| 摘要 |
The present invention provides an apparatus and method for controlling the force and velocity of a piston (27) within the clamp assembly (113) of an injection molding machine (10). The control unit (100) comprises the following elements: a PI based cascade compensator (111); an estimator (114) coupled to the clamp assembly (113) and the cascade compensator (111), wherein the estimator (114) is utilized to estimate the position of the clamp assembly piston; a velocity position controller (115) coupled to the clamp assembly (113) and the estimator (114), wherein the velocity position controller (115) is adapted to generate a velocity error signal based on the piston velocity signal; and an auto selector (112) coupled to the cascade compensator (111), wherein the auto selector (112) is adapted to select between the velocity error signal and the force error signal to generate a valve command signal. The present invention additionally employs a method for determining the velocity profile of the piston of a clamp assembly. The method comprises the following steps: determining the maximum displacement xS of the servo valve; selecting a final velocity vS of the piston; choosing a ratio alpha of the piston ramp-down interval to the servo valve displacement "x" during a ramp-up interval, selecting a desired maximum piston velocity (vmax) during the ramp-up interval and a constant speed interval; and determining servo valve displacement xu from simulations or estimate from previous cycles.
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