The thesis is devoted to the study of curvilinear motion of wheeled vehicles and the class of tractors with 4K2 and 4k4 wheel formulas. A greater focus is placed on studying and investigating the curvilinear motion of a four-wheeled tractor. All conclusions and provisions apply equally to any four-wheeled vehicle with front steerable wheels.
One of the most important tasks of modern tractor production is the automation of unit control. At the same time, such classical problems as kinematics and dynamics of curvilinear motion remain unresolved in full, taking into account various factors affecting the trajectory of movement and its parameters. Curvilinear motion (pivoting motion) takes place in the operation of any transport or traction machine. The theory of turning includes a large number of different models of movement. These specific features are important when designing new or studying the operation of existing machines. Therefore, the study of curvilinear motion of machines remains an important topic of scientific research.
The theoretical studies of the curvilinear motion of a tractor require, first of all, obtaining the mathematical equations of the trajectory of motion when driving into the curve, during the so-called static turn with a constant heading angle and at the section of driving out of the curve. There are main reasons for the need for equations of motion. One of them is related to the introduction of automatic machine-tractor aggregates (MTA) control into the practice of performing field operations when growing plants. The full automation of MTA operation control without the driver’s participation requires obtaining accurate information on the position of the vehicle relative to the specified trajectory during the entire operating time. A given trajectory of motion is called a control trajectory, and there is a theoretical function of curvilinear motion, which should be obtained with sufficient accuracy for any conditions of motion of the tractor.
The paper presents the results of using a universal equation in parametric form to make the trajectory of a four-wheeled vehicle with front steerable wheels for the areas of driving into the curve and driving out of the curve in the function of the angle of rotation of the frame of the vehicle, taking into account the intensity of rotation of the front wheels or steering wheel. A program for constructing a complicated trajectory and a method for interfacing its individual sections are presented. These equations may be used for planning MTA reversals during processing and performing technological operations, as well as for automatic control of aggregates and machines.
In conditions of small field size, the tractor aggregate’s U-turns during agricultural work make up a significant part of the total amount of work. This results in a compacted, deformed land area. In fact, this is a decrease in soil fertility. Therefore, the issues of economic efficiency of optimizing the curvilinear motion of a tractor aggregate, which are still insufficiently highlighted in the scientific literature, are becoming increasingly practical.
There is still little research on such a source of energy savings as unproductive energy costs, which include turning tractor aggregates while working in the fields. The MTA covers many tens of kilometers long during operation. Therefore, the main task of kinematics and dynamics of motion of the aggregate is to choose the method of motion of MTA, which will meet such requirements as work quality, maximum productivity with the lowest consumption of fuel and other resources per unit of work performed; safe operation of machine operators; minimal negative impact on the environment.
The paper presents the results of an analytical study of the motion of a four-wheeled vehicle along a curved trajectory, general equations of the trajectory of driving into the curve and driving out of the curve are obtained, and numerical solutions of equations are given on the example of an aggregate based on the MTZ-80 tractor. The factors that cause wheel deflection are considered. A method for taking into account the influence of lateral wheel deflection on the trajectory of curvilinear motion of the vehicle is proposed. An analytical method for obtaining the trajectory of curvilinear motion of two-axle wheeled vehicles is developed, taking into account the influence of the phenomenon of wheel deflection. The trajectories of movement are determined using analytical equations that make it possible to create software for controlling the movement of machines.
The paper analyzes the latest scientific research and publications on the issues of curvilinear motion of vehicles and provides equations for the curved trajectory of the center of gravity of a four-wheeled vehicle with front steerable wheels.
