# US 2014/0197773 A1 · Motor control device for compensating backlash

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- Number: US 2014/0197773 A1
- Document ID: US20140197773A1
- Status: Published application
- Kind: A1
- Application number: 14/151,233
- Filed: 2014-01-09
- Published: 2014-07-17
- Earliest claimed: 2013-01-11
- Assignees: Fanuc Corporation
- Applicants: Fanuc Corporation
- Inventors: Satoshi Ikai; Tsutomu Nakamura
- Web page: https://patentgrep.com/patent/US20140197773A1

## 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 2219/41078: Backlash acceleration compensation when inversing, reversing direction
- 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 motor control device includes a position command generating unit, a difference calculating unit for calculating a difference between a positional detection value of a movable unit and a positional detection value of a driven unit, a retaining unit for retaining, as an engaging difference, the difference when the movable unit is moved in a first or second direction to engage with the driven unit, in association with the first direction and the second direction, and a compensation amount calculating unit for calculating a backlash compensation amount based on the difference calculated by the difference calculating unit and the engaging difference retained by the retaining unit. It is determined whether or not the movable unit is engaged with the driven unit by comparing a movement amount of the driven unit with a threshold.

## Claims

### Claim 1

A motor control device for compensating backlash between a movable unit driven by a motor and a driven unit driven by the movable unit, the motor control device comprising:
a position command generating unit for generating a position command for the driven unit;
a first position detecting unit for detecting a position of the movable unit;
a second position detecting unit for detecting a position of the driven unit;
a difference calculating unit for calculating a difference between a first positional detection value detected by the first position detecting unit and a second positional detection value detected by the second position detecting unit;
a judging unit for judging whether or not the movable unit is engaged with the driven unit when the movable unit is driven in a first direction and in a second direction opposite to the first direction;
a retaining unit for retaining the difference calculated by the difference calculating unit as an engaging difference, in association with the first direction or the second direction, when the judging unit determines that the movable unit is engaged with the driven unit; and
a compensation amount calculating unit for calculating a backlash compensation amount, based on the difference calculated by the difference calculating unit, and the engaging difference retained by the retaining unit,
wherein the judging unit is adapted to determine that the movable unit is engaged with the driven unit when a movement amount of the driven unit exceeds a threshold.

### Claim 2 (depends on 1)

The motor control device according to claim 1, wherein the position command generating unit is adapted to generate a position command for a preliminary movement of the driven unit when the judging unit judges whether or not the movable unit is engaged with the driven unit.

### Claim 3 (depends on 2)

The motor control device according to claim 2, wherein the position command for a preliminary movement of the driven unit is set so as to be smaller than a unit of the position command for the driven unit.

### Claim 4 (depends on 3)

The motor control device according to claim 3, wherein the position command for a preliminary movement of the driven unit is set to be half a unit of the position command for the driven unit.

### Claim 5 (depends on 2)

The motor control device according to claim 2, wherein the position command generating unit is adapted to generate the position command for a preliminary movement of the driven unit, when at least one of the engaging difference in the first direction and the engaging difference in the second direction is not retained by the retaining unit.