
- Effect of feedback on control system and on external disturbances
- Linearization effect of feedback
- Regenerative feedback
Unit 2 Time response analysis 12 topics
- Standard test signals
- Time response of 1st order system
- Time response of 2nd order system
- Steady-state errors and error constants
- Effects of addition of poles and zeros to open loop and closed loop system
- Concept of stability of linear systems
- Effects of location of poles on stability
- Necessary conditions for stability
- Routh-Hurwitz stability criteria
- Relative stability analysis
- Root Locus concept
- Guidelines for sketching Root-Locus
Unit 3 Frequency response analysis 8 topics
- Correlation between time and frequency response
- Polar plots
- Bode plots
- All-pass and minimum-phase systems
- Log-magnitude versus Phase-Plots
- Closed-loop frequency response
- Nyquist stability criterion
- Assessment of relative stability using Nyquist plot and Bode plot (phase margin, gain margin and stability)
Unit 4 Approaches to system design 6 topics
- Design problem
- Compensation techniques
- Design of phase-lag compensator
- Design of phase-lead compensator
- Design of phase lead-lag compensator in time and frequency domain
- Proportional, derivative, integral and composite controllers
Unit 5 State space representation of systems 7 topics
- State space representation of systems
- Block diagram for state equation
- Transfer function decomposition
- Solution of state equation
- Transfer matrix
- Relationship between state equation and transfer function
- Controllability and observability
Exam insights
Counted from 8 past EC-404 papers.
Marks asked per paper, by unit
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Unit 1 Introduction to Control system 27 marks
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Unit 2 Time response analysis 25 marks
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Unit 3 Frequency response analysis 20 marks
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Unit 4 Approaches to system design 18 marks
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Unit 5 State space representation of systems 16 marks
Average marks of the questions from each unit in one paper. You answer only some of them, so the total is more than the paper’s maximum.
Asked again and again
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Explain proportional (P), integral (I), derivative (D) and composite / PID controllers
Asked 6 times: 2026, 2025, 2024, 2023
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Find / determine the transfer function $Y(s)/U(s)$ from a given signal flow graph using Mason's gain formula.
Asked 4 times: 2025, 2024, 2023
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Using Nyquist criterion, determine closed-loop stability for a given open-loop transfer function $G(s)H(s)$.
Asked 3 times: 2025, 2024