Device and method of controlling machine tool, to control synchronized operation of spindle axis and feed axis

• US 10,095,222 B2
• Filed: 01/20/2017
• Issued: 10/09/2018
• Est. Priority Date: 01/26/2016
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Morita, Yuuki, Tajima, Daisuke
• Primary Examiner(s): Lo, Kenneth M
• Assistant Examiner(s): Sivanesan, Sivalingam
• Application Number:
  US15/411,875
• Publication Number:
  US 20170212502A1
• Time in Patent Office: 627 Days
• Field of Search: 700159
• CPC Class Codes: G05B 19/414 Structure of the control system, e.g. common controller or multiprocessor systems, interface to servo, programmable interface controller
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/49108 Spindle speed

Abstract

A controller for controlling a synchronized operation of spindle and feed axes. A spindle-axis control section includes an initial-motion control section for accelerating a spindle axis at maximum capacity from a starting position; a maximum-acceleration detecting section for detecting a maximum acceleration of the spindle axis; a residual rotation-amount detecting section for detecting a residual rotation amount of the spindle axis; a current-speed detecting section for detecting a current speed of the spindle axis; a decelerating-motion control section for decelerating the spindle axis to reach an intermediate speed, after the acceleration; a positioning-motion control section for decelerating the spindle axis to reach the target position after reaching the intermediate speed; a flux-content predicting section for predicting an actual motor-flux content at the intermediate speed; and a deceleration determining section for determining a deceleration for a positioning operation, based on the maximum acceleration, the motor-flux-content command value and the motor-flux content.

Claims

1. A controller of a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the controller comprising:

a numerical control section configured to prepare a spindle-axis command and a feed-axis command based on a tapping program;

a spindle-axis control section configured to control a rotational motion of the spindle axis in accordance with the spindle-axis command;

a rotation detecting section configured to detect a rotational position of the spindle axis; and

a feed-axis control section configured to control a feed motion of the feed axis in accordance with the feed-axis command, based on the rotational position;

the numerical control section comprising;

a spindle-axis command outputting section configured to obtain, from the tapping program, a total rotation amount and a maximum rotation speed of the spindle axis during a period when the spindle axis operates from a starting position to a target position, and to send the total rotation amount and the maximum rotation speed as the spindle-axis command to the spindle-axis control section;

the spindle-axis control section comprising;

an initial-motion control section configured to make the spindle axis perform an accelerated rotation at maximum capacity from the starting position, by a velocity control in which the maximum rotation speed is set as a target value;

a maximum-acceleration detecting section configured to detect a maximum acceleration of the spindle axis during the accelerated rotation at maximum capacity, based on the rotational position;

a residual rotation-amount detecting section configured to detect a residual rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the target position, based on the total rotation amount and the rotational position;

a current-speed detecting section configured to detect a current speed of the spindle axis based on the rotational position;

a decelerating-motion control section configured to execute a velocity control for making the spindle axis perform a decelerated rotation at maximum capacity so as to reach a predetermined intermediate speed, after the accelerated rotation at maximum capacity;

a positioning-motion control section configured to execute a position control for making the spindle axis perform a decelerated rotation so as to reach the target position, after the spindle axis reaches the intermediate speed;

a flux-content predicting section configured to predict an actual motor-flux content at the intermediate speed, based on a motor-flux-content command value for making the spindle axis reach the intermediate speed; and

a deceleration determining section configured to determine a deceleration during the decelerated rotation by the position control, based on the maximum acceleration, the motor-flux-content command value and the motor-flux content;

the positioning-motion control section configured to execute the position control, based on the residual rotation amount, the current speed and the deceleration.

2. The controller of claim 1, wherein the flux-content predicting section is configured to estimate as needed a flux content of a spindle motor during operation, the spindle motor configured to rotationally operate the spindle axis, and predict the motor-flux content at the intermediate speed, based on the motor-flux-content command value and the flux content estimated at a start of the decelerated rotation by the velocity control.

3. The controller of claim 1, wherein the starting position corresponds to a process start position of a tapping process, and wherein the target position corresponds to a target thread depth of the tapping process.

4. The controller of claim 1, wherein the starting position corresponds to a target thread depth of a tapping process, and wherein the target position corresponds to a return completion position of the tapping process.

5. A method of controlling a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the method comprising the steps, executed by a controller, of:

obtaining, from a tapping program, a total rotation amount and a maximum rotation speed of the spindle axis during a period when the spindle axis operates from a starting position to a target position;

making the spindle axis perform an accelerated rotation at maximum capacity from the starting position, by a velocity control in which the maximum rotation speed is set as a target value;

detecting a maximum acceleration of the spindle axis during the accelerated rotation at maximum capacity, based on a rotational position feedback of the spindle axis;

detecting a residual rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the target position, based on the total rotation amount and the rotational position feedback;

detecting a current speed of the spindle axis based on the rotational position feedback;

executing a velocity control for making the spindle axis perform a decelerated rotation at maximum capacity so as to reach a predetermined intermediate speed, after the accelerated rotation at maximum capacity;

executing a position control for making the spindle axis perform a decelerated rotation so as to reach the target position, after the spindle axis reaches the intermediate speed;

predicting an actual motor-flux content at the intermediate speed, based on a motor-flux-content command value for making the spindle axis reach the intermediate speed; and

determining a deceleration during the decelerated rotation by the position control, based on the maximum acceleration, the motor-flux-content command value and the motor-flux content;

the step of making the spindle axis reach the target position including the step of executing the position control, based on the residual rotation amount, the current speed and the deceleration.

6. The method of claim 5, wherein the step of predicting the motor flux-content includes the step of estimating as needed a flux content of a spindle motor during operation, the spindle motor configured to rotationally operate the spindle axis, and predicting the motor-flux content at the intermediate speed, based on the motor-flux-content command value and the flux content estimated at a start of the decelerated rotation by the velocity control.

7. The method of claim 5, wherein the starting position corresponds to a process start position of a tapping process, and wherein the target position corresponds to a target thread depth of the tapping process.

8. The method of claim 5, wherein the starting position corresponds to a target thread depth of a tapping process, and wherein the target position corresponds to a return completion position of the tapping process.