Title: Tribological debris analysis system
Abstract: A tribological debris analysis system includes a general purpose computer; and a tribological sensor system for generating data. The sensor system includes an optical flow cell a pump for pumping a fluid through the optical flow cell, a laser for illuminating the fluid flowing through the optical flow cell, and an imaging device for detecting any debris in the fluid illuminated by the laser. The imaging device sends the object information—in either the form of object elements or objection segments—representative of the debris to the general purpose computer for analysis. The general purpose computer classifies the debris according to size, any trends associated with the size of the debris, generating shape features of the imaged debris and identifying a type of object wear based upon the shape features.
Patent Number: 7,019,834 Issued on 03/28/2006 to Sebok, et al.
| Inventors:
|
Sebok; Thomas J. (Tallmadge, OH);
Sebok; Dale R. (Tallmadge, OH);
Kolp; Joseph P. (North Canton, OH)
|
| Assignee:
|
Lockheed Martin Corporation (Akron, OH)
|
| Appl. No.:
|
162380 |
| Filed:
|
June 4, 2002 |
| Current U.S. Class: |
356/335; 382/199; 382/224; 382/225 |
| Current Intern'l Class: |
G01N 15/02 (20060101); G06K 9/62 (20060101) |
| Field of Search: |
356/335,336,337,338,342,343,246
|
References Cited [Referenced By]
U.S. Patent Documents
| 3198064 | Aug., 1965 | Moore.
| |
| 3947121 | Mar., 1976 | Cotter et al.
| |
| 4393466 | Jul., 1983 | Deindoerfer et al.
| |
| 4582684 | Apr., 1986 | Vogel et al.
| |
| 4804267 | Feb., 1989 | Greenfield.
| |
| 4807267 | Feb., 1989 | Rifu et al.
| |
| 5030421 | Jul., 1991 | Muller.
| |
| 5098661 | Mar., 1992 | Froehlich et al.
| |
| 5241189 | Aug., 1993 | Vandagriff et al.
| |
| 5449622 | Sep., 1995 | Yabe et al.
| |
| 5471299 | Nov., 1995 | Kaye et al.
| |
| 5572320 | Nov., 1996 | Reintjes et al.
| |
| 5594544 | Jan., 1997 | Horiuchi et al.
| |
| 5721433 | Feb., 1998 | Kosaka.
| |
| 5766957 | Jun., 1998 | Robinson et al.
| |
| 5780865 | Jul., 1998 | Miura et al.
| |
| 5786894 | Jul., 1998 | Shields et al.
| |
| 5883721 | Mar., 1999 | Gilby et al.
| |
| 5911002 | Jun., 1999 | Mitsuyama et al.
| |
| Foreign Patent Documents |
| 0 556 971 | Feb., 1993 | EP.
| |
| 0644 414 | Aug., 1994 | EP.
| |
| 1245 945 | Mar., 2002 | EP.
| |
| 2 116 704 | Jan., 1979 | GB.
| |
| 2378 526 | Feb., 2003 | GB.
| |
| 62-112034 | May., 1987 | JP.
| |
| 218417 | Aug., 1995 | JP.
| |
| WO 95/1211/8 | May., 1995 | WO.
| |
Other References
Search Report UK Patent Office dated Sep. 9, 2002.
|
Primary Examiner: Toatley, Jr.; Gregory J.
Assistant Examiner: Punnoose; Roy M.
Attorney, Agent or Firm: Renner Kenner Greive Bobak Taylor & Weber
Claims
What is claimed is:
1. A tribological debris analysis system comprising:
a general purpose computer; and
a tribological sensor system for placing a fluid in a field of view and generating
data, said sensor system comprising:
an optical flow cell;
a fluid delivery system for delivering said fluid to said optical flow cell;
a laser for illuminating the fluid flowing through said optical flow cell; and
an imaging device for collecting imagery information of debris in the fluid illuminated
by said laser and generating a digital video signal, said imaging device having
an internal field programmable gate array for receiving said digital video signal
and for processing said imagery information and generating object segments comprising
a contiguous group of pixels in a row which are collectively representative of
the debris, said field programmable gate array sending said object segments to
said general purpose computer for analysis.
2. The system according to claim 1, wherein said field programmable gate array
applies a threshold to said digital video signal to generate said object segments.
3. The system according to claim 2 wherein said object segments are converted
into serial data.
4. The system accordingly to claim 1, wherein said general purpose computer comprises:
a generating component for receiving said object segments and configuring said
object segments into object elements which have continuity between adjacent rows
of pixels;
a classifying component for receiving and classifying said object elements according
to predetermined characteristics; and
an analyzing component for determining machine conditions based upon said classified
object elements, wherein said classified object elements are associated with a
type of wear.
5. The system according to claim 4, wherein said classifying component classifies
said object elements according to shape, wear type, size and trends of element size.
6. The system according to claim 5, further comprising:
a database component operative to maintain a database identifying wear properties
of debris for comparison to said object elements by said classifying component.
7. The system according to claim 1, wherein said fluid delivery system comprises:
a pump for pumping a fluid through said optical flow cell.
8. The system according to claim 1, wherein said imaging device comprises:
a camera for generating an image from the field of view;
wherein said field programmable gate array manipulates said image into object
segments comprising a contiguous group of pixels in a row;
at least one memory device connected to said field programmable gate array for
storing said manipulated image; and
an interface device connected to said field programmable gate array for exporting
said manipulated image.
9. The system according to claim 8, wherein said field programmable gate array
controls operation of said fluid delivery system, said laser, and said camera.
10. The system according to claim 9, wherein said sensor system further comprises:
a bypass valve interposed between said fluid delivery system and said optical
flow cell, said bypass valve facilitating the flow of fluid through said optical
flow cell, said bypass valve controlled by said field programmable gate array.
11. The system according to claim 9, wherein said at least one memory device
is a random access memory device in communication with said field programmable
gate array to store an illumination map of a plurality of said images.
12. The system according to claim 9, wherein said at least one memory device
is a first-in first-out memory device in communication with said field programmable
gate array to store said object information for analysis.
13. The system according to claim 8, further comprising a microcontroller interposed
between said interface device and said field programmable gate array for processing
said manipulated image prior to exporting.
14. The system according to claim 1, wherein said sensor system further comprises:
a microcontroller in communication with said field programmable gate array, said
microcontroller configuring said object segments into object elements which have
continuity between adjacent rows of pixels to reduce bandwidth transmission to
said general purpose computer.
Description
TECHNICAL FIELD
The present invention relates generally to fluid inspection systems. More particularly,
the invention relates to a system to ensure accurate imaging of debris viewed through
an optical flow cell. Specifically, the invention relates to a system that controls
various components in the system and the exchange of data between those components.
BACKGROUND ART
It is known to provide fluid sampling devices using optical near-field imaging
as disclosed in U.S. Pat. No. 5,572,320, which is incorporated herein by reference.
Such a device is employed to determine the quantity, size, characteristics, and
types of particulate matter in fluids. Examples of fluids which are monitored in
such a system are lubricating oils used in engines and rotating machinery; hydraulic
fluid used in various machinery; and fluids used in industrial quality control,
food processing, medical analysis, and environment control. In its most common
use, such a device monitors engine oil for metal particulates or flakes, wherein
a size, number, and shape of particulates correspond to an engine condition and
can alert one to particular problems with the engine. Non-metallic debris in the
fluid can also be detected, such as fibers, sand, dirt and rust particles. Predicting
failure is critically important in aircraft engines to avoid accidents and loss
of life.
The early stages of engine wear cause small particulate matter, of about 50 microns
or less in size, to be generated. These particulates have characteristic shapes
indicative of the type of wear produced by specific wear mechanisms. As the wear
process progresses, the amount and size of particulates increase. Accordingly,
imaging and identifying smaller particles allows early identification of faults,
thus, allowing more time for corrective maintenance and preventing unexpected catastrophic failures.
The advantage of the aforementioned system over previous systems is readily apparent
when one considers that the previous systems only measured the amount of light
passing through the material-laden oil, but gave no consideration as to the particular
shape of the material. As best seen in FIGS. 1A-G, the various types of images
rendered by a known system can provide a clear indication of the types of problems
that are likely to occur based upon the shape and structure of the debris monitored.
For example, in FIG. 1A, sliding wear particles are shown and these particles are
believed to be caused by metal-to-metal contact due to overloading, misalignment,
high speed and/or low oil viscosity. The debris shown in FIG. 1B represents fatigue
wear particles which are gear or bearing pieces generated due to surface stress
factors such as excessive load, contamination, and the like. FIG. 1C shows cutting
wear particles that are generated by surface gouging, two body cutting due to break-in,
misalignment, and three body cutting due to particle abrasion. FIG. 1D shows oxide
particles which are caused by contamination, and red oxide caused by water or insufficient
lubrication of the subject machinery.
It will also be appreciated that certain elements may be in the oil that generate
false readings. These elements are classified and may be disregarded by the imaging
system. For example, as shown in FIG. 1E, fibers are shown which are normally occurring
or may be caused by improper sample handling. In particular, fibers can be from
mishandling the fluid which generate false readings. But, valid readings of fibers
may be indicative of problems in the system. For example, a filter or composite
bearing may be disintegrating. In any event, occurrences of fibers are monitored.
Instrument problems due to incomplete removal of air bubbles are represented in
FIG. 1F. Finally, FIG. 1G shows flow lines which are a result of instrument problems
caused by insufficient replacement of a new sample.
Known tribological debris analysis systems consist of a fluid sample that is
connected to a pumping device. The pump is actuated and the fluid is drawn through
an optical flow cell which is illuminated by laser light. A discrete input/output
board connected to a dedicated computer system controls operation of the pump and
the laser in a coordinated manner. An analog camera positioned opposite the laser
light obtains an analog video image of particles passing through the optical flow
cell. The dedicated computer system processes the analog video by sending the video
signal to a digitizer which converts the signal to a digital image. The computer
system processes the digital image to determine the shape and size of the particles
rendered by the system. About ninety percent of the computer system's processing
time is dedicated to pixel level processing associated with the analysis of an
image and the detection of object elements. Accordingly, the system requires that
the raw video input be directly sent to the general purpose computer for processing
and analyzing of the images. It has been found that the known system is quite expensive
and easily overloaded. Since the computer system is a dedicated device, it is limited
in its ability to analyze the particles and detect any trends associated with the
particles. Moreover, the known computer system is unable to check the lifetime
history of a particular device when periodic samples are taken from the device.
Therefore, such prior art systems, although effective, are not easily adapted for
large scale use and implementation.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide a tribological debris
analysis system.
The foregoing and other objects of the present invention, which shall become
apparent as the detailed description proceeds, are achieved by tribological debris
analysis system, comprising a general purpose computer; and a tribological sensor
system for generating data, the sensor system comprising an optical flow cell;
a pump for pumping a fluid through the optical flow cell; a laser for illuminating
the fluid flowing through the optical flow cell; and an imaging device for detecting
debris in the fluid illuminated by the laser, and generating object segments representative
of the debris and sending the object segments to the general purpose computer for analysis.
Other aspects of the present invention are attained by a tribological sensor
system for imaging particles in a fluid comprising a fluid illumination delivery
system for placing the fluid in a field of view; and an imaging device for detecting
any particles in the field of view and generating object information representative
of the particles for analysis.
Still other aspects of the present invention are attained by a computerized
method for classifying particles in a fluid taken from a device, wherein the particle-containing
fluid is imaged into object segments, the computerized method comprising receiving
the plurality of object segments; generating a plurality of object elements from
the plurality of object segments; and classifying the plurality of object elements
according to predetermined characteristics.
It is another aspect of the present invention to provide a computerized method
for classifying particles in a fluid taken from a device, wherein the particle-containing
fluid is imaged into object information, the computerized method comprising: classifying
the object information according to predetermined characteristics.
These and other objects of the present invention, as well as the advantages
thereof over existing prior art forms, which will become apparent from the description
to follow, are accomplished by the improvements hereinafter described and claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
For a complete understanding of the objects, techniques and structure of the
invention, reference should be made to the following detailed description and accompanying
drawings, wherein:
FIGS. 1A-G are examples of different types of particles detected by an optical
debris analysis system according to the present invention;
FIG. 2 is a schematic diagram of the system according to the present invention;
FIG. 3 is a processing flow chart showing functions of an imaging device and
a general purpose computer according to the present invention;
FIG. 4 is a block diagram of the imaging device according to the present invention;
FIG. 5 is a block diagram of an alternative embodiment of the imaging device
according to the present invention; and
FIG. 6 is a block diagram of a field programmable gate array utilized by the
system of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawings and, more particularly to FIG. 2, a tribological
debris analysis system according to the present invention is designated generally
by the numeral
10. The system
10 includes an illumination delivery
system
12 and an imaging device
14 which generates a data signal
15 received by a general purpose computer
16. A power supply
18
supplies power to the particular components of the system
10. Although a
general purpose computer
16 may be used in the preferred embodiment it will
be appreciated that most any computing device with the necessary memory, hardware
and software could be utilized in the system
10. In all likelihood, the
general purpose computer
16 is powered separately.
The illumination delivery system
12 includes a fluid container
20
for holding the fluid material to be analyzed. The fluid may be a lubricating oil
used in engines and rotating machinery; hydraulic fluid used in various machinery;
and fluids used in industrial quality control, food processing, medical analysis,
and environmental control. Typically, the fluid sample is taken from and identified
with a particular unit or device and if the device has multiple ports that particular
port is identified. This information is input into the general purpose computer
for cataloging purposes. In any event, the fluid container
20 is connected
to a pump
22 which draws the fluid in the container through an optical flow
cell
24. As the fluid is being drawn through the flow cell
24 a laser
26 illuminates one side of the flow cell
24 to generate an image
that is detected by the imaging device
14. After the appropriate processing
of the image, the imaging device
14 generates a data signal
15 that
is received by the general purpose computer
16.
Referring now to FIG. 3, a flow chart describing the general operational
features of the system
10 is shown. The imaging device
14 generates
a digital video signal at step
30. Initially, when the fluid begins flowing
through the optical flow cell, an illumination map is generated. In the preferred
embodiment, the illumination map comprises the first 32 frames of video to establish
a base line illumination pattern. This allows the system to take into account the
characteristics of the laser beam, which is circularly polarized light, and other
artifacts associated with the system. And since various types of fluid material
with different opacities are likely to be tested it is important to establish a
base line level of illumination for analysis of the particles contained within
the fluid.
After generation of the illumination map, the system performs a thresholding
step
32. The digital video signal is initially provided at 256 levels of
gray corresponding to the illumination map. The threshold step converts the 256
different levels of illumination to a bi-level image. In other words, if a particular
pixel is deemed to have an intensity value in the lighter half of the 256 levels
then it is designated as being an 'off' pixel. But, if the pixel is in the darker
half of the spectrum then the pixel is deemed to be associated with an object and
it is designated as an 'on' or darkened pixel. The thresholding process determines
whether each pixel should be designated as part of an object or not. It will also
be appreciated that the thresholding step could be further defined as four levels—instead
of two—or however many levels are appropriate depending on the base thresholding level.
After completion of thresholding step
32, the thresholded information
is used to generate object segments at step
34. An object segment is a contiguous
group of pixels in a row wherein all pixels in the group have the 'not off' value.
In other words, the object segments are individual rows of an object detected which
are defined by a row number, a column start position, and a column stop position.
The object segments are included in the data
15 that is sent to the general
purpose computer
16.
The general purpose computer
16 receives the object segments in the data
15 and generates a set of object elements at step
40. It will be
appreciated that the object elements are configured object segments which have
some continuity between adjacent rows of pixels. Formation of the object elements
may also be configured by filtering routines as deemed appropriate or based upon
the past history of particles detected. In any event, after the generation of the
object elements they are classified at step
42 according to different types
of particles or debris as discussed in the description of FIGS. 1A-G. Upon completion
of the classifying step, the general purpose computer at step
44 may access
a hierarchical database
44 for comparing known types of particles with those
particles detected in the fluid. Finally, at step
46, based upon the comparison
of the particles and other features, a machine condition is determined. The computer
16 may use neural networks or other algorithms to classify the particles.
This information is displayed by the general purpose computer with recommendations
and/or information for the purpose of determining the wear conditions of the machinery
from which the fluid was obtained. And if fluid is drawn from several different
ports of the machinery this information can also be correlated and stored.
The classifying step
42 includes the steps of sizing the objects detected
at step
50 which correlates to the expected useful life of the machinery
from which the fluid was drawn. The size of the objects may be input directly to
step
46 to determine the machine condition. In addition, the object sizes
are input to process step
52 to determine the trend of the object sizes.
In other words, at step
52 if there is an increase in object size or a decrease
in object size this information can be detected and monitored. The trending in
object sizes may also be used to analyze previous fluid samples taken from a particular
port of a machine or used to compare similar machines to one another. At step
54,
the general purpose computer may utilize the object elements to generate shape
features which are indicative of the type of wear being experienced by the machine
from which the fluid sample was drawn. This information is utilized at step
56
to identify the object wear type by comparing the shape features to those in the
database. This information can be further utilized to determine the machine condition
at step
46.
Referring now to FIG. 4, the circuitry of the imaging device
14
will now be discussed. Light from the laser is projected at 830 nm through the
flow cell onto a CMOS imager
60 which is 640×480 pixels and that operates
at an update rate of 30 hz. The imager
60, which may also be referred to
as a camera, generates a digital video signal of the laser-illuminated fluid sample.
This information is transferred to a field programmable gate array
62 which
performs the pixel processing, image filtering, image thresholding, segment detection
and generation of global image statistics. Additionally, the array
62 functions
to control the other components of the imaging device. These components include
an interface device
74, which in the preferred embodiment is a universal
serial bus (USB), the imager
60, the memory devices contained within the
imaging device
14, the pump
22 and the laser
26. The USB interface
74 sends the object segment to the general purpose computer and receives
instructions back from the general purpose computer. The array
62 also controls
relays
68 that control the directional flow of the fluid through the pump
22 and a relay
70 that controls a bypass valve
72 which is
utilized to "prime" the pump
22 prior to imaging any fluid flowing through
the optical flow cell
24. In communication with the array
62 is a
synchronous dynamic random access memory (SDRAM) device which is utilized to store
the illumination map needed for thresholding the video signal. The SDRAM is a 16
by 1 megabyte memory device. Of course, it will be appreciated that any appropriately
sized memory device could be implemented in the present invention. Another memory
device associated with the imaging device
14 is a first-in first-out (FIFO)
memory device
66 used to store the data processed by the array
62
until the general purpose computer
16 is in need of it.
An alternative embodiment of the imaging device
14 is shown in FIG. 5.
This device operates in much the same manner as the device shown in FIG. 4, but
in this instance the imager
60 may be provided with a faster updating frequency.
And in this embodiment a microcontroller
76 may be in communication with
the array
62 to allow for different types of interface devices
78
to be in communication with the general purpose computer
16. The microcontroller
76 controls the interfaces and may take on additional object processing
chores which allows for the detected segments to be converted into the object elements
in the imaging device instead of by the general purpose computer. In any event,
the object information transmitted to the general purpose computer will be object
elements instead of object segments resulting in a further reduction in the required
bandwidth and further enabling the user to use a less expensive general purpose
computer or to more easily send the serial data to an appropriate computing device.
Referring now to FIG. 6 a detailed schematic diagram of the array
62
is shown. As noted previously, the array
62 is in communication with the
imager device
60 and memory devices
64 and
66. Output devices
connected to the array include the general purpose computer
16 via the data
signal
15, the pump
22, the bypass valve
72 and the laser
26. The array
62 includes a series of controllers which are utilized
to control various aspects of these components that are connected to the array.
In particular, the individual controllers include but are not limited to an I
2C
controller
80 which generates the necessary protocol to allow the programming
and operation of the CMOS imager
60. Also provided is a SDRAM controller
82 which provides the necessary circuitry to provide the appropriate signals
to control the operation of the SDRAM memory chip
64. Likewise, an FIFO
controller
84 is responsible for controlling the operation of the first-in
first-out memory
66 used to store objects segments until the computer
16
asks for them. A USB microcontroller
86 is responsible for controlling the
USB interface
74 which organizes how data is sent to the general purpose
computer. A pump relay controller
88, a bypass relay valve controller
90
and a pulse controller
92, which is associated with the laser
26,
are also provided. The controllers
80,
86,
88,
90 and
92 are in communication with one another via a control bus
94
The array
62 may include initializing devices to facilitate the operation
of the imaging device
14. In particular, a camera initializing device
100
sends appropriate signals to the I
2C controller through a multiplexer
120 which also receives controller signals via the control bus
94.
A second multiplexer
122 receives input signals from the FIFO controller
84 and the SDRAM memory controller
82. These signals are sent to
the USB microcontroller
86 as deemed appropriate.
The array
62 may include a finite impulse response (FIR) filter used
110
to apply a high pass filter to the digital video signal. This filtered signal is
then sent to a thresholding device
112 which converts the eight-bit gray
level image into a bi-level image. The filtered signal is also sent to a collect
statistics circuit
118 which examines the digital video stream coming in
and determines the average intensity value for each frame of video. Additionally,
the collect statistics circuit
118 determines the relative amount of video
saturation present. The data from the circuit
118 is sent to the USB microcontroller
86 via the multiplexer
122 and is used by the general purpose computer
16 to implement an automatic gain control routine to properly set the laser
pulse width and camera gain by the controller
92 for optimal lighting of
the fluid under test. The thresholded video signal is sent by the thresholding
device to a run length limited (RLL) encoder
116 which is responsible for
detecting the object segments which are horizontally adjacent pixels in a row that
the threshold device
112 has determined to be part of an object. Detected
object elements are submitted to the FIFO memory device
66, and subsequently
to the general purpose computer via the multiplexer
122.
Based upon the foregoing, the advantages of the present system are readily
apparent. In particular, the present system allows for processing the digital video
signal within the imaging device so as to allow for faster and more efficient processing
of the images. In other words, it is now possible for the imaging device to generate
'object information'—object segments as shown in FIG. 4 or both object segments
and object elements as shown in FIG.
5—that is then processed by the
general purpose computer
16. The improvements discussed herein eliminate
the need for a dedicated general purpose computer system to conduct all of the
video image processing. Accordingly, the results can be displayed on most any off-the-shelf
computing device while providing a system which is much less expensive. Additionally,
the present device eliminates the need for a separate input/output board to control
the general purpose computer and it removes the extra cabling and electronics needed
to implement the previous system.
Thus, it can be seen that the objects of the invention have been satisfied
by the structure and its method for use presented above. While in accordance with
the Patent Statutes, only the best mode and preferred embodiment has been presented
and described in detail, it is to be understood that the invention is not limited
thereto or thereby. Accordingly, for an appreciation of the true scope and breadth
of the invention, reference should be made to the following claims.
*
