Apparatus for estimating quantity of state relating to motor, and electric tool

Patent metadata

Field	Value
Publication number	US-9425730-B2
Application number	US-201213980941-A
Country	US
Kind code	B2
Filing date	Jan 19, 2012
Priority date	Feb 10, 2011
Publication date	Aug 23, 2016
Grant date	Aug 23, 2016

Abstract

The present application discloses an apparatus including: a motor model that reflects a characteristic of a motor and includes at least inputs pertaining to a first quantity of state and a second quantity of state and an output pertaining to a third quantity of state; a comparator that calculates a difference between the third quantity of state in an actual motor and the third quantity of state output from the motor model; and an amplifier that amplifies an output of the comparator at a predetermined gain. The first quantity of state in the actual motor is input into the motor model as the first quantity of state, and an output of the amplifier is input into the motor model as the second quantity of state. The apparatus then uses the output of the amplifier as an estimated value of the second quantity of state in the actual motor.

First claim

The invention claimed is:

1. An apparatus for estimating a quantity of state relating to a motor, comprising:
a motor model that includes at least inputs comprising a voltage applied to the motor and a torque acting on the motor, and an output comprising a current flowing through the motor;
a comparator that calculates a difference between the current in an actual motor and the current output from the motor model; and
an amplifier that amplifies an output of the comparator at a predetermined gain,
wherein:
the voltage in the actual motor is input into the motor model,
the motor model calculates the current output based on the voltage and torque inputs by performing a numerical calculation not including a differentiation operation, and
an output of the amplifier is set as an estimated value of the torque in the actual motor and is input into the motor model.

2. The apparatus according to claim 1 , wherein
the motor is controlled by causing a current to flow thereto intermittently,
the motor model further includes an output comprising the voltage applied to the motor,
the apparatus further comprises:
a second comparator that calculates a difference between the voltage applied to the motor in the actual motor and the voltage applied to the motor output from the motor model; and
a second amplifier that amplifies an output of the second comparator at a predetermined gain,

the output of the amplifier is added to an output of the second amplifier, and
a value obtained by adding the output of the second amplifier to the output of the amplifier is set as the estimated value of the torque acting on the actual motor and is input into the motor model.

3. The apparatus according to claim 2 , wherein
the motor is installed in an electric tool provided with a tool unit and a power transmission unit for transmitting a rotation of the motor to the tool unit,
the apparatus further comprises a power transmission unit model that includes an input comprising a torque acting on the power transmission unit from the tool unit, and an output comprising the torque acting on the motor from the power transmission unit,
the output of the amplifier is set as an estimated value of a torque acting on an actual tool unit rather than the estimated value of the torque acting on the actual motor and is input into the motor model via the power transmission unit model.

4. The apparatus according to claim 1 , further comprising:
a first filter that removes at least high frequency components; and
a second filter having identical characteristics as the first filter,
wherein
the motor is controlled by flowing a current intermittently,
the current flowing through the motor in the actual motor is input to the comparator via the first filter, and
the voltage applied to the motor in the actual motor is input to the motor model via the second filter.

5. The apparatus according to claim 4 , wherein
the motor is installed in an electric tool provided with a tool unit and a power transmission unit for transmitting a rotation of the motor to the tool unit,
the apparatus further comprises a power transmission unit model that includes an input comprising a torque acting on the power transmission unit from the tool unit, and an output comprising the torque acting on the motor from the power transmission unit,
the output of the amplifier is set as an estimated value of a torque acting on an actual tool unit rather than the estimated value of the torque acting on the actual motor and is input into the motor model via the power transmission unit model.

6. The apparatus according to claim 1 , wherein
the motor is installed in an electric tool provided with a tool unit and a power transmission unit for transmitting a rotation of the motor to the tool unit,
the apparatus further comprises a power transmission unit model that includes an input comprising a torque acting on the power transmission unit from the tool unit, and an output comprising the torque acting on the motor from the power transmission unit,
the output of the amplifier is set as an estimated value of a torque acting on an actual tool unit rather than the estimated value of the torque acting on the actual motor and is input into the motor model via the power transmission unit model.

7. An electric tool comprising the apparatus according to claim 1 .

8. The apparatus according to claim 1 , wherein the numerical calculation includes a numerical integration.

9. The apparatus according to claim 8 , wherein the numerical integration relates to simultaneous integral equations as follows:

i
=

∫

(

1
L

⁢
V

-

R
L

⁢
i

-

K
⁢

⁢
B

L

⁢
ω

)

⁢

ⅆ
t

ω
=

∫

(

K
⁢

⁢
T

J

⁢
i

-

B
J

⁢
ω

-

1
J

⁢
τ

)

⁢

ⅆ
t

where i is the current output, ω is a rotation speed of the motor, V is the voltage input, τ is the torque input, L is an inductance of the motor, R is a resistance value of the motor, KB is a power generation constant of the motor, J is a moment of inertia of a rotor of the motor, KT is a torque constant of the motor, and B is a friction constant of the motor.

Assignees

• Sako Masahiko
• Yamamoto Hirokatsu
• Osada Takaaki
• Makita Corp

Inventors

• Sako Masahiko
• Yamamoto Hirokatsu
• Osada Takaaki

Classifications

• H02P6/34

  Modelling or simulation for control purposes · CPC title

• H02P23/12

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title

• H02P31/00 Primary

  Arrangements for regulating or controlling electric motors not provided for in groups H02P1/00 - H02P5/00, H02P7/00 or H02P21/00 - H02P29/00 · CPC title

• H02P6/06

  Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed · CPC title

• H02P23/14

  Estimation or adaptation of motor parameters, e.g. rotor time constant, flux, speed, current or voltage · CPC title