| With the development of belt conveyor toward long distance,high belt speed and large capacity,its tensioning device has devolved from the original simple mechanical structure to the dynamic automatic tensioning mechanism of Electromechanical-hydraulic integration.Dynamic automatic tensioning device is mainly hydraulic automatic tensioning and frequency conversion automatic tensioning.Hydraulic automatic tensioning device has some problems in practical application,such as slow speed of tension adjustment,low reliability and high failure rate.Frequency conversion automatic tensioning device can effectively avoid the above problems,but the traditional frequency conversion automatic tensioning device often adopts the drive form of "frequency converter + motor + reducer".The structure is more complex and the drive system is driven by the presence of reducer.Efficiency and reliability are reduced,manufacturing costs and post-maintenance difficulties are increased.Permanent magnet synchronous motor(PMSM)has been applied in coal mines.Because of its good low-speed load-carrying capacity,it can be used to replace the drive mode of "motor + reducer",simplify the structure of frequency conversion automatic tensioning device,and improve its drive efficiency.Based on the theoretical analysis of frequency conversion automatic tensioning device of belt conveyor,this paper calculates the tension of conveyor belt of DSJ140/300/3*450 retractable belt conveyor,and obtains the minimum tension required by tensioning device.In view of the shortcomings of traditional frequency conversion automatic tensioning device driving mechanism,an automatic tensioning device with low speed direct drive permanent magnet synchronous motor as driving mechanism is proposed and designed.The speed loop controller of permanent magnet synchronous motor based on double closedloop vector control is optimized and simulated by using MATLAB/Simulink,and the effects of PID,fuzzy PID and fuzzy PID controller based on improved gravity search algorithm on its speed and torque are analyzed and compared.The whole model of belt conveyor is built in AMESim and completed by joint simulation with Simulink.The analysis of tension,acceleration,speed and displacement at the key characteristic points of belt conveyor and frequency conversion tensioner under full load condition.Finally,the dynamic characteristics of belt conveyor and its frequency conversion tensioner from start to smooth operation are analyzed by joint simulation.The main results are as follows:(1)The speed loop controller of double closed-loop vector control permanent magnet synchronous motor speed control system adopts the fuzzy PID controller based on improved gravity search algorithm optimization.Compared with the traditional PID and fuzzy PID controller,it effectively eliminates the overshoot of motor speed when starting and load suddenly change,and when the motor speed suddenly changes,the electromagnetic torque ripple of the motor is small and no vibration.(2)When the belt conveyor is in full load operation,the elastic wave propagates to the tail after the conveyor belt runs 51.4 seconds at the head-to-head meeting point,and the acceleration of the tail is much greater than the acceleration of the head,so the impact is more prone to oscillation;the tension of the head conveyor belt is about 3.3 times of the tension of the tail when running smoothly,so the head parts are more vulnerable to damage than the tail parts;The action of the tightening trolley lags behind the change of belt tension by 4.2s;the displacement of the tightening trolley reaches the maximum value of 8m and the maximum speed is 0.19m/s when the belt conveyor is about to start.Permanent magnet frequency conversion automatic tensioning device can meet the requirements of belt conveyor tension in different stages of operation,and realize real-time adjustment of belt tension.(3)Different parameters of conveyor belt have different effects on the dynamic characteristics of belt conveyor and frequency conversion automatic tensioning device.The tension of conveyor belt,the ratio of tension of conveyor belt at encounter point,encounter point and run-off point,and the displacement of tensioning trolley increase with the increase of conveyor load.The greater the elastic modulus of conveyor belt,the faster the rising speed of tension and the propagation speed of elastic wave in conveyor belt at encounter point,the smaller the maximum speed and displacement of tensioning trolley,and the conveyor belt.The maximum tension of the belt is not affected by the elastic modulus of the belt;the larger the rheological coefficient of the belt,the smaller the fluctuation of the speed and displacement of the tension trolley of the frequency conversion automatic tension device,and the stronger the resistance to tension impact.During the operation of the conveyor,once the power failure occurs,the tension of the conveyor belt will rise sharply,which is likely to lead to the fracture of the conveyor belt and cause accidents. |
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