Research On Self-adaptive Speed Regulation Principle For High Efficiency Cutting Of Shearer

Drum type shearer is the main equipment of fully mechanized coal mining face,which is widely used in the exploitation of different kinds of coals.At present,the traction speed of the mainstream shearer can be regulated while the drum rotational speed is constant,which largely limites the shearer cutting performance.Therefore,this thesis studies the unite speed regulation of traction speed and drum rotational speed for high efficiency cutting.The motion of the picks is periodic and its locus equation can not be expressed by only one general equation,but should be divided into two sections respectively: [0,?] and [?,2?].In the motion period of the pick,from the beginning the cutting thickness increases to the maximum value and then begins to decrease.The maximum cutting thickness is v?/?,and the ordinate of the maximum cutting thickness spot is not zero but-v/?.The fluctuation of cutting thickness increases with the increasing of traction speed and decreases with the increasing of drum rotational speed.The shape of the cutting crescent moon plane is determined by the ratio of shearer drum rotational speed and traction speed.And,because of the existence of the empty pick area which is called leng tiao,in theory,Dh_max is not the area of the cutting crescent moon plane but the sum of the crescent moon area and the leng tiao area.However,the area of leng tiao is very small relative to the area of the cutting crescent moon plane and can be negligible,so the area of the cutting crescent moon plane can be approximately calculated by Dh_max.An optimization method for MG500/1180-WD electric haulage shearer is put forward.The optimization targets include specific energy consumption,production efficiency and lump coal rate.The optimization variables consist of shearer traction speed and drum rotational speed.The optimization constraints are coal loading capacity,cutting torque,cutting power,traction force and traction power.The relation between optimized traction speed and drum rotational speed and Protodikonov's hardness coefficient is obtained through optimization by MATLAB.The cutting energy efficiency parameters calculated by shearer kinematic parameters before and after optimization are compared.After comparision,the result shows that the shearer cutting energy efficiency is obviously improved generally as the shearer adopts the optimized kinematic parameters.The specific energy consumption is obviously decreased and the lump coal rate is obviously increased.The production efficiency is obviously improved when the hardness coefficient is less than 2.88 and the production efficiency is slightly reduced as the hardness coefficient is greater than 2.88.From the aspects of speed regulation criterion and speed regulation process,the unite speed regulation of traction speed and drum rotational speed is studied when the shearer encounters suddenly changing load.This chapter introduces two speed regulation strategies,namely the rated torque and constant power speed regulation strategy.The two speed regulation strategies have different goals and characteristics: the constant torque speed regulation strategy aims at the higher production efficiency and the constant power speed regulation strategy aims at the lower specific energy consumption.In the coal mining process,the shearer should decide the priority of the two speed regulation strategies and accordingly make an appropriate selection based on the different load conditions on the mining face.Switches of the two speed regulation strategies can also be achieved in the mining process to maximize the cutting energy efficiency of shearer.The simulation model of MG500/1180-WD shearer in Simulink is established,and the response of shearer under different working conditions is simulated.The shearer model consists of the cutting unit and the traction unit which are both composed of a driving motor and a reducer.The cutting motor and the traction motor are driven and controlled by the direct torque control method.At the experiment site,the stator rms currents of the cutting motor on MG500/1180-WD shearer as traction speed are 1.5m/min,3m/min and 5m/min.After the above three kinds of working conditions are simulated in Simulink,the stator rms currents of the cutting motor obtained from simulation and that obtained from the field test are compared then the rationality of the shearer model is proved.In the Simulink environment,the shearer operates with unoptimized and optimized kinematic parameters as cutting coals of different Protodikonov's hardness coefficients.The specific energy consumption,production efficiency and lump coal rate before and after optimization are analyzed and calculated.The simulation results show that the energy efficiency of the shearer has been greatly improved when the shearer operates under optimized kinematic parameters which means the shearer can cut more efficiently.At the same time,trational speed regulation strategy,constant torque control strategy and constant power speed regulation strategy are all simulated and analyzed under suddenly changing load condition.The simulation results shows that comparing with traditional speed regulation strategy,the traction speed is higher and the traction speed and drum rotational speed restore stability faster as using constant torque speed regulation strategy and the load fluctuations are lower as using constant power speed regulation strategy.Consequently,if conditions are meet,the constant torque control strategy is preferred for speed regulation under suddenly changing load condition.