Simulated and Experimental Analysis of a Log Crane With Conventional and Direct Driven Hydraulics

The present paper compares the efficiency and dynamic behavior of a log crane while using two alternative transmissions. Firstly, the conventional mobile hydraulic valves with a load-sensing pump is used, and secondly, a novel electric-hydraulic energy converter and a direct driven hydraulic actuator is used. By applying lumped parameter models and the theory of centralized pressure, the hydraulic system models are constructed in MATLAB & Simulink environment. MathWorks Simscape Multibody is used in modeling of the multi-body system of the crane. The results of the simulation models are compared with those measured in the laboratory. Based on the verification results, such modes of operation in which the agreement between simulated results is the closest are selected for further investigation. The effectiveness of the system equipped with an electro-hydraulic converter is compared with that of the conventional system with a load sensing pump. Detailed models for components are given in the paper, and the results are discussed based on what obtained through simulation and experiments. The electric-hydraulic converter used in direct driven circuit is a novel prototype developed at LUT University. It has good power stiffness, and it provides good torque properties in a wide RPM area. The prototype is used in operating the lift or tilt cylinder, which is altered by using fast switching valves. The actual test circuit does not have electric storage. The ability of the converter to recover potential energy from the lifting system inertia is approximated in the efficiency comparisons.

APPLICATION OF ELECTRICAL TECHNOLOGIES FOR THE RESTORATION OF AGRICULTURAL MACHINERY PARTS

The technology of non-galvanized ironing of parts in the electrolyte flow with simultaneous hydromechanical activation of the plated surface is proposed, its advantages over the traditional type of coating are shown. The technological process of coating hydraulic control valve spools has been developed. The technological process of restoring spools consists of the following operations: preliminary surface preparation (mechanical treatment), degreasing, washing, anodic treatment, electrodeposition and final mechanical treatment. The designs of the installation and the electrochemical cell for ironing hydraulic control valve spools, providing optimal hydrodynamic conditions when applying coatings on worn surfaces, are proposed. Optimal modes and composition of ironing electrolyte have been defined, providing a high rate of precipitation growth (1.5...3 mm/h), adhesion strength and wear resistance of coatings. Bench and field tests of hydraulic valves with restored spools were performed, which confirmed the results of laboratory studies and the high efficiency of the proposed technology.

Modelling and Validation of Cavitating Orifice Flow in Hydraulic Systems

Cavitation can occur at the inlet of hydraulic pumps or in hydraulic valves; this phenomenon should be always avoided because it can generate abnormal wear and noise in fluid power components. Numerical modeling of the cavitation is widely used in research, and it allows the regions where it occurs more to be predicted. For this reason, two different approaches to the study of gas and vapor cavitation were presented in this paper. In particular, a model was developed using the computational fluid dynamics (CFD) method with particular attention to the dynamic modeling of both gaseous and vapor cavitation. A further lumped parameter model was made, where the fluid density varies as the pressure decreases due to the release of air and the formation of vapor. Furthermore, the lumped parameter model highlights the need to also know the speed of sound in the vena contracta, since it is essential for the correct calculation of the mass flow during vaporization. A test bench for the study of cavitation with an orifice was set up; cavitation was induced by increasing the speed of the fluid on the restricted section thanks to a pump located downstream of the orifice. The experimental data were compared with those predicted by CFD and lumped parameter models.

A Note on Leakage Jet Forces: Application in the Modelling of Digital Twins of Hydraulic Valves

The proper modelling of fluid flow through annular gaps is of great interest in leakage calculations for many applications in fluid power technology. However, while detailed numerical simulations are certainly possible, they are very time consuming, in various cases prone to numerical instabilities and may not even include all physically relevant effects. This is an issue especially in system simulations, where a large set of computations is needed in order to prepare the lookup-tables for the required input fields. In this work, an analytical approximation for the shear force, which is induced by viscous flow between two eccentric cylinders, is presented. This relation, and its derivation, mimics and enhances the well-known Piercy-relation for the corresponding volume flow that is utilized in state-of-the-art system simulation tools. To determine its range of validity, the analytical relation for the shear force is compared to 3D-simulations. Additionally, an application of this approximation for creating digital twins of hydraulic valves is also discussed in this work.

Monitoring the degradation in the Switching behavior of a Hydraulic Valve using Recurrence Quantification Analysis and Fractal Dimensions

Valves are crucial components of a hydraulic system that enable reliable fluid management. Hydraulic valves, actuated by a solenoid are prone to degradation in their switching behavior, which may induce undesirable fluctuations in the fluid pressure and flow rate, thereby impairing the system performance and limiting its predictability and reliability. Therefore, it is imperative to monitor the switching behavior of solenoid-actuated hydraulic valves. Firstly, Recurrence Quantification Analysis (RQA) has been applied to the experimental flow sensor signals from a hydraulic circuit to understand the complex switching behaviour of the valve. Using RQA the monotonicity of six recurrence-based parameters has been assessed. In addition, two more nonlinear features, namely, Higuchi and Katz fractal dimensions have been extracted from the flow signals. Based on these eight features (six RQA derived features and two nonlinear features) a feature matrix is formulated. Secondly, in a parallel approach, eight different statistical features are extracted from the flow signal to construct another feature matrix. Subsequently, different machine learning methods namely Ensemble learning, KNN and SVM have been trained to these two feature sets to predict the valve switching characteristics. A comparison between two feature sets shows that ensemble learning gives better prediction accuracy (99.95 % versus 92.2 % using statistical features) when fed with RQA features combined with fractal dimensions. Therefore, this study demonstrates by utilizing recurrence plots and machine learning techniques on the flow rate signals, the degradation in the switching behavior of hydraulic valves can be monitored effectively with high prediction accuracy.

Development of a Computerized Automated System for Feed, Water and Sanitation Management in Animal Farms

Frequent visits into animal farms either for cleaning, feed or water dispensation are a possible means of viral, and bacteria propagation into and out of the farms. The need for these visits compels the farmer to live in the farm and devote considerable time to these activities. A well-controlled automatic feed dispensation/water management system can considerably reduce labor and prevent frequent farm visits. This can in turn promote social distancing especially during the outbreak of epidemics. A solar energy powered automatic system for feed, water dispensation and sanitation management was developed for animal farms. It was made up of an Arduino UNO board, a water level/or feed sensor, a DS1307 Real Time Clock (RTC), two potentiometers, a buffer, an sim900 mini v3, a relay module for Arduino, a display (LCD) for visual monitoring of events. It was programmed to periodically command electric motors to release a desired quantity of feed and water into different troughs as well as open hydraulic valves to spray a jet of high pressure water to clean the enclosure. Required data was fed into the program by the farmer depending on the daily needs which in turn depend on the animal species, age and husbandry requirements. The system communicated with the farmer through a GSM card after each operation. Initial tests of the prototype revealed minimum of 83.33% efficiencies for all the units. The module was able to report to the farmer minutes after completing each task. It was concluded that such a system can considerably reduce labor in animal farms as well as disease propagation.