Forecasting the technical condition of hydraulic transmissions of agricultural machines based on kinematic viscosity and pressure indicators of oil

Maintenance of the technical condition of hydrostatic transmission of agricultural machines is not fully provided by the existing repair and maintenance system of Ukraine, which determines the search for available methods for early detection of hydraulic drive malfunctions. The purpose of the study was to synthesise a method for predicting the technical condition of the hydraulic transmission of modern agricultural machines by controlling the dynamics of changes in the values of the empirical dependence of pressure on the kinematic viscosity of oil in conditions of insufficient material and technical equipment of the production base. Generally accepted methods were applied to achieve this goal: analysissynthesis, induction, observation, experiment, graphic method. As a result of the study, the author’s hypothesis was confirmed, according to which the change in the kinematic viscosity of the working fluid relative to the initial value is determined by the current state of the hydraulic transmission, which is controlled by pressure measurement. Based on the identified shortcomings and problems of the current system of maintenance and repair, a methodology was proposed that provides for monitoring the operational indicators of agricultural machines and the kinematic viscosity of working fluid samples taken from their hydraulic transmissions. Kinematic viscosity values for constructing the predictive model were obtained by the capillary method and calculated using the Walter formula, and the dependence of viscosity on influencing factors was determined by bilinear interpolation. A regression model of pressure from kinematic viscosity was obtained by the least squares method, and the exponent was used as an approximating function. Based on the results of testing the models according to the Fischer criterion, their adequacy was confirmed, and the deviation of the theoretical values of the controlled parameters calculated using the most accurate model from the empirical ones was 0.34% for pressure and 1.3% for kinematic viscosity. The practical value of the study lies in the fact that the results allow reducing unproductive time costs associated with the downtime of equipment, due to emergency failures of hydraulic transmission units and contribute to the adaptation of the planned preventive maintenance system for agricultural machinery to the needs of the Ukrainian agro-industrial complex