Renata Wagnerova

Piezoelectric actuators in the active vibration control system of journal bearings

The advantage of journal hydrodynamic bearings is high radial load capacity and operation at high speeds. The disadvantage is the excitation of vibrations, called an oil whirl, after crossing a certain threshold of the rotational speed. The mentioned vibrations can be suppressed using the system of the active vibration control with piezoactuators which move the bearing bushing. The motion of the bearing bushing is controlled by a feedback controller, which responds to the change in position of the bearing journal which is sensed by a pair of capacitive sensors. Two stacked linear piezoactuators are used to actuate the position of the bearing journal. This new bearing enables not only to damp vibrations but also serves to maintain the desired bearing journal position with an accuracy of micrometers. The paper will focus on the effect of active vibration control on the performance characteristics of the journal bearing.

Effects of Active Vibration Control of Journal Bearings

The article deals with the stability of the movement of the journal inside the bushing of the hydrodynamic plain bearings, which limits the operational range of rotor rotational speed. The purpose of active vibration control using piezoactuators is to increase the limit of the rotor rotation speed without onset of a whirl. It is also required maintaining the bearing journal position without vibration and reducing friction losses at the steady-state rotation. The main topic is the presentation of the results of the test of the journal bearing with the use of a test bench. Abstrakt Clanek se zabýva stabilitou pohybu cepu uvnitř pouzdra kluzneho hydrodynamickeho ložiska, ktera omezuje provozni rozsah otacek rotoru. Ucelem aktivni kontroly vibraci pomoci piezoaktuatorů je zvýsit hranici rychlosti otaceni rotoru, aniž by vznikl vir, tj. krouženi osy rotoru kolem osy pouzdra. Je take zapotřebi udržet polohu cepu ložiska bez vibraci a snižit ztraty třenim při ustalených otackach. Hlavnim tematem clanku je prezentace výsledků testu kluzneho ložiska na zkusebnim stavu.

Internal model pre-processing tool

In industry the model predictive control (MPC) solutions are for their high computational requirements usually implemented to the PC-based devices. The main goal of our study is to implement an MPC algorithm to the programmable logic controller (PLC). This paper describes an initialization part of our solution, which represents an internal model pre-processing algorithm implemented to the function blocks created in PLC programming standard IEC 61131-3. The pre-processing algorithm changes model representation form of multivariable system (MIMO) from continuous transfer function matrix to generalized discrete state-space model. At the end of the paper there is shown created comfortable interface used for inserting of transfer functions, process model parameterization and future MPC tuning. This interface communicating with pre-processing algorithm running on PLC allows to specify MIMO internal model by continuous transfer function matrix and the discrete state-space internal model used during control is created automatically. The operator does not have to use MATLAB or other expansive mathematical software for creation of discrete state-space representation and the most widespread mathematical description in industry known like continuous transfer function can be used. The constants of transfer functions are usually obtained by operator from current visualizations on the plant.