| 摘要 |
The present invention provides a apparatus and method for controlling the force and velocity of a piston within the clamp assembly of a injection molding machine. The control unit comprises the following elements: a PI based cascade compensator; an estimator coupled to the clamp assembly and the cascade compensator, wherein the estimator is utilized to estimate the position of the clamp assembly piston; a velocity position controller coupled to the clamp assembly and the estimator, wherein the velocity position controller is adapted to generate a velocity error signal based on the piston velocity signal; and an auto selector coupled to the cascade compensator, wherein the auto selector 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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