Search

Hydraulic support is the key support equipment for underground coal mining. The frequent impact load during the mining process easily causes damage to the hinge joints and reduces the stability of the hydraulic support. To improve the stability of the hydraulic support, a rigid-flexible coupling numerical model of the support has been developed. The validity of the model is verified through the static loading test. Next, the impact loading test of the hydraulic support is carried out. The force response characteristics of the hinge joints and the vibration response characteristics of the leg system are discussed when both the canopy and goaf shield bear impact load. The results indicate that when only the canopy bears the impact load, the hinge joint of the front leg is the most sensitive (up to 139.4 %). When the impact load acts both on the canopy and goaf shield, the dynamic response of each hinge joint of the hydraulic support (except the rear leg) reaches the peak value. With the backward movement of the impact load on the goaf shield, the hinge joint force presents different pressure-relief characteristics.

Screw conveyors are widely employed in industrial fields for conveying bulk materials. The shearer drum which uses the screw conveying principle is responsible for excavation and conveying coal particles onto the chain conveyor. Screw conveyor performance is affected by potential factors, such as the blade axial tilt angle and style, core shaft form and diameter. The effect of blade axial tilt angle on the conveying performance was investigated with the help of DEM. In the case of the screw conveyor, the mass flow rate, and particle axial velocity increased with increasing positive axial tilt angle, and declined with increasing negative axial tilt angle. In the case of the drum, the mass flow rate, particle axial velocity, and loading rate first increased and then decreased with increasing positive axial tilt angle, and decreased with increasing negative axial tilt angle. These results can be considered as a benchmark for screw conveyor and drum structural designs with axial tilt screw blades.

The automatic height adjustment of a shearer cutting drum is a key technology for shearer automation. However, a fundamental and important requirement for underground electronic products is explosion-proof rating, which creates great challenges to the research on the control method of the shearer height adjustment system. To address this problem, a novel shearer height adjustment control method was proposed based on basic fuzzy control, and the feasibility of the height adjustment method was studied with the help of multisoftware cosimulation technology. First, the drum cutting coal model was established using Finite Element Method (FEM) software LS-DYNA, the mechanical model of the gear transmission system model and the height adjustment system were constructed with the multibody dynamics software ADAMS, the hydraulic height adjusting system model was constructed with AMESim, and a fuzzy controller for shearer height adjustment was developed in Simulink. Then, the data conversion interface between the mentioned models was constructed using MATLAB, to obtain the cosimulation model for the shearer automatic height adjustment. Finally, with the help of fuzzy control method, the feasibility of the cosimulation model used in the adaptive control method of the shearer drum height adjustment was verified. The results show that the cosimulation model can adequately describe the height adjustment process of a shearer, which lays a foundation for the optimization of adaptive height adjustment method. At the same time, the proposed model is also applicable for studying the dynamic characteristics of the mechanical-electrical-hydraulic coordination in the process of shearer adaptive height adjustment.

Dynamic characteristics analysis on shearer drum is an important aspect in shearer design and a well-structured shearer drum provides better performance in vibration reduction and service life extension. To make reference for structure improvement, many researchers have focused on the dynamic analysis on cutting pick. However, the simplified model such as single pick, linear motion and continuous coal in the previous study made it divorced from actual situations underground. On basis of this, the model of shearer drum with several arranged picks and the coal model with some distributed rock have been set up in order to consist with the real working conditions. Through simulation, it can be found that the mean force in X-direction is little influenced by rock distribution, but the peak force in X-direction fluctuates greatly under different rock distribution. During the analysis on the peak force, it can be found that this kind of force could be cut down effectively when the rock was distributed on the top of the shearer cutting range. Based on these conclusions, we can program the cutting strategy to lower the influence of cutting forces on the shearer and its drum in the future.

The extremely poor loading performance of a thin coal shearer drum affects the mining efficiency in thin seam mining seriously on account of the restriction by the complicated mining environment and seam thickness. The coal loading performance of the drum is influenced by several complex factors, such as motion parameters and structural parameters, including the structure and form of the hub. The form of the drum hub is cylindrical in general, and in order to study the influence of the hub form on the coal loading rate of the drum, seven drums with different hub forms and structures were designed. The influence of the complexity of hub structures on the coal loading performance was studied by discrete element method (DEM) simulation in this paper. The change curves with the research object of different drums, such as coal loading rate, velocity field distribution, and contact force between fallen coal particles, were obtained. The results showed that the conical hub drum can improve the coal loading performance than the cylindrical hub drum, and the curve-shaped hub drum had a more obvious promotion on the coal loading performance. The coal loading rate increased first and then decreased with the increase of hub cone angle. Compared with the conical hub drum, the curve-shaped hub drum can not only improve the coal loading rate, but also has a larger space containing coal. This study has proposed a drum with a new form hub which could increase the coal loading rate, and the methods and conclusions provide the guidance for drum hub design.

The cutting unit of a mining shearer is composed of a drum, gear transmission and hydraulic height adjusting mechanism. To obtain the dynamic characteristics of crucial components in the coal cutting process, a model of a drum cutting coal was constructed using LS-DYNA. The model of gear transmission was constructed with Adams, and a model of the hydraulic height adjusting system was constructed with AMESim. Data transmission and co-simulation of these three models were implemented with MATLAB. Changes of the meshing force, acceleration and amplitude–frequency characteristics of key gears under different conditions were obtained. From the research, we conclude that it is effective and feasible to apply the multi-software co-simulation used by this paper to research a complex mechanical–hydraulic system such as a shearer cutting unit; supports from a hydraulic cylinder can decrease the meshing force of gears to some extent; and the meshing force of gears increases significantly as the mining height of the drum increases.