Data processing: measuring – calibrating – or testing – Measurement system – Performance or efficiency evaluation
Reexamination Certificate
1998-04-29
2002-02-26
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Performance or efficiency evaluation
C702S179000
Reexamination Certificate
active
06351723
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a failure diagnostic method and apparatus for equipment, and more particularly to a failure diagnostic method and apparatus for carrying out a failure diagnosis for equipment based on an operating state of the equipment. In addition, the present invention relates to a recording medium in which a program causing a computer system to execute a process in accordance with the method is stored.
For example, as to manufacturing equipment, it is required for the equipment to be stably operated. Thus, it is necessary to watch an operating state of the equipment. Due to watching the operating state of the equipment, a failure of the equipment is detected and a state where the equipment has failed is rapidly detected, so that the stable operation of the equipment can be realized. As a result, products having even quality can be manufactured.
BACKGROUND OF THE INVENTION
In a conventional watching process for watching the state of the equipment, a detected parameter value of the state of the equipment is compared with a threshold of an alarm point or a fault point. When the detected parameter value exceeds such a threshold, it is diagnosed that the equipment is becoming a failure state or that the equipment has failed.
For example, as to a mass flow controller which is a gas flow control device of semiconductor manufacturing equipment, Japanese Laid Open Patent Application No. 4-350705 discloses that an alarm issuance level is automatically changed when a set level is changed by a valve voltage comparing circuit of the mass flow controller and that a valve voltage corrected based on a flow rate of gas, a pressure and a temperature is compared with a reference valve voltage so that a failure is prevented.
In an actual mass flow controller, as shown by a solid line I in
FIG. 6
, for example, supposing a normal gas flow, a value of 14SLM (Standard Liter per Minute) is set as the gas flow rate (a set voltage V
1
). In the middle of a process, supposing a case where the valve voltage increases due to a failure of the mass flow controller, the set value of gas flow rate is changed to 13.5SLM (a set voltage V
2
). That is, the case where the gas flow rate is set at 14SLM by the set voltage V
1
is a normal state and the case where the gas flow rate is set at 13.5SLM by the set voltage V
2
is an abnormal state. Since a variation range of the valve voltage in the normal state overlaps with a variation range of the valve voltage in the abnormal state, it is difficult to determine whether the valve voltage varying as shown by a solid line II is normal or abnormal.
In a case shown in
FIG. 6
, when the gas flow rate is set at 14SLM, the average of the valve voltage is equal to −2.66 volts and the standard deviation thereof is equal to 0.063. When the gas flow rate is set at 13.5SLM, the average of the valve voltage is equal to −2.62 volts and the standard deviation thereof is equal to 0.067.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide novel and useful failure diagnostic method and apparatus for equipment in which the disadvantages of the aforementioned prior art are eliminated and a recording medium in which a program causing a computer system to execute a process in accordance with the method is stored.
A specific object of the present invention is to provide a failure diagnostic method and apparatus which can accurately detects a state where the equipment has failed or a state where the equipment is becoming failure.
The above objects of the present invention are achieved by a failure diagnostic method for diagnosing a failure of equipment based on an operating state of the equipment, the method comprising steps of: obtaining operating state parameters, in time series, which represent the operating state of the equipment; selecting a predetermined number of operating state parameters from among the obtained operating state parameters; calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; and determining a state regarding a failure of the equipment based on the value of the deviation process capability.
According to such a failure diagnostic method, every time the predetermined number of operating state parameters are selected from among the operating state parameters which have been obtained in time series, the determination regarding the failure of the equipment is carried out based on the value of the deviation process capability calculated from the predetermined number of operating state parameters.
That is, the variation of the predetermined number of operating state parameters is numerically represented using the value of the deviation process capability. Even if the range of the variation in the normal state overlaps with the range of that in the abnormal state, since the variation is numerically represented, the degree of failure of the equipment (normal, becoming failure and has failed) can be represented. Thus, the state where the equipment has failed or is becoming failure can be accurately determined from the operating state of the equipment.
In addition, since the value of the deviation process capability is calculated every time the predetermined number of operating state parameters are selected from among the operating state parameters which have been obtained in time series, the state of the equipment in a period in which the predetermined number of operating state parameters were obtained is determined.
The operating state parameter representing the operating state of the equipment includes various kinds of control parameters for controlling the equipment (a set voltage used to set a gas flow rate in a gas flow controller) and detected values, such as the temperature and the driving speed.
To grasp the time variation of the state regarding the failure of the equipment, in the above failure diagnostic method according to the present invention, the predetermined number of operating state parameters which are successive in time series may be shifted on a time scale and selected from among the obtained operating state parameters.
According to such a failure diagnostic method, since the predetermined number of operating parameters which are successive in time series are shifted on the time scale and selected, the time variation of the value of the deviation process capability which is calculated every time the predetermined number of operating state parameters are selected corresponds to the time variation of state of the equipment.
In addition, to grasp the time variation of the state of the equipment at a real time (every time the operating state parameters are actually obtained), in the present invention, every time an operating state parameter of the equipment is obtained, the latest predetermined number of operating state parameters including the obtained operating state parameter may be selected.
According to such a failure diagnostic method, the operating state parameters are shifted by an interval at which the operating state parameter is obtained so that the latest predetermined number of operating state parameters are selected.
The above objects of the present invention are achieved by a failure diagnostic apparatus for diagnosing a failure of equipment based on an operating state of the equipment, comprising: parameter obtaining means for obtaining operating state parameters, in time series, which represent the operating state of the equipment; parameter selecting means for selecting a predetermined number of operating state parameters from among the obtained operating state parameters; calculating means for calculating a value of a deviation process capability from the predetermined number of operating state parameters every time the predetermined number of operating state parameters are selected; determining means for determining a state regarding a failure of the equipment based on the value of the deviation process capability; an
Barbee Manuel L.
Hoff Marc S.
LandOfFree
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