BEE Bachelor of Electrical Engineering Control System Principles Questions and Answers Flashcards

Which method graphically represents all possible closed-loop pole locations as a parameter (typically gain) varies from zero to infinity?

Answer: Root locus method

The root locus method traces the paths of closed-loop poles in the s-plane as the loop gain varies from zero to infinity.

For a second-order underdamped system, which parameter directly determines the frequency of oscillation in the transient response?

Answer: Damped natural frequency

The damped natural frequency equals the undamped natural frequency multiplied by the square root of one minus the damping ratio squared, and it sets the oscillation frequency.

What is the transfer function of a PID controller in the Laplace domain?

Answer: Kp + Ki/s + Kd·s

A PID controller combines proportional, integral, and derivative actions, yielding the standard form Kp + Ki/s + Kd·s in the Laplace domain.

In the Nyquist stability criterion, what must be counted to determine closed-loop stability?

Answer: Encirclements of the -1+j0 point by the Nyquist plot

The Nyquist criterion relates the number of encirclements of -1+j0 to the difference between open-loop and closed-loop right-half-plane poles.

What does the term 'observability' refer to in state-space control theory?

Answer: The ability to determine all internal states from output measurements

Observability means that every internal state of the system can be inferred from knowledge of the output and input over a finite time interval.

What is the steady-state error of a Type 1 system subjected to a unit ramp input?

Answer: 1/Kv, where Kv is the velocity error constant

A Type 1 system has one integrator, giving a finite steady-state error of 1/Kv for a ramp input, where Kv is the velocity error constant.