Positive Position Feedback (PPF) is one of the most attractive vibration control method due to its stability and ease of implementation. On the other hand, low robustness makes the PPF design more complicated in multimodal control case. It is known that a little change in optimal parameters setup, especially the change in controller frequency, can strongly degrade the control effort. Thus knowing a good approximation of optimal PPF parameters can be very helpful in practical implementations and simplified analytical relations between optimal parameters and modal properties of the structure are inevitable for efficient control design. In this paper derivation of such relations is introduced, based on simplified transfer function of controlled structure. Furthermore influence of the parallel PPF controllers in multimodal vibration suppression is analyzed and formulae for optimal parameters updating are suggested. Optimal multimodal PPF control design is demonstrated on experimental example of vibration suppression of beam structure. and Obsahuje seznam literatury
Test stand for investigation of the influence of bearing bushing movement control on behaviour of a rigid rotor supported in sliding journal bearings was designed. The stand was equipped with two pairs of piezoactuators, enabling to move each bearing bushing in two directions, and with two pairs of relative sensors tracing shaft movement at both bearings. The initial tests showed quite unexpected phenomena, which should be cleared up, before experiments with controlled bearing bushing movement could be started. Finally the system began to operate according to predictions and it was possible to start intended experiments. Some results of the rotor behaviour with and without piezoactuator action are presented.