Control System Statements Analysis

This question requires evaluating the definitions and characteristics of open-loop and closed-loop control systems based on given statements.

Statement Evaluation

• Statement A: "In any open loop control system, the output is not compared with the reference input."
  • Analysis: This is the fundamental definition of an open-loop system. The control action is independent of the system's output.
  • Verdict: Correct
• Statement B: "Traffic control by means of signals operated on a time basis is an example of closed loop control."
  • Analysis: Traffic signals operating on a fixed timer without sensing traffic flow are open-loop systems. They do not use feedback to adjust signal timing based on the output (traffic congestion).
  • Verdict: Incorrect
• Statement C: "Closed loop control always implies the use of feedback control action in order to reduce system error."
  • Analysis: Feedback is the core component of closed-loop systems, enabling comparison between the desired output (reference input) and the actual output to calculate and minimize the error.
  • Verdict: Correct
• Statement D: "Washing machine is an example of open loop system."
  • Analysis: A standard washing machine operates on pre-set timings for different cycles (wash, rinse, spin) without measuring the cleanliness of clothes. This lack of output measurement and feedback makes it an open-loop system.
  • Verdict: Correct
• Statement E: "Stability is a major concern in open loop control system."
  • Analysis: Stability is primarily a critical concern in closed-loop systems, where feedback can potentially lead to oscillations or instability. Open-loop systems are generally stable unless their components have inherent instability issues.
  • Verdict: Incorrect

Conclusion

Based on the analysis, statements A, C, and D are correct. Therefore, the option including only these statements is the correct answer.