Investigation On Electromechanical Characteristics Of The Cutting Transmission System Of The Long-wall Shearer Under Non-stationary Conditions

The coal is main power source at present and for a long time in future in China, moreover, the coalmining is developing to deep coal seam. The hostile environment of high temperature, high pressure, and high humiditybrings stricter requirement for the mechanization, unmanned operation and adaptability to kinds of operation conditions for the mining equipments. The long-wall shearer is the main mining equipment that is well adaptive to all kinds of coal seam. The cutting unit is one of the main parts of the long-wall shearer, including the electric motor, gear transmission, and drum. The drum load possesses the properties of large fluctuation and intensive impact, because of the uneven hardness of coal, brittle crack of the coal, hard inclusion, and rock intercalation when the drum cuts the coal seam, moreover, the transmission chain of the cutting part is long with large number of transmission elements for the cutting transmission system, which make the cutting electromechanical transmission system a weak part of the long-wall shear. The drum speed cannot be adjusted for the common long-wall shearer at present(named as ?constant cutting speed long-wall shearer?), so the hauling speed usually decreases when the coal hardness increase. Though this operation can reduce the drum load and internal dynamic loads of the transmission system, the coal production will decrease. Therefore, the drum speed is designed to be adjusted for the long-wall shearer in future to improve the adaptivity to kinds of operation conditions and the reliability of the long-wall shearer, and guarantee coal production. This kind of long-wall shearer is named as ?variable cutting speed long-wall shearer?. The reliability and adaptivity to kinds of operation conditions is closely relative to the electromechanical dynamic characteristics of the cutting transmission system, moreover, the long-wall shearer works under non-stationary operation conditions(sudden-changing load, variable speed process), so it is an important duty to study the electromechanical dynamic characteristics of the cutting transmission systemunder non-stationary operation conditions in the design of long-wall shearer.According to the 4thtaskof The National Major Basic Research Program of China(973 Program, Grant No. 2014CB046304), the electromechanical dynamic characteristics are study for the cutting transmission system of the long-wall shearer under non-stationary operation conditions(sudden-changing drum load, variable speed process) in the aspects of theory and experiment. These research achievements provide some advices for optimization mechanical parameters, chosen of electric driving system, and design of control system for the long-wall shearer, laying the foundation of improving the reliability and adaptivity to operation conditions of the long-wall shearer. The investigations including the followings:(1) The electromechanical dynamic modeling of the cutting transmission system of the long-wall shearerTo construct the electromechanical dynamic model, three kinds of models are needed including the electric motor model, gear dynamic model, and drum load model. The electric motor model and drum load model existing at present can be used directly. The gear dynamic models at present are mainly proposed forthe problems of gear vibration, whose nominal angular velocity is constant(the following ?the dynamic model of variable speed process? is pertinent at this), and the vibratory angular displacements are chosen asthe general coordinates.Given this, the dynamic models of variable speed process for herringbone gears(parallel-axis gears and planetary gears) are proposed, because the spur gears in the long-wall shearer may be replaced by herringbone gears and the herringbone gear dynamic models can also be used for spur gears. In these models, the angular displacementsare chosen as the general coordinates, and the time-varying meshing stiffness is regard as the periodic function of the angular displacement directly, so these modelsare convenient to be connected to the electric motor dynamic model and can also be used in variable speed process. The electric motor model, drum load model, and the gear dynamic model of variable speed process proposed herein are combined to construct the electromechanical dynamic model of the cutting transmission system of the long-wall shear.(2) Investigation of electromechanical dynamic characteristics of the cutting transmission system of the constant cutting speed long-wall shearer under the sudden-changing loadThe constant cutting speed long-wall shearer refers to the common shearer at present, whose drum speed cannot be adjusted. The following investigations of electromechanical dynamic characteristics of the cutting transmission system of the constant cutting speed long-wall shearer under the sudden-changing load are conducted:1) The dynamic characteristics of the cutting transmission system of the constant cutting speed long-wall shearer are investigated under sudden-changing load. Based on this investigation, the effect of mechanical parameters(stiffness, damping, etc.) on the dynamic characteristics is analyzed to give some advices for the mechanical design of the cutting transmission system.2) The electrical characteristics of the cutting transmission system of the constant cutting speed long-wall shearer are investigated under sudden-changing load. The feasibility is explored that the stator current is used as the feedback signal of the control system to reflect the drum load.3) The steady-state and dynamic electric motor model are compared about the effect on the electromechanical dynamic characteristics obtained by simulation to provide some advices for the electromechanical dynamic modeling of the cutting transmission system of the long-wall shearer(3) Investigation of electromechanical dynamic characteristics of the cutting transmission system of the variable cutting speed long-wall shearerThe variable cutting speed long-wall shearer is the long-wall shearer whose drum speed can be adjusted. The drum load can be reduced by increase the drum speed, avoiding the decrease of the coal production due to the decrease of the hauling speed, when the shearer cuts from the soft to hard coal seam.The following investigations of electromechanical dynamic characteristics of the cutting transmission system of the variable cutting speed long-wall shearer are conducted:1) The electromechanical dynamic characteristics of the cutting transmission system of the variable cutting speed long-wall shearer are investigated under variable kinds of drum loads including pulse, step, and random load, to provide some advices for the mechanical design, monitor of cutting condition, and chosen of feedback signal of the cutting transmission system of the variable cutting speed long-wall shearer.2) The electromechanical dynamic characteristics of the cutting transmission system of the variable cutting speed long-wall shearer are investigated under different variable speed processes, to provide some advices for the design of the control strategy of the variable cutting speed long-wall shearer.(4) The experimental and simulating investigation of electromechanical dynamic characteristics of the cutting transmission system of the long-wall shearerTo validate the electromechanical dynamic modeling method and the obtained electromechanical dynamic characteristics, the test rig of the cutting transmission system of the long-wall shearer is constructed. On the test rig, the electromechanical dynamic characteristics of the cutting transmission system are investigated, validating the electromechanical dynamic characteristics obtained in this dissertation. The electromechanical dynamic model of the experimental cutting transmission system are constructed based the modeling method in this dissertation. The modeling method in this dissertation is validated by comparison the simulated and experimental result, laying the foundation of deep electromechanical dynamic analysis of transmission system and control system design based on the electromechanical dynamic analysis for the long-wall shearer.