Analysis of Hydraulic Circuit Efficiency for Manipulator-Type Machine Slewing Mechanism Based on Speed Performance and Actuator Loading Characteristics

Abstract

The article investigates the influence of different hydraulic circuit configurations on the dynamic characteristics of the slewing mechanism of manipulator-type machines, including crane-manipulators, excavators, and loaders. The slewing mechanism is one of the most loaded assemblies of such machines, determining their productivity and reliability. Five variants of hydraulic circuits are analyzed: with throttles in pressure and drain lines with diameters of 2.5 mm and 3 mm; with throttles equipped with check valves of 2.5 mm and 3 mm diameters; without throttling devices; with a 2.5 mm diameter throttle connecting the hydraulic cylinder chambers. A mathematical model based on a system of differential equations describing column rotation and working fluid flow in the slewing cylinder chambers has been developed. The model accounts for working fluid compressibility, hydraulic system element compliance, leakages, and characteristics of hydraulic distributors and relief valves. Numerical simulation of transient processes was conducted at nominal pump delivery of 80 l/min, load moment of 90 kN·m, and rotation angle of 180°. Dependencies of pressure changes in pressure and drain chambers of the hydraulic cylinder, as well as angular velocity of column rotation versus time, were obtained for different throttle orifice diameters. It was established that the use of throttles with check valves of 3 mm diameter ensures reduction of dynamic loads by an average of 1.2 times compared to circuits with throttles without check valves of the same diameter, by 1.2-1.4 times compared to circuits without throttles during rotation and braking respectively, and by 1.3-1.55 times compared to circuits with a throttle connecting the cylinder chambers. Pressure peaks during braking decrease by 2-6 MPa in the pressure chamber and 1-2 MPa in the drain chamber. Column rotation time is reduced by 1.2-1.3 times compared to circuits with throttles without check valves, indicating increased mechanism speed performance. Check valves ensure free passage of working fluid during column acceleration and limit flow during braking, reducing pressure peaks. The research results allow for substantiated selection of hydraulic circuit configurations for slewing mechanisms to ensure optimal balance between speed performance and dynamic load levels on hydraulic drive elements.