ME or MEng Master of Engineering Control Systems and Dynamics

Question 1

How is the transfer function of a linear time-invariant system formally defined?

Accepted Answer

The ratio of the Laplace transform of output to input with zero initial conditions

Answer

The transfer function is the Laplace transform of the output divided by the Laplace transform of the input, assuming all initial conditions are zero.

Question 2

In a closed-loop control system, what is the primary purpose of feedback?

Accepted Answer

To compare the output with the desired input and reduce error

Answer

Feedback compares the actual output with the reference input to generate an error signal, which the controller uses to drive the error toward zero.

Question 3

A PID controller combines which three control actions?

Accepted Answer

Proportional, Integral, and Derivative

Answer

PID stands for Proportional, Integral, and Derivative — actions that reduce error magnitude, eliminate steady-state offset, and improve transient response, respectively.

Question 4

What is the steady-state error to a step input for a Type 1 control system?

Accepted Answer

Zero

Answer

A Type 1 system contains one open-loop integrator, which drives the steady-state error to zero for a step (position) input.

Question 5

In the s-domain, what is the transfer function of an ideal differentiator?

Accepted Answer

s

Answer

Differentiation in the time domain corresponds to multiplication by s in the Laplace domain, so the transfer function of a differentiator is simply s.

ME or MEng Master of Engineering Practice Test

ME or MEng Master of Engineering Practice Test

ME or MEng Master of Engineering Control Systems and Dynamics