U.S. patent application number 09/739760 was filed with the patent office on 2001-05-10 for condition analyzer.
This patent application is currently assigned to SPM Instrument AB. Invention is credited to Aronson, Carsten.
Application Number | 20010001135 09/739760 |
Document ID | / |
Family ID | 20403319 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010001135 |
Kind Code |
A1 |
Aronson, Carsten |
May 10, 2001 |
Condition Analyzer
Abstract
The invention relates to a method for evaluating the condition
of a machine (100) with a measuring point (90), which method is
performed by a movable analysis apparatus (30). The method
comprises the steps of producing a condition value, by means of
measuring at the measuring point, which condition value is
dependent on the actual condition of the machine, and storing the
condition value in a writable information carrier (120) which is
placed by, or in the vicinity of, the measuring point (90) so that
the condition value subsequently can be used as a reference
condition value. The invention further relates to an apparatus for
performing the method and a device for co-operating with the
analysis apparatus and for mounting by a measuring point on the
machine (100).
Inventors: |
Aronson, Carsten;
(Strangnas, SE) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET 2ND FLOOR
ARLINGTON
VA
22202
|
Assignee: |
SPM Instrument AB
Strangnas
SE
|
Family ID: |
20403319 |
Appl. No.: |
09/739760 |
Filed: |
December 20, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09739760 |
Dec 20, 2000 |
|
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|
09214291 |
Jan 4, 1999 |
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Current U.S.
Class: |
702/34 ;
702/33 |
Current CPC
Class: |
G07C 3/00 20130101; G01H
1/003 20130101; G01D 18/008 20130101 |
Class at
Publication: |
702/34 ;
702/33 |
International
Class: |
G01B 005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 5, 1996 |
SE |
9602694-3 |
Claims
What is claimed is:
1. A portable vibration monitor, comprising: a housing; a sensor
unit; a transducer coupled to said sensor unit, wherein said
transducer is substantially enclosed within said housing, and
wherein said transducer has as an output an analog signal
representative of vibrations present in a piece of vibrating
machinery contacted by said sensor unit; an analog to digital
converter coupled to said output of said transducer, and configured
to digitize said analog signal; a processing circuit configured to
receive said digitized analog signal and to produce digital data
comprising a value indicative of the degree of bearing wear derived
from said digitized analog signal, and an interface circuit
configured to receive said digital data from said processing
circuit and to transmit said digital data to a device external to
said housing.
2. The monitor of claim 1, wherein the processing circuit further
produces a vibration parameter comprising velocity.
3. The monitor of claim 1, wherein the processing circuit further
produces a vibration parameter comprising enveloped
acceleration.
4. The monitor of claim 1, wherein the processing circuit further
produces a vibration parameter comprising a frequency domain
spectrum.
5. A method of monitoring the condition of a machine, comprising
the steps of: storing data indicative of bearing service or bearing
assembly in a memory located proximate to a measuring point on a
machine; mechanically coupling a transducer to said measuring
point; processing an output of said transducer to produce data
indicative of one or more characteristics of vibrations of said
machine; and storing said data indicative of one or more
characteristics of vibrations of said machine in said memory.
6. The method of claim 5, additionally comprising the step of
subsequently retrieving said data from said memory.
7. A handheld probe for monitoring the condition of machines, said
handheld probe comprising: a housing; a piezoelectric transducer
within said housing; electrical circuitry within said housing; a
probe comprising a coupler for connecting to a device located at a
measuring point on a machine, wherein said probe is mechanically
coupled to said piezoelectric transducer; and a contact located
proximate to said probe, said contact coupled to said electrical
circuitry so as to transmit electrical signals between said
electrical circuitry and one or more devices external to said
housing, whereby both an electrical and mechanical coupling between
the device at the measuring point is made when said probe is
connected to said device.
8. The handheld probe of claim 7, wherein said probe comprises a
threaded portion adapted for engagement with a probe receiving
location on the machine.
9. An interface between a vibration measuring point on a machine
and a digital data processor, said interface comprising: a
portable, housing; a probe having a first portion external to said
housing which is configured to mechanically couple to said
vibration measuring point, said probe additionally comprising a
second portion coupled to a vibration transducer; a circuit in said
housing translating an analog electrical signal output from said
transducer into digital data; wireless communication circuitry
within said housing receiving said digital data, and for wirelessly
transmitting said digital data.
10. A method of monitoring the condition of a machine, the method
comprising the steps of: contacting a measuring point on said
machine with a portable probe comprising a vibration transducer;
converting an output of said transducer to first data indicative of
one or more characteristics of vibrations of said machine; and,
electronically evaluating said data by determining the rate of
change of the value of said data.
Description
TECHNICAL FIELD
1. The present invention relates to a method for generating a
condition value for a measuring point on a machine having a
measuring point, and a system for performing the method.
STATE OF THE ART
2. Machines with moving parts are subject to wear with the passage
of time, which often causes the condition of the machine to
deteriorate. Examples of such machines with movable parts are
motors, pumps, generators, compressors, lathes and CNC-machines. It
is known to, more or less regularly, investigate the operating
condition of such machines. The operating condition can be
determined by measuring the amplitude of vibrations in the bearings
and by measuring temperature changes on the casing of the machine,
which temperatures are dependent on the operating condition of the
bearing. Such condition checks of machines with rotating or other
moving parts are of great significance for safety and also for the
length of the life of such machines. It is known to perform such
measurements on machines completely manually. This ordinarily is
done bv an operator with the help of a measuring instrument
performing measurements at a number of measuring points on a
machine. The measuring data obtained by means of the measuring
instrument for each measuring point is noted down on a pre-printed
formula. For a machine it can be necessary to have a number of
measuring points in order to later be able to determine the overall
operating condition of the machine. For example, three measuring
points are often used for the measurement of vibrations of a motor,
in such a way that the vibrations are measured in three mutually
perpendicular directions, i.e. in the X-direction, in the
Y-direction and in the Z-direction. The operator must note down
each measured value on the formula. It is furthermore necessary for
the operator to evaluate the measured values so that he can make a
judgement on whether the measured amplitude measurement values
indicate a change for a measuring position so that the machine can
be serviced if the measured values indicate wear. This places a
large demand on the professional knowledge of the service personnel
of which vibration and temperature measurement values are
acceptable and which measurement values are not acceptable.
3. In order to identify damage to bearings it is known to use a
shock impulse measuring apparatus by means of which damage to
bearings can be determined in machines with rotating machine parts.
In order to perform such measurements at a measuring point, the
diameter of the shaft and the rotational speed of the shaft are set
on a measuring scale. These values, which are set by hand function
as a reference level. If the measured values measured by means of
the measuring instrument are greater than the reference level, this
can be indicated by means of a warning lamp or by means of a sound
signal.
4. It is known from EP-0 194 333 to provide each measuring point
with identity data which is automatically readable by means of a
separate reading probe. EP-0 194 333 also describes that the
characteristic data values for the measuring point are readable at
the measuring point so that the above described reference value can
be generated automatically. The reference value is consequently
calculated in a standardized and unambiguous way from the
characteristic data values. Consequently, according to this known
technique, the one and the same reference value is valid for all
bearings with a certain shaft diameter and a certain rotational
speed.
5. EP-0 211 212 describes a measuring instrunent for detecting and
evaluating data representative of the condition of a machine. The
described measuring instrument has a measuring probe which is
combined with a sensor probe for reading a measuring point code,
whereby the measuring probe and the code, sensing probe are
provided in a common mobile casing.
DESCLOSURE OF THE INVENTION
6. The problem which is to be solved by means of the present
invention is to provide a method which permits an increased
accuracy in detecting changes of the condition of a machine.
7. This problem is solved according to the invention by means of a
method for evaluating the condition of a machine with a measuring
point, which method is performed by a movable analysis apparatus
comprising the steps of:
8. producing a condition value, by means of a measurement at the
measuring point, which condition value is dependent on the current
condition of the machine; and
9. storing the condition value in a writable information carrier
(120) which is placed on, or in the vicinity of the measung point
90 so that the condition value subsequently can be used as a
reference condition value.
10. According to a preferred embodiment, the reference condition
value is produced depending on a measured value, such as a
vibration measured value measured in connection with the final
inspection of a newly manufactured machine, and on relevant
interpreting information, such as shaft diameters and rotational
speeds for a rotatable shaft on a machine. With the object of
providing a determination of whether some measurable condition
change is present, a method according to the invention is performed
which comprises the steps of:
11. a) producing a condition value, which condition value depends
upon the actual condition of the machine at the measuring point;
and of
12. b) acquiring a reference value, indicating the condition of the
machine at the measuring point at an earlier time point, from an
information carrier which is placed by, or in the vicinity of the
measuring point.
DESCRIPTION OF THE DRAWINGS
13. In order to make the present invention easy to understand and
produce, it will be described with reference to the appended
drawings:
14. FIG. 1 shows a schematic block diagram of an embodiment of a
condition analyzing system according to the invention.
15. FIG. 2A shows an embodiment of a sensor unit which comprises an
interface for communication with an information carrier at a
measuring point.
16. FIG. 2B shows an embodiment of a device at a measuring point
comprising an information carrier and an interface for
communication with the interface according to FIG. 2A.
PREFERRED EMBODIMENTS
17. FIG. 1 shows a schematic block diagram of an embodiment of a
condition analyzing system 10 according to the invention. The
condition analyzing system comprises a sensor unit 20 for producing
a measured value dependent on movement and more precisely,
dependent on vibrations.
18. The sensor unit 20 is connected to an analysis apparatus 30 via
a conductor 32. The analysis apparatus 30 comprises a non-volatile
memory 40, a microprocessor 50 and a read/write memory 60. A
computer program is stored in the read memory 40, and by means of
this computer program the function of the analvsis apparatus 30 is
controlled. When it is written below that the microprocessor 50
performs a certain function, it shall be understood that the
microprocessor runs a certain part of the program which is stored
in the memory 40.
19. The microprocessor 50 is connected to a display unit 62. By
means of the display unit 62 a user of the condition analyzing
system is informed of the condition of the current measuring point
in clear text. The production of a condition value is described
more closely below. The display arrangement can cornprise, on the
one hand a screen, on the other hand a printer unit, so that the
user can have the condition value from the measuring point printed
out if so desired.
20. According to a preferred embodiment the analysis apparatus 30
comprises a screen 62 on which relevant information is shown during
the measuring, and a diskette station 64 in which a diskette is
introduceable. In this way the user with the help of the analysis
apparatus 30 collects the condition values for a plurality of
measuring points and save all the information on a diskette
removably introduced into the diskette unit 64. The microprocessor
50 is further connected to an information port 66, by means of
which the apparatus 30 can be connected to a separate information
processing unit.
21. The analysis apparatus 30 is equipped with an interface 70 for
the exchange of data, with a device 80. When the system is
operative, the device 80 is firmly mounted on or at a measuring
point 90 on a machine 100 with a movable part 110. A measuring
point can comprise a connection coupling firmly attached to the
casing of the machine to which the sensor unit is removably
attachable. The connection coupling can, for example, be formed of
a bayonet coupling. A measuring point can cornprise a threaded
recess in the casing in which the sensor unit is screwable. In the
last case the sensor unit 20 comprises corresponding threads so
that it can be introduced into the recess like a screw.
22. Alternatively, the measuring point is marked on the casing of
the machine only with a painted mark.
23. The machine 100 exemplified in FIG. 1 has a rotating shaft 110
with a certain shaft diameter d.sub.1. Shaft 110 in the machine 100
rotates at a certain speed of rotation V.sub.1 when the machine is
in use.
24. The apparatus 80 comprises an information carrier 120 which is
equipped with information on the identity of the measuring point
and interpreting information. The information carrier is
furthermore equipped with at least one condition value K.sub.ref
which can be used as reference for determining a possible chance in
the condition.
25. The identity information can be formed of, for example, the
identity number of the measuring point or of a data string which
identifies both the machine 100 and the measuring point 90. The
machine 100, which is only partly shown in FIG. 1, can comprise a
number of measuring points and a number of moving parts so that the
condition of different parts of the machine can be determined
individually. The interpretation data stored in the measuring point
device 80 can comprise a first computer word indicating the above
mentioned shaft diameter d.sub.1, and a second computer word
indicating the speed of rotation V.sub.1. The information carrier
120 is connected to an interface unit 130 for exchanging
information with the interface unit 70 of the analysis apparatus
30. An operator transports the portable analysis apparatus 30 to
the measuring point for which the condition value is to be
determined and attaches the sensor unit 20 to the measuring point
90. According to one embodiment the sensor unit 20 is provided with
a change-over switch (not shown) which closes in dependence of the
sensor unit being brought into contact with the measuring point 90.
When the change-over switch closes, an activating signal is
produced which, via the bus 32 is delivered to the microprocessor
50 and thereby activates the microprocessor to perform an analysis
routine. An actual condition value is determined bv the analysis
routine, and a reference value Kref acquired from the information
carrier 120. The reference value K.sub.ref indicates the condition
value for the individual machine for the same measuring point at an
earlier point of time. The reference value K.sub.ref is stored in
the information carrier in the same way as described below.
26. When the machine is new from the factory or when a bearing for
a rotatable shaft 111 is renovated or exchanged, a condition value
K.sub.ref for each measuring point 90 of the machine 100 is
determined.
27. The condition reference value for the measuring point is
determined according to a preferred embodiment by producing a
measured value indicating the vibration or temperature of the
machine at the measuring point and, in a known way, with the help
of interpretation information, such as shaft diameter and speed of
rotation of the shaft, transforming the measured value into a
condition value. Because this condition value K.sub.ref is produced
when the corresponding machine part is new or newly renovated,
possible later condition changes can be advantageously determined
by comparison with the reference K.sub.ref.
28. When the apparatus 30 is used to produce the reference
condition value K.sub.ref, a keyboard is connected to the
information port 66 and the microprocessor is instructed to perform
a reference-producing routine. The reference-producing routine
involves the microcomputer 30 acquiring a measuring value from the
sensor unit 20 and the display unit 62 showing a request for the
operator to input the interpretation information which applies for
the measuring point.
29. The interpretation information can be inputted, for example,
via the keyboard or by means of a diskette which is introduced into
the diskette station 64.
30. The microcomputer calculates the actual condition value
K.sub.ref indicating the condition of the individual measuring
point depending on the measured value and the inputted
interpretation information.
31. Both the condition reference value K.sub.ref and the inputted
interpretation information determined in this way are delivered to
the information carrier 120 via the interface 70.
32. Alternatively, the interpretation data as well as the reference
value K.sub.ref can be delivered to the diskette unit 64 or the
display unit screen 62 in order to be inputted to the information
carrier 120 in another way.
33. According to a preferred embodiment of the invention the device
80 comprises a readable and writable memory 120 which can exchange
information in both directions with the interface 130. According to
one embodiment the device 80 comprises a photoelectric cell which
provides the power supply to the memory 120 and the interface
130.
34. Because the device 80 in the above described way is applied
with a condition reference value which is individual for the
machine and for the measuring point, later condition measuring can
give advantageously accurate indications about changes in the
condition. This means that the analysis apparatus does not have to
be provided with any information at all about the machine or its
measuring point, and despite this it is still possible to achieve
an accurate evaluation of whether any changes in the condition have
occurred. This is of considerable advantage, for example, during
the checking of the condition of machines fixed to the floor in a
large manufacturing industry, where the number of machines and
measuring points is very large. It further provides a very good
security as the risk of mixing of the data in a data base is
eliminated by the reference condition value being stored directly
at the measuring point.
35. A method for determining a possible change in the condition is
usually performed with a certain regularity by maintenance
personnel. A first example of when such a process can be performed,
according to the invention, is when a machine has just been
installed after delivery. In this situation there is already a
condition reference value in the information carrier which has been
generated and stored there in connection with the final inspection
at the manufacturer of the machine.
36. When the installator has just installed the machine, the
process is performed for determining a possible change in the
condition with the purposed of verifying that the installation is
correct and that the condition of the macnine has not deteriorated
during the transport from the manufacturer.
37. The method comprises the steps of:
38. producing a measured value which depends on a movement of the
machine;
39. acquiring interpretation information from an information
carrier which is mounted by the measuring point;
40. producing an actual condition value, indicating the actual
condition of the measuring point on the machine, dependent on the
measured value and the interpretation;
41. acquiring a second condition value, indicating the condition of
the measuring point at an earlier point of time, from the
information carrier;
42. producing a relation value dependent on the actual condition
value and the second condition value, which relation value
indicates a change in the condition.
43. This process can be performed by the microprocessor 50 by it
running an analysis routine which is stored in the memory 40.
44. The analysis routine comprises the step of the microprocessor
50 requesting measured values from the sensor unit 20. According to
one embodiment of the invention the sensor unit comprises an
accelerometer 140 with a piezo-electric element. When the measuring
point 90 vibrates, the sensor unit 20, or at least a part of it,
also vibrates and the accelerometer 140 then produces an electrical
sional of which the frequency and amplitude depend on the
mechanical vibration frequency and the vibration amplitude of the
measuring point 90, respectively. The electrical signal is
delivered to the analog-digital converter 34 which with a certain
sampling frequency f.sub.s converts the analog signal to
consecutive digital words in a known way. The microcomputer 50
stores a series of digital words which correspond to a time
sequence of the electrical signal in the memory 60, and then
performs an analysis of the signal sequence, whereby the frequency
and amplitude of the signal is determined. Consequently, a measured
value for the vibration amplitude A.sub.v and the vibration
frequency f.sub.v is determined. The microcomputer then take the
interpretation information and the reference value K.sub.ref from
the device 80 by reading information from the interface 70.
45. According to one embodiment, the interface 130 on the device 80
comprises an opto-transmitter which transfers data serially to the
interface 70 in the form of trains of pulses of infrared light.
46. The device 80 can be activated depending on an information
request which is received via the interface 130. Alternatively, the
device 80 comprises a detector element which senses if the sensor
unit 20 is applied to the measuring point 90 and then activates the
device 80 to send information to the interface 130.
47. In this way the microcomputer receives information on the
identity of the measuring point and interpretation information,
such as the diameter value d.sub.1 and the rotational speed value
V.sub.1.
48. With knowledge of the interpretation information d.sub.1 resp.
V.sub.1, each measured vibration amplitude value A.sub.v can be
easily converted to an actual condition value K.sub.a. A
predetermined interpretation algorithm is stored in the memory 40
and starting from an amplitude value A.sub.v and interpretation
information, such as d.sub.1 and V.sub.1, the microcomputer
produces a corresponding condition value K.sub.a dependent thereon.
Such an interpretation algorithm is based on an embodiment of a
method for producing a condition value described in the Swedish
Laid-Open Document 339 576.
49. According to one embodiment, the interpretation algorithm is
based on the machine classification standard ISO 2954.
50. The actual condition value K, produced and the reference
condition value K.sub.ref acquired from the information carrier 120
are delivered to the screen 62 so that the operator can judge if
the two values correspond. If K.sub.a is essentially similar to
K.sub.ref the condition is essentially unchanged. If there is a
discrepancy between the two values, then this indicates that the
condition of the machine has changed.
51. Because the actual condition value K.sub.a according to the
invention can be compared with an earlier measured condition value
K.sub.ref for the same measuring point, an extremely accurate
indication of changes is achieved. In this way, advantageously
well-judged decisions can be made on when maintenance is required,
which in turn leads to that the life length of the machine can be
increased.
52. According to a preferred embodiment, the microcomputer produces
a relation value in dependence of the actual condition value
K.sub.a and the reference condition value K.sub.ref.
53. By dividing the value K.sub.a with the reference K.sub.ref, a
relation value is achieved which gives a percentage change of the
condition of the machine part or parts to which the measuring
points relate. According to another embodiment the relation value
is produced as the difference between the value K.sub.a and the
reference K.sub.ref.
* * * * *