Inertia estimating method and inertia estimation apparatus of position control apparatus

Patent metadata

Field	Value
Publication number	US-9952249-B2
Application number	US-201414262371-A
Country	US
Kind code	B2
Filing date	Apr 25, 2014
Priority date	Apr 25, 2013
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A torque command value and an acceleration detection value are accumulated when a driven portion is subjected to acceleration/deceleration driving, and, from a ratio between the two, inertia of a movable portion is calculated. By executing the acceleration/deceleration driving about a position where influence of gravity torque is zero, the influence of the gravity torque included in the torque command value before and after the center position is offset, whereby inertia can be estimated correctly even with a machine structure in which the influence of gravity differs depending on the position of the motor.

First claim

What is claimed is:

1. An inertia estimating method for estimating an inertia of a movable portion including a motor and a driven portion connected to the motor and mounted on an apparatus that drives the motor according to a torque command value, the torque command value determined from a position command value and a position detection value of the motor or the driven portion connected to the motor, the method comprising the steps of:
driving the movable portion;
determining, when the movable portion is driven, an acceleration/deceleration condition to determine one or more of an acceleration driving condition or a deceleration driving condition, such that a cumulative value of a gravity torque or acceleration of the movable portion has a symmetric characteristic about a zero position where the gravity torque that cancels an influence of gravity is zero;
calculating the position command value of the motor according to the acceleration driving condition or the deceleration driving condition determined in the step of determining the acceleration/deceleration condition;
driving the motor based on the position command value calculated in the step of calculating the position command value, and obtaining the torque command value when the motor is driven and obtaining an acceleration detection value of the motor or the driven portion; and
calculating the inertia of the movable portion using a ratio between a cumulative value of the torque command value and a cumulative value of the acceleration detection value of the motor or the driven portion.

2. The inertia estimating method according to claim 1 , including determining the zero position using the position detection value obtained when a polarity of the torque command value is inverted when the driven portion is driven at a constant velocity.

3. The inertia estimating method according to claim 1 , wherein,
when the driven portion is subjected to acceleration driving or deceleration driving, adjusting an acceleration time or a deceleration time so that the cumulative value of the gravity torque is the same before and after passing the zero position.

4. The inertia estimating method according to claim 1 , wherein
the step of determining the acceleration/deceleration condition includes monitoring the torque command value when the driven portion is reciprocally driven at a constant velocity, and
further comprising determining the zero position using a middle point between the position detection value obtained at a timing when a polarity of the torque command value is inverted in a going path and the position detection value obtained when the polarity of the torque command value is inverted in a returning path.

5. The inertia estimating method according to claim 1 , wherein
the step of determining the acceleration/deceleration condition includes determining both the acceleration driving condition and the deceleration driving condition such that the magnitude of the cumulative value of the gravity torque or the acceleration is changed in line symmetry about the zero position,
the step of calculating the inertia includes monitoring the torque command value and the acceleration detection value when the motor is driven according to the determined acceleration driving condition and the determined deceleration driving condition, and
utilizing an average value of a ratio between the cumulative value of the torque command value and the cumulative value of the acceleration detection value during the acceleration driving condition, and a ratio between the cumulative value of the torque command value and the cumulative value of the acceleration detection value during the deceleration driving condition.

6. The inertia estimating method according to claim 1 , wherein
the step of determining the acceleration/deceleration condition includes determining both the acceleration driving condition and the deceleration driving condition such that the magnitude of the cumulative value of the gravity torque or the acceleration is changed in line symmetry about the zero position,
the step of calculating the inertia includes monitoring the torque command value and the acceleration detection value when the motor is driven according to the determined acceleration driving condition and the determined deceleration driving condition, and
utilizing a ratio between an added value of the cumulative value of the torque command value during the acceleration driving condition and the deceleration driving condition, respectively, and an added value of the cumulative value of the acceleration detection value during the acceleration driving condition and the deceleration driving condition, respectively.

7. An inertia estimating apparatus configured to estimate an inertia of a movable portion including a motor and a driven portion connected to the motor and mounted on an apparatus that drives the motor according to a torque command value, the torque command value determined from a position command value and a position detection value of the motor or the driven portion connected to the motor, comprising:
an acceleration/deceleration condition determining unit configured to determine, when the movable portion is driven, one or more of an acceleration driving condition or a deceleration driving condition, such that a cumulative value of a gravity torque or acceleration of the movable portion has a symmetric characteristic about a zero position where the gravity torque that cancels an influence of gravity is zero;
a position command value calculating unit configured to calculate the position command value for driving the motor according to said one or more of an acceleration driving condition or an deceleration driving condition determined by the acceleration/deceleration condition determining unit;
a controller configured to drive the motor based on the position command value calculated by the position command value calculating unit; and
an inertia calculating unit configured to receive a torque command value generated by a velocity controller when the motor is driven according to one or more of the acceleration driving condition or the deceleration driving condition, and to obtain an acceleration detection value of the motor or the driven portion, and to calculate the inertia of the movable portion using a ratio between a cumulative value of the torque command value and a cumulative value of the acceleration detection value.

8. An apparatus as defined in claim 7 , further including a position detector configured to detect a position of the motor or the driven portion.

9. A method as defined in claim 1 , wherein the apparatus that drives the motor is a machine tool with a feed axis, and the method further comprises determining parameters, based on the calculated inertia, for driving the feed axis according to a desired position and velocity, and driving the feed axis according to the desired position and velocity.

10. A method as defined in claim 1 , further comprising controlling one or more of a velocity or a position of one or more of the motor or the driven portion using the calculated inertia.

11. An apparatus comprising:
a movable portion including
a motor; and
a driven portion connected to the motor,

wherein the motor is configured to drive the driven portion;
an acceleration/deceleration condition determining unit configured to determine, when the movable portion is driven, one or more of an acceleration driving condition or a deceleration driving condition, such that a cumulative value of a gravity torque or acceleration of the movable portion has a symmetric characteristic about a zero position where the gravity torque that cancels an influence of gravity is zero;
a pos

Assignees

• Okuma Machinery Works Ltd

Inventors

• Miyaji Masashi

Classifications

• G01M1/10 Primary

  Determining the moment of inertia · CPC title

• G01P15/0802 Primary

  Details · CPC title