Feedback Systems Questions and Answers for Viva

Answer-1: A feedback system is a control system where a portion of the output is "fed back" to the input to regulate the system's behavior.

Answer-2: Feedback is primarily used to regulate or control the output of a system, ensuring it remains stable and/or follows a desired setpoint.

Answer-3: The two main types of feedback are negative feedback and positive feedback.

Answer-4: Negative feedback reduces the output deviation from the desired setpoint by feeding a portion of the output signal back to the input in such a way that it opposes the input signal.

Answer-5: Negative feedback improves stability, accuracy, and disturbance rejection in control systems.

Answer-6: An example of a system with negative feedback is a thermostat controlling the temperature of a room. As the room temperature deviates from the setpoint, the thermostat adjusts the heating or cooling system to bring it back to the desired temperature.

Answer-7: Positive feedback amplifies the output deviation from the setpoint, leading to instability or oscillation in the system.

Answer-8: Positive feedback can lead to instability, oscillation, and even system failure if left unchecked.

Answer-9: Loop gain represents the overall gain of the feedback loop and determines the stability and performance of the system.

Answer-10: High loop gain can lead to instability or oscillations in a system, while low loop gain can result in sluggish response or poor disturbance rejection.

Answer-11: A compensator is used to adjust the loop gain and improve the stability, performance, or transient response of a feedback system.

Answer-12: Feedback control adjusts the system's output based on its current state, while feedforward control anticipates disturbances and adjusts the system's input accordingly.

Answer-13: In an open-loop system, the output is not directly influenced by the system's performance, while in a closed-loop system, the output is continuously monitored and adjusted based on feedback.

Answer-14: Gain margin represents the amount of gain that can be increased before the system becomes unstable, while phase margin represents the amount of phase shift that can be introduced before instability occurs.

Answer-15: Series-Series Feedback Systems, also known as series current feedback, operates as a voltage-current controlled feedback system. In the series current configuration the feedback error signal is in series with the input and is proportional to the load current, Iout.

Answer-16: Shunt-Shunt Feedback Systems, also known as shunt voltage feedback, operates as a current-voltage controlled feedback system. In the shunt-shunt feedback configuration the signal fed back is in parallel with the input signal. 

Answer-17: Shunt-Series Feedback, also known as shunt current feedback, operates as a current-current controlled feedback system. The feedback signal is proportional to the output current, Io flowing in the load. The feedback signal is fed back in parallel or shunt with the input.

Answer-18: Series-Shunt Feedback, also known as series voltage feedback, operates as a voltage-voltage controlled feedback system. The error voltage fed back from the feedback network is in series with the input. The voltage which is fed back from the output being proportional to the output voltage, Vo as it is parallel, or shunt connected.