Introduction
Through the layout of energy resources in our country, coal resources still dominate and will not change in the short term. In recent years, the development of intelligent coal mining has been rapid. To achieve the smooth implementation of intelligent coal mining, it is necessary to ensure the high efficiency and reliability of underground mining equipment. Currently, the application of permanent magnet synchronous motors to coal mining machinery can effectively shorten the transmission chain, reduce transmission components, improve overall system reliability, and is also one of the new technologies for intelligent driving, energy conservation, unmanned and intelligent coal mining. It is of great significance for the promotion of intelligent coal mining technology. The application of permanent magnet synchronous motor to the cutting section of a coal mining machine constitutes a new type of transmission form for the cutting section of the coal mining machine. This new type of coal mining machine cutting transmission system removes the traditional planetary gear at the end of the cutting section and replaces the three-phase asynchronous motor with a permanent magnet motor with low-speed and high torque characteristics. It can effectively solve the problem of long transmission links and high failure rates of high-speed spur gears and low-speed planetary gears, while reducing the speed of the spur gear area and ensuring the cutting torque of the end drum. Of course, the new system still faces complex mining environments, and the gangue in the coal seam will further intensify the stress on the cutting part. Therefore, in order to ensure the normal operation of the new system, it is necessary to conduct research on the reliability of the gear transmission system of the cutting part of the new coal mining machine. In the study of coal rock cutting, in order to reduce the wear of the conical pick during the rotary drilling cutting process, an interference model for drilling cutting was established based on coal cutting theory; The load acting on the spiral drum of the coal mining machine was simulated, and the smoothness of the cutting drum’s operation was verified through virtual software simulation. In the study of transmission system reliability, failure correlation has become a hot topic in system reliability research. In order to improve analysis accuracy, a more comprehensive gear reliability calculation method is proposed based on Copula theory; A stochastic wind load model was established with wind turbines as the research object, and the influence of different parameters on system reliability was studied; Revealed the impact of failure correlation and strength degradation on the reliability of wind turbine gears; A study was conducted on the nonlinear dynamic system of gear transmission systems with wear faults. In addition, a structural fatigue life prediction model based on strength damage was established for composite materials to address the issue of material strength. On this basis, an alloy was selected as the test material, and the applicability of the above model was verified.
The study focuses on the gear transmission system of the cutting section of a coal mining machine driven by a permanent magnet motor, and conducts reliability analysis of the system under complex working conditions. Based on the load characteristics of coal seam cutting under the condition of containing gangue, a dynamic model of the gear transmission system of the cutting part of the coal mining machine driven by a permanent magnet motor under the influence of load is constructed using the concentrated mass method. The dynamic behavior of the gear transmission system during service is explored, and the dynamic meshing force of the gears is analyzed. By using the rainflow counting method, discrete loads are obtained, and the stress load spectrum is determined using the wave center method. And based on the stress and strength degradation characteristics of gears, a residual strength model under multi-level random loading is established. Finally, the dynamic reliability evaluation of the system under failure related conditions is completed based on the stress strength interference theory, laying the foundation for the stable operation and structural optimization of the cutting part of the coal mining machine.
Due to the meshing of various gears, the gear pairs are connected by transmission shafts, and the components interact with each other and bear the same load. The failure of any component will directly affect the operation of other components and even the entire system. Therefore, the reliability evaluation of the system must consider the failure correlation between components. Obtain the corresponding failure rate curve from the dynamic reliability of each gear. It can be observed that after 8 years of service, the failure rate of the gear system begins to rapidly increase. The dynamic reliability of the system obtained through two methods of gear failure correlation and mutual independence analysis shows that the reliability decay rate gradually increases from slow to fast, and the reliability under failure correlation is always greater than that under mutual independence, which is in line with Ditlevsen’s upper and lower narrow boundary theory. Therefore, under the same conditions, structures designed according to the principle of mutual independence will be more redundant, while structures designed according to the principle of failure correlation will be more redundant The reliability of the analysis is more reasonable.