Fuzzy SPC filter for a feed-forward control system for a three-phase oil field centrifuge

In this work we describe a signal filter for a feed-forward controller based on the application of fuzzy logic combined with statistical process control (SPC). The feed-forward controller is for a three-phase oil field centrifuge. The centrifuge system is used to separate meta-stable three-phase emulsions consisting of oil and water stabilized by solids. These emulsions are considered to be unusable wastes and must be disposed of in an environmentally acceptable manner. The centrifuge is capable of turning these wastes into clean saleable oil, water that can be reused in an operating process or re-injected into oil wells and, solids that can be disposed of in landfills. The feed-forward controller is used for feed disturbance rejection. It works in conjunction with and, is capable of over-riding the actions of, a feedback controller. The measured feed variables for the feed-forward controller each exhibit reasonably large random fluctuations. It is therefore quite important to use a signal filter that truly recognizes the difference between random noise and a "caused" event, in order to prevent overriding a perfectly good correction from the feedback controller.