Description:
Invention
Title
Software for analyzing the root cause of oscillatory
behavior in control loop systems.
Executive
Summary
The invention described is a software based tool for use
in diagnosing the cause of oscillation in systems using multiple control loops.
The problem of oscillation in control loop systems leads to millions of dollars
in additional operating expense for manufacturing plants yearly. Additionally,
an oscillatory control loop limits the maximum quality achievable by the system.
This software can detect oscillation in the control loops, and describe the root
cause(s) of that oscillation without requiring costly offline time for the
system. The additional ability of this software to differentiate between
external causes, stiction, and poor tuning allows system managers to schedule
maintenance and tuning intelligently as the system requires. All of these
features allow the system to be adjusted more closely to the actual output
required, because the need to account for standard error is nearly eliminated.
Product
Description
The software described is based on
an algorithm in which the only required input is commonly measured parameters
around control loops. Consequently, the inventor has been allowed to test the
software using measurement data from several manufacturing plants. The hardware
requirements are minimal even for large control loop systems, allowing a
manufacturing plant to run a simulation every night and adjust the control loops
according to outputs read every morning. The advantages of this system over
competing products are its ability to detect all three causes of oscillation and
also to describe from which root causes individual control loops are suffering.
Also, the algorithm can diagnose oscillation as due to multiple root causes
simultaneously.
Inventor Background
Prof.
Raghunathan Rengasamy is a researcher
in the chemical engineering department at Texas Tech University. He has multiple
research interests, including several inventions targeted at alleviating control
loop oscillation problems in manufacturing plants.
http://www.depts.ttu.edu/che/faculty/rrengasamy/interests.php
Publications
U.
Nallasivam, B. Srinivasan and R. Rengaswamy, “Stiction
Identification in Nonlinear Process Control Loops”, accepted, Computers
and Chemical Engineering, doi:10.1016/j.compchemeng.2010.02.040,
2010.
Ranganathan Srinivasan,
Raghunathan Rengaswamy and Randy Miller, “A Modified
Empirical Mode Decomposition (EMD) Process for Oscillation Characterization in
Control Loops”, Control Engineering Practice, 15(9), pp 1135-1148,
2007.