BEE BEE Bachelor of Electrical Engineering Control System Principles Questions and Answers 2 — Questions and Answers
Question 1: What is the primary purpose of a lead compensator in a control system?
- To improve transient response by adding phase lead (Correct answer)
- To eliminate steady-state error entirely
- To reduce the system bandwidth
- To convert an open-loop system to closed-loop
Correct answer: To improve transient response by adding phase lead
A lead compensator adds positive phase to the system near the crossover frequency, improving transient response and stability margins.
Question 2: In a Bode plot, what does a slope of -40 dB/decade indicate about the system's transfer function?
- Two poles at that frequency range (Correct answer)
- A single pole and a single zero
- A single integrator
- A derivative term
Correct answer: Two poles at that frequency range
Each pole contributes -20 dB/decade, so -40 dB/decade indicates two poles are dominating in that frequency range.
Question 3: Which criterion determines the absolute stability of a linear time-invariant system by examining the characteristic equation coefficients?
- Routh-Hurwitz criterion (Correct answer)
- Nyquist criterion
- Bode stability criterion
- Gain margin criterion
Correct answer: Routh-Hurwitz criterion
The Routh-Hurwitz criterion uses the coefficients of the characteristic polynomial to determine whether all roots lie in the left-half plane.
Question 4: What does a phase margin of 0 degrees indicate about a feedback control system?
- The system is on the verge of instability (Correct answer)
- The system is overdamped
- The system has infinite gain margin
- The system has zero steady-state error
Correct answer: The system is on the verge of instability
A phase margin of 0 degrees means the open-loop phase is exactly -180 degrees at the gain crossover frequency, placing the system at the boundary of instability.
Question 5: In state-space representation, what does the controllability matrix being full rank guarantee?
- The system state can be driven to any desired state using the input (Correct answer)
- The system output can be measured from all states
- The system is asymptotically stable
- The system has no transmission zeros
Correct answer: The system state can be driven to any desired state using the input
Full rank of the controllability matrix ensures that every state is reachable from any initial condition through appropriate input signals.
Question 6: What effect does adding a pole at the origin to an open-loop transfer function have on system type?
- It increases the system type by one (Correct answer)
- It decreases the system type by one
- It has no effect on system type
- It makes the system type zero
Correct answer: It increases the system type by one
Adding a pole at the origin increases the number of free integrators, raising the system type by one and improving steady-state error performance.
BEE BEE Bachelor of Electrical Engineering Control System Principles Questions and Answers 2
What is the primary purpose of a lead compensator in a control system?