The objective of this paper is to present a novel, hybrid group multi-criteria decision approach that can be used to evaluate alternatives for the optimal synthesis of loader drive mechanisms. In most product design engineering groups, experts have expertise in different areas and robust decision-making is necessary to integrate a number of opposing opinions, attitudes, and solutions. This study presents the application of an integrated approach for decision-making, i.e., the generation of a robust decision-making rule for group decision-making (RDMR-G) by combining different multi-criteria decision-making (MCDM) methods and Taguchi’s robust quality engineering principles. The basic idea behind this article was to create an approach that enables the comprehensive and robust consideration of expert opinions given the existence of numerous objective and subjective methods for determining the criteria weights, which are crucial to the final ranking of alternatives in any decision-making problem. In order to set the optimal configuration of a loader drive mechanism, five experts, all with a high level of experience and knowledge in this field, considered twenty-six different kinematic chain construction solutions, i.e., alternatives, and evaluated them with respect to six criteria. The obtained results and rankings provided by each expert and each criteria weighting method were compared using Kendall’s τ_b and Spearman’s ρ tests. As an example, this paper demonstrates the practical application of a RDMR-G approach and in doing so contributes to the literature in the fields of product design engineering and decision-making.

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 analyzes functional, structural and tribological parameters of kinematic pairs (joints) of the kinematic chain and manipulator drive mechanisms in hydraulic excavators. On the basis of the conducted analysis the tribological criterion is defined, as one of a number of criteria, for the optimal synthesis of manipulator drive mechanisms in hydraulic excavators. The criterion indicator is determined as a mechanical degree of efficiency of drive mechanisms, to reflect the tribological loss of power of the excavator drive system due to friction between the elements of the joints in manipulator drive mechanisms. As an example, the paper provides experimental results of tribological research and tribological criterion indicators during examination and synthesis of manipulator drive mechanisms in a hydraulic excavator of 17,000 kg in mass. Scientia Iranica (SCI)

TRIZ methodology provides an opportunity for improving the classical engineering approach based on personal knowledge and experience. This paper presents the application of TRIZ methods for improving vehicle maintenance where special equipment is installed. A specific problem is the maintenance of the periscopes with heating system. Protective glass panels with heating system are rectangular glass elements. Their purpose is to perform mechanical protection of built-in prisms and provide heating of the prisms. Aging and long-term use leads to failure of these elements. The practice requires solutions in order to extend the lifetime of the system. New solution is evaluated by simulation and experiment.

The paper presents the results of the conducted researches related to the analysis of the parameters of the drive system, the crawler hydraulic excavator, with hydraulic pumps with collective regulation according to the criterion of constant hydraulic power and the regulator of ideal hyperbolic characteristics. A crawler excavator weighing 16,000 kg with a three-member manipulator with boom, arm and bucket with a volume of 0.6 m3 was tested. The paper discusses the principles of volumetric regulation of hydrostatic systems, which is achieved by changing the specific flow rate of the hydraulic pumps. For pumps with constant specific flow rates, regulation is performed by reducing the flow through the hydraulic motors, which increases the pressure in the pump's delivery line and is controlled by a safety valve. This method, however, can lead to oil heating and energy loss. In contrast, pumps with variable specific flow rates use modular regulators that adjust the pump's characteristics based on system parameters, ensuring efficient operation under varying load conditions. The study's findings indicate that the use of hydraulic pumps with combined power regulation and an ideal hyperbolic characteristic regulator allows for the maintenance of constant hydraulic power even with changing loads. This regulation method ensures efficient use of the engine's power and prevents motor overload, enhancing the overall performance and longevity of the excavator. The research underscores the significance of proper hydraulic pump regulation in achieving optimal machine efficiency and durability.

The paper presents the results of the conducted researches related to the analysis of the parameters of the drive system, the crawler hydraulic excavator, with hydraulic pumps with collective regulation according to the criterion of constant hydraulic power and the regulator of ideal hyperbolic characteristics. A crawler excavator weighing 16,000 kg with a three-member manipulator with boom, arm and bucket with a volume of 0.6 m3 was tested. During the test, the following parameters of the hydrostatic system of the excavator were measured and determined: pressure and flow in the pressure lines of the hydraulic pumps, the number of revolutions of the diesel engine and the hydraulic power of the hydraulic pumps during the operational task with operations: digging, transfer, unloading of land of category III and returning to a digging start point.