BEE Control System Principles 3

Question 1

The Nyquist stability criterion states that the number of unstable closed-loop poles equals:

Accepted Answer

The number of encirclements of -1+j0 minus open-loop RHP poles

Answer

N = Z - P, where N is net clockwise encirclements of -1, P is open-loop RHP poles, and Z is closed-loop RHP poles; solving for Z gives stability information.

Question 2

Which of the following describes a marginally stable system?

Accepted Answer

Poles on the imaginary axis with no repeated poles there

Answer

Marginal stability occurs when poles lie on the imaginary axis (non-repeated) and none are in the right-half plane, producing sustained oscillations.

Question 3

For the transfer function G(s) = 100/[(s+1)(s+10)], what is the DC gain?

Accepted Answer

10

Answer

DC gain is G(0) = 100/[(0+1)(0+10)] = 100/10 = 10.

Question 4

In root locus design, where do the branches begin and end as gain K goes from 0 to infinity?

Accepted Answer

From poles to zeros (finite or at infinity)

Answer

Root locus branches originate at open-loop poles (K=0) and terminate at open-loop zeros or at infinity (K→∞).

Question 5

An integrating element (1/s) in a control loop ensures zero steady-state error to which type of input?

Accepted Answer

Step

Answer

A single integrator (Type 1 system) eliminates steady-state error for step (position) inputs due to the infinite DC gain of the integrator.

BEE - Bachelor of Electrical Engineering Practice Test

BEE - Bachelor of Electrical Engineering Practice Test

BEE Control System Principles 3