BEE Bachelor of Electrical Engineering Control Systems Theory Questions and Answers

Question 1

A closed-loop control system has a characteristic equation given by s³ + 2s² + 4s + K = 0. For the system to remain stable, what is the valid range for the gain K?

Accepted Answer

0 < K < 8

Answer

K > 8

Answer

K < 0

Answer

The system is always unstable

Question 2

In a Proportional-Integral-Derivative (PID) controller, what is the primary function of the integral (I) term?

Accepted Answer

To eliminate steady-state error for step inputs.

Answer

To anticipate future error and improve transient response by reducing overshoot.

Answer

To decrease the system's rise time and increase speed of response.

Answer

To provide an initial corrective action proportional to the current error.

Question 3

A unity feedback control system is subjected to a unit ramp input, r(t) = t. The system is observed to have a constant, finite steady-state error. Based on this observation, what is the 'type' of the system?

Accepted Answer

Type 1

Answer

Type 0

Answer

Type 2

Answer

The system type cannot be determined from this information.

Question 4

Which of the following statements accurately describes a fundamental property of a root locus plot for a feedback control system?

Accepted Answer

The root locus branches start at the open-loop poles and terminate at the open-loop zeros or at infinity.

Answer

The root locus is the path of the open-loop poles as a system parameter is varied.

Answer

The root locus plot is always symmetric with respect to the imaginary axis.

Answer

The number of branches of the root locus is equal to the number of open-loop zeros.

Question 5

An engineer analyzes the Bode plot of a minimum-phase, open-loop transfer function G(s)H(s). The gain margin is found to be 10 dB and the phase margin is 45 degrees. What does this imply about the stability of the corresponding closed-loop system?

Accepted Answer

The closed-loop system is stable.

Answer

The closed-loop system is unstable.

Answer

The closed-loop system is marginally stable.

Answer

Stability cannot be determined without the Nyquist plot.

Question 6

Which of the following is a primary advantage of using the state-space representation of a system over the classical transfer function representation?

Accepted Answer

It provides a complete representation of the system's internal states, not just the input-output relationship.

Answer

It is only applicable to single-input, single-output (SISO) systems.

Answer

It simplifies frequency response analysis by directly providing Bode plots.

Answer

It is only applicable to linear time-invariant (LTI) systems.