PID for Vacuum System Automation

PID Integral.jpgPID is an acronym for using a closed loop feedback system with the terms Proportional, Integral and Derivative.  While it uses calculus-type words, it is straightforward to configure and is what many industrial processes rely on for predictable automation.  It works on the principal of minimizing the error between the current vacuum reading and the desired set point vacuum pressure.   While PID can work on any closed system, it is also very useful for vacuum systems.  The balancing act is tuning the response to get your vacuum level to respond quickly, but also converge and not become unstable.
For our upstream vacuum control systems, we recommend performing initial testing with the system to characterize and set the response under a variety of likely conditions.
  1. Create a scenario that mimics your end cases: Maybe a vessel full of product and a vessel void of product; whatever the extreme scenarios of volume and gas that exist in the system you are trying to control.
  2. For each extreme, test control
    1. Start with P small, I=0, and D=0
    2. Double P and disturb set point. Repeat until the system oscillates about the set point
    3. Decrease P by…..
For the full set of tuning instructions and more download our white paper, “PID Control in Vacuum Systems”.