Derivative control action: Too much will cause which type of closed-loop response?

Derivative control action: Too much will cause which type of closed-loop response?

• A. No effect on the response
• B. Overshoot
• C. Underdamped oscillations
• D. Stairstep shaped closed-loop response

Answer: (D)

Derivative action aims to anticipate future error by reacting to the rate at which the error is changing, which helps damp the response and speed up settling. But when the derivative gain is too large, the controller becomes extremely sensitive to high-frequency components, such as measurement noise or rapid, small disturbances. In a real system with discrete sampling or actuator quantization, those rapid signals are captured as a series of distinct updates. The controller then drives the actuator in noticeable steps rather than a smooth curve, producing a stairstep shaped closed-loop response. In other words, excessive derivative action magnifies rapid changes and discretization effects, so the output ends up jumping in steps instead of following a smooth trajectory.

Derivative action aims to anticipate future error by reacting to the rate at which the error is changing, which helps damp the response and speed up settling. But when the derivative gain is too large, the controller becomes extremely sensitive to high-frequency components, such as measurement noise or rapid, small disturbances. In a real system with discrete sampling or actuator quantization, those rapid signals are captured as a series of distinct updates. The controller then drives the actuator in noticeable steps rather than a smooth curve, producing a stairstep shaped closed-loop response. In other words, excessive derivative action magnifies rapid changes and discretization effects, so the output ends up jumping in steps instead of following a smooth trajectory.