Study On Vibration Characteristics Of Roadheader System With Active Excitation And Its Influence On Cutting Load

Roadheader machine as one of the main mechanical equipment in fully mechanized mining face,high efficiency production capacity has always been the research focus and pursuit goal of researchers and technical workers.Because the roadheader is affected by many factors such as bad working environment,continuous change of the cutting arm working angle and uneven bottom plate,the whole machine vibration is obvious,and the vibration of the block system will affect the cutting load.Therefore,this subject relies on the project of National Natural Science Foundation of China,"study on cutting load characteristics and optimal Control of step-by-step active Vibration excavator(Project No.:51874158)".Based on the difficulties of roadheader in underground coal mine and the actual environment of cutting and breaking technology,the influence of system vibration characteristics and cutting load on the excavator is deeply studied.In this paper,a new direction of cutting rock breaking with active excitation assisted cutter is put forward,and the main research work is as follows:Based on the main design parameters of cutting head of roadheader,the spatial trajectory motion model of horizontal swing and vertical swing of cutter with vibration characteristics of cutting head is constructed,and then the block diagram of cutting load of cutting head with vibration feature is established.The concrete example is solved to provide the basis for the follow-up study of the whole machine dynamics model;Based on multibody dynamics theory and Lagrangian equation,the differential equation of multi-degree system is constructed.the dynamic response of the whole machine in the process of horizontal and vertical cutting is obtained by solving the other path of the variable length four-five-order Runge-Kutta method.The modal analysis of the whole machine provides a reference for further theoretical analysis of the vibration characteristics of the cutting arm of the roadheader;A new type of auxiliary cutting method,active excitation assisted cutting method,is proposed in this paper.Based on the continuous beam with variable cross-section and Euler-Bernoulli theory and singular function method,the differential equations of vibration under single load(cutting load)and double load(cutting load and active excitation)are constructed respectively.The analytical solution of the vibration differential equation is obtained by the method of separating variables,and the steady-state response of the forced vibration of the cutting part of the variable cross-section is simulated,and the dynamic response characteristics of each part of the cutting arm under different external excitation are obtained.The dynamic model of roadheader system with active vibration characteristics is constructed and the dynamic response of key parts in horizontal cutting process is obtained by numerical analysis;Based on the theory of active vibration assisted cutting head impacting coal and rock,the mechanical model of coal and rock medium under vibration excitation is established.Based on the vibration characteristics of cutting head under double loads(cutting load and active vibration),according to the law of conservation of energy,the mathematical model of cutting rock with vibration characteristics at different cutting depths is established,and the impact force,excitation frequency and excitation vibration of cutting teeth are obtained.The optimal excitation frequency and amplitude are selected by the function expression of the amplitude,and the load simulation block diagram of the cutting head under the excitation characteristics is constructed.Compared with the cutting load with or without excitation,the cutting load after excitation is significantly smaller than that without excitation,which shows that the active excitation is beneficial to the cutting effect;Based on the physical similarity theory,the similarity criterion of the cutting part of the roadheader and the model of the experimental prototype as well as the main parameters of the experimental prototype are determined,so as to establish the active vibration assisted cutting test bench.Compared with the change rule of the contact force,cutting current and cutting specific energy consumption of the coal sample with or without the active vibration characteristics,the results show that the contact force of the cutting teeth with the vibration characteristics is smaller,The cutting current is small and the cutting specific energy consumption is small,which is verified with the theoretical results to confirm the rationality of the active vibration assisted cutting of coal and rock;the influence of different vibration frequencies on the contact force of the cutting teeth,the cutting specific energy consumption and the lump coal rate of coal and rock is analyzed,and the optimal vibration frequency is obtained,which provides certain theory and basis for the follow-up research of the active vibration assisted cutting.There are 82 diagrams,18 tables and 152 references in the paper.