Appendix 2, Pid Theory And Adjustment; Pid Controller Theory - Idex Pulsafeeder MPC Vector Installation, Operation & Maintenance Manual

22. Appendix 2, PID Theory and Adjustment

The PID control method allows the MPC Vector to accurately maintain a specific desired set point for flow rate from
the pump it is connected to.
The PID Control Loop is a widely accepted general purpose control algorithm which is built into the MPC Vector. A
PID control loop consists of three components which each have their own specific responsibilities in the control loop;
the Proportional, Integral, and Derivative components. Although these mathematical terms are derived from calculus,
and are internally implemented as such, the PID can be tuned without using a calculator by simply understanding the
roles each of the three components play. Note that if you aren't interested in a semi-technical discussion of PID
Control Loops you can skip ahead to Section 21.3.
22.1

PID Controller Theory:

The basic PID Control Loop consists of an input command, the control system, and feedback (see diagram, following
page). The user enters an input flow rate. This command is sent through the control system which decides what the
new motor speed should be. That motor speed command is sent to the pump which then changes the output rate. A
flow meter at the output of the pump measures the output flow and feeds the data back to the controller. Based on the
feedback the control system adjusts the motor speed and subsequently the flow in an attempt to meet the required set
point. This process is repeated continuously bringing the flow rate closer and closer to the target until it eventually
settles on the target. In the drawing, both the Requested Flow Rate and Control System are integrated into the MPC
Vector controller.
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