A Compensation Method for Foundation Effects in Rotating Systems Through Shape Optimization

Abstract

Rotating systems operating in different foundations structures can present distinct dynamic response. In case of a compliant foundation, interaction between machine and its supports leads to a more complex system with additional degrees of freedom. These degrees of freedom introduce new natural frequencies and vibration modes for the system. When these foundation-induced modes are in the rotor operating range of frequency, a serious problem may arise, since a machine cannot be tested for every different foundation type expected in industry environment, especially in preliminary design phase. Furthermore, foundation replacement or adaptation are costly operations. A significant improvement in machine-foundation compatibility is possible by the introduction of some compensation in machine to change these additional critical frequencies. Therefore, this paper proposes a compensation method for foundation effects through finite element analysis and shape optimization. An optimization is used to find a compromise between minimum mass increase and manufacturing time to ensure a low cost shape, as a result the cost of machine adjustments is reduced. The algorithm is designed to be simple enough to run on cheap micro-controllers. Consequently, the complete system can be embedded in the machine for a negligible amount of its total cost. Simulations’ results show the method as effective in compensating the influence of foundations with minor loss of precision due to simplifications required to make the algorithm less computational intensive than a full-fledged solution designed to run in workstations. In this way, the method is promising for future applications in rotating machines present in industrial plants.