🔍 Key Concepts

• Closed-loop control system – how the system measures the output and compares it to the setpoint to get an error signal • The basic idea of proportional control (P-control) in relation to the size (magnitude) of that error at any instant • Difference between proportional, integral, and derivative control actions

💭 Think About

• Ask yourself: in proportional control, what quantity is the controller’s output directly tied to at any given moment? • Which choice describes something that depends on the instantaneous size of the error, not its history and not how fast it is changing? • Look for the option that best distinguishes proportional action from integral (past error) and derivative (rate of change of error) actions.

✅ Before You Answer

• Identify which option sounds like integral control (accumulation of error over time) and rule it out for this question. • Identify which option describes derivative control (related to how fast the error is changing) and rule it out. • Confirm that the remaining option links the controller’s output directly and immediately to the present value of the error.