Dynamic Characteristics Analysis And Control Of Shearer Electromechanical Short-length Cutting Drivetrain

A longwall shearer has the characteristics of powerful cutting ability and high productivity,which can improve the level of mechanization in coal mining.Conventional cutting transmissions are arranged in the ranging arm of a longwall shearer.Housing deformation of ranging arms can cause uneven tooth load distribution over the gear face width and failure of the transmission.An electromechanical short-length cutting drivetrain is proposed to improve the reliability of the cutting transmission.The new drivetrain is charactized by compact structure and can be installed inside cutter drums.There exist multiple motors in the short-length cutting drivetrain,a coupling gear train(CGT)couples power of the multiple motors,and the power is transmitted to the cutter drum by a planetary gear train(PGT).Dynamic behavior of the short-length cutting drivetrain,particularly load sharing behavior among the multiple transmission paths,influences the carrying capacity of the drivetrain.Moreover,drum cutting performance in coal mining is needed to be considered.Studies in this dissertation were supported by the project "Efficient power transmission principle and self-adaptive control methods in heavy load mutation condition"(Grant No.: 2014CB046304)in the National Basic Research Program of China "Key fundamental research on the unmanned mining equipment in deep dangerous coal bed"(Grant No.: 2014CB046300).Load sharing and dynamic behavior and control of the electromechanical short-length cutting drivetrain and comprehensive performances optimization of longwall shearers were studied,to improve the carrying capacity of the electromechanical short-length cutting drivetrain and comprehensive performances of longwall shearers.Main contents are as follows:(1)Because the housing deformation of ranging arms can cause failure of the traditonal cutting transmission,an electromechanical short-length cutting drivetrain was proposed which consists of three electric motors,a CGT and PGT.In the drivetrain,there exist three parallel transmission paths to improve the power density.The drivetrain can be installed inside the cutter drum to avoid influence of the housing deformation of ranging arms.Parameters of the electromechanical short-length cutting drivetrain were matched by taking MG300/700 longwall shearer as an application object.Models of the direct torque control(DTC)and electric motor were established.Torsional-translational coupled dynamic models of the CGT and PGT were established by using lumped parameter methods.Models of the electric motor,CGT and PGT were coupled together by utilizing models of the shafts between these parts.Thus,an electromechanical coupling model of the drivetrain was acquired.The electromechanical coupling model can lay the foundation for studying load sharing behavior and dynamic behavior of the short-length cutting drivetrain.(2)Three inputs of the CGT are unsynchronized in the electromechanical short-length cutting drivetrain.Causes of unsynchronized input speeds and unsynchronized input torques of the CGT were analyzed.Influence of the unsynchronized input speeds and unsynchronized input torques on the load sharing behavior and dynamic behavior was studied.Effects of these two kinds of unsynchronized inputs were compared.Reuslts can provide the basis for studying how to improve behaviors of the electromechanical short-length cutting drivetrain.(3)To address issues of the unsynchronized input speeds affect load sharing and dynamic behaviors of the electromechanical short-length cutting drivetrain,a virtual damping was introduced to suppress the input speed fluctuation amplitude.Then,speed synchronization control was studied to avoid a shortcoming that the virtual damping is subject to parameter design of the drivetrain.Relative speed and relative displacement along the line of action in the CGT were selected as feedback variables.The speed synchronization controller causes the three input speeds of the CGT to tend to the same target value by adjusting motor torques.The Lyapunov theory is used to derive the stability condition of speed synchronization control.Gain scheduling was analyzed to adjust speed synchronization controller parameters according to load torques,thus,adaptability of the controller to fit different conditions can be improved.Load sharing behavior and dynamic behavior of the electromechanical short-length cutting drivetrain are improved through reducing the speed synchronization error.(4)Based on analyzing influence of the drum speed and haulage speed on electromechanical short-length cutting drivetrain load and drum cutting performance,a multi-objective optimization model was established by considering load in the short-length cutting drivetrain(i.e.mean dynamic meshing force in the PGT),lump coal rate,and coal mining productivity.The drum speed and haulage speed were optimized according to cutting conditions during operation of the longwall shearer,the optimization results were used to cutting-haulage speed adjusting of the longwall shearer.Finally,effect of the speed synchronization control was analyzed in the process of cutting-haulage speed adjusting.These studies can lay the foundation for reliable operation and efficient production of longwall shearers.(5)A test bench of the electromechanical short-length cutting drivetrain was built,and a data acquisition and control system was developed.Characteristics of unsynchronized input speeds of the CGT in the test bench were analyzed.Dynamic model validation of the short-length cutting drivetrain,speed synchronization control experiment,and shearer speed adjusting experiment were carried out.The dynamic model of the drivetrain and the theoretical results obtained in this study were verified.