Pulsafeeder MPC Vector - Manual (Page 64)

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21. Appendix 2, PID Theory and Adjustment
The PID control method allows the MPC Vector to accurately maintain a specific desired setpoint 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.
21.1 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 feed back 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.