State Prediction in the Presence of Input, State and Output Delays: Application to Compressor Surge Control Using Active Magnetic Bearings

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

The objective of this research project is to develop new design methods for controlling engineering systems in the presence of time delays arising in the inputs, outputs, and states. These methods will help engineers alleviate the adverse effects of delays on stability and performance. Multistage centrifugal compressors are one of the most widespread types of industrial equipment, and consume significant amounts of energy. They are used to drive natural gas pipelines and are essential components for building heating, ventilation, and air conditioning systems. Application of the project results to surge instability will enable higher efficiency operation of these compressors, thereby lowering operating costs and reducing overall energy use. Through the Rotating Machinery and Controls (ROMAC) consortium at the University of Virginia, the research team will interact with engineers from major compressor manufacturers, to formulate and disseminate solutions to major technical challenges faced by the industry. Conventional predictor feedback in time-delay systems leads to noncausal control laws when the input delays are larger than the state delays. Initial investigations indicate that it is possible to construct a causal state predictor even for this case. The fundamental idea is to partition the prediction time into sections that are each shorter than the maximum state delay, and carry out the prediction recursively over the prediction time. The resulting state predictor is causal, but infinite dimensional. The thrust of this project is to devise methods to safely implement the infinite-dimensional predictor. The results are expected to lead to powerful new tools for control of systems subject to simultaneous input, state and output delays. An integrated part of the project is to apply the theoretical results to the control of surge instability in multistage centrifugal compressors by use of active magnetic bearings.