🔍 Key Concepts

• Proportional, integral, and derivative (PID) control actions in automatic control systems • How each action responds differently: to present error, accumulated past error, or rate of change of error • Meaning of "speed at which the controlled variable is changing" in control theory

💭 Think About

• Ask yourself: which type of control action looks at how fast the process variable is changing, rather than just how big the error is right now or how long it has existed? • Think about which option is associated with the rate of change (slope) of the error signal, like predicting where the error is heading. • Eliminate the choice that deals with accumulated (summed over time) error, and the one that deals only with present error.

✅ Before You Answer

• Verify which action corresponds to rate of change of the error signal. • Confirm which term in PID control is associated with predictive or damping behavior in response to rapid changes. • Make sure you are not mixing up integral (area under the curve over time) with the one that looks at how steeply the curve is changing.