Electric press, bend-point detection method, and program

1. An electric press comprising:

a detection unit configured to detect a press position and a first data sequence of a load at the press position;

an input and storage unit configured to input and store a value serving as a reference that determines a bend point in a relation between the press position and the first data sequence of the load at the press position;

a slope calculation unit configured to calculate a slope of the load based on the press position and the first data sequence of the load at the press position detected, according to a first regression line, wherein the slope of the load is calculated by the following formula, (i),

the

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slope

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of

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the

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load

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Formula

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a slope-of-slope calculation unit configured to calculate a slope of the slope of the load calculated by the slope calculation unit as an amount of change of an amount of change of a load value with respect to the press position by using the formula (i) for calculating a slope of the first regression line, according to a second regression line,

wherein, in the formula (i), n denotes a number of data, xi denotes position data of a pressurization part, and yi denotes data of a load; and

a bend-point determination unit configured to determine a point, at which the calculated slope of the slope of the load exceeds the value serving as the reference for determining the bend point, as the bend point.

2. The electric press according to claim 1 ,

wherein the slope calculation unit smoothes the press position and the first data sequence of the load at the press position detected, and calculates the slope of the load based on the press position and the load at the press position smoothed, and

wherein the slope-of-slope calculation unit smoothes the press position and the second data sequence of the slope of the load at the press position smoothed, and calculates the slope of the slope of the load based on the press position and the load at the press position smoothed.

3. A bend-point detection method of an electric press having at least a detection unit, an input and storage unit, a slope calculation unit, and a bend-point determination unit, the bend-point detection method including:

a first step of detecting a press position and first data sequence of a load at the press position by the detection unit;

a second step of inputting and storing a value serving as a reference for determining a bend point in a relation between the press position and the load at the press position by the input and storage unit;

a third step of calculating a slope of the load based on the press position and the first data sequence of the load at the press position detected by the slope calculation unit, according to a first regression line, wherein the slope of the load is calculated by the following formula (i),

the

⁢

⁢

slope

⁢

⁢

of

⁢

⁢

the

⁢

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load

=

n

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∑

i

=

1

n

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y

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x

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n

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y

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=

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n

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x

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2

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=

1

n

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x

i

)

[

Formula

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(

i

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]

a fourth step of calculating a slope of the slope calculated by the slope calculation unit, as an amount of change of an amount of change of a load value with respect to the press position by using the formula (i) for calculating a slope of the first regression line, according to a second regression line,

wherein, in the formula (i), n denotes a number of data, xi denotes position data of a pressurization part, and yi denotes data of a load; and

a fifth step of determining a point, at which the calculated slope of the slope of the load exceeds the value serving as the reference for determining the bend point, as the bend point by the bend-point determination unit.