THE 29th scientific-professional meeting with international participation - HIPNEF 2004 was held from 18th to 21th May 2004, in Vrnjačka Banja. This traditional meeting of experts in oil hydraulics, pneumatics, automatic control and other related areas was organized by the University of Niš, Faculty of Mechanical Engineering in collaboration with the Association of Mechanical and Electrical Engineers and Technicians of Serbia (SMEITS) from Belgrade.

The meeting organization has been financially supported by local branches of some international firms (Rexroth Bosch Group, Yumo, WIG, ICM Electronic, and Festo) as well several domestic firms (Informatika, Nissal, Tigar, Min Holding „Mont”, Prva Petoletka).

The meeting was opened by Professor Aleksandar Sedmak, PhD, Assistant Minister of Science and Environmental Protection. In the invited lecture titled „Innovation centres-innovation policy and innovations”, Mr. Sedmak spoke about development researche, knowledge transfer, technologies and innovations. He specially emphasized our chance in software development, bioinformatic nanotechnologies, in areas requesting high knowledge, small investments providing big savings. Moreover, Mr. Sedmak spoke about researches and development investments which, at the request of the European Union, should achieve 3 % of the GNP (1.4 % should be obtained from budget and the remainder from economy) by 2010..

The audience was also greeted by Professor Miroslav Pilipović, PhD, Assistant Minister of Education and Sport. In his paper titled „Knowledge economy and high education” he spoke about human resourses development, Bolonja's declaration and our restrictive budget.

The organizer of this year’s meeting provided three preliminary lectures:

HIPNEF TECHNOLOGIES AND TRENDS OF DEVE-LOPMENT, Miodrag Stojiljković, Dragoljub Vujić, Dragan Šešlija, Steva Stankovski - SMEITS, Belgrade

The authors for the first time consider HIPNEF technology as a hybrid system comprising hydraulics, pneumatics, electronics and fluids both in the energetics and the control domains. It is of special interest in the fields of flexible control systems and, in general, in automation of all comprehensive technological processes. This technology is analyzed with indications of possible further development trends.

MACHINE LEARNING TECHNIQUES FOR PRO-CESS MODELING AND CONTROL: SELECTED EXAMPLES, Dragan Obradović - Siemens Corporate Technology, Information and Communications Division, Munich, Germany

In this very interesting lecture, Mr Obradović has presented a brief overview of the machine learning methods for developing deterministic and probabilistic process models, which are further used for system control and/or diagnostics. He has also presented some real life applications of these methods.

BIONIC ASSEMBLY SYSTEM: CONCEPT, STRUC-TURE AND FUNCTION, Vedran Kordić - Vienna University of Technology, Vienna, Austria

The scope of this paper was to present the current state of development of biologically inspired self-organizing complex flexible assembly systems. The self-organizing systems have a very strong tendency to act autonomously. This characteristic is a positive one from the standpoint of robustness of system functionality and efficiency. On the other side, the bionic assembly system is a part of a lager computer integrated production structure (factory, concern) and has to follow the aims coming out from this subordination. This conflict is resolved through the functional integration of vertical and horizontal communication.

After the plenary session, the meeting continued in two separate parallel sections. The authors from our country and from abroad (Romania, Bulgaria, Ukraine, Germany, Austria) submitted 100 papers printed in the Proceedings. All papers were classified into the following thematic groups: HYDRAULICS (12 papers), PNEUMATICS (8 papers), ELECTRICAL ENGINEERING AND ELECTRONICS (11 papers), FLUIDS (16 papers), FLEXIBLE CONTROL SYSTEMS (16 papers), FLEXIBLE AUTOMATION (22 papers), EXPLOITATION AND MAINTENANCE (15 papers).

Some papers are results of researches supported finan-cially by the Ministry of Science and Environment of the Serbian Government and they are a part of projects currently in realization.

Several new technologies are presented in the exposed papers. For instance, in the area of contemporary electro hydraulic systems a new standard modem digital BUS interface is presented instead of analog signal transfer. Instead of an expensive cable installation of low flexibility, fixed analog controllers and limited diagnostics, new digital systems enable signal transfer by BUS interface, easy system compensation by additional components and parameters changing during operation, precise failure detection, etc. New Rexroth proportional and regulation valves with BUS interface and integrated digital controllers are exam-ples of those systems.

In the area of hydraulic, pneumatic and electrical drive control a general trend based on using programmable logic controllers is emphasized. In small and middle configurations world wide they participate with 6.5 to 8 million per year.

In the area of monitoring and diagnostic systems there is an emphasis on a significant application of sensors in detecting system health and forecasting its failure. This is a new multiple sensor approach in the maintenance domain which reduces operational costs and increases system relia-bility. 

Here will be presented the most important papers from the sessions that could be of interest for the readers of the Scientific-Technical Review.

HIGH PRESSURE PUMP – HEART OF THE MACHI-NE FOR COUNTOUR CUTTING BY AN ABRASIVE WATER JET, Predrag Janković, Miroslav Radovanović – Faculty of Mechanical Engineering, Niš, Nebojša Vićovac, Water Jet YU, Velika Krsna

This paper presents types and principles of pumps in waterjet systems. Waterjets (and Abrasivejets) are quickly becoming a new standard tool in machine workshops around the world. This is because they are fast, flexible, reasonably precise, and in the last few years they have become friendly and easy to use. They use the technology of high pressure water being squirted through a small hole to concentrate an extreme amount of energy in a small area to cut material. The pump is the heart of the waterjet system. The pump pressurizes the water and delivers it contin-uously.

SIMULINK MODEL OF PNEUMATIC ACTUATOR SYSTEM, Miodrag Stojiljković, Vladislav Blagojević – Faculty of Mechanical Engineering, Niš, Čedomir Milosavljević – Faculty of Elecronic Engineering, Niš

In this paper, a detailed mathematical model of dual action pnematic actuators controlled by proportional spool valves was developed, and shown in the simulink. The effects of the nonlinear flow through the valve, air compres-sibility in cylinder chambers, leakage between chambers, end of stroke inactive volume, and time delay and attenuation in the pnematic lines were carefully considered. This mathematical model can be used in the development of high performance controllers, with applications in automation and robotics.

NEW APPROACHES IN VALVE TERMINAL INTE-GRATION, Stevan Stankovski – Faculty of Technical Sciences, Novi Sad, Ljubomir Miladinović, Branch of FESTO, Belgrade

A concept of distributed control systems imposes communication as a key factor in automated processes. A large number of fieldbus protocols restrain faster integration with a business part of a production system. Involving Ethernet in fildbus communications opens a new trend in integration of industrial equipment. In this paper a new concept of the FESTO valve terminal based on PLC with Ethernet communications is presented.

DEVELOPMENT TREND OF LASER SYSTEMS, Miroslav Radovanović – Faculty of Mechanical Engineering, Niš

Investments in laser systems keep on growing every year. Growing demands imposed development of high-po-wer lasers, new technological solutions, and development of hybrid laser systems. The paper shows trends in laser system development with a special attention to the development of laser systems for sheet contour cutting. The first part shows a trend of laser system development in the last ten years in relation to laser purpose and types. The second part gives development trends concerning laser systems for sheet contour cutting, new technological solutions and laser based hybrid technologies.

          The authors from Serbia and Montenegro's Army participated with several papers. The Proceedings include 7 papers, 6 papers from the Military Technical Institute and one paper from the Military Academy. However, aut of 14 authors or co-authors, only 2 participants from the Military Technical Institute took part in the meeting. For that reason, one co-author presented even four papers.

SOPHISTICATED DIAGNOSTIC SYSTEMS IN AIR-CRAFT ENGINES, Dragoljub Vujić – Military Technical Institute, Belgrade

Modern knowledge-based diagnostic systems and their application in state forecasting and failure detection are considered. A special attention is devoted to a new sensor technology in oil contamination monitoring and fuel delivery monitoring in aircraft engines. A case-based reasoning diagnostic system is presented in particular.

VISUALIZATION AND NUMERICAL SOLUTION OF THE FLOW AROUND FRONT PART OF TORPEDO MODEL, Slavica Ristić, Aleksandar Vitić, Dušan Matić - Military Technical Institute, Belgrade

Examination of the flow around a torpedo model was done in the trisonic wind tunnel in the VT facilities for free flow velocities at = 0.3. The visualization of the boundary layer flow was achieved with paraffin and powder emulsions. The numerical simulation of the flow was done by the Fluent 6.0 finite volume code. The distribution of numerical streamlines shows good agreement with experimental ones, as illustrated in the photos.

BASIC FINNER MODEL ROLL-DUMPING CHA-RACTERISTICS MEASUREMENTS IN THE T-38 TRISONIC WIND TUNNEL, Marija Samardžić, Dragan Marinkovski - Military Technical Institute, Belgrade

Wind tunnel tests were conducted on the Basic finner model at Mach number 0.2. A roll-dumping mechanism based on small amplitude and the forced oscillation technique were used for obtaining stability derivatives of the model at the angles of attack from – 4° to +16°. The roll-dumping derivatives are found to be a high non-linear function of the angle of attack. Wind tunnel tests were conducted for investigation and verification of the roll-dumping test mechanism. The tests results are compared with other experi-mental sources and calculated results.

CALLIBRATION OF WATER CAVITATION TUN-NEL WITH CLASSICAL METHODS AND LASER DOPPLER ANEMOMETRY, Mirjana Puharić, Slavica Ristić - Military Technical Institute, Belgrade

The methodology of the VTI water-cavitation tunnel test section calibration is shown. Comparative tests have been made by measuring the static and total pressure in the periphery of the test section, by the pitot probe and by the „rake”. At the same time, the fluid velocity measurements have been carried out by a contactless, optical method, by Laser Doppler Anemometry (LDA). One velocity component, parallel to the water tunnel axis has been measured. The results of investigation have shown that classical methods are satisfactory for standard tests.

EXPERIMENTAL DETERMINATION OF AXIAL FAN FLOW, Biljana Ilić, Goran Ocokoljić- Military Technical Institute, Belgrade

Air flow through an axial fan, a component of the vehicle engine cooling system, is determined. The measuring installation, previously constructed, enables fan flow determination to be reduced to flow measurement in a pipe of circular cross-section. The method of local velocity measurement, based on velocity measurements in a number of cross-section points, is applied. On the basis of experi-mentally obtained data, the mean velocity profile is obtained. The air flow through the pipe cross-section, i.e. fan air flow, is computed by the integration of the mean velocity profile.

DEFINING RESISTANCE FLOW COEFFICIENT ON THE FLUID IN HYDRAULIC BRAKE OF ARTIL-LERY WEAPON, Zoran Ristić, Aleksandar Kari – Mili-tary Academy, Belgrade

The fluid flow resistance coefficients are determined on a hydraulic recoil brake (HB) a model. The relations of flow resistance coefficients for primary and additional fluid flows through the HB bores, are determined on the basis of the numerical-experimental method during the recoiling process. The law of flow resistance coefficient change is obtained on the basis of experimental values for fluid pressure and piston displacement velocity in a form of a functional polynomial. The comparative analysis of the obtained results and literature data is given as well as some proposals for further application.

This well prepared and organized meeting of specialists from oil hydraulics area, pneumatics, automatic control and other related areas was highly evaluated. The presented papers were most comprehensive and had a very high scientific-professional level. Although the meeting was held in very difficult economic conditions, a general opinion is that this traditional meeting was very successful and that it fulfulled organizers' expectations.