Numerical Assessment of a Polar Fuzzy Controller for Centrifugal Compressors

The aim of this study was to develop and to apply a new control approach dedicated to turbomachinery. The controller is fuzzy based usinginputs expressed in polar coordinates. The advantage is that it manages two significant physical quantities, namely tangential and radial speeds that are related to steady state and transient behaviors respectively. A simple synchronous filter is associated to the controller in order to enhance the ratio command force / bearing dynamic capacity. The approach was previously applied experimentally with success for the control of an academic test rig. It is adapted here for the control of an industrial compressor whose flexible rotor is supported by Active Magnetic Bearings (AMB). At this stage, only numerical investigations are performed. The controller has to satisfy the standards and the end users requirements. In addition, it should be easy to implement. The behavior of the machine studied is assessed for several configurations of unbalances. Tests that correspond to usual industrial excitations (subsynchronous excitation, impulse response at nominal speed) are also carried out. Results obtained are satisfactory and give insight into the potential of the approach. In addition, and as the fuzzy controller parametersare independent from the rotor design, the approach is a first step for the standardization ofmagnetic bearing controller synthesis.