Vol 90, No 2 (2023)

BACKGROUND: Automotive engines are one of the environment pollutants with harmful substances and greenhouse gases. Recently, the field of carbon-free or carbon-neutral energy has become the most relevant. In this regard, the task of reducing the carbon footprint of automotive equipment equipped with internal combustion engines remains urgent. This can be done by complete or partial replacement of the fuel with the carbon-neutral one, such as plant-origin biofuels.

AIMS: Study of low-temperature properties of fuel blends based on biodiesel derived from frying oil wastes.

MATERIALS AND METHODS: The vegetable oil ether was derived from purified frying oil wastes by esterification. Then fuel blends were obtained by mixing the derived ether with diesel fuel of different brands and butanol. The study of viscosity-temperature properties and density of the obtained fuel blends was carried out in the temperature range from -20°C to 40°C. The methods and equipment for determining these parameters meet the requirements of GOST.

RESULTS: The obtained study results helped to conclude that blended biodiesel in certain proportions can be used as fuel even at negative ambient temperatures, which is not uncommon for the start of a sowing campaign in spring and the end of field work in autumn in sharply continental climatic conditions.

CONCLUSIONS: The practical value of the study lies in the possibility of using fuel blends based on biodiesel derived from frying oil wastes at low temperatures.

BACKGROUND: Operating companies and consumers have demands to vehicles for efficiency improvement and cost cut. A part of substantial expenses is fuel cost, therefore use of vehicles with electric drive such as hybrid or pure electric (battery-electric) has potential for agriculture. It is mainly important for them to have the drivetrain characterized by high efficiency that increases autonomous mileage for one charge. To achieve this, it is necessary to control electric motors in the way to ensure maximal surface grip coefficient without wheel slipping. In this case, real-time defining of wheel resistance torque in necessary for efficient control.

AIMS: Development of the theoretical basis and the law of optimal estimation of the resistance torque at a shaft of traction electric motor of transport vehicles for the sake of efficient control of traction electric drive.

METHODS: Simulation of the law of optimal estimation of the resistance torque at a shaft of traction electric motor was carried out in the MATLAB/Simulink software package.

RESULTS: The article provides with theoretical basis of formatting the law of optimal estimation of the resistance torque at a shaft of traction electric motor of transport vehicles for the sake of efficient control of traction electric drive, the law of optimal estimation of the resistance torque at a shaft of traction electric motor and the results of simulation of the law of optimal estimation of the resistance torque at a shaft of traction electric motor obtained in the MATLAB/Simulink.

CONCLUSIONS: Practical value of the study lies in ability of using the proposed control laws for development of transport vehicles drivetrain control system.

BACKGROUND: One of the relevant issues to study is the motion of a cotton-harvesting machine (CHM) at the turning lanes of the cotton field along curvilinear path. At the same time, the CHM’s wheels rolling occurs with lateral slip of tires, so the machine may have unacceptable, according to the conditions for raw cotton harvesting, deviations in the lateral direction of the motion path when turning to enter the beds of the cotton field, and the traction performance of the CHM’s steered wheels declines significantly.

AIMS: Building mathematical models and carrying out kinematic simulations to determine the motion parameters and the values of lateral forces, the side slip resistance coefficients of tires of the CHM’s guide wheels necessary to achieve the required performance and to maintain the specified accuracy of the path motion along the headland of the cotton field with acceptable traction indicators.

METHODS: Dynamic processes are hugely complicated and difficult to analyze in full. The developed models are based on the balance equations and the wheels motion is not considered separately, taking into account tire deflections.

RESULTS: The kinematic scheme of turning of the MKh-1.8 CHM with front driving and rear steered wheels was considered. It was assumed that the MKh-1.8 CHM moves at a low constant velocity, so the centrifugal force can be neglected. In addition, lateral slip is the very parameter that reflects the impact of external force factors that go with the curvilinear motion on the machine.

CONCLUSIONS: Analyzing the obtained results, the following can be noted: during the curvilinear motion of the CHM, the main parameters that determine the turning of the machine are the CHM wheelbase, the average steering angle of the steered wheels and the slip angles of the rear axle. Moreover, it should be noted that the slip angles of the front and rear axles of the CHM, their values and change have a significant impact on the machine turning kinematics. The presence of lateral slip is the main reason of significant deviations from the given path of the CHM motion at a headland of a cotton field.

BACKGROUND: Due to the excessive vertical and angular vibrations of suspensionless vehicles used in agriculture and road construction that occur during movement, the velocity of their motion is limited, which, in the conditions of a constant traffic flow, reduces the road capacity. Therefore, the search for ways to improve the vibration-isolating properties of wheeled suspensionless vehicles is a relevant issue, the solution of which affects not only on traffic safety and driving comfort, but also on average speed and fuel efficiency.

AIMS: To determine the lateral stiffness of the pneumatic wheel from the rear axle of the MTZ-82 “Belarus” tractor at different tire pressures, basing on bench tests.

METHODS: On the basis of the hydraulic pulsation test rig of the Automatic Units department of the VolgGTU, a special-purpose movable supporting and measuring device was developed and assembled, the feature of which is that 4 rollers with flanges are installed on top of the hydraulic actuator force sensor, a flat rectangular base plate is supported on these rollers and connected with a vertical frame of the rig through a force-measuring device by means of a screw mechanism. The tested wheel is mounted on the base plate, the wheel’s axle is fixed on a vertically-moving traverse, on top of which weights creating the necessary vertical force are fixed. The test procedure consisted in measuring the lateral force and lateral displacement of the base plate until the tire slip occurred at the following tire pressures: at the recommended pressure of 0.16 MPa and at reduced pressures of 0.12, 0.08 and 0.04 MPa.

RESULTS: Based on the test results, the elastic characteristic curves of the lateral stiffness of the tested wheel were obtained. These characteristic curves have a regressive form, as their slope significantly decreases with a significant reduce in tire pressure. Thus, when the tire pressure is reduced from 0.16 to 0.12 MPa, there is practically no difference in the obtained values of lateral stiffness, which reaches 112.5 kN/m. After a 2-fold tire pressure reduction, the lateral stiffness decreases by 7%, and after a 4-fold reduction, by 28%. At the same time, the static tire deflection increases from 22 to 32 mm, which significantly increases the contact patch of the tire with the ground.

CONCLUSIONS: By means of the tests carried out, it is established that tire pressure reduction by 25–50% of the recommended value does not have a significant effect on the loss of lateral stiffness of the pneumatic wheel of the rear axle of the MTZ-82 “Belarus” tractor, which is important to use in order to increase traction and improve ride comfort of wheeled tractors.

The vehicle cross-country power depends both on the mover type and its weight-and-dimensional parameters, and on the physico-mechanical soil properties. Research of the interaction between the mover and a deformable soil at the stage of research and development using mathematic simulation makes it possible predicting the vehicle cross-country power.

The main mechanical soil parameters are the angle of internal friction and cohesion, which affect the process of interaction of the wheel with the deformable soil, since both normal and shear forces in the contact area. In this paper, sandy soil mathematical model is proposed and verified, and its parameters are determined for further research.

The developed mathematical model of the interaction of the wheel mover with a deformable soil is based on the application of the method of discrete elements. In this paper, the wheel mover force factors when moving on cohesionless soil are analyzed and also forms the dependence of the specific traction force on the specific circumferential force for various wheel rolling modes was obtained. As a result of applying the method of discrete elements to study the interaction of a wheel mover with a deformable support base, it is possible to determine the traction characteristic. Thus, the application of this method will reduce the number and scale of field tests.

Using the developed mathematical model the planetary wheeled mover traction characteristic was obtained and the comparative analysis with the nature test results was carried out.

BACKGROUND: Currently, almost all agricultural work is performed using tractors. As the transport speed of a tractor train increases, the amplitude of lateral and horizontal oscillations of its coupled units emerges and increases. At certain velocities, these oscillations become so large that they can lead to a rollover, in addition, shock loads occur in coupling devices, which make it difficult to handle a tractor train. The traditional method to prevent this is the velocity limit, which does not guarantee a positive result.

AIMS: Development of methods to improve stability, handling and safety of wheeled tractor trains by reducing the galloping and yawing of a truck tractor when towing heavy loads.

METHODS: The following options of the design of the system for countering the occurrence of self-oscillations in the design of a wheeled tractor train ensuring a reduction in the level of self-oscillations, increasing the stability, handling and safety of the tractor train have been proposed: the coupling device equipped with hydraulic damping devices operating at longitudinal and lateral folding; the control system for the individual traction electric drive of a truck tractor preventing the loss of wheel grip with the ground surface; the combined use of the control system for the individual traction electric drive of a truck tractor and the coupling device equipped with hydraulic damping devices; the combined use of the coupling device equipped with hydraulic damping devices and a steering correction system.

RESULTS: With use of simulation modeling methods, it has been established that the coupling device equipped with hydraulic damping devices adjustable by the folding angle of the tractor train and by the yaw angle oscillations of a truck tractor body should be recognized as the most acceptable and effective system for reducing self-oscillations of a wheeled tractor train at the current state of the art.

CONCLUSIONS: The practical value of the study lies in the possibility of using the proposed methods to eliminate the risk of self-oscillating processes in the design of promising types of agricultural machinery.

BACKGROUND: Soil-cultivating machinery and tools equipped with rotary working bodies are effectively used at operations of surface tillage. However, the subject of furrow formation with rotary working bodies is unaddressed to the full extent that makes it a relevant issue for the study.

AIMS: Revealing the patterns of furrow formation with rotary working bodies equipped with the cutting blades made along the elliptical line at the angle to the working body rotation plane.

METHODS: The grapho-analytical method is presented in the article and used for defining the parameters of a furrow formed with the following types of rotary working bodies: a spherical disk with a closed surface, an annular working body and a rotary working body with the cutting blades made along the elliptical line and set up at the acute angle to the rotation axis. The experiments were carried out in controlled laboratory conditions with a physical model of the rotary working body with the cutting blades made along the elliptical line in a soil channel filled with dampened sand. During the experiments, the attack angle was 20-40° with a step of 10° and the kinematic coefficient, which is the ratio of circumferential velocity to transverse velocity, had the following values: 1, 1.4, 1.8 and 2.2.

RESULTS: The cutting blades made along the elliptical line form short furrows with the ellipse-shaped cross-section and with the angle of inclination from the movement direction of 20-40° depending on the attack angle and the kinematic coefficient. Meanwhile, the furrows formed with the working body have the form of a parallelogram at the top view.

CONCLUSIONS: The practical value of the study lies in revealing the features of furrow formation with rotary working bodies equipped with the cutting blades made along the elliptical line aimed to making a flat bottom of a furrow necessary for grain planting.

On April 7, 2023, our colleague, Doctor of Technical Sciences, Professor, Honorary Worker of Higher Professional Education, Deputy General Director for Science of the Central Research Automobile and Automotive Institute (NAMI), a member of the editorial boards of the “Tractors and Agricultural Machines” and “Izvestiya “MAMI”” journals Sergey V. Bakhmutov passed away.

Sergey V. Bakhmutov was a prominent specialist in the following scientific fields: vehicle dynamics, active safety, optimization of design parameters, highly automated transport and technological facilities.

He was the author and co-author of about 170 scientific papers, including 20 books, 22 certificates of authorship and patents for inventions and utility models.