Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1989-05-17
1990-08-07
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
36457101, G05B 1918
Patent
active
049470957
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to an expert system of a machine tool equipped with an NC unit and, more particularly, to an expert system for diagnosing failure of an NC unit or machine tool.
2. Background Art
In a machine tool equipped with an NC unit, the NC unit and machine tool undergo various alarm checks and self-diagnoses depending upon the respective category. In the NC unit, for example, various checks are performed, such as determining whether a machining command tape contains an error or whether a servo system is abnormal. If an anomaly occurs, an alarm is generated to so inform the operator.
In the machine tool also a number of checks are performed regarding the machine. For example, an axis-movement interlock is provided on the NC unit side in such a manner that an axis will not move if a spindle is not rotating at the start of cutting, and a lamp is lit to inform the operator of a malfunction.
Generally, when an alarm is generated, the operator is informed only of the contents of the alarm and not about its cause nor what measures to take. This means that the operator must consult a manual to determine the cause of the alarm and how to deal with it. However, since several conceivable causes of an alarm may be described in the manual, there are many cases in which the operator cannot determine the cause of a failure and its remedy in a simple and accurate manner.
By way of example, when the amount of offset of a servo system becomes excessive and a servo system alarm is issued during movement along an axis, all that is done is to inform the operator of an alarm by the message "ALARM OF EXCESSIVE SERVO SYSTEM OFFSET", so that the operator is left almost totally uninformed of the cause of the alarm. In other words, an alarm as used in the prior art generally does nothing more than inform the operator that the machine will be damaged and that subsequent processing will not be able to continue unless a check is made. Thus, the alarm is merely a precaution and gives almost no consideration to a rapid recovery from a failure.
As a consequence of the foregoing, downtime of a machine tool equipped with an NC unit is prolonged and the efficiency of the machining operation declines.
In a case where a number of causes of one alarm are conceivable, it would be possible to deal with a malfunction in an extremely timely fashion if it were possible to automatically deduce the cause of the malfunction based on a knowledge source (which refers to a collection of knowledge regarding a single phenomenon) for an alarm when the alarm is generated.
Accordingly, an object of the present invention is to provide an expert system of a machine tool equipped with an NC unit, in which an operator is rapidly informed of the cause of a failure when the failure occurs, thereby making it possible to minimize downtime. Specifically, the invention provides an expert system of a machine tool equipped with an NC unit wherein when an "EXCESSIVE SERVO SYSTEM OFFSET ALARM" is generated, by way of example, the operator is rapidly informed of the name of the alarm and the cause thereof, such as whether the alarm is due to a set value error in a parameter, a faulty servomotor or a faulty detector.
Another object of the present invention is to provide an expert system of a machine tool equipped with an NC unit, in which the cause of a failure is automatically investigated when the failure occurs and the operator is informed of the cause.
DISCLOSURE OF THE INVENTION
An expert system of a machine tool equipped with an NC unit in accordance with the present invention is provided with a knowledge base storing expert knowledge regarding investigation of the causes of various failures, and a reasoning mechanism for deducing the cause of a failure based on the expert knowledge stored in the knowledge base, wherein the knowledge base section further stores knowledge for extracting digital input/output information, which is exchanged by the NC unit and machine tool, as well as information internally of the NC unit, wit
REFERENCES:
patent: 4825394 (1989-04-01), Beamish
Endou Takashi
Kawamura Hideaki
Sasaki Takao
Bergmann Saul M.
Fanuc Ltd
Shoop Jr. William M.
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