Study of a Synchronous Positioning Control at Pressure Control between Multi-AC Servomotors Driven in Injection Molding Machine

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In coping with the trend toward the much higher powered electric-motor driven injection molding machine, multi-AC servomotors control system have become necessary in order to control the molding machine mechanism. Thus, it is inevitable to use the synchronous positioning control technique not to cause the excessive mechanical stress in the molding machine body. Accordingly, it is much necessary to have a load simulator of the molding machine to study the synchronous control technique.Firstly this study clarifies the similarity law between the actual molding machine and the simulator so that we are able to estimate the control performance at the actual machine from that at the simulator and to get the control gain parameters at the actual machine from that at the simulator to realize the same control performance as the simulator. This study also shows the design method of the simulator based on the similarity law at the injection molding control and the manufactured simulator is used to study the synchronous positioning control technique.Secondly it is possible to realize the synchronous positioning control in the injection velocity control by using position feedback signals from each motor pulse-generators. However in the injection pressure control it is much difficult to realize the synchronous positioning control because the pressure-detector signal have to be used in place of the position feedback signals. This study clarifies the synchronous positioning control method during the injection pressure control by using both the pressure-detector signal and position feedback signals. The experimental results by using the simulator showed that the synchronous positioning control error was much less than 1 micrometer in the pressure control. This study also showed the bumpless transfer technique from the injection velocity control to the injection pressure control.