| As one of the key equipments in the fully mechanized face,the shearer's dynamic characteristics affect the reliability and stability of the whole machine directly.Thus,the paper studies the dynamic characteristics of shearer by combining theoretical modeling,numerical simulation and experimental verification systematically.The main contents of the paper are as follows:The shearer drum load test tests were carried out under five different traction speeds by using the experiment platform for the mechanical testing and analysis of the shearer working face.The fitting formula of the traction speed correction coefficient of the drum load was constructed by the data fitting method,and the fitting formula was verified by the experimental method.In order to study the influence of the meshing characteristics of the moving wheel and the pin row of shearer on the stability of the whole machine during the coal cutting process,the tangential contact stiffness model of the flat boot and the middle groove was established from the microscopic angle by using the three-dimensional fractal theory.Based on the Hertz contact theory,the normal meshing stiffness model of the shearer moving wheel and the pin row joint surface with clearance was established.According to the structure and working principle of the shearer height adjusting cylinder,the support stiffness model of the height adjusting cylinder was established.The rocker bending stiffness model and the tensile-vertical bending joint stiffness model between the fuselage and the traction section were established by using the Hooke's law.Based on the above models,using the theory of vibration mechanics and multi-body dynamics,a 13-degree-of-freedom nonlinear dynamic model of the shearer in the traction direction was established.The numerical analysis method was used to solve the nonlinear vibration characteristics of the key components such as the shearer drum,the rocker and the fuselage under the condition that the shearing speed of the shearer is 3m/min,the coal rock solid coefficient f=3 and the mining pitch angle are 0.The results showed that under the experimental modified load,the main vibration frequencies of the front rocker,the walking box and the fuselage of the shearer are 17.57Hz,11.89Hz and 8.83Hz,respectively.The vibration swing angle and displacement fluctuation range of the front drum,the rocker arm and the walking box were-0.4rad-0.8rad,-0.1 rad?0.5rad,±12 mm respectively,wherein the load impacts of the front drum and the walking box of the shearer were largest in the traction direction,and the vibration acceleration fluctuation range was ±500mm/s2 and ±400mm/s2 respectively.As the hardness of coal rock increased from f=3 to f=5,the mean value of the vibration displacement of the front box of the shearer was the largest,with a range of 5.94mm?7.12mm.When the shear traction speed changed from 1.5m/min to 3.5m/min,the mean range of the front drum and rocker vibration swing angles was 0.18rad?0.37rad and 0.17rad-0.32rad respectively.When the shearer pitch angle changed from 0 to 30°,the range of vibration angle and displacement of the front drum,the rocker and the walking box varied from 0.32rad to 0.48rad,0.25rad to 0.47rad,and 4.46mm to 2.64mm respectively.In order to study the influence of verticality and swing vibration characteristics on the stability of the whole machine during the shearer cutting process,the contact friction characteristics with clearance of the shearer fuselage,rocker and traction section are considered comprehensively.The tensile-vertical and horizontal bending connection stiffness model of the fuselage and traction section,the connection stiffness model of the rocker and the traction section,and the contact model of the boot and the scraper conveyor were established respectively.Based on the above models,a nonlinear dynamic model of 13-degree-of-freedom of the shearer with vertical swing coupling was established,and the nonlinear vibration characteristics of the key components of the shearer are numerically solved.The results showed that under the experimental modified load,the main vibration frequencies of the shearer front traction section,the walking box and the fuselage were 7.47Hz,11.06Hz,and 9.21 Hz respectively.The vibration displacement range of the front rocker and the traction section is-1mm?5mm,-2mm?5mm respectively,and the vibration acceleration fluctuation range of the front rocker is±400rad/s2±400mm/s2.When the traction speed changed from 1.5m/min to 3.5m/min,the average range of vibration angle and displacement of the front drum,the rocker,the walking box and the traction section are 0.17rad?0.34rad,2.07mm?5.70mm,0.30mm?2.37mm,0.11mm?2.01mm respectively.As the hardness of coal rock changed from f=3 to f=5,the mean value of vibration displacement of the front walking box varied from 1.96 to 4.64 mm.When the shearer pitch angle of changed from 0 to 30°,the range of vibration angle and displacement of the front drum,the rocker and the walking box varied from 0.36rad to 0.52rad,0.27rad to 0.50rad,and 2.29mm to 4.32mm respectively.In order to study the influence on the shearer stability in the oblique cutting process,the contact friction characteristics of the shearer components under the oblique cutting conditions were considered,and the normal contact stiffness model with clearance of both ends of the pin row,the tangential stiffness model with clearance of both ends of the pin row with pin top surface,the tangential stiffness model of flat boot and middle groove,the normal contact stiffness with clearance of rocker and traction section surface,the tensile-horizontal bending joint stiffness model of fuselage and traction section were established respectively.Based on the above models,a nonlinear dynamic model of 13-degree-of-freedom of the shearer under the oblique cutting condition was established,and the nonlinear vibration characteristics of the key components of the shearer under the specified working conditions were solved.The results showed that under the experimental modified load,the main vibration frequencies of the front drum and the walking box of the shearer are 16.63Hz and 12.14Hz respectively.The vibration swing angle and displacement fluctuation range of the front roller,the rocker and the walking box were-0.6rad?0.3rad,-0.4rad?0.1rad,and-14mm?14mm respectively,and the vibration acceleration fluctuation range of the front rocker and the walking box was ±300rad/s2.When the shear traction speed changed from 1.5m/min to 3.5m/min,the range of vibration angle and displacement of the front drum,the rocker and the walking box varied from-0.16rad?-0.44rad,-0.15rad?-0.39rad,and-4.61mm?-6.67mm respectively.Finally,the vibration characteristics of the shearer were verified by experiments by using the Shearer Face Mechanical Testing Analysis Experimental Platform of the National Energy Mining Equipment R&D Experimental Center.The average value of the vibration acceleration of the shearer front box obtained by theoretical calculation was less than the experimental value,and the vibration frequency was greater than the vibration frequency obtained by the experiment.The average value of the vibration displacement of each section of the shearer obtained by theoretical calculation under different working conditions was smaller than the experimental value,but the dynamic parameter eigenvalues obtained by the above theoretical calculation are not much different from the experimental ones,and the relative error was basically below 10%,theoretical analysis and experimental research were basically consistent.There are 59 pictures,12 tables,and 160 references in the paper. |
PDF Full Text Request