Assessment of the Effectiveness of a Polar Fuzzy Approach for the Control of Centrifugal Compressors

The aim of this study is to assess the possibility to apply a new control approach dedicated to turbomachinery. The controller is fuzzy based using inputs expressed in polar coordinates. The advantage is that it manages two significant physical quantities, namely tangential and radial velocities that are related to steady state and transient behaviors, respectively. A 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. A test that corresponds to usual industrial excitations (subsynchronous excitations at nominal speed) is also carried out. Results obtained are satisfactory and give insight into the potential of the approach. In addition, and as the fuzzy controller parameters are independent from the rotor design, the approach is a first step for the standardization of magnetic bearing controller synthesis.