US 2011/0248661 A1Published application

Method for controlling positioning of actuator comprising wave gear device

AssigneeHarmonic Drive Systems Inc.

InventorsYoshifumi OKITSU, Yuki KATO, Kozo SASAKI, Makoto IWASAKI

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Abstract

A method for controlling positioning of an actuator having a wave gear device uses a strict linearization technique to compensate for the effects relative to positioning control of a load shaft in the, as caused by the non-linear spring characteristics of the wave gear device. In the method, a plant model is constructed from the actuator to be controlled, the model being linearized using a strict linearization technique; measurements are taken of the non-linear elastic deformation of the wave gear device relative to load torque; the non-linear spring model τg(θtw) is defined using a cubic polynomial with the constant defined as zero to allow the measurement results to be recreated; and the current input into the plant model and the motor position of the plant model when a load acceleration command is a command value are entered into a semi-closed loop control system for controlling the positioning of the load shaft, as a feed-forward current command and a feed-forward motor position command.

A method for controlling positioning of an actuator which reduces a rotational output of a motor via a wave gear device and transmitting the output from a load shaft, and controls positioning of the load shaft based on a rotational position and speed of a motor shaft of the motor, the method being characterized in comprising:

performing non-linear spring compensation for inhibiting a reduction in the accuracy with which positioning of the load shaft is controlled, as caused by non-linear elastic deformation in relation to a load torque of the wave gear device;
and
in the non-linear spring compensation,
constructing a plant model that has been linearized using a strict linearization technique from the actuator to be controlled, and defining the linearization feedback α(x) and input conversion β(x) as well as the characteristics of the expansion system from input v to output y according to formulae (A), (B), and (C), respectively;
[
FORMULA


A
]
α

(
x
)
·
x
=
-
J
m

J
l

N
D
g

K
t

{
1
J
l



t

τ
g

(
θ
tw
)
-
(
D
l
+
D
g
J
l
2
+
D
g
J
m

J
l

N
2
)

τ
g

(
θ
tw
)
+
(
(
D
l
+
D
g
)
2
J
l
2
+
D
g
2
J
m

J
l

N
2
)

ω
l
-
(
D
l

D
g
+
D
g
2
J
l
2

N
+
D
m

D
g

N
2
+
D
g
2
J
m

j
l

N
3
)

ω
m
}
(
A
)
[
FORMULA


B
]
β

(
x
)
·
υ
=
J
m

J
l

N
D
g

K
t

υ
(
B
)
[
FORMULA


C
]

3

y

t
3
=
υ
(
C
)
measuring the non-linear elastic deformation in relation to the load torque of the wave gear device;
defining the non-linear spring model τg(θtw) using a cubic polynomial as shown in formula (D), with the constant defined as zero, to be able to recreate the measurement results;
and
[FORMULA D]
τg(θtw)=Kg3θtw3+Kg2θtw2+Kg1θtw (D)
respectively inputting into a semi-closed loop control system for controlling the positioning of the load shaft, as a feed-forward current command and a feed-forward motor position command, the current input into the plant model and the motor position of the plant model when a load acceleration command is a command value.

204 more elements

Abstract

Claims1