Hydrostatic Steering Research Articles

DEVELOPMENT OF THE STAND FOR EXPERIMENTAL RESEARCH OF THE DOSER PUMP OF THE HYDROSTATIC STEERING SYSTEM OF SELF-PROPELLED AGRICULTURAL MACHINERY

Hydrovolumetric steering systems have today become widely used in heavy agricultural machines, such as combines, loaders, etc. The reliability and quality of operation of these machines largely depends on the quality of these systems and their elements. During the operation of these systems, a number of shortcomings were identified, which require additional research and the application of new design solutions. From the analysis of modern developments of the leading manufacturers of elements of these hydraulic systems, it follows that the main design changes are caused by the need to ensure the operability of these systems in abnormal or emergency situations. To check the performance of these devices in laboratory conditions, it is necessary to provide bench equipment with the ability to simulate abnormal situations and ensure the recording of the received information for the purpose of its further analysis and the formation of a set of measures aimed at eliminating the identified deficiencies and meeting the requirements of current standards. The authors have developed an original method of experimental research of individual steering control units for hydrostatic steering systems of special vehicles. It is proposed to create a load on the steering control unit in the form of a pressure difference in its output channels without using supporting hydraulic cylinders. To implement the proposed method, an electro-hydraulic scheme of the stand was developed. This makes it possible to analyze the quality of the steering unit's operation in conditions corresponding to different operating modes of the steering system, and to determine the corresponding characteristics of the steering unit under oncoming and passing loads.

FEATURES OF THE STAND AND METHODS FOR EXPERIMENTAL STUDIES OF PUMP-DOSING PUMPS OF HYDRAULIC STEERING SYSTEMS OF SELF-PROPELLED VEHICLES UNDER THE ASSOCIATED LOAD

The article discusses a special stand for experimental research of dosing pumps of hydrostatic steering systems of self-propelled machines, which makes it possible to analyze the quality of the dosing pump under conditions that correspond to different control actions and loads that arise during the operation of the steering system. An electro-hydraulic scheme of the stand has been developed to determine the characteristics of a dosing pump under the action of a associated load. The characteristics of control and measuring devices for determining parameters that are controlled both in statics and in dynamics are presented. To record changes in signals over time, a recording system has been developed that realizes the recording of signals on a computer and their processing using the «PowerGraph» program. A feature of this stand is that the load for the dosing pump is formed in the form of a pressure drop in its outlet channels. This makes it possible to evaluate the performance of these products regardless of their working volume and facilitates the experimental study of the behavior of the system when reproducing certain modes of its operation over a period of time that is not limited to the stroke of the executive hydraulic cylinder of the steering system. The stand implements an original technique for reproducing the associated load in the outgoing channels of the dosing pump, for which an additional pump driven by a hydraulic motor is installed in the outgoing channels of the metering pump. Regulation of the speed of rotation of the drive motor makes it possible to set the required value of the associated load. The method for determining the quality indicator of the dosing pump operation under the action of a associated load is briefly described In this case, the indicator of relative flow rates in the outgoing channels of the metering pump is determined, which shows how many times the actual flow rate of the working fluid increases in comparison with the nominal one, which is determined for the dosing pump with a certain working volume by the speed of rotation of the input shaft.

Concept and Preliminary Simulations of a Driver-Aid System for Transport Tasks of Articulated Vehicles with a Hydrostatic Steering System

Heavy-wheeled vehicles with articulated hydraulic steering systems are widely used in construction, road building, forestry, and agriculture, as transport units and tool-carriers because they have many unique advantages that are not available in car steering systems, based on the Ackermann principle, such as—high cross-country mobility, excellent maneuverability, and high payload and lift capacity, due to heavy axles components. One problem that limits their speed of operation and use efficiency is that they have poor directional stability. During straight movement, articulated tractors’ deviate from a straight line and permanent driver correction is required. This limits the vehicles’ speed and productivity. In this study, we describe a driver-aid system concept that would improve the directional stability of articulated vehicles. Designing such a system demands a comprehensive knowledge of the reasons for the snaking phenomenon and driver behaviors. The results of our articulated vehicle directional stability investigation are presented. On this basis, we developed models of articulated vehicles with hydraulic steering systems and driver interaction. We next added the stabilizing system to the model. A simulation demonstrated the possibility of directional stability improvement.

정유압조향장치의 피스톤 슈와 경사판 사이에서의 유동특성 해석

The hydrostatic steering unit is composed of pumps, motors, manifold assembly, servo actuators and various valves. It is a key device for steering of tank according to the request of driver. Especially, lubrication between the piston shoe and the swash plate greatly affects the performance and durability of the product. Proper lubrication between the rotating part and the fixed part plays an important role in reducing the frictional force, but excessive leakage reduces the volumetric efficiency of the hydrostatic steering unit. In this study, the lubrication characteristics according to the variation of lubrication gap between the piston shoe and the swash plate of the hydrostatic steering were analyzed using Ansys CFX. The results of the present study can be useful information for a hydrostatic steering unit.

Modelling and Simulation of a Hydrostatic Steering System for Agricultural Tractors

The steering system of a vehicle impacts on the vehicle performance, safety and on the driver’s comfort. Moreover, in off-road vehicles using hydrostatic steering systems, the energy dissipation also becomes a critical issue. These aspects push and motivate innovation, research and analysis in the field of agricultural tractors. This paper proposes the modelling and analysis of a hydrostatic steering system for an agricultural tractor to calculate the performance of the system and determine the influence of its main design parameters. The focus here is on the driver’s steering feel, which can improve the driver’s behavior reducing unnecessary steering corrections during the working conditions. The hydrostatic steering system is quite complex and involves a hydraulic circuit and a mechanical mechanism to transmit the steering to the vehicle tires. The detailed lumped parameters model here proposed allows to simulate the dynamic behavior of the steering system and to both enhance the understanding of the system and to improve the design through parameters sensitivity analysis.

Design and calculation of hydrostatic steering

Hydrostatic steering is widespread in the construction of modern tractors. In recent years, it began to apply in designs of haulage trucks and high-speed crawler vehicles. This steering allows for the free arrangement of its main units, simplifies the design, reduces the material consumption of the machine and improves the working conditions of the driver. At the same time, the cost of manufacturing a hydrostatic power steering in recent years has significantly decreased due to the development of high technologies for the manufacture of its units. Hydrostatic steering is a purely hydraulic transmission with flexible connecting pipelines (hoses) of relatively high pressure, less reliable in operation than mechanical tractions, this requires increased attention to the reliability and safety of its operation. For this reason, it is not recommended for use on vehicles with transport speeds above 50 ... 60 km / h. In the known scientific literature there are practically no publications on methods for designing and calculating hydrostatic steering. In the educational literature on tractors, published by professors of the Moscow Polytechnic University, information is given on the design and methods for designing and calculating hydrostatic steering. The task of designing and calculating such a steering is selecting the necessary parameters for the hydraulic cylinder, the metering pump and the power source (drive pump) for it. These units are produced serially, from which the hydrostatic steering is designed. The technique of design and calculation of single-circuit and dual-circuit hydrostatic steering is considered. Information is provided on the characteristics of gerotor type metering pumps of foreign and domestic production.

Hydrostatic steering: Design and evaluation for agricultural tractor

A hydrostatic steering unit was designed for agricultural tractor and its performance was evaluated at different values of front wheel inflation pressure and toe-in under stationary condition. In field condition, tests were performed at different values of front wheel inflation pressure, toe-in, front axle load and forward speeds. The hydrostatic steering performance was also compared with that of mechanical steering under the above conditions. The steering effort of hydrostatic steering was observed to be only 1/80 • of the mechanical steering.