Dynamics And Stability Analysis Of Shearer Hydraulic Height-adjusting System

The hydraulic height-adjusting system of the shearer adjusts the height of the drum through the cylinder,which make the drum overcome all kinds of resistance along the coal rock interface.In this process,The hydraulic height-adjusting system not only meets the requirements of the maximum height and the undercover of the drum,but also provides sufficient torque to overcome the self weight of the rocker arm and the drum.The stability of the hydraulic system directly affects the stability of the running speed of the cylinder and the smoothness of the drum height adjustment.In addition,because the load on the drum is random and changeable,the force change leads to the vibration of the cylinder and the shaking of the rocker arm,resulting in the wear and leakage of the hydraulic components,and the slow speed of the hydraulic control system,which affects the drum height and the working reliability of the shearer.Therefore,it is very important to ensure the stability of the hydraulic pressure regulating system and minimize the vibration of the high oil cylinder,which is very important to the safe and efficient production of the shearer.The stroke size of the oil cylinder affects the total compression volume of the cylinder,thus changing the hydraulic spring stiffness,the natural frequency and the damping ratio of the hydraulic system,and ultimately affects the stability and dynamics characteristics of the hydraulic height-adjusting system.In this paper,the motion relation and constraint conditions of the main parameters of the hydraulic height-adjusting system are analyzed.On this basis,the influence of the stroke size of the oil cylinder on the dynamic characteristics and stability of the hydraulic height-adjusting system is studied.The main contents are as follows:(1)The corresponding relation between the displacement of the cylinder and the swing angle of the rocker and the height of the drum is analyzed,as well as the speed of the cylinder,the swing speed of the rocker and the speed of the drum.The movement locus and the cutting thickness of the shearer under different motion state are analyzed.(2)The structural parameters of the hydraulic height adjustment system are restricted by the height of the drum and the overall structure of the shearer.The influence of the stroke size and the installation position of the oil cylinder on the height of the drum is analyzed.When the design requirements and the relevant structural parameters of the hydraulic height-adjusting system of the shearer are known,the stroke of the oil cylinder can be determined according to the relevant formula;for the oil cylinder of different stroke,the position of hinged point can be installed by changing the high oil cylinder,so that the cylinder can reach the same maximum height and the amount of undercover.(3)The load of the single cutting tooth,the load of the drum and the load on the oil cylinder are analyzed under the working condition of the towing edge of the shearer.Based on the established dynamic model of the shearer hydraulic height-adjusting system,the influence of oil cylinder stroke size on the dynamic characteristics of hydraulic height-adjusting system is analyzed.The results show that the smaller of the cylinder stroke,the smaller cylinder compression volume,the higher the stiffness of the hydraulic spring,the smaller the vibration amplitude of the cylinder,the vibration of the hydraulic height-adjusting system decreases.(4)The mathematical model of the hydraulic height-adjusting system of the shearer is set up,and the open loop transfer function is obtained.On this basis,the influence of the stroke size of the oil cylinder on the stability of the hydraulic height-adjusting system is analyzed.The results show that the smaller of the height-adjusting cylinder stroke,the smaller cylinder compression volume,the higher the damping ratio,and the greater hydraulic damping ratio phase and gain margin of the system,which lead to a better relative stability.In conclusion,Because the stroke of oil cylinder is restricted by the height of the drum and the installation position of the oil cylinder.Therefore,we need to optimize the structural parameters such as stroke and installation position of the oil cylinder,so as to get the best cylinder stroke and make the shearer meet the design requirements of the maximum mining height and the underside volume,and the hydraulic height-adjusting system has better stability and dynamic characteristics.