| The paper depicted research and application status of the soft-start technology used in large belt conveyors. A new type soft-start equipment was designed with hydraulic braking system and differential gear control technology.The speed control principle of differential gear train was analyzed, and the dynamic model for differential gear speed controlling system was establised based on lagrange's equations of the second kind. Through analysis on the model, the braking torque and braking power on the ring gear were known. What's more, the interrelation between the divergence of the valve and starting acceleration was determined. Comparing current hydraulic braking system, a hydraulic braking system with simplied structure and easy control system was designed based on electro-hydraulic proportional control technology, and the brake characteristic curve of hydraulic proportional control system was given. Critical type hydraulic components were determined.According to the characteristics of electro-hydraulic proportional control valve, the proportional amplifier was designed.The PLC-based electrical control system was designed according to the working principle of the soft-starting device. Working flow diagrams under the soft starting and soft stoping conditions were studied. The advanced PID control algorithm was empolyed in the control system. Aimed at speed control, belt conveyor S-type speed curve comed ture.At last, principles for soft-starting, soft-stopping, variable speed controlling, power balancing with multi-level drives and overload protection were discussed. Using MATLAB simulation tools, the soft start device was modeled and working processes based on PID control were simulated. The simulation showed that the device could achieve large-scale equipment such as belt conveyors S-velocity curve uder soft-starting and soft stopping processes. |
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