Robust Control in Turbomachinery Configurations

Abstract

An experimental study of two different robust control approaches, namely H ∞ - and an improved slope-seeking control is presented. The H ∞ -control is used within an axial turbomachine and a highly loaded compressor cascade. The flow field within both configurations can be stabilized whereby the pressure at the trailing edge of the compressor cascade can be controlled to prespecified values and disturbances are suppressed. Within the axial turbomachine stall can be prevented. The applied robust controller is capable of effectively rejecting large ambient disturbances while driving the plant to different operating points at the same time. By this, the usable aerodynamic range can be extended, concomitantly with an increase of performance. In both configurations, a higher pressure increase is attained by this closed-loop active flow control. Moreover, the H ∞ -controller is compared for the axial fan case to an improved version of an adaptive controller, a so called slope-seeking controller exploiting an extended Kalman filter for accelerated estimation of a gradient.