Servo motor control unit for press-forming machine

A servo motor control unit for a press-forming machine comprising a position detector for detecting a position of a die fastening member of said press-forming machine or a servo motor for driving said die fastening member, a speed detector for detecting a speed of said servo motor, a position control processing part for preparing a speed command from a position error comprised of a difference between a position command and a position feedback, and a speed control processing part for preparing a torque command from a speed error comprised of a difference between the speed command and a speed feedback, said servo motor control unit adapted to drive said servo motor based on the prepared torque command to machine a workpiece,

• wherein said servo motor control unit further comprises:
• a pressure detector for detecting an actual pressure applied to said workpiece;
• a pressure control processing part for preparing a speed command from a pressure error comprised of a difference between a pressure command and the actual pressure;
• a comparing means for comparing the speed command output from said position control processing part with the speed command output from said pressure control processing part;
• and
• a switching means for selecting, based on the results of comparison at said comparing means, one of the speed command output from said position control processing part and the speed command output from said pressure control processing part and transferring the selected speed command to said speed control processing part.