U ovom radu predstavljen je metod za eksperimentalno određivanje parametara pogonskog mehanizma obrtne platforme hidrauličnih bagera sa dubinskim manipulatorom. Definisan je matemetički model kojim se određuju kinematički i dinamički parametri pogonskog mehanizma obrtne platforme hidrauličkih bagera, na osnovu mrenih veličina stanja rada bagera u eksploatacionim uslovima. Dobijeni eksperimentalni rezultati pokaziju da su najveća opterećenja aksijalnog lezaja pogona okretanja platforme pri operaciji kopanja. Osim toga izrazite dinamičke promene parametara hidrostatičkog sistema pogonskog mehanizma obrtne platforme javljaju se pri operaciji prenosa materijala.

The paper presents the results of a numerical and experimental analysis of the dynamic stability of hydraulic excavators. The analysis has employed the software developed on the basis of a defined general dynamic mathematical model of an excavator grounded in Newton-Euler equations as well as the measured quantities of the excavator operating state in exploitation conditions. The defined model is used to model the members of the excavator kinematic chain using rigid bodies while the actuators (hydraulic cylinders and hydraulic motors) of the excavator drive mechanisms are modeled with elastically dampened elements. The elastically dampened characteristics of the actuators are defined with regard to the size of the actuator as well as to the compressibility and temperature of the hydraulic oil used in the excavator hydrostatic drive system. To illustrate the analysis, the paper provides the results of the analysis of the dynamic stability of a 16000 kg tracked excavator equipped with a manipulator digging bucket of 0.6 m3 in capacity.

The paper defines the general mathematical model of hydraulic excavators for determining the boundary and possible digging resistances and equivalent loads of the axial bearing of the slewing platform drive mechanism throughout the excavator’s working area. Using a developed mathematical model and program, in the case of a 100000 kg hydraulic excavator with a shovel manipulator bucket volume of 6,5 m3, a detailed analysis was performed to examine the influence of the position and digging resistance on the loading of the axial bearing of the excavator slewing platform drive mechanism. The results of the performed analysis show that the equivalent loads, relevant for the selection of axial bearing of the excavator slewing platform, occur in the zone of the working area when the kinematic chain of the excavator has positions in which the manipulator mechanisms have coordinated interaction when they can overcome the greatest resistance forces in the stable operation of the excavator.

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Freight transport is a composite dynamic system that forms the unity of the infrastructure, vehicles, and personnel and which has its purpose or aim. Evaluating operation performance for freight transport systems is important for the government, companies, and users. This paper will use one of the most famous Multiple Criteria Decision-Making (MCDM) techniques to assess the operational performance of freight transport systems. At beginning, the authors will create the evaluation indicator system based on official data with four basic indicators and two sub-indicators for freight transport. These operational data/indicators represent the input of the chosen MCDM method. After that, the Analytic Hierarchy Process (AHP) method will use to calculate the indicator and sub-indicators weight and also will use to calculate the universal evaluate values and rankings of each transport mode performance. The Serbian freight transport system for the 2021st year will be selected as a case study for testing the AHP method within the MCDM approach; the associated suggestions to freight transport will also be given.