Електропривод електромобіля з двоступеневою коробкою передач

Abstract

Thesis for the degree of Doctor of Philosophy in specialty 141 "Electrical power engineering, electrical engineering and electromechanics" (14 – Electrical engineering) – National Technical University "Kharkiv Polytechnic Institute", 2021. The work was carried out at the Department of "Automated Electromechanical Systems" of the National Technical University "Kharkiv Polytechnic Institute" of the Ministry of Education and Science of Ukraine. The object of research is the automatic control system of an electric drive of an electric vehicle with a two-speed gearbox, which ensures synchronization of the speeds and phases of the shafts. The subject of research is electromechanical and electromagnetic processes in the electric drive of an electric vehicle when switching a two-speed gearbox with the synchronization of the speeds of the shafts and their phases. The thesis is devoted to improving the energy efficiency of an electric drive of an electric vehicle through the use of a two-speed gearbox, which is simpler than a traditional multistage gearbox and therefore more reliable, cheaper and lighter, and does not require mechanical synchronizers to align the shaft speeds. It is proposed, in contrast to the known technical solutions, not only to synchronize the speeds of the shafts, but also to ensure the automatic synchronization of their phases, which is supported by the patent of Ukraine, obtained by the author. At the same time, the speed of step switching, elimination of shock increases, and the smoothness of movement is improved. The thesis is connected with the actual world problem of saving fuel organic energy resources, especially important for Ukraine, which is provided with its own resources only by half and consumes most of the oil and gas at the expense of foreign exchange. As it is known, this relevance is determined not only by the need to store organic resources, it is a raw material for the manufacture of plastics, herbicides, paints, etc., but also contributes to the solution of the environmental problem, because now in large cities the level of exhaust gases reaches, and sometimes exceeds critical. In the introduction, the choice of the research topic and the relevance of the thesis are substantiated, the aim and objectives are formulated, the object, subject and methods of research are determined, the connection of work with scientific topics according to the plans of the Ministry of Education and Science of Ukraine is shown, scientific novelty is provided and the practical significance of the results obtained is formulated. The first section is devoted to a review of literary sources on the thesis topic, in particular, a comprehensive analysis of the state of automobile electric vehicles, a typical solution for the construction of transmissions for cars and electric vehicles. The main components of the traction electric drive of electric vehicles are considered, a comparison is made of various types of power supplies, semiconductor converters, electric motors and the choice of their types for the construction of control systems and simulation of electromagnetic, electromechanical and mechanical processes is substantiated. The physical nature of the increase in the energy efficiency of the electric drive of an electric vehicle using a two-stage gearbox has been clarified. Research objectives are formulated. In the second section, the possibility of simplifying the shape of the dogs of the gear and sleave is noted, as well as the reasonably functional diagram of the electromechanical control system and the schematic diagram of the power unit of the traction electric drive, taking into account the electric vehicle created at the department on the basis of a "Lanos" car. In the third section, a mathematical and computer model of the electromechanical system of an electric vehicle is built. The mathematical model included four groups of equations: the equations of mechanics, the equation of power electric circuits, the equations of electromechanical energy conversion, and the control equation. The equations of mechanics took into account the nonlinearity of the aerodynamic resistance component, the change in the moment of inertia converted to the speed of the electric motor shaft when switching the speeds from the first to neutral, from neutral to the second and vice versa. Considering the significant frequency of the pulse-width modulation of the semiconductor converter, the electromagnetic inertia of the armature circuit of the electric motor and the large mechanical inertia of the moving parts of the electric vehicle, the mathematical model of the converter and electromechanical energy conversion by the electric motor is represented by a smooth component – namely, the aperiodic link of the first order. The control of the electric drive was chosen to be microprocessor-based, which made it possible, in addition to solving the problems of coordinate control, to solve the necessary logical tasks. With a high clock frequency of the microcontroller, the control signals can be considered analog. It is proposed to solve the problem of matching the speeds of the shafts and their phases using a cascade control system. A PI controller is synthesized for the current loop, and a P controller is synthesized for the speed loop. The phase alignment of the shafts is ensured by the addition of the above-mentioned position feedback, the value of which is calculated by the microprocessor based on the encoder signals. The computer model was built in the MATLAB/Simulink environment according to the structural diagrams of all components of the electromechanical system of an electric vehicle electric drive. The fourth section provides input data for computer modeling, which included the parameters of the gearbox, electric motor, electric vehicle, the coefficients of the rolling friction and aerodynamic resistance. The process of acceleration of an electric vehicle with sequential gear shifting is considered in the following cases: 1 – only the shaft speed synchronization system functions; 2 – the system for synchronizing the speeds of shafts and phases is functioning when tuning to the modal optimum; 3 – the speed and phase control system is functioning at a reduced coefficient of the P controller. It is shown that the 2nd option causes phase fluctuations in the transient process, which are avoided with the implementation of the 3rd option. Verification by computer simulation of the process of automatic coordination of the speeds of the shafts of the electric motor and the output shaft of the gearbox showed that the speed of the coordination of the speeds of the shafts depends on the initial conditions and the more, the greater their inconsistency. As can be seen from the timing diagrams, with a sufficiently significant inconsistency, their coordination takes 60-68 ms. Phase synchronization starts after speed matching and is completed in 28-29 ms. That is, the total synchronization of the speeds and phases of the shafts is 88-97 ms, which is significantly less than the standard data for passenger vehicles (150-200 ms). In the fifth section, a laboratory bench for experimental research is developed and a two-stage gearbox is created using the 3D modeling method, and the possibility of simplifying the dogs of the gearshift clutch and gears is proved to ensure reliable gear shifting. The theoretical and applied results of the thesis were used in the educational process of the department "Automated electromechanical systems" NTU "KhPI" for training students in the specialty 141 "Electric power, electrical engineering and electromechanics" in the lecture courses "Electrical equipment of an electric vehicle", "Actual problems of modern electric drive" and in the preparation of laboratory workshop. The thesis results were introduced during the implementation of the program M3423 of the Ministry of Education and Science of Ukraine "Research of an energy-efficient electric drive of a dual-use electric vehicle with increased traction and camouflage characteristics", in which the section "Improving the energy efficiency of an electric vehicle using a simplified gearbox" was performed by the author of the thesis personally.