# US 12,216,446 B2 · Ballbar testing tune-up method for machine tool

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- Number: US 12,216,446 B2
- Document ID: US12216446B2
- Status: Granted
- Kind: B2
- Application number: 17/451,924
- Filed: 2021-10-22
- Published: 2023-02-09
- Granted: 2025-02-04
- Earliest claimed: 2021-08-06
- Assignees: National Yang Ming Chiao Tung University
- Applicants: National Yang Ming Chiao Tung University
- Inventors: Ching-Hung Lee; Shun-Fu Wu
- Web page: https://patentgrep.com/patent/US12216446B2

## CPC

- G05B 19/401: characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes (G05B19/19 takes precedence)
- B23Q 17/22: for indicating or measuring existing or desired position of tool or work {(B23Q16/005 takes precedence)}
- G05B 19/404: characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia (G05B19/19, G05B19/41 take precedence)
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)
- B23Q: DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g. ARRANGEMENTS FOR COPYING OR CONTROLLING (tools of the kind used in lathes or boring machines B23B27/00); MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OF PARTICULAR DETAILS OR COMPONENTS; COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOT DIRECTED TO A PARTICULAR RESULT

## Abstract

A ballbar testing tune-up method for machine tool includes the steps of letting a machine tool system execute a ballbar test; obtaining a phase characteristic and a peak-value characteristic; creating a Lagrange interpolation polynomial and inputting a servo controller parameter, a phase characteristic and a peak-value characteristic of the machine tool system each time when executing the ballbar test, and obtaining a proposed servo parameter. This method is simple and easy without incurring additional equipment costs, but just using existing equipment to find the proposed servo parameter quickly and input it into a machine tool system, so as to improve the response issue of a servo system and reduce manufacturing contour error to enhance the working precision of the machine tool system.

## Claims

### Claim 1

A method for calibrating a Computer Numerical Control Machine (CNC Machine), the method comprising:
providing a CNC Machine, the CNC Machine including:
a tool head;
at least two servomotors corresponding to at least two orthogonal directions of movement of the tool head, and a first direction of movement is defined as a first axis and a second direction of movement is defined as a second axis;
a servocontroller for controlling a corresponding one of each of the at least two servomotors, each servocontroller including at least a position controller and a velocity controller coupled thereto;
a processor; and
an optical ruler coupled to the processor;
executing a plurality of ballbar tests using the optical ruler as a measurement tool for determining which of the two orthogonal directions of movement has a response characteristic less than that of the other, wherein execution of each ballbar test includes:
actuating each servocontroller to control a corresponding one of each of the at least two servomotors to selectively move the tool head in at least a portion of a circular path with respect to the at least two orthogonal axes; and
obtaining a phase characteristic and a peak-value characteristic with respect to a tracking result with respect to the at least a portion of a circular path, wherein the phase characteristic is an average value of a difference between a radius sampled at a position of the first axis and the second axis with a contour error fixed cycle in a corresponding ballbar test and an average radius of the corresponding ballbar test, wherein the peak-value characteristic is a difference of peak values at the first axis and the second axis in the corresponding ballbar test;
generating a Lagrange interpolation polynomial subsequent to execution of each ballbar test, and increasing an interpolation order of a corresponding Lagrange interpolation polynomial according to a number of executed ballbar tests, and inputting at least into a corresponding Lagrange interpolation polynomial a servo controller parameter of a servocontoller of a respective servomotor associated with a corresponding ballbar test and at least one of the phase characteristic and the peak-value characteristic associated with the corresponding ballbar test for generation of a proposed servo parameter; and
inputting the proposed servo parameter into the processor for selectively actuating the at least one of a position controller or a velocity controller of a respective servocontroller of a corresponding servomotor to appropriately compensate the corresponding response characteristic in the respective direction of movement, thereby improving a contour precision of the tool head of the CNC Machine.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the peak-value characteristic with respect to the tracking result with respect to the at least a portion of a circular path is, further, defined by defining a sampling time based on a neighborhood of the peak values of the first axis and the second axis associated with a corresponding ballbar test, and the sampling time is operated upon to define a filter range for calculating an average value of the peak values associated with the corresponding ballbar test to perform a filtering operation, and the difference between the peak values of the first axis and the second axis associated with the ballbar test subsequent to the filtering operation defines the peak-value characteristic.

### Claim 3 (depends on 1)

The method according to claim 1, wherein each servo controller includes a position loop, and the proposed servo parameter is inputted as a position controller parameter into the position loop.

### Claim 4 (depends on 3)

The method according to claim 3, wherein the proposed servo parameter is generated by inputting the phase characteristic associated with a corresponding ballbar test into the Lagrange interpolation polynomial.

### Claim 5 (depends on 1)

The method according to claim 1, wherein each servo controller includes a velocity loop, and the proposed servo parameter is inputted as a controller parameter into the velocity loop.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the proposed servo parameter is generated by inputting the phase characteristic and the peak-value characteristic associated with a corresponding ballbar test into the Lagrange interpolation polynomial.