US 8,013,560 B2Granted

Method for compensating for angular transmission error of an actuator

AssigneeHarmonic Drive Systems Inc.

InventorsKozo Sasaki, Yoshifumi Okitsu, Toshio Yajima, Makoto Iwasaki

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Abstract

The non-linear elastic deformation component included in the angular transmission error of an actuator provided with a wave gear drive is a component of the angular transmission error occurring due to elastic deformation of a flexible externally-toothed gear when the direction of rotation of the motor shaft changes. This component can be analyzed by driving the motor in a sine-wave shape. A model of the non-linear elastic deformation component (non-linear model) obtained from the analysis results is used to store data or a function for compensating for this component in a motor-control device. Compensation for the non-linear elastic deformation component (θHys) is added to a motor-shaft angle command (θ*M) as a compensation input (Nθ*TE) for feed-forward compensation. As a result, the non-linear elastic deformation component (θHys) can be effectively reduced, and the positioning precision of the actuator can be improved.

Claims2

Dependent claims

A method for compensating for angular transmission error of an actuator provided with a motor and a wave gear drive, comprising:

in a control system for positioning an output shaft of the actuator using a non-linear model composed of a mathematical model given by equations (1) through (3) to stipulate dynamic characteristics of a non-linear elastic deformation component included in the angular transmission error of the actuator and brought about by elastic deformation of a flexible externally-toothed gear of the wave gear drive:
θ
Hys
⁡
(
δ
)
=
{
sgn
⁡
(
ω
M
)
⁢
(
2
⁢
⁢
θ
def
⁢
g
⁡
(
ξ
)
-
θ
Hys
′
)
:
⁢

δ

<
θ
r
⁢
⁢
and
⁢
⁢
⁢

θ
Hys

<
θ
def
sgn
⁡
(
ω
M
)
⁢
θ
def
:
⁢

δ

≥
θ
r
⁢
⁢
or
⁢
⁢
⁢

θ
Hys

≥
θ
def
(
1
)
g
⁡
(
ξ
)
=
{
1
2
-
n
⁢
(
ξ
n
-
1
-
(
n
-
1
)
⁢
ξ
)
⁢
:
⁢
n
≠
2
ξ
⁡
(
1
-
ln
⁢
⁢
ξ
)
⁢
:
⁢
n
=
2
(
2
)
δ
=

θ
M
-
δ
0

,
ξ
=
δ
/
θ
r
(
3
)
where θr:
Width of unsteady region
n:
Constant representing the hysteresis bulge
δ:
Rotational distance after reversal of rotational direction
θ′Hys:
Non-linear elastic deformation component θHys(δ) during reversal of rotational direction
θdef:
Direction-dependent deformation angle (offset component)
δ0:
Motor-shaft angle θM during reversal of rotational direction;
determining a non-linear elastic deformation component θHys during reversal of a motor-shaft rotational direction using the motor-shaft angle θM and the non-linear model;
adding a compensation input NθHys (N:
reduction ratio of the wave gear drive) to a motor-shaft angle command θ*M as feed-forward compensation, to thereby obtain a compensated motor-shaft angle command;
and
using the compensated motor-shaft angle command to control driving of the motor;
whereby the non-linear elastic deformation component included in the angular transmission error of an output shaft of the actuator is compensated for.

172 more elements

A method for compensating for angular transmission error of an actuator provided with a motor and a wave gear drive, comprising:

using a non-linear model composed of a mathematical model given by equations (1) through (3) to stipulate dynamic characteristics of a non-linear elastic deformation component included in the angular transmission error of the actuator and brought about by elastic deformation of a flexible externally-toothed gear of the wave gear drive:
θ
Hys
⁡
(
δ
)
=
{
sgn
⁡
(
ω
M
)
⁢
(
2
⁢
⁢
θ
def
⁢
g
⁡
(
ξ
)
-
θ
Hys
′
)
:
⁢

δ

<
θ
r
⁢
⁢
and
⁢
⁢
⁢

θ
Hys

<
θ
def
sgn
⁡
(
ω
M
)
⁢
θ
def
:
⁢

δ

≥
θ
r
⁢
⁢
or
⁢
⁢
⁢

θ
Hys

≥
θ
def
(
1
)
g
⁡
(
ξ
)
=
{
1
2
-
n
⁢
(
ξ
n
-
1
-
(
n
-
1
)
⁢
ξ
)
⁢
:
⁢
n
≠
2
ξ
⁡
(
1
-
ln
⁢
⁢
ξ
)
⁢
:
⁢
n
=
2
(
2
)
δ
=

θ
M
-
δ
0

,
ξ
=
δ
/
θ
r
(
3
)
where θr:
Width of unsteady region
n:
Constant representing the hysteresis bulge
δ:
Rotational distance after reversal of rotational direction
θ′Hys:
Non-linear elastic deformation component θHys(δ)during reversal of rotational direction
θdef:
Direction-dependent deformation angle (offset component)
δ0:
Motor-shaft angle θM during reversal of rotational direction;
determining a non-linear elastic deformation component θHys during reversal of a motor-shaft rotational direction using the motor-shaft angle θM and the non-linear model;
adding a compensation input NθHys (N:
reduction ratio of the wave gear drive) to a motor-shaft angle command θ*M as feed-forward compensation;
whereby the non-linear elastic deformation component included in the angular transmission error of an output shaft of the actuator is compensated for;
causing the motor to rotate in a clockwise direction and in a counter-clockwise direction;
measuring a motor-shaft synchronized component (fixed component), the motor-shaft synchronized component (fixed component) being an angular transmission error component in each of the motor-shaft angles θM occurring in synchronization with rotation of a motor shaft;
calculating an average value θTEMotor of a measured value of clockwise rotation and counter-clockwise rotation of the motor;
and
adding a compensation input Nθ*TE to the motor-shaft angle command θ*M as feed-forward compensation, the compensation input Nθ*TE including the compensation value θHys of the non-linear elastic deformation component and the compensation value θTEMotor of the motor-shaft synchronized component (fixed component), whereby the non-linear elastic deformation component and the motor-shaft synchronized component (fixed component) included in the angular transmission error of the output shaft of the actuator are compensated for.

175 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/353,115Filed 13 Jan 2009
Priority: JP 2008-0281957 Feb 2008
Published: US 2009/0200979 A113 Aug 2009
Granted: 6 Sep 2011
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G05B 19/404
Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to…
G05B 2219/41032
Servomotor, servo controller till figures: backlash
G05B 2219/41148
Servomotor, servo controller till figures: model, from position, speed, acceleration derive compensation
G05B 2219/41358
Servomotor, servo controller till figures: transmission, variable gear ratio