Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1999-04-13
2002-12-24
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C073S570000, C342S192000
Reexamination Certificate
active
06498992
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a defect diagnosis in a friction system, such as bearings and/or gears in a rotational machine, and to a defect diagnosis in a construction system, such as an unbalance in rotating masses and/or a misalignment where two rotational machines run off an axis thereof.
A sudden and/or unexpected stoppage of manufacturing machinery equipment brings about extremely large economic loss. In facilities utilizing the manufacturing equipment, precautionary maintenance is practiced for preventing such trouble such as a sudden unexpected stoppage. As an example of the method of precautionary maintenance for preventing such trouble, a sound or/and a vibration being generated by the machinery equipment in operation is measured so as to determine the condition thereof. Such a procedure is called a “state-base precaution”. Here, the conventional arts will be explained in terms of the state-base precaution, by taking a vibration measurement as an example.
When making the diagnosis of the presence of troubles by measuring the vibration of machinery equipment, it is decided whether the measured vibration exceeds a reference value or not in the magnitude thereof. Ordinarily, two kinds of reference values are prepared for the decisions. Namely, if the detected value exceeds the reference value being the smaller of the reference values, it is found to be in a domain of caution, therefore observation must be performed frequently, though the equipment operation will be continued. If the detected value exceeds the reference value being the larger of the reference values, it is found to be in a domain of danger, therefore equipment operation must be stopped in order for the equipment to be restored or repaired immediately. When the state of the machinery equipment reaches to the caution domain, a time when it reaches to the danger domain is predicted from a guide such as a chart or a graph indicating a tendency in the past of changes from a normal state into the caution domain, so as to provide for production planning which has the highest economic efficiency and a planning of maintenance, including the restoration or repair.
The equipment of the manufacturing machines located in a factory or works of a company varies depending upon the purposes thereof, i.e., there are used various kinds or sorts of machinery, being different in revolution speed, electric power consumption (torque), and/or loads, including large or small values thereof, or a machine having a large vibration or one having a small vibration.
Each reference value for deciding the presence of the defect or failure is unique and characteristic to each particular machinery equipment, and the reference values are decided on the basis of a large accumulated number of sample data representative of the defect or failure conditions, as well as those representative of the normal conditions. However, for fully obtaining the effect of the state-base precaution, an appropriate reference value for decision is needed.
A significant investment of labor is needed to determine the above reference for decision, since enough sample data may not be obtainable due to a rareness or scarcity of the troubles or accident, or since the kinds or sorts of the machines to be inspected is too large in number. Further, there are many companies which cannot apply the state-base maintenance, because of such reasons as that there is no engineer for maintenance work who has applied knowledge in trouble or defect diagnosis, therefore the sample data cannot be gathered.
Though the state-base maintenance is an economical and superior method of maintenance with reduced costs or expenses, the most suitable possible decision reference or criterion must be decided upon so as to apply the state-base maintenance, as mentioned previously. Many companies are unable to apply the state-base maintenance, since this reference for decision cannot be appropriately decided thereby.
SUMMARY OF THE INVENTION
According to the present invention, an object is to provide a diagnosis method wherein attention is paid to a difference of a probability density function of amplitude obtained by normalizing a wave-form of a measured signal, such as the wave-form of vibration which is generated by the machine, from a normal distribution, thereby proposing the decision criterion which can be applied in common to the different facilities of many rotational machines, and also to provide a trouble or defect diagnosis apparatus comprising those functions.
The present invention is based upon a principle that the amplitude probability density function of a measured signal, such as the vibration being generated by an object to be detected, for example, a machine, etc., operating under a normal condition, coincides with the normal distribution, however, it is shifted from the normal distribution when trouble or abnormal condition arises in the machine.
According to the present invention, while no component information relating to the measured signal is utilized, such as the amplitude and the vibration number thereof which is generated by the object such as a machine to be inspected, the normalized amplitude probability density function is decided to coincide with the normal distribution or not, fully independent of specifications such as the revolution number, the electric power consumption, the load and the scale of the structure of the machine.
Namely, according to the present invention, there is provided a defect diagnosis method for an object to be inspected, comprising:
detecting a measured signal being generated by said object to be inspected;
expanding orthogonally an amplitude probability density function of a wave-form of the obtained measured signal in a Gram-Charlier series; and
calculating the Gram-Charlier series so as to make a diagnosis of a defect in the object to be inspected.
Here, the defect in the present invention means indicates the condition where the machine operates differently from operation under the normal condition, but not that it is already in an inoperable condition.
Further, according to the present invention, there is provided a defect diagnosis method for an object to be inspected, comprising:
detecting a measured signal being generated by said object to be inspected;
expanding orthogonally an amplitude probability density function of a wave-form of the obtained measured signal in a Gram-Charlier series; and
Further, according to the present invention, there is provided a defect diagnosis method for an object to be inspected, comprising:
detecting a measured signal being generated by said object to be inspected;
expanding a wave-form of the obtained measured signal obtained in a Fourier series to obtain a frequency spectrum;
expanding orthogonally an amplitude probability density function by viewing the obtained frequency spectrum from an axis of an amplitude thereof in a Gram-Charlier series; and
calculating the Gram-Charlier series so as to make diagnosis of a defect in said object to be inspected.
Further, according to the present invention, there is provided a defect diagnosis method for an object to be inspected, comprising:
detecting a measured signal being generated by said object to be inspected;
expanding a wave-form of the obtained measured signal in a Fourier series to obtain a frequency spectrum;
expanding orthogonally an amplitude probability density function by viewing the obtained frequency spectrum from an axis of an amplitude thereof in a Gram-Charlier series; and
calculating a difference from a normal distribution so as to make a diagnosis of a defect in the object to be inspected. In the invention defined in the above, the measured signal may be a vibration.
In the invention defined in the above, the measured signal may be an acoustic, an acoustic emission, fluctuations of current or of effective electric power rather than a vibration.
In the invention defined in the above, the object to be inspected can include a vehicle, an aircraft and a construction other than an ordinary m
Jinyama Hou
Komura Hidemichi
Niho Tomoya
Toyota Toshio
Charioui Mohamed
Hoff Marc S.
Merchant & Gould P.C.
Rion Co. Ltd.
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