GB2109552A

GB2109552A - Fault detection in machinery

Info

Publication number: GB2109552A
Application number: GB08131153A
Authority: GB
Inventors: Christopher Cordingley; Edward Trevor Marshall
Original assignee: GSM ELECTRICAL CONTROLS Ltd
Current assignee: GSM ELECTRICAL CONTROLS Ltd
Priority date: 1981-10-15
Filing date: 1981-10-15
Publication date: 1983-06-02

Abstract

A method and apparatus for detecting fault conditions in running machinery having one or more parts moving with rotary motion, wherein vibrations or movements caused by the running machinery are converted into a corresponding periodic electrical signal whose waveform is arranged to be continuously analysed to detect any repeating pattern in the waveform. Any subsequently occurring deviation of a predetermined magnitude from this pattern is used to indicate the presence of a fault condition and may stop the machinery. The invention may be applied to knitting machines. <IMAGE>

Description

SPECIFICATION Fault detection in machinery The present invention is concerned with the detection of faults in machinery, particularly in rotating machinery.

There is a need for a means to be provided for detecting the occurrence of faults in machinery, while that machinery is running, whereby, for example, to be able to close down the machinery before any major damage is incurred as a result of the fault condition.

It is an object of the present invention to provide a method and apparatus for performing such fault detection.

In accordance with the present invention, vibrations or movements caused by the running machinery are converted into a corresponding periodic electrical signal whose waveform is continuously analysed to detect any repeating pattern in the waveform, any subsequently occurring deviation of predetermined magnitude from this pattern being used to indicate the presence of a fault condition.

Thus, the mechanical movement or vibration of a machine or part of a machine is converted into an electrical signal by means of a transducer. This signal is sampled and converted into digital form for subsequent recording and analysis by an electronic computer. The computer analyses the extracted digital information for any repeating pattern. This pattern or complex periodic waveform corresponds to the satisfactory operation of the machine under surveillance. The computer is arranged to indicate a fault condition or machine failure when a deviation from this periodic waveform is detected.

The invention is described further hereinafter, by way of example with reference to the accompanying drawings, in which: Fig. 1 shows very diagrammatically the waveform of the vibrations, and the corresponding electrical signal, for a typical normally running machine; and Fig. 2 is a highly simplified block diagram of a fault detection system in accordance with the invention.

Any machine 10 containing parts which move with a rotary motion will produce vibrations in its mounting and the surrounding air, which will be of a periodic nature. If the moving parts are metal the surrounding magnetic flux will also be disturbed.

These disturbances can be turned into a proportionally varying electrical signal by means, for example, of an electromagnetic transducer, piezo-electric transducer, Hall-effect transducer, acoustic transducer or strain gauge. One such transducer is indicated at 12 in Fig. 2. A typical output of the transducer might be as shown in Fig. 1.

The periodic nature of the vibration waveform implies that the amplitude waveform shown in Fig. 1 will repeat with time provided that the machine continues to run normally. Hence, once the periodic nature of the waveform has been established, the amplitude of the signal at any instant can be anticipated.

As indicated in Fig. 2, the complex electrical signal from the transducer 1 2 is fed via a sampler and digitizer 14 to an electronic computer (e.g. a micro-processor) 1 6. The electrical signal is sampled continuously (as indicated by the vertical arrows in Fig. 1) and the amplitude values converted into digigal form (i.e. a binary number.) These values are stored in an electronic memory.

The microprocessor 1 6 is arranged to compare one value (say point A) with successive values.

When a second equal value, within any desired tolerance, is found (say point B) then all successive values between points A and B are compared with successive values following point B. If the successive comparisons all yield equivalence, then the microprocesor 1 6 is considered to be synchronised to the pattern of the signal. If not, then the microprocessor searches the memory for another point of equal magnitude to point A and the process is repeated.

Once synchronised, the microprocessor continues to scan the sampled incoming signal and compares it with the A-B amplitude pattern.

When the incoming signal differs from the A-B pattern (beyond any desired tolerance) the microprocessor outputs a signal which may be used to stop the motion of the machine 10 and/or to activate an indicator 1 8.

An important feature of the method of the present invention is that the computer is not preprogrammed with fault conditions but learns the norm and then searches for deviations from that norm in the incoming data.

One specific example of a machine to which this fault detection technique can be applied is in a knitting machine where movement of needles on a rotating drum can be converted into an electrical signal by means of a transducer. For example, the transducer can be realised utilising the movement of the needles which disturbs the magnetic flux surrounding a magnetically sensitive element (e.g. a coil of wire and associated magnet) close to the needle path. If a needle should break or bend, the derived electrical waveform changes and the change is detected by the above described technique. The resulting fault condition signal is used to stop the machine.

Claims

1. A method of detecting faults in running machinery having one or more parts moving with rotary motion, wherein vibrations or movements caused by the running machinery are converted into a corresponding periodic electrical signal whose waveform is continuously analysed to detect any repeating pattern in the waveform, and subsequently occurring deviation of predetermined magnitude from this pattern being used to indicate the presence of a fault condition.

2. An apparatus for detecting faults in running machinery having one or more parts moving with rotary motion, the apparatus comprising

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Fault detection in machinery The present invention is concerned with the detection of faults in machinery, particularly in rotating machinery. There is a need for a means to be provided for detecting the occurrence of faults in machinery, while that machinery is running, whereby, for example, to be able to close down the machinery before any major damage is incurred as a result of the fault condition. It is an object of the present invention to provide a method and apparatus for performing such fault detection. In accordance with the present invention, vibrations or movements caused by the running machinery are converted into a corresponding periodic electrical signal whose waveform is continuously analysed to detect any repeating pattern in the waveform, any subsequently occurring deviation of predetermined magnitude from this pattern being used to indicate the presence of a fault condition. Thus, the mechanical movement or vibration of a machine or part of a machine is converted into an electrical signal by means of a transducer. This signal is sampled and converted into digital form for subsequent recording and analysis by an electronic computer. The computer analyses the extracted digital information for any repeating pattern. This pattern or complex periodic waveform corresponds to the satisfactory operation of the machine under surveillance. The computer is arranged to indicate a fault condition or machine failure when a deviation from this periodic waveform is detected. The invention is described further hereinafter, by way of example with reference to the accompanying drawings, in which: Fig. 1 shows very diagrammatically the waveform of the vibrations, and the corresponding electrical signal, for a typical normally running machine; and Fig. 2 is a highly simplified block diagram of a fault detection system in accordance with the invention. Any machine 10 containing parts which move with a rotary motion will produce vibrations in its mounting and the surrounding air, which will be of a periodic nature. If the moving parts are metal the surrounding magnetic flux will also be disturbed. These disturbances can be turned into a proportionally varying electrical signal by means, for example, of an electromagnetic transducer, piezo-electric transducer, Hall-effect transducer, acoustic transducer or strain gauge. One such transducer is indicated at 12 in Fig. 2. A typical output of the transducer might be as shown in Fig. 1. The periodic nature of the vibration waveform implies that the amplitude waveform shown in Fig. 1 will repeat with time provided that the machine continues to run normally. Hence, once the periodic nature of the waveform has been established, the amplitude of the signal at any instant can be anticipated. As indicated in Fig. 2, the complex electrical signal from the transducer 1 2 is fed via a sampler and digitizer 14 to an electronic computer (e.g. a micro-processor) 1 6. The electrical signal is sampled continuously (as indicated by the vertical arrows in Fig. 1) and the amplitude values converted into digigal form (i.e. a binary number.) These values are stored in an electronic memory. The microprocessor 1 6 is arranged to compare one value (say point A) with successive values. When a second equal value, within any desired tolerance, is found (say point B) then all successive values between points A and B are compared with successive values following point B. If the successive comparisons all yield equivalence, then the microprocesor 1 6 is considered to be synchronised to the pattern of the signal. If not, then the microprocessor searches the memory for another point of equal magnitude to point A and the process is repeated. Once synchronised, the microprocessor continues to scan the sampled incoming signal and compares it with the A-B amplitude pattern. When the incoming signal differs from the A-B pattern (beyond any desired tolerance) the microprocessor outputs a signal which may be used to stop the motion of the machine 10 and/or to activate an indicator 1 8. An important feature of the method of the present invention is that the computer is not preprogrammed with fault conditions but learns the norm and then searches for deviations from that norm in the incoming data. One specific example of a machine to which this fault detection technique can be applied is in a knitting machine where movement of needles on a rotating drum can be converted into an electrical signal by means of a transducer. For example, the transducer can be realised utilising the movement of the needles which disturbs the magnetic flux surrounding a magnetically sensitive element (e.g. a coil of wire and associated magnet) close to the needle path. If a needle should break or bend, the derived electrical waveform changes and the change is detected by the above described technique. The resulting fault condition signal is used to stop the machine. Claims

2. An apparatus for detecting faults in running machinery having one or more parts moving with rotary motion, the apparatus comprising transducer means for converting vibrations or movements caused by the running machinery into a corresponding electrical signal, and means for continuously analysing the waveform of said electrical signal to detect any repeating pattern in the waveform and then to detect any subsequently occurring deviation of predetermined magnitude from this pattern to indicate the presence of a fault condition.

3. An apparatus as claimed in claim 2 wherein the analysing means includes means for sampling the electrical waveform from the transducer means and converting same into digital form and a digital computer which analyses the extracted digital information to search for said repeating pattern, the computer being arranged to indicate p fault condition or a machine failure when a aviation of said predetermined magnitude from tpis periodic pattern is detected.

4. An apparatus as claimed in claim 3 wherein the digitized amplitude values of the electrical signal are stored in an electronic memory and the computer is arranged to compare a selected one of said values (point A) with successive values until a second equal value (point B) is found, whereupon all successive values between points A and B are compared with successive values following point B.

5. A method of detecting faults in running machinery having one or more parts moving with rotary motion, substantially as hereinbefore described with reference to the accompanying drawings.

6. Apparatus for detecting faults in running machinery having one or more parts moving with rotary motion, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.