Frequency Velocity Technology Research For The Injection Machine

Stable performance, high speed and energy saving are the key factors ininjection molding package equipment. Current injection machine equipped withthree-phase asynchronous motor, which can not adjust the rotation speed. Theflow of the hydraulic can not be changed by quantative pump. The redundanthydraulic flow has to reture back to oil tank via relief valve, which resultes inenergy wasted. Since the hydraulic oil full speed flow and has worse wear outwith hydraulic parts. It leads in the high oil temperature, big noise and short lifeof mechanical parts. Based on the variable frequency speed regulation andcurrent speed double closed loop system control theory and injection productprocess parameters, a variable frequency speed regulation is designed to improveinjection product quality, stabilize process parameters and realize system energysaving.In this paper, the technicial method of variable frequency, classification andcharacteristics of the frequency control are introduced. The national andinternational status of FOC is researched. Since three-phase asynchronous motoris a multi-input multi-output, nonlinear, strongly coupled objects, the mathematicmodel of three-phase AC asynchronous motor in two-phase rotating coordinatesis educed from the mathematic model in three-phase coordinates by Clarktransform and Parke transform. Based on the rotor flux orientation theory andthis mathematic model, the rotor flux observer is designed to make sure themagnetizing and torque current components of asynchronous motor is decoupledsuitably. Based on the SVPWM control method, the mathematic model ofSVPWM was built. The related soft and hardware platform solution of SVPWMwere designed, which achieve the variable frequency speed control technology ofthree-phase AC asynchronous motor.A SVPWM control circuit with DSP system as the core and main inverter,driving circuit and signal acquisition circuit are designed. Make the frequencycontrol strategy into actualization by using assembler language in theenvironment of CCS. The output frequency of convertor was controlled byanalyzing the signal of voltage or current from the different processing stage in injection molding machine. Therefore, the rotation speeed of the oil pump (three-phase AC asynchronous motor) was controlled as well. The output hydrolic flowcould be adjusted according to the processing requirement of injection moldingmachine. The power consumption was saved by reducing the hydrolic oilprocessing from relief valve to oil tank.Based on above technology, the energy saving, product quality improvementand working parameter stabilization were achieved by the frequency converterretrofit in the injection molding machine and the speed contol of three-phase ACasynchronous motor. The demonstration result showed the feasibility of theproposed scheme.