Jaromír Škuta

Active Vibration Control of Hydrodynamic Journal Bearings

Rotor instability is one of the most serious problems of high-speed rotors supported by sliding bearings. With constantly increasing parameters, new machines problems with rotor instability are encountered more and more often. Even though there are many solutions based on passive improvement of the bearing geometry to enlarge the operational speed range of the journal bearing, the paper deals with a working prototype of a system for the active vibration control of journal bearings with the use of piezoactuators. The actively controlled journal bearing consists of a movable bushing, which is actuated by two piezoactuators. It is assumed that the journal vibration is measured by a pair of proximity probes. Force produced by piezoactuators and acting at the bushing is controlled according to error signals derived from the proximity probe output signals. The active vibration control was tested with the use of a test rig, which consists of a rotor supported by two controllable journal bearings and driven by an inductive motor up to 23,000 rpm. As it was proved by experiments the active vibration control extends considerably the range of the rotor operational speed.

Equipment for 3-D Picturing and Measurement of Atherosclerotic Plaque

Equipment for 3-D Picturing and Measurement of Atherosclerotic Plaque This contribution presents a management system with the achieved results of a complex grant project focused on the development of equipment for the 3-D picturing of a carotid artery. This problem was solved during years 2006 - 2008 by specialists from the Faculty of Mechanical Engineering VŠB-TUO, Faculty of Electrical Engineering and Computer Science VŠB-TUO and Neurological Clinic FN Ostrava during the solving of research project GA 101/06/0491 supported by the Czech Science Foundation. The main goal is mechanical system for the exact measurement of Atherosclerotic Plaque (AC plaque) in a carotid artery, including the control system and synchronizations with the heart activity. The obtained pictures enable the necessary analysis and acquisition of data for Atherosclerotic Plaque with appropriate accuracy and recurring measurements. These results open the way for medical use.

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.

Advances in the development of an imaging device for plaque measurement in the area of the carotid artery

This paper describes the advances in the development and subsequent testing of an imaging device for three-dimensional ultrasound measurement of atherosclerotic plaque in the carotid artery. The embolization from the atherosclerotic carotid plaque is one of the most common causes of ischemic stroke and, therefore, we consider the measurement of the plaque as extremely important. The paper describes the proposed hardware for enhancing the standard ultrasonic probe to provide a possibility of accurate probe positioning and synchronization with the cardiac activity, allowing the precise plaque measurements that were impossible with the standard equipment. The synchronization signal is derived from the output signal of the patient monitor (electrocardiogram (ECG)), processed by a microcontroller-based system, generating the control commands for the linear motion moving the probe. The controlling algorithm synchronizes the movement with the ECG waveform to obtain clear images not disturbed by the heart activity.