Study Of Electro-hydraulic Proportional Control System For Grinding Gap Of Refiner

The grinding gap of the refiner refers to the vertical distance between the surface of stationary disc and the surface of rotating disc in refining zone,which has a crucial influence on the quality and energy consumption of the fiber separation.Normally,the grinding gap should be kept within the range of 0.2?0.5mm,and the precision should be reached 0.01mm.However,due to the disc abrasion,the change of the grinding temperature and pressure,uneven force acting on grinding disc,and the error caused by the bearing clearance,the preset grinding gap is easily changed in the actual process of fiber separation.At present,mechanical adjustment and hydraulic adjustment are commonly used to adjust the grinding gap,but both of them have the problems of slow adjustment speed,poor precision and low degree of automation,which lead to unsatisfactory fiber quality.Therefore,it has important practical significance for improving efficiency and fiber quality to design a kind of automatic control system based on electro-hydraulic proportional control technology,which can automatically detect the grinding gap and make timely and accurate adjustment according to the change of the grinding gap in real time.Based on the main structure and working principle of the refiner,the main factors affecting the change of the grinding gap are analyzed and summarized.By studying the measurement and adjustment methods of the typical grinding gaps,a scheme is proposed,which adopts electro-hydraulic proportional control technology to adjust the grinding gap,and makes use of the principle that the pressure of the hydraulic system is inversely proportional to the value of the grinding gap in the process of fiber grinding to automatically compensate the gap error caused by the disc abrasion.The control principle of the system is explained,and the selection of key hydraulic components is completed.The mathematical model of the grinding gap control system is established and the parameters of the model are calculated to obtain the open-loop transfer function of the grinding gap control system.The mathematical model is applied to analyze the stability,rapidity and accuracy of the system,and to judge whether the system performance meets the design requirements.The system model is established based on AMESim,and the performance of the system is corrected by PID control.The parameters of PID are tuned by genetic algorithm,and the corrected system is obtained.Comparing the performance difference before and after system correction to verify the system correction effect.The adjustment error of the system and the adjustment effect under unit displacement are analyzed to verify the control accuracy of the system.The adjustment of grinding gap under the fluctuation of load force is analyzed to verify the anti-interference ability of the system.The results show that the designed hydraulic proportional control system has the advantages of good stability,quick response and high precision,which meets the control requirements of the grinding gap of the refiner.