BME Control Systems

Question 1

What is the primary purpose of a feedback control system?

Accepted Answer

To compare the output with the desired value and reduce error

Answer

A feedback control system continuously compares the actual output to the desired setpoint and uses the resulting error to adjust the input, minimizing deviations.

Question 2

For a unity-feedback closed-loop system with forward transfer function G(s), the closed-loop transfer function T(s) is:

Accepted Answer

G(s) / (1 + G(s))

Answer

For unity feedback (H(s) = 1), the standard closed-loop formula G(s)H(s)/(1 + G(s)H(s)) reduces to G(s)/(1 + G(s)).

Question 3

A first-order system reaches what percentage of its final value at exactly one time constant (τ)?

Accepted Answer

63.2%

Answer

A first-order system follows an exponential step response y(t) = 1 − e^(−t/τ), which evaluates to 1 − e^(−1) ≈ 63.2% at t = τ.

Question 4

Steady-state error in a feedback control system is defined as:

Accepted Answer

The difference between desired and actual output as time approaches infinity

Answer

Steady-state error is the residual difference between the reference input and the actual system output after all transients have died out (t → ∞).

Question 5

Which system type can track a unit step reference with zero steady-state error without a proportional controller alone?

Accepted Answer

Type 1 system

Answer

A type-1 system contains one integrator in the open loop, which provides infinite DC gain and drives the steady-state error to zero for a step input.

BME - Bachelor of Mechanical Engineering Practice Test

BME - Bachelor of Mechanical Engineering Practice Test

BME Control Systems