A derivative term is the PID component whose control output follows how quickly the error changes. It provides anticipatory action, helping the controller respond before the error grows further. section 8.7
Room-temperature control
In a heater controller, error is the difference between the desired and measured room temperatures. The derivative term reacts to the rate of that difference: as temperature approaches the set point rapidly, it helps reduce overshoot. Increasing Kd typically decreases overshoot and settling time, while producing only a small change in rise time and steady-state error. section 8.7
Table 8.6 Effects of adding PID controller parameters on the system’s response (view table figure)
| Parameter |
Rise time |
Overshoot |
Settling time |
Steady-state error |
|---|---|---|---|---|
| Kp |
Decreases |
Increases |
Small change |
Decreases |
| Ki |
Decreases |
Increases |
Increases |
Decreases significantly |
| Kd |
Small change |
Decreases |
Decreases |
Small change |
Compare the typical effects of Kd with proportional and integral terms across rise time, overshoot, settling time, and steady-state error. section 8.7
