Fuzzy logic control of torsional lateral modal reponse in offset geared machine trains

Energy conservation is providing the driving force behind the development of variable frequency drives for medium voltage AC motors. Significant energy savings can be realized by varying the speed of a turbomachine to provide a better match with the application specific system requirements. Many of these drives will be retrofitted to existing equipment which normally run at fixed operating speeds. Energy saving measures for future automated plants will require these machines to operate smoothly over a significant speed range. Resonance response at certain "critical" speeds will inevitably lead to excessive vibration for many of these applications.; This work concentrates on machine trains containing a parallel shaft offset gearbox which results in a coupling of the torsional and lateral dynamic regimes of the rotating elements. This is manifested most significantly through the physical offset of the shaft centerlines giving rise to both lateral and torsional forcing functions.; The new development introduced herein is an extension to the concept of the well known Lanchester damper combined with a fuzzy logic controller. A semi-active damper/absorber is used to provide an optimal damping/inertia torque for control of the machine train response using artificial intelligence techniques. The result is a very effective and economical control responding to the lateral vibration via the coupled torsional regime. The unique control is basically a three step procedure to locate the minimum lateral response of the gearbox by varying inertia addition and torsional damping. The torsional damper/absorber is attached to the free end of the high speed shaft.; This is a general development which can be readily applied to offset geared machine trains in industry. This represents a major step forward in the provision of a convenient new method which combines and extends known technology to solve a complex problem that has plagued industry for years.