JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV CONTROL SYSTEMS DESIGN Previous Question Paper (July/August-2022 - R18)

Time domain specifications are performance criteria used to evaluate the transient response of a control system to a unit step input. These parameters define the speed, stability, and accuracy of the system:

1. Delay Time (t_d): The time required for the response to reach 50% of its final value for the first time.
2. Rise Time (t_r): The time required for the response to rise from 0% to 100% (for underdamped systems, usually 10% to 90%) of its final value. It indicates the speed of the system.
3. Peak Time (t_p): The time required for the response to reach the first peak of the overshoot. It is inversely proportional to the natural frequency.
4. Maximum Peak Overshoot (M_p): The difference between the peak value and the steady-state value, expressed as a percentage. It is a measure of the relative stability of the system.
5. Settling Time (t_s): The time required for the response to reach and stay within a specified tolerance band (typically 2% or 5%) of the final value. It indicates how quickly the transient oscillations die out.

Adding poles to the open-loop transfer function of a system significantly alters its dynamic characteristics and stability:

• Stability Reduction: Adding poles to the left of the existing poles in the s-plane pulls the root locus toward the right half of the s-plane, which reduces the relative stability and gain margin of the system.
• Increased Oscillations: The addition of poles generally increases the maximum peak overshoot, leading to a more oscillatory transient response.
• Slower Response: Adding poles increases the order of the system, which typically increases the settling time and decreases the speed of the response.
• Bandwidth Reduction: The system bandwidth is reduced, making the system less capable of tracking high-frequency signals.