# US 9,471,055 B2 · Servo control device reducing deflection of front end point of machine

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- Number: US 9,471,055 B2
- Document ID: US9471055B2
- Status: Granted
- Kind: B2
- Application number: 14/728,494
- Filed: 2015-06-02
- Published: 2015-12-10
- Granted: 2016-10-18
- Earliest claimed: 2014-06-05
- Assignees: Fanuc Corporation
- Applicants: Fanuc Corporation
- Inventors: Naoto Sonoda
- Web page: https://patentgrep.com/patent/US9471055B2

## CPC

- 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 19/19: characterised by positioning or contouring control systems, e.g. to control position from one programmed point to another or to control movement along a programmed continuous path
- G05B 2219/41139: Compensate dynamic deflection of slide, calculated with position, speed, torque deflection values
- 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)

## Abstract

A servo control device having a position control unit and a speed control unit to control a front end point of a machine of a machine tool, comprising: a position detecting unit for detecting a position of a motor; a first position error calculating unit for calculating a first position error based on a position command to a motor and position feedback from the position detecting unit; a torsion estimating unit for estimating an amount of torsion of the front end point of the machine; a second position error calculating unit for adding the first position error and estimated amount of torsion to calculate a second position error; a coefficient adapting unit for determining a coefficient of feedforward control so as to minimize the second position error; and a higher order feedforward control unit for performing feedforward control by using the determined coefficient and the position command.

## Claims

### Claim 1

A servo control device which comprises a position control unit and a speed control unit and which controls the position and speed of a motor to control a front end point of a machine of a machine tool, the control device comprising:
a position detecting unit configured to detect a position of a driven member which is driven by the motor or the motor;
a first position error calculating unit configured to calculate a first position error on the basis of a position command to a motor and position feedback from said position detecting unit;
a torsion estimating unit configured to estimate an amount of torsion of the front end point of the machine;
a second position error calculating unit configured to add said first position error and estimated amount of torsion to calculate a second position error;
a coefficient adapting unit configured to determine a coefficient of feedforward control so as to minimize said second position error; and
a higher order feedforward control unit configured to perform the feedforward control by using said determined coefficient and the position command to the motor.

### Claim 2 (depends on 1)

The servo control device according to claim 1 further comprising an acceleration detecting unit configured to detect acceleration of the front end point of the machine,
wherein said torsion estimating unit estimates an amount of torsion of the front end point of the machine on the basis of the acceleration which is fed back from said acceleration detecting unit.

### Claim 3 (depends on 1)

The servo control device according to claim 1 further comprising:
a speed detecting unit configured to detect a speed of the motor; and
a current detecting unit configured to detect a current of the motor,
wherein said torsion estimating unit estimates an amount of torsion of the front end point of the machine on the basis of the speed of said motor and current of said motor.

### Claim 4 (depends on 1)

The servo control device according to claim 1 further comprising a speed detecting unit configured to detect a speed of the motor,
wherein said torsion estimating unit estimates an amount of torsion of the front end point of the machine on the basis of the speed of said motor and torque command to said motor.