An integral term is the PID component whose control output reflects both the magnitude and duration of accumulated error—the area under the error curve. It helps reduce steady-state error, though increasing its gain can also increase overshoot and settling time. section 8.7
Room-temperature control
In a heater controller, persistent room-temperature error accumulates over time. The integral contribution therefore grows while the measured temperature remains below the set point, helping the system reach the desired steady state. section 8.7
Figure 8.17 PID-based closed-loop control system—the PID controller takes the error signal and produces a control signal to reduce the error to zero.
Use the closed-loop diagram to trace how temperature error becomes a heater control signal. section 8.7
