| At present,the belt conveyor is generally driven by asynchronous motor series reducer,hydraulic coupler and other transmission mechanisms in coal mines,which has the disadvantages of low mechanical efficiency,serious waste of electric energy,large space occupied by driving equipment and high maintenance cost.In order to solve the above shortcomings,this paper studied the driving system of coal mine belt conveyor;the outer rotor permanent magnet synchronous motor was embedded in the driving roll of coal mine belt conveyor to drive directly,and the intermediate transmission device such as reducer was omitted,so as to achieve the purpose of high efficiency and energy saving.In this paper,a low-speed and high-torque outer rotor permanent magnet motor was designed,and the speed control strategy of the external rotor direct drive system was studied.Low-speed and high-torque outer rotor permanent magnet synchronous motor is prone to produce large cogging torque due to its multi-stage structure,which has an impact on the stable operation of the motor.Therefore,the influence of cogging torque was fully considered in the design of the motor.Based on the energy method,the cogging torque mathematical model of the surface mounted outer rotor permanent magnet motor was established.Through the analysis of the model,the relationship between the main parameters of the motor and the cogging torque was obtained,and the cogging torque was restrained by reasonably designed parameters of the motor.In order to improve the energy density of the motor and control the volume of the motor to realize the built-in direct drive,combined with the winding characteristics of fractional slot winding and centralized winding,the winding form of centralized winding was optimized by changing the winding span topology,so that each winding block was independent,and the winding distribution coefficient was improved.The main parameters of the motor were optimized and analyzed through the Ansoft RMxprt software,and the corresponding parameters were revised to obtain the optimal electromagnetic scheme.A simulation of the electromagnetic scheme and temperature field of the motor was carried out respectively by Ansoft-Maxwell 2D and ANSYS software,which verified that the motor can meet the requirements of direct drive and the design was reasonable.The coal mine belt conveyor adopts the direct drive mode,and the load disturbance directly acts on the direct drive motor,which has a serious impact on the steady state accuracy of the speed control.Taking full account of the uncertainty and saturation of the system parameters,taking the transient and steady-state performance into account,the mathematical model of external rotor direct drive system was established to restore the load characteristics through the dynamic analysis of the coal mine belt conveyor combined with the mathematical model of the external rotor permanent magnet motor;the combined nonlinear feedback(CNF)control was used to dynamically change the damping ratio of the system,so that the system can respond quickly and reduce the overshoot;the speed fluctuation was reduced by integrated synovial membrane control(ISMC)to compensate for the uncertainties of the system;a combined nonlinear feedback and integrated synovial membrane(ISMC-CNF)controller was designed.The simulation results of the controller random load by Simulink software showed that the system response was fast,and the speed fluctuation was small and almost no overshoot when adopting ISMC-CNF control strategy.This paper has 101 figures,11 tables and 70 references. |
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