Pressing machine and motor torque control method in pressing machine

A pressing machine for applying pressing force, comprising:

• a torque limiting device restricting torque commands in a motor control circuit, whereby the output torque of a motor is restricted by restricting torque commands through said torque limiting device;
• and
• a torque limit correction value calculating device determining an acceleration from a command velocity or a detected velocity from a velocity detector for detecting velocity of the motor, and calculating a torque limit correction value from said acceleration,
• wherein the torque limit value of said torque limiting device is derived by adding the torque limit correction value determined by said torque limit correction value calculating device to a torque limit value corresponding to a target pressing force.

A pressing machine for applying pressing force, comprising:

• a torque limiting device restricting torque commands in a motor control circuit, in which the output torque of a motor is restricted by restricting torque commands through said torque limiting device;
• an observer for estimating and outputting acceleration values, wherein said observer inputs the actual velocity as detected by a velocity detector and a torque command delivered to the current loop, and outputs a estimated acceleration;
• and
• a calculating device calculating a torque value required for acceleration or deceleration from the estimated acceleration output by said observer, and outputting this calculated torque value to said torque limiting device,
• wherein the torque limit value of said torque limiting device is derived by adding the torque value required for acceleration or deceleration as calculated from the output of said observer to a torque limit value corresponding to a target pressing force.

A motor control apparatus controlling an output torque of a motor comprising:

• a velocity detector detecting a velocity of the motor;
• an observer estimating an acceleration based on a torque command and the velocity of the motor;
• and
• a torque correcting device, upon acceleration or deceleration of the motor as determined by input from the velocity detector, correcting the torque to correspond with a target pressing force using the estimated acceleration.

A method of controlling an output torque of a motor, comprising:

• detecting a velocity of the motor;
• estimating an acceleration based on a torque command and the velocity of the motor;
• and
• correcting, upon acceleration or deceleration of the motor, the torque to correspond with a target pressing force using the estimated acceleration.