Research On Low Back Pressure Control System Of Injection Molding Machine Based On Fuzzy Decision

With the extensive application of injection molding products,improving the performance of injection molding machines can bring great economic benefits.The performance of injection molding machine mainly includes injection speed and metering accuracy.The measurement accuracy is affected by many factors,such as temperature,viscosity and storage pressure.The way to control the metering accuracy is to adjust the return oil back pressure of the injection cylinder,for example,V9 valve and proportional relief valve are used to adjust the back pressure.However,the cost of V9 valve is high,and the lowest starting pressure is not low enough,its zero back pressure control performance still has room for improvement.To reduce the cost of back pressure control system and achieve excellent low back pressure control performance,this paper presents a passive back pressure control method of injection molding machine based on fuzzy decision algorithm.The specific research work involved in this paper includes:(1)Combined with the hydraulic schematic diagram,the principle of controlling the return oil back pressure according to the return speed of the injection cylinder is analyzed.The formula for regulating the return oil back pressure through back pressure and cylinder flow is derived.The rules and membership functions of the fuzzy controller are designed according to the formula,and a joint simulation model based on MATLAB and AMESim is built.The algorithm is verified by simulation.(2)The method of fuzzy control using look-up table is studied.First,a two-dimensional table of valve core opening is generated to replace the fuzzy rule table,then a two-dimensional interpolation algorithm is used to achieve anti fuzziness,and finally,the position coordinates of input parameters in the table are determined using the optimization method.The feasibility of the algorithm is verified by software simulation.(3)The software and hardware of the special electronic amplifier for controlling the proportional directional control valve are designed,and the basic functions of the hardware are tested.(4)A test bench was built to test the control performance of the back pressure control system of the injection molding machine.The results show that compared with traditional schemes such as adjusting V9 valve in the oil inlet circuit,the back pressure of the system is faster,the accuracy is close to the closed-loop control,and the minimum back pressure can be zero.There is still a large flow under the lowest back pressure,and the control performance is excellent,which can replace the traditional closed-loop control,thus saving the system cost.