Abnormality detection system and method of detecting abnormality

Abstract

An abnormality detection system includes a measurement unit, a decision unit, an alarm unit, and storage units, and serves to detect the abnormality in a control characteristic value of a plurality of products manufactured on the same production line. The decision unit receives the control characteristic value stored in the storage unit, and decides whether an abnormality exists, based on that value. More specifically, the decision unit decides that the control characteristic value is abnormal when, with respect to m (m is a natural number) pieces of the products that are consecutively manufactured, an absolute value of a difference in control characteristic value between each of the products and another manufactured immediately before the former is equal to or less than a predetermined constant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of an abnormality detection system according to an embodiment of the present invention;

FIG. 2 is a graph for explaining the method of detecting abnormality according to the embodiment of the present invention;

FIG. 3 is a graph for explaining the method of detecting abnormality according to the embodiment of the present invention;

FIG. 4 is a graph for explaining the method of detecting abnormality according to the embodiment of the present invention;

FIG. 5 is a graph for explaining a control chart display apparatus according to the patent document 1;

FIG. 6 is a graph for explaining a conventional abnormality decision rule based on a control chart method;

FIG. 7 is a graph for explaining another conventional abnormality decision rule based on the control chart method;

FIG. 8 is a graph for explaining still another conventional abnormality decision rule based on the control chart method;

FIG. 9 is a graph for explaining still another conventional abnormality decision rule based on the control chart method;

FIG. 10 is a graph for explaining still another conventional abnormality decision rule based on the control chart method;

FIG. 11 is a graph for explaining still another conventional abnormality decision rule based on the control chart method;

FIG. 12 is a graph for explaining still another conventional abnormality decision rule based on the control chart method;

FIG. 13 is a graph for explaining still another conventional abnormality decision rule based on the control chart method;

FIG. 14 is a graph for explaining a type-1 error and a type-2 error;

FIG. 15 is a graph for explaining a problem regarding the conventional technique;

FIG. 16 is a graph for explaining another problem regarding the conventional technique; and

FIG. 17 is a graph for explaining still another problem regarding the conventional technique.

Claims

1. An abnormality detection system that detects an abnormality in a control characteristic value of a plurality of products manufactured on a same production line, comprising: a storage unit that stores said control characteristic value measured with respect to said products; anda decision unit that acquires said control characteristic value from said storage unit to decide whether the following condition (i) is satisfied:(i) with respect to m pieces (m is a natural number) of said products that are consecutively manufactured, an absolute value of a difference in said control characteristic value between each of said products and said product manufactured immediately before the former is equal to or less than a predetermined constant,and decides that said control characteristic value is abnormal when said condition (i) is satisfied.

2. The abnormality detection system according to claim 1, wherein said constant is zero.

3. A method of detecting an abnormality in a control characteristic value of a plurality of products manufactured on a same production line, comprising: storing in a storage unit said control characteristic value measured with respect to said products;acquiring said control characteristic value from said storage unit to decide whether the following condition (i) is satisfied:(i) with respect to m pieces (m is a natural number) of said products that are consecutively manufactured, an absolute value of a difference in said control characteristic value between each of said products and said product manufactured immediately before the former is equal to or less than a predetermined constant; anddeciding that said control characteristic value is abnormal when said condition (i) is satisfied.