US-12623428-B2 - Die cushion control device, die cushion control method, and storage medium

US12623428B2US 12623428 B2US12623428 B2US 12623428B2US-12623428-B2

Abstract

A die cushion control device for controlling a die cushion mechanism includes: a pressure command generation unit that outputs a first pressure command on pressure or force to be generated between the die cushion mechanism and a slide; a deviation prediction unit that predicts a pressure deviation that is the difference between the pressure or the force in the first pressure command and a detected pressure caused when the die cushion mechanism is controlled according to the first pressure command, and outputs the predicted pressure deviation as a correction pressure command; a pressure command correction unit that corrects the first pressure command with the correction pressure command to calculate a second pressure command; and a pressure control unit that calculates a speed command to cause the detected pressure to follow the second pressure command, and outputs the speed command to a speed control unit.

Inventors

Koichiro Ueda
Koji Mahara

Assignees

MITSUBISHI ELECTRIC CORPORATION

Dates

Publication Date: 20260512
Application Date: 20210604

Claims (12)

1 . A die cushion control device to control a die cushion mechanism to generate pressure or force against a slide of a press using a servomotor as a drive source, the die cushion control device comprising: a first processor; and a first memory to store a first program which, when executed by the first processor, performs processes of: outputting a first pressure command that is a command on the pressure or the force to be generated between the die cushion mechanism and the slide; acquiring information on the pressure or the force generated between the die cushion mechanism and the slide as a detected pressure, predicting a pressure deviation that is a difference between the pressure or the force in the first pressure command and the detected pressure caused when the die cushion mechanism is controlled according to the first pressure command, based on translational acceleration of the slide, control parameters used when the pressure or the force of the die cushion mechanism is controlled, and a die cushion travel amount per revolution of the servomotor, and outputting the predicted pressure deviation as a correction pressure command; correcting the first pressure command with the correction pressure command to calculate a second pressure command; and calculating a speed command to cause the detected pressure to follow the second pressure command, and outputting the speed command to output a drive current corresponding to the speed command to the servomotor.
2 . The die cushion control device according to claim 1 , wherein the first processor performs proportional-integral control using a proportional gain and an integral gain, and predicts the pressure deviation by dividing the translational acceleration of the slide by the proportional gain, the integral gain, and the die cushion travel amount per revolution of the servomotor.
3 . The die cushion control device according to claim 2 , wherein the first processor performs switching between first processing to output the first pressure command as the second pressure command, and second processing to output the second pressure command obtained by correcting the first pressure command with the pressure deviation, and the first processor causes the first processing to be executed until a specific condition is satisfied, and switches from the first processing to the second processing when the specific condition is satisfied.
4 . The die cushion control device according to claim 3 , further comprising an inference apparatus to infer a deviation maximum value that is a maximum value of the pressure deviation at a time of a transient response of the detected pressure after the specific condition is satisfied, the inference apparatus including a second processor; and a second memory to store a second program which, when executed by the second processor, performs processes of: acquiring control conditions that are conditions used to control the die cushion mechanism, and the deviation maximum value when the die cushion mechanism is controlled using the control conditions, and inferring the deviation maximum value from the control conditions acquired, using a learned model for inferring the deviation maximum value from the control conditions, and calculating a switching timing from the first processing to the second processing for reducing the deviation maximum value during the time of the transient response, based on the inferred deviation maximum value, wherein the first processor switches from the first processing to the second processing at the switching timing.
5 . The die cushion control device according to claim 4 , further comprising a learning apparatus to generate the learned model, the learning apparatus including a third processor; and a third memory to store a third program which, when executed by the third processor, performs processes of: acquiring training data including the control conditions and the deviation maximum value, and generating the learned model using the training data.
6 . The die cushion control device according to claim 1 , wherein the first processor performs switching between first processing to output the first pressure command as the second pressure command, and second processing to output the second pressure command obtained by correcting the first pressure command with the pressure deviation, and the first processor causes the first processing to be executed until a specific condition is satisfied, and switches from the first processing to the second processing when the specific condition is satisfied.
7 . The die cushion control device according to claim 6 , further comprising an inference apparatus to infer a deviation maximum value that is a maximum value of the pressure deviation at a time of a transient response of the detected pressure after the specific condition is satisfied, the inference apparatus including a second processor; and a second memory to store a second program which, when executed by the second processor, performs processes of: acquiring control conditions that are conditions used to control the die cushion mechanism, and the deviation maximum value when the die cushion mechanism is controlled using the control conditions, and inferring the deviation maximum value from the control conditions acquired, using a learned model for inferring the deviation maximum value from the control conditions, and calculating a switching timing from the first processing to the second processing for reducing the deviation maximum value during the time of the transient response, based on the inferred deviation maximum value, wherein the first processor switches from the first processing to the second processing at the switching timing.
8 . The die cushion control device according to claim 7 , further comprising a learning apparatus to generate the learned model, the learning apparatus including a third processor; and a third memory to store a third program which, when executed by the third processor, performs processes of: acquiring training data including the control conditions and the deviation maximum value, and generating the learned model using the training data.
9 . The die cushion control device according to claim 1 , wherein the die cushion mechanism is driven using the servomotor, a hydraulic cylinder, and a rotary pump, and the die cushion travel amount per revolution of the servomotor is determined from a value obtained by dividing a discharge volume of hydraulic fluid per revolution of the rotary pump by a pressure-receiving cross-sectional area of the hydraulic cylinder.
10 . The die cushion control device according to claim 1 , wherein the die cushion mechanism is driven using the servomotor, a ball screw, a timing belt, and a speed reducer, and the die cushion travel amount per revolution of the servomotor is determined from a value obtained by dividing a ball screw pitch that is a travel amount per revolution of the ball screw by a pulley ratio of the timing belt and a reduction ratio of the speed reducer.
11 . A die cushion control method to control a die cushion mechanism to generate pressure or force against a slide of a press using a servomotor as a drive source, the die cushion control method comprising: outputting a first pressure command that is a command on the pressure or the force to be generated between the die cushion mechanism and the slide; detecting information on the pressure or the force generated between the die cushion mechanism and the slide as a detected pressure; predicting a pressure deviation that is a difference between the pressure or the force in the first pressure command and the detected pressure caused when the die cushion mechanism is controlled according to the first pressure command, based on translational acceleration of the slide, control parameters used when the pressure or the force of the die cushion mechanism is controlled, and a die cushion travel amount per revolution of the servomotor, and outputting the predicted pressure deviation as a correction pressure command; correcting the first pressure command with the correction pressure command to calculate a second pressure command; and calculating a speed command to cause the detected pressure to follow the second pressure command to output a drive current corresponding to the speed command to the servomotor.
12 . A non-transitory computer readable storage medium storing a die cushion control program to control a die cushion mechanism to generate pressure or force against a slide of a press using a servomotor as a drive source, the die cushion control program causing a computer to perform: outputting a first pressure command that is a command on the pressure or the force to be generated between the die cushion mechanism and the slide; detecting information on the pressure or the force generated between the die cushion mechanism and the slide as a detected pressure; predicting a pressure deviation that is a difference between the pressure or the force in the first pressure command and the detected pressure caused when the die cushion mechanism is controlled according to the first pressure command, based on translational acceleration of the slide, control parameters used when the pressure or the force of the die cushion mechanism is controlled, and a die cushion travel amount per revolution of the servomotor, and outputting the predicted pressure deviation as a correction pressure command; correcting the first pressure command with the correction pressure command to calculate a second pressure command; and calculating a speed command to cause the detected pressure to follow the second pressure command to output a drive current corresponding to the speed command to the servomotor.

Description

CROSS-REFERENCE TO RELATED APPLICATION The present application is based on PCT filing PCT/JP2021/021414, filed Jun. 4, 2021, the entire contents of which are incorporated herein by reference. FIELD The present disclosure relates to a die cushion control device, a die cushion control method, and a die cushion control program for controlling a die cushion mechanism. BACKGROUND Machine tools for press forming such as bending, drawing, and blanking include presses with a die cushion mechanism. The die cushion mechanism applies additional pressure to a slide that is a moving-side support member supporting one die, from a cushion pad that is a support member supporting the other die. Thus, the die cushion mechanism can prevent or reduce occurrence of defects such as wrinkles in a press-formed product. A die cushion mechanism called a servo die cushion uses a servomotor as a drive source and can arbitrarily change additional pressure during one forming process. By using the servo die cushion, presses can improve formability, quality stability, and yield. In the servo die cushion, pressure during press operation is detected, and the servomotor is controlled so that the pressure follows a predetermined pressure command value. In the servo die cushion, even if pressure control is performed, a phenomenon can occur in which an actual pressure drops against a desired pressure in the final phase of pressurization operation. In this case, the pressure drop becomes a factor that causes wrinkles in a press-formed product due to insufficient additional pressure. To eliminate this pressure drop phenomenon, a control device of Patent Literature 1 acquires the acceleration of the slide and corrects a speed command value and a current command value instructed to the die cushion mechanism, based on a signal obtained by multiplying the acceleration by a constant. CITATION LIST Patent Literature Patent Literature 1: Japanese Patent Application Laid-open No. 2007-905 SUMMARY Technical Problem However, in the technique of Patent Literature 1, if the constant by which the acceleration is multiplied is larger than an appropriate value, overcompensation is made, that is, the pressure becomes larger than a target value of the pressure command value. If the constant is smaller than the appropriate value, the pressure does not reach the target value of the pressure command value, and the pressure drop cannot be sufficiently compensated. Therefore, in the technique of Patent Literature 1, it is required to determine the constant by trial and error to perform compensation so that the pressure reaches the level of the pressure command value. Thus, the compensation for the pressure drop takes time and effort disadvantageously. The present disclosure has been made in view of the above, and an object thereof is to provide a die cushion control device capable of easily compensating for a pressure drop. Solution to Problem In order to solve the above-described problem and achieve the object, the present disclosure is a die cushion control device for controlling a die cushion mechanism that generates pressure or force against a slide of a press using a servomotor as a drive source, the die cushion control device including a pressure command generation unit that outputs a first pressure command that is a command on the pressure or the force to be generated between the die cushion mechanism and the slide. The die cushion control device also includes a deviation prediction unit that acquires information on the pressure or the force generated between the die cushion mechanism and the slide as a detected pressure, predicts a pressure deviation that is the difference between the pressure or the force in the first pressure command and the detected pressure caused when the die cushion mechanism is controlled according to the first pressure command, based on the translational acceleration of the slide, control parameters used when the pressure or the force of the die cushion mechanism is controlled, and a die cushion travel amount per revolution of the servomotor, and outputs the predicted pressure deviation as a correction pressure command. The die cushion control device also includes a pressure command correction unit that corrects the first pressure command with the correction pressure command to calculate a second pressure command, and a pressure control unit that calculates a speed command to cause the detected pressure to follow the second pressure command, and outputs the speed command to a speed control unit that outputs a drive current corresponding to the speed command to the servomotor. ADVANTAGEOUS EFFECTS OF INVENTION The die cushion control device according to the present disclosure has the effect of being able to easily compensate for a pressure drop. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram illustrating a configuration of a processing system including a die cushion control device according to a first embodiment. FIG. 2 is a diagram