ALPHABETIC REFERENCE EXCEL CARE CONTROL ICONS
74-5577–33 (US) 196
EN2B-0184 GE51 R0518 (Europe)
PD Controller To use the proportional and derivative terms of the PID controller, set Integral action
time to zero. Input the other parameters as explained for the P Controller.
PID Controller Parameter
Settings The PID controller is the fastest controller that can completely stabilize a deviation.
The following diagrams show the stabilization of setpoint jumps with a PID controller
that is set optimally.
The following three graphs show the effects of all three modes on the controlled
variable at system start-up. With proportional control (Fig. 1), the output is a function
of the deviation of the controlled variable from the setpoint. As the control point
stabilizes, offset occurs. With the addition of integral control (Fig. 2), the control
point returns to setpoint over a period of time with some degree of overshoot. The
significant difference is the elimination of offset after the system has stabilized.
Figure 3 shows that adding the derivative element reduces overshoot and
decreases response time.
Fig. 1. Proportional Control.
Fig. 2. Proportional-Integral Control.
Fig. 3. Proportional-Integral-Derivative Control.
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