Control device for die cushion mechanism

A control device of a die cushion mechanism of a press machine, for generating a force applied to a slide of the press machine by using a servomotor as a driving source, the control device comprising:

• a force commanding part for outputting a commanded force value to be generated by the die cushion;
• a force detecting part for outputting a detected force value generated by the die cushion mechanism based on the commanded force value;
• a force controlling part for controlling the servomotor based on deviation between the commanded force value and the detected force value;
• and
• a correcting part for correcting a time-series of the deviation, obtained during the force control in a first press working cycle carried out by the force controlling part, when the force controlling part carries out the force control in a second press working cycle next to the first cycle,
• wherein the correcting part includes a learning control part for calculating a correction value based on the deviation in the first press working cycle and an arithmetic part for adding the correction value to the deviation in the second press working cycle, and
• wherein the learning control part includes a low-pass filter for removing a high-frequency component of the deviation and a phase-progress filter for progressing the correction value corresponding to the time lag in relation to a response of the commanded servomotor.