Control Theory MCQs Aeronautical Engineering

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What does PID stand for in control systems? A) Proportional-Integral-Derivative B) Proportional-Integration-Differentiation C) Proportional-Inductive-Differential D) Proportional-Inverse-Differential Answer: A) Proportional-Integral-Derivative 2. In control systems, what is the primary function of the Proportional (P) term in a PID controller? A) To eliminate steady-state error B) To provide a corrective action proportional to the error C) To integrate the error over time D) To differentiate the error Answer: B) To provide a corrective action proportional to the error 3. What does the Integral (I) term in a PID controller do? A) Corrects the system for steady-state error B) Provides a proportional correction based on the error C) Differentiates the error with respect to time D) Reduces the oscillatory behavior Answer: A) Corrects the system for steady-state error 4. The Derivative (D) term in a PID controller is used to: A) Predict future error based on its rate of change B) Eliminate steady-state error C) Integrate the error over time D) Provide a steady proportional response Answer: A) Predict future error based on its rate of change 5. In aeronautical control systems, what does the term ‘stability’ refer to? A) The ability of the system to return to equilibrium after a disturbance B) The system’s ability to track a reference signal C) The system’s response time D) The system’s ability to handle multiple inputs Answer: A) The ability of the system to return to equilibrium after a disturbance 6. Which theorem is used to analyze the stability of control systems using frequency response? A) Routh-Hurwitz theorem B) Nyquist theorem C) Bode theorem D) Laplace theorem Answer: B) Nyquist theorem 7. What is the purpose of a ‘lead compensator’ in control systems? A) To improve the phase margin and speed up the response B) To reduce steady-state error C) To introduce lag in the system response D) To increase the system’s gain margin Answer: A) To improve the phase margin and speed up the response 8. In control theory, what does ‘Bode plot’ represent? A) The frequency response of a system B) The time-domain response of a system C) The state-space representation D) The root locus of a system Answer: A) The frequency response of a system 9. Which parameter is used to measure the system’s ability to follow a reference signal? A) Gain margin B) Phase margin C) Tracking error D) Rise time Answer: C) Tracking error 10. In the Laplace domain, what does the transfer function of a system represent? sql Copy code – A) The relationship between the output and input of the system – B) The time response of the system – C) The stability of the system – D) The phase response of the system – **Answer:** A) The relationship between the output and input of the system 11. In control systems, what does ‘overshoot’ refer to? markdown Copy code – A) The amount by which the response exceeds the desired value – B) The time it takes for the system to reach the steady-state value – C) The distance traveled by the system before settling – D) The rate of change of the system’s output – **Answer:** A) The amount by which the response exceeds the desired value 12. What is a ‘pole’ in the context of control systems? sql Copy code – A) A value of s in the transfer function where the function becomes infinite – B) A value of s where the transfer function is zero – C) A parameter that affects the gain of the system – D) A point where the phase of the transfer function is zero – **Answer:** A) A value of s in the transfer function where the function becomes infinite 13. What is the main advantage of using state-space representation in control systems? less Copy code – A) It allows for a more comprehensive analysis of multi-input, multi-output systems – B) It simplifies the frequency domain analysis – C) It directly provides the time-domain response – D) It makes the design of compensators easier – **Answer:** A) It allows for a more comprehensive analysis of multi-input, multi-output systems 14. What is ‘root locus’ used for in control systems? sql Copy code – A) To analyze how the roots of the system change with variations in system parameters – B) To determine the stability of the system in the frequency domain – C) To design the PID controller parameters – D) To measure the time-domain response of the system – **Answer:** A) To analyze how the roots of the system change with variations in system parameters 15. What does ‘frequency response’ of a control system describe? css Copy code – A) How the system responds to different frequencies of input signals – B) The system’s response to a step input – C) The system’s stability over time – D) The transient response of the system – **Answer:** A) How the system responds to different frequencies of input signals 16. In control systems, what does the term ‘phase margin’ indicate? markdown Copy code – A) The amount of additional phase lag that can be tolerated before the system becomes unstable – B) The maximum phase shift of the system’s response – C) The speed of the system’s response – D) The maximum gain the system can handle – **Answer:** A) The amount of additional phase lag that can be tolerated before the system becomes unstable 17. Which method is commonly used for designing compensators in control systems? markdown Copy code – A) Root locus method – B) Frequency response method – C) Time-domain method – D) State-space method – **Answer:** B) Frequency response method 18. In control systems, what does ‘dead time’ refer to? sql Copy code – A) The time delay between the application of a control input and the response of the system – B) The period when the system is inactive – C) The time it takes for the system to reach equilibrium – D) The duration of the transient response – **Answer:** A) The time delay between the application of a control input and the response of the system 19. What does the term ‘stability margin’ refer to in control systems? markdown Copy code – A) The amount of deviation from nominal conditions that the system can tolerate before becoming unstable – B) The maximum allowable gain before instability occurs – C) The maximum allowable phase shift before instability occurs – D) The speed of the system’s response to changes in input – **Answer:** A) The amount of deviation from nominal conditions that the system can tolerate before becoming unstable 20. In a control system, what does ‘gain crossover frequency’ signify? vbnet Copy code – A) The frequency at which the open-loop gain is equal to one – B) The frequency at which the phase margin is zero – C) The frequency at which the closed-loop system has a crossover point – D) The frequency at which the gain is at its maximum – **Answer:** A) The frequency at which the open-loop gain is equal to one 21. What does the term ‘Nyquist plot’ represent? less Copy code – A) A plot of the frequency response of a system – B) A plot of the time-domain response of the system – C) A plot of the root locus of the system – D) A plot of the state-space representation – **Answer:** A) A plot of the frequency response of a system 22. In control theory, what is the purpose of a ‘lag compensator’? vbnet Copy code – A) To improve the stability of the system and reduce high-frequency noise – B) To increase the system’s response speed – C) To reduce the steady-state error – D) To introduce phase lead into the system – **Answer:** A) To improve the stability of the system and reduce high-frequency noise 23. What does the term ‘zero-pole plot’ represent? less Copy code – A) A plot showing the locations of poles and zeros of a transfer function in the s-plane – B) A plot of the system’s response to a step input – C) A plot of the system’s phase response – D) A plot of the system’s gain margin – **Answer:** A) A plot showing the locations of poles and zeros of a transfer function in the s-plane 24. What is ‘adaptive control’ in aeronautical systems? less Copy code – A) A control strategy that adjusts its parameters based on changes in the system dynamics – B) A control method that uses fixed parameters for all operating conditions – C) A method for controlling the system based on pre-defined rules – D) A technique to eliminate all system disturbances – **Answer:** A) A control strategy that adjusts its parameters based on changes in the system dynamics 25. What does the term ‘control effort’ refer to in control systems? css Copy code – A) The input required to achieve the desired system response – B) The system’s output response to a given input – C) The effort needed to design the control system – D) The time it takes for the system to reach the steady-state – **Answer:** A) The input required to achieve the desired system response 26. In a control system, what is meant by ‘steady-state error’? markdown Copy code – A) The difference between the desired output and the actual output when the system reaches a steady state – B) The error present during the transient response – C) The rate of change of the system output – D) The error in the system’s response to sudden changes – **Answer:** A) The difference between the desired output and the actual output when the system reaches a steady state 27. What is ‘bode stability criterion’ used for? css Copy code – A) To determine the stability of a control system based on its frequency response – B) To design the PID controller parameters – C) To analyze the time-domain response of the system – D) To calculate the state-space representation – **Answer:** A) To determine the stability of a control system based on its frequency response 28. What does ‘phase lead compensator’ do to the system’s frequency response? markdown Copy code – A) It increases the phase margin and improves system stability – B) It decreases the phase margin and slows down the response – C) It reduces the steady-state error without affecting stability – D) It introduces a lag in the system’s response – **Answer:** A) It increases the phase margin and improves system stability 29. In control systems, what is ‘closed-loop transfer function’? sql Copy code – A) The transfer function of a system with feedback applied – B) The transfer function of the system without feedback – C) The transfer function of the system’s open-loop response – D) The transfer function describing the input-output relationship without any control actions – **Answer:** A) The transfer function of a system with feedback applied 30. What is the ‘root locus’ method primarily used for? css Copy code – A) To analyze how the location of the poles of a system changes with varying feedback gains – B) To design frequency domain compensators – C) To compute the state-space matrices – D) To measure the transient response of the system – **Answer:** A) To analyze how the location of the poles of a system changes with varying feedback gains 31. What is the primary advantage of using state feedback control? markdown Copy code – A) It can improve the system’s performance and stability by placing the poles at desired locations – B) It simplifies the controller design process – C) It reduces the computational complexity of the control system – D) It directly improves the system’s frequency response – **Answer:** A) It can improve the system’s performance and stability by placing the poles at desired locations 32. What does ‘tracking’ refer to in control systems? less Copy code – A) The system’s ability to follow a reference input accurately – B) The measurement of the system’s stability – C) The rate at which the system responds to changes in input – D) The analysis of the system’s phase response – **Answer:** A) The system’s ability to follow a reference input accurately 33. What does ‘time constant’ represent in a first-order system? sql Copy code – A) The time required for the system’s response to reach approximately 63.2% of the final value – B) The time it takes for the system to reach steady-state – C) The duration of the system’s transient response – D) The maximum time the system can handle before becoming unstable – **Answer:** A) The time required for the system’s response to reach approximately 63.2% of the final value 34. In control systems, what is the purpose of a ‘lead-lag compensator’? vbnet Copy code – A) To combine the effects of both lead and lag compensators to improve the system’s stability and performance – B) To directly increase the system’s gain margin – C) To eliminate the steady-state error of the system – D) To simplify the design of the controller – **Answer:** A) To combine the effects of both lead and lag compensators to improve the system’s stability and performance 35. What does the term ‘closed-loop stability’ mean? perl Copy code – A) The system’s ability to remain stable when feedback is applied – B) The system’s performance in the open-loop configuration – C) The system’s response to disturbances in the absence of feedback – D) The stability of the system’s frequency response – **Answer:** A) The system’s ability to remain stable when feedback is applied 36. What is the primary characteristic of a ‘second-order system’? vbnet Copy code – A) The system’s response is governed by two poles in the s-plane – B) The system’s response is influenced by three poles and zeros – C) The system’s behavior is determined by a single pole – D) The system exhibits a time response similar to a first-order system – **Answer:** A) The system’s response is governed by two poles in the s-plane 37. What does the term ‘transient response’ refer to in control systems? perl Copy code – A) The system’s response to changes before reaching a steady-state – B) The system’s steady-state output – C) The system’s response to a sinusoidal input – D) The long-term behavior of the system – **Answer:** A) The system’s response to changes before reaching a steady-state 38. Which term describes the time it takes for the system response to reach and stay within a specified range of the final value? less Copy code – A) Settling time – B) Rise time – C) Peak time – D) Delay time – **Answer:** A) Settling time 39. In control theory, what does the term ‘system damping’ refer to? sql Copy code – A) The system’s ability to reduce oscillations and return to equilibrium – B) The system’s response to high-frequency input – C) The system’s ability to handle multiple inputs – D) The rate at which the system’s gain decreases over time – **Answer:** A) The system’s ability to reduce oscillations and return to equilibrium 40. What is the ‘Nyquist criterion’ used to determine? perl Copy code – A) The stability of the system based on the frequency response – B) The time-domain response of the system – C) The state-space representation of the system – D) The transient behavior of the system – **Answer:** A) The stability of the system based on the frequency response 41. Which of the following is a characteristic of a ‘lead compensator’? markdown Copy code – A) It increases the phase margin and improves the system’s transient response – B) It decreases the system’s gain margin and introduces lag – C) It eliminates the steady-state error without affecting stability – D) It directly influences the system’s time constant – **Answer:** A) It increases the phase margin and improves the system’s transient response 42. In a control system, what is the effect of increasing the system gain? markdown Copy code – A) It typically improves the system’s speed of response but can decrease stability – B) It decreases the system’s responsiveness – C) It eliminates all transient behavior – D) It directly affects the system’s steady-state error without altering stability – **Answer:** A) It typically improves the system’s speed of response but can decrease stability 43. What does ‘gain margin’ measure in control systems? markdown Copy code – A) The amount by which the gain can be increased before the system becomes unstable – B) The maximum allowable phase shift before instability occurs – C) The speed at which the system’s response changes – D) The maximum time required for the system to reach steady-state – **Answer:** A) The amount by which the gain can be increased before the system becomes unstable 44. What is the main purpose of a ‘lag compensator’ in control systems? vbnet Copy code – A) To improve the system’s steady-state accuracy and reduce high-frequency noise – B) To introduce phase lead to enhance the transient response – C) To directly increase the system’s gain margin – D) To reduce the system’s response time – **Answer:** A) To improve the system’s steady-state accuracy and reduce high-frequency noise 45. What is the ‘phase crossover frequency’? vbnet Copy code – A) The frequency at which the phase angle of the system’s open-loop transfer function is -180 degrees – B) The frequency where the system’s gain margin is maximized – C) The frequency where the system’s gain crosses zero – D) The frequency at which the system’s response becomes stable – **Answer:** A) The frequency at which the phase angle of the system’s open-loop transfer function is -180 degrees 46. What does ‘open-loop transfer function’ represent in a control system? sql Copy code – A) The transfer function of the system without feedback – B) The transfer function including feedback – C) The function describing the system’s response to disturbances – D) The transfer function of the controller alone – **Answer:** A) The transfer function of the system without feedback 47. What is the ‘pole-zero plot’ used for in control systems? vbnet Copy code – A) To analyze the system’s stability and transient response – B) To design the system’s control gains – C) To compute the system’s steady-state error – D) To measure the system’s time constant – **Answer:** A) To analyze the system’s stability and transient response 48. Which type of compensator is used to improve the stability and transient response by adding phase lead? markdown Copy code – A) Lead compensator – B) Lag compensator – C) Proportional compensator – D) Integral compensator – **Answer:** A) Lead compensator 49. What is the function of a ‘PID controller’ in a control system? css Copy code – A) To provide proportional, integral, and derivative control actions to improve system performance – B) To analyze the system’s frequency response – C) To design compensators for the system – D) To measure the system’s phase margin – **Answer:** A) To provide proportional, integral, and derivative control actions to improve system performance 50. What does the ‘root locus’ technique primarily analyze? perl Copy code – A) The behavior of the system poles as the feedback gain varies – B) The effect of noise on the system’s output – C) The time-domain response of the system – D) The stability of the open-loop system – **Answer:** A) The behavior of the system poles as the feedback gain varies

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