Press machine

A press machine comprising:

• a cushion shaft connected to a lower die;
• a press shaft connected to an upper die and configured to press a workpiece between the upper die and the lower die in cooperation with the cushion shaft;
• a motor configured to drive the upper die through a mechanical mechanism generating a steady disturbance in the press machine, the steady disturbance originating in change in a moment of inertia of the mechanical mechanism;
• and
• a motor control device configured to supply electric power to the motor and configured to detect an abnormal state in the press machine by discriminating an abnormal disturbance originating in a foreign object between the press shaft and the cushion shaft, and the steady disturbance,
• wherein the motor control device comprises a disturbance observer configured to calculate an estimated disturbance value with respect to the motor based on a torque command and a motor velocity of the motor,
• wherein the motor control device is configured to determine an integrated value of an absolute value of the estimated disturbance value, and
• wherein the motor control device is configured to determine that the foreign object is caught when the integrated value exceeds a set value defined in advance.

A press machine comprising:

• a cushion shaft connected to a lower die;
• a press shaft connected to an upper die and configured to press a workpiece between the upper die and the lower die in cooperation with the cushion shaft;
• a motor configured to drive the upper die through a mechanical mechanism generating a steady disturbance in the press machine, the steady disturbance originating in change in a moment of inertia of the mechanical mechanism;
• and
• a motor control device configured to supply electric power to the motor and configured to detect an abnormal state in the press machine by discriminating an abnormal disturbance originating in a foreign object between the press shaft and the cushion shaft, and the steady disturbance,
• wherein the motor control device comprises
• a disturbance observer configured to calculate an estimated disturbance value with respect to the motor based on a torque command and a motor velocity of the motor,
• an absolute value calculator configured to receive the estimated disturbance value and to calculate an absolute value of the estimated disturbance value,
• an integrator configured to integrate the absolute value of the estimated disturbance value during a period in which the upper die is moved over a predetermined zone within a movable range of the upper die, and
• a comparator configured to sample an output of the integrator per predetermined time, to compare a current sampling value with a sampling value in a just preceding cycle or a further before cycle, and to determine, based on a comparison result, whether the foreign object is caught.

A press machine comprising:

• a cushion shaft connected to a lower die;
• a press shaft connected to an upper die and configured to press a workpiece between the upper die and the lower die in cooperation with the cushion shaft;
• a motor configured to drive the upper die through a mechanical mechanism generating a steady disturbance in the press machine, the steady disturbance originating in change in a moment of inertia of the mechanical mechanism;
• and
• a motor control device configured to supply electric power to the motor and configured to detect an abnormal state in the press machine by discriminating an abnormal disturbance originating in a foreign object between the press shaft and the cushion shaft, and the steady disturbance,
• wherein the motor control device comprises
• a disturbance observer configured to calculate an estimated disturbance value with respect to the motor based on a torque command and a motor velocity of the motor,
• an absolute value calculator configured to receive the estimated disturbance value and to calculate an absolute value of the estimated disturbance value,
• a position coefficient processor configured to receive the absolute value of the estimated disturbance value and to assign a weight to the estimated disturbance value depending on a position of the upper die,
• an integrator configured to integrate an output of the position coefficient processor during a period in which the upper die is moved over a predetermined zone within a movable range of the upper die, and
• a comparator configured to sample an output of the integrator per predetermined time, to compare a current sampling value with a sampling value in a just preceding cycle or a further before cycle, and to determine, based on a comparison result, whether the foreign object is caught.