In order to improve the cutting speed control performance of the ball screw sub-laser cutting platform, based on the principle of double power reaching law and fuzzy control a controller of gain fuzzy adaptive double power reaching law was designed. The Lagrangian dynamic model of the ball screw pair motion system was established by lumped parameter method for considering the various axial and torsional vibrations of ball screw pair. Meanwhile, the Stribeck friction model was introduced to estimate the friction that high-precision control systems were greatly affected by the high nonlinearity of friction. Due to the chattering of the traditional double power reaching law, the saturation function was introduced instead of the symbol function, which inhibited the chattering of control system to some extent. The fuzzy relationship between the laser cutting depth, velocity and gain was analyzed and established.The fixed gain was difficult to ensure the optimal dynamic control effect of the laser cutting, based on the laser cutting depth as the adaptive reference, the fuzzy controller based on the fuzzy rule table adaptively adjusted the control gain, which enhanced the robustness and adaptability of the system. Simulation and experimental results showed that it was not only solved the overshoot problem of the control system, but also improved the response speed and robustness of the system, effectively weakened the chattering of the system compared with the PI controller and the traditional double power reaching law controller. Meanwhile, the laser cutting laboratory platform was built. It was found that the best laser cutting depth range was 1/2～2/3 the thickness of the cell, and the best laser cutting speed was 200 m/s by the laser cutting experiment on the ball screw sub-laser cutting platform. On this basis, the PI controller, the traditional double power reaching law controller and the control method proposed in this paper were used for laser cutting. By comparing and analyzing the slit image of battery obtained by the metallographic microscope, it was showed that the slit of the cell obtained by the control method proposed in this paper is flat, which verifies the superiority of the control method proposed in the laser cutting speed control performance..
In recent years, the development of new energy vehicles industry is accelerating. Lithium nickel cobalt manganese/aluminum oxide ternary cathode materials (NCM/NCA), especially with the nickel content ≥50%, has aroused great interest in both academia and industry. This is mainly due to the fact that the aggregative parameters of performance and cost of NCM/NCA are superior to those of traditional cathode materials, such as LiCoO2 and LiFePO4. However, the application of NCM/NCA is affected by a number of drawbacks, including poor safety and insufficient cycle stability and so on, which are mainly attributed to its crystal and surface structure. Researchers have carried out various efforts to solve these problems and further improve the performance of NCM/NCA. Some remarkable results have been achieved in the past few years. In this review, the latest research progress on coating and doping of Ni-rich ternary cathode materials is summarized from the view on the mechanism of structural and electrochemical improvement of NCM/NCA. Finally, the perspective for the development of NCM/NCA cathode materials is also prospected..
The permeability characteristics of iron tailings are one of the important factors affecting the stability of the dam. The permeability coefficient is an important indicator of its permeability. Many formulas for calculating permeability coefficient have been proposed by scholars at home and abroad. However, these formulas are mostly applicable to coarse-grained soil, and its applicability to iron tailings is not clear. Therefor it is necessary to verify the accuracy of these formula and establish a calculation model for the permeability coefficient of iron tailings. The permeability properties of iron tailings sand were analyzed from various angles such as FC value, gradation, particle size, specific surface area and inter-particle void ratio with water head test in laboratory. The results showed that the permeability coefficient of iron tailings sand is affected by the fine content. The threshold of fine content is about 40%. The traditional formula for calculating the permeability coefficient was applied, but the results are inaccurate. The relationship among permeability coefficient of the iron tailings sand and the non-uniform coefficient Cu, the curvature coefficient Cc, the average particle size, the weighted average particle size, the volume ratio surface and the interparticle void ratio es is nonlinear. It is difficult to characterize the change of permeability coefficient when the fine content is large. However, the relationship between permeability coefficient of the iron tailings sand and the effective particle size and inter-particle void ratio is linear. A formula was developed for the determination of permeability coefficient of iron tailings sand by analyzing the effective particle size and inter-particle void ratio data. It is significant for the seepage field analysis and stability calculation of the Chenkeng tailings dam. This can be used to calculate the permeability coefficient of magnetite tailings..
The seismic effect created by blasting operations vibrates adjacent buildings and disturbs residents living in these buildings, often leading to disputes and complaints. In this paper, the vibration acceleration was calculated based on the measured blasting vibration velocity using the wavelet denoising-based four-point forward difference method. The infinite impulse response (IIR) digital filter was used to obtain the frequency weighting of acceleration, so as to calculate comfort assessment indexes such as vibration dose value (VDV), maximum weighted vibration severity (KBFmax and annoyance rate. Combined with the survey of engineering cases, comparative analysis was conducted on the indexes and standards that were suitable for the comfort assessment of blasting vibration. The results indicated that VDV, KBFmax, and annoyance rate indexes could all reflect the impact of blasting vibration on comfort to a certain extent, and that while the first two indexes could only be used for qualitative assessment, the annoyance rate index could be used for quantitative comfort assessment. In addition, by applying these assessment indexes for the comfort assessment of blasting vibration, preliminary control standards were provided..
A coupled dynamic model, which contains helical gears-shafts-bearings for a wind turbine gearbox transmission system, was built considering nonlinear factors of the time-varying mesh stiffness, the external varying load, and the dynamic transmission error at first. The model is confirmed to be right after comparing the theoretical data with the experimental load sharing values, and also it is found that the static load sharing is conservative to evaluate the non-equilibrium effect of a planetary gear system. Besides, the analyzing results of the influence of average error and amplitude error on the load sharing show that the load sharing could be decreased if the error goes up a little. Then, by means of treating the static tracing point as the dynamic initial values, we analyzed the initial position’s influence on the load sharing of transmission system to provide a theoretical basis of load sharing control. Furthermore, we explored the influence of high-speed shaft position angle on the load sharing and the dynamic load factor of gears fixed on the parallel shafts. The results provide useful theoretical guidelines for the design of parallel shaft gear system in the wind turbines..