U.S. patent application number 10/000849 was filed with the patent office on 2003-05-01 for method of locking onto and tracking a target.
Invention is credited to Welke, James M..
Application Number | 20030081502 10/000849 |
Document ID | / |
Family ID | 21693268 |
Filed Date | 2003-05-01 |
United States Patent
Application |
20030081502 |
Kind Code |
A1 |
Welke, James M. |
May 1, 2003 |
METHOD OF LOCKING ONTO AND TRACKING A TARGET
Abstract
A method of tracking an object comprising the steps of acquiring
the position of at least one object; selecting the at least one
object as a target; determining a sampling window which envelopes
the target; obtaining an echo; repeating the foregoing step of
obtaining an echo a predetermined number of times; determining
valid echoes from the target; calculating the current position of
the target from the received echoes; and repeating the steps of
obtaining, repeating, determining, and calculating as desired. The
step of obtaining an echo comprises the steps of transmitting a
pulse at a desired frequency from a transducer; scanning for echoes
within the sampling window by a receiver; and receiving at least
one echo of the pulse at the receiver which are within the sampling
window, the at least one echo having a frequency that matches the
outgoing pulse frequency.
Inventors: |
Welke, James M.; (Ferndale,
MI) |
Correspondence
Address: |
William L. King
Suite 300
305 Hoover Blvd.
Holland
MI
49423
US
|
Family ID: |
21693268 |
Appl. No.: |
10/000849 |
Filed: |
November 1, 2001 |
Current U.S.
Class: |
367/97 ;
367/908 |
Current CPC
Class: |
G01F 23/2962 20130101;
G01S 7/527 20130101; G01S 15/101 20130101; G01S 15/88 20130101;
Y10S 367/908 20130101 |
Class at
Publication: |
367/97 ;
367/908 |
International
Class: |
G01S 015/88 |
Claims
What is claimed is:
1. A method for acquiring the position of at least one object,
comprising the steps of: providing a sampling window; obtaining an
echo comprising the steps of: transmitting a pulse at a desired
frequency from a transducer; scanning for echoes within the
sampling window by a receiver; and receiving at least one echo of
the pulse at the receiver which are within the sampling window, the
at least one echo having a frequency that matches the frequency of
the outgoing pulse; repeating the foregoing step of obtaining an
echo a predetermined number of times; determining which of the at
least one echoes received by the receiver comprises a valid echo;
and determining if any of the at least one echoes corresponds to a
valid target.
2. The method of claim 1, wherein the step of valid echo
determining comprises the steps of: establishing a threshold
amplitude; storing portions of each of the at least one received
echo which are outside of the threshold amplitude; correlating the
frequency of the received at least one echo to the frequency of the
respective pulse; and storing the at least one echo if the
frequency of the received at least one echo substantially
corresponds to the frequency of the respective pulse as a possible
target echo.
3. The method of claim 2, wherein the step of obtaining further
comprises the step of: dismissing the at least one echo if the
frequency of the received at least one echo does not substantially
correspond to the frequency of the respective pulse.
4. The method of claim 2, further comprising the step of:
determining the time of occurrence of the at least one echo
determined to be a valid echo.
5. The method of claim 4, wherein the step of time of occurrence
determining comprises the step of: interpolating one of a first
amplitude maxima and minima with a predetermined later amplitude
maxima and minima, to, in turn, determine the temporal occurrence
of the at least one echo.
6. The method of claim 5, wherein the step of interpolating
utilizes the greater of the first amplitude maxima and minima with
the greater of the fifth amplitude maxima and minima.
7. The method of claim 1, wherein the predetermined number of times
comprises ten times.
8. The method of claim 1, wherein the step of target determining
comprises the steps of: comparing each of the at least one valid
echoes to each other; grouping echoes which are temporally related
into an echo group; and identifying each echo group having a
predetermined number of related echoes as a target.
9. The method of claim 8, wherein the predetermined number of
related echoes comprises at least seventy percent of the
predetermined number of pulses.
10. The method of claim 1, wherein the step of providing a sampling
window comprises the steps of: providing a range within which to
acquire a target; and dividing the range into a plurality of
sampling windows.
11. A method of tracking an object comprising the steps of:
acquiring the position of at least one object; selecting the at
least one object as a target; determining a sampling window which
envelopes the target; obtaining an echo comprising the steps of:
transmitting a pulse at a desired frequency from a transducer;
scanning for echoes within the sampling window by a receiver; and
receiving at least one echo of the pulse at the receiver which are
within the sampling window the at least one echo having a frequency
that matches the outgoing pulse frequency; repeating the foregoing
step of obtaining an echo a predetermined number of times;
determining valid echoes from the target; calculating the current
position of the target from the received echoes; and repeating the
steps of obtaining, repeating, determining and calculating as
desired.
12. The method of claim 11, wherein the predetermined number of
times comprises ten times.
13. The method of claim 11, further comprising the step of:
providing output to an output device corresponding to the current
position of the target.
14. The method of claim 11, wherein the step of acquiring comprises
the steps of: providing a sampling window; obtaining an echo
comprising the steps of: transmitting a pulse at a desired
frequency from a transducer; scanning for echoes within the
sampling window by a receiver; and receiving at least one echo of
the pulse at the receiver which are within the sampling window, the
at least one echo having a frequency that matches the outgoing
pulse frequency; repeating the foregoing step of obtaining an echo
a predetermined number of times; determining which of the at least
one echoes received by the receiver comprises a valid echo; and
determining if any of the at least one echoes corresponds to a
valid target.
15. The method of claim 11, further comprising the step of:
reacquiring the position of the at least one object if the step of
determining a valid target fails to determine a target.
16. The method of claim 15, wherein the step of reacquiring
comprises the steps of: expanding the previously selected sampling
window; and reexecuting the step of repeating with the expanded
sampling window.
17. The method of claim 11, further comprising the steps of:
comparing the current position of the target relative to the
position of the target during a prior obtained calculation;
determining a direction of movement for the target; and expanding
the sampling window in the direction of movement.
18. The method according to claim 17, further comprising the step
of: contracting the sampling window in the direction opposite of
the movement.
19. The method according to claim 11, wherein the step of selecting
comprises the step of: automatically selecting the object closest
to a predetermined point.
20. The method according to claim 11, wherein the step of selecting
comprises the steps of: outputting parameters corresponding to the
various acquired objects to the output device; and inputting the
desired object to be tracked by way of the input device.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention is directed primarily to the tracking of
objects (targets), and more particularly, to an apparatus and
method of locking onto and tracking objects. While not limited
thereto, the invention is well suited to the tracking of fluid
levels (i.e. the top surface of a fluid) within a container, such
as a container or tank of fuel.
[0003] 2. Background Art
[0004] Ultrasonic measurement has long been used in the art to
track various objects, such as the top surface of a fluid within a
tank. Various prior art designs are known in the art, including
U.S. Pat. No. 5,511,041; U.S. Pat. No. 5,587,969; U.S. Pat. No.
5,157,639; and U.S. Pat. No. 5,131,271. While the above-identified
references address various different issues relative to ultrasonic
measurements, they remain problematic for a plurality of reasons.
For example, many of the disclosed apparatuses and methods are not
particularly well suited to the tracking of rapidly moving targets,
such as fluid within a moving container (i.e. fuel in the tank of a
moving vehicle). Moreover, others are not particularly well suited
to the tracking of fluid levels when the fluid or the area
proximate the fluid includes obstructions therein (i.e. material
floating on or in the fluid).
[0005] Therefore, one object of the present invention is to
facilitate the tracking of moving targets, particularly rapidly
moving targets.
[0006] It is another object of the present invention to facilitate
the tracking of moving targets which include obstructions within or
near the fluid (i.e. internal tank structures).
[0007] These and other objectives will become apparent in light of
the present specification, claims, and drawings appended
hereto.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to a method for acquiring
the position of at least one object. The method includes the steps
of (a) providing a sampling window; (b) obtaining an echo; (c)
repeating the foregoing step of obtaining an echo a predetermined
number of times; (d) determining which of the at least one echoes
received by the receiver comprises a valid echo; and (e)
determining if any of the at least one echoes corresponds to a
valid target. The step of obtaining an echo comprises the steps of
(a) transmitting a pulse at a desired frequency from a transducer;
(b) scanning for echoes within the sampling window by a receiver;
and (c) receiving at least one echo of the pulse at the receiver
which are within the sampling window, the at least one echo having
a frequency.
[0009] In a preferred embodiment, the step of determining a valid
echo comprises the steps of (a) establishing a threshold amplitude;
(b) storing portions of each of the at least one received echo
which are outside of the threshold amplitude; (c) correlating the
frequency of the received at least one echo to the frequency of the
respective pulse; and (d) storing the at least one echo if the
frequency of the received at least one echo substantially
corresponds to the frequency of the respective pulse as a possible
target echo.
[0010] In one such embodiment, the step of obtaining an echo
further comprises the step of dismissing the at least one echo if
the frequency of the received at least one echo does not
substantially correspond to the frequency of the respective
pulse.
[0011] In another such embodiment, the method comprises the step of
determining the time of occurrence of the at least one echo
determined to be a valid echo. In one such embodiment, the step of
occurrence determining comprises the step of interpolating one of a
first amplitude maxima and minima with a predetermined later
amplitude maxima and minima, to, in turn, determine the temporal
occurrence of the at least one echo. In another embodiment, the
step of interpolating utilizes the greater of the first amplitude
maxima and minima with the greater of the fifth amplitude maxima
and minima.
[0012] In another embodiment, the step of target determining
comprises the steps of (a) comparing each of the at least one valid
echoes to each other; (b) grouping echoes which are temporally
related into an echo group; and (c) identifying each echo group
having a predetermined number of temporally related echoes as a
target. In one such embodiment, the predetermined number of related
echoes comprises at least seventy percent of the predetermined
number of pulses.
[0013] In yet another preferred embodiment, the step of providing a
sampling window comprises the steps of (a) providing a range within
which to acquire a target; and (b) dividing the range into a
plurality of sampling windows.
[0014] In another aspect of the invention, a method of tracking an
object is presented. The method includes the steps of (a) acquiring
the position of at least one object; (b) selecting the at least one
object as a target; (c) determining a sampling window which
envelopes the target; (d) transmitting a pulse at a desired
frequency from a transducer; (e) obtaining an echo; (f) scanning
for echoes within the sampling window by a receiver; (g) receiving
at least one echo of the pulse at the receiver which are within the
sampling window, the at least one echo having a predetermined
frequency; (h) repeating the foregoing step of obtaining an echo a
predetermined number of times; (i) determining valid echoes from
the target; (j) calculating the current position of the target from
the received echoes; and (k) repeating the steps of obtaining,
repeating, determining and calculating as desired.
[0015] In another preferred embodiment, the method further
comprises the step of providing output to an output device
corresponding to the current position of the target.
[0016] In one embodiment, the step of acquiring comprises the steps
of (a) providing a sampling window; (b) obtaining an echo; (c)
repeating the foregoing step of obtaining an echo a predetermined
number of times; (d) determining which of the at least one echoes
received by the receiver comprises a valid echo; and (e)
determining if any of the at least one echoes corresponds to a
valid target. The step of obtaining an echo comprising the steps
of: (a) transmitting a pulse at a desired frequency from a
transducer; (b) scanning for echoes within the sampling window by a
receiver; and (c) receiving at least one echo of the pulse at the
receiver which are within the sampling window, the at least one
echo having a frequency that matches the predetermined
frequency.
[0017] In one embodiment, the method further comprises the step of
reacquiring the position of the at least one object if the step of
determining a valid target fails to determine a target. In one
embodiment, the step of reacquiring comprises the steps of: (a)
expanding the previously selected sampling window; and (b)
reexecuting the step of repeating with the expanded sampling
window.
[0018] In another preferred embodiment, the method further
comprises the steps of (a) comparing the current position of the
target relative to the position of the target during a prior
obtained calculation; (b) determining a direction of movement for
the target; and (c) expanding the sampling window in the direction
of movement. In one such embodiment, the method further comprises
the step of contracting the sampling window in the direction
opposite of the movement.
[0019] In yet another preferred embodiment, the step of selecting
comprises the step of automatically selecting the object closest to
a predetermined point.
[0020] In a preferred embodiment, the step of selecting comprises
the steps of (a) outputting parameters corresponding to the various
acquired objects to the output device; and (b) inputting the
desired object to be tracked by way of the input device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will now be described with reference to the
drawings wherein:
[0022] FIG. 1 of the drawings is a side elevational view of a tank
having a transducer positioned therein which is programmed to
operate pursuant to a method of the present invention; and
[0023] FIG. 2 of the drawings is a graphical representation of a
received echo from a potential target.
DETAILED DESCRIPTION OF THE INVENTION
[0024] While this invention is susceptible of embodiment in many
different forms, there is shown in the drawings and will be
described in detail, one specific embodiment with the understanding
that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not
intended to limit the invention to the embodiment illustrated.
[0025] A method of tracking an object (i.e. a target) is disclosed
which generally comprises a series of steps, including the steps of
(a) acquiring the position of at least one object; (b) selecting
the at least one object as a target; (c) determining a sampling
window which envelopes the target; (d) transmitting a pulse at a
desired frequency from a transducer; (e) obtaining an echo; (f)
scanning for echoes within the sampling window by a receiver; and
(g) receiving at least one echo of the pulse at the receiver which
are within the sampling window, the at least one echo having a
predetermined frequency; (h) repeating the foregoing step of
obtaining an echo a predetermined number of times; (i) determining
valid echoes from the target; (j) calculating the current position
of the target from the received echoes; (k) repeating the steps of
obtaining, repeating, determining, and calculating as desired; and
(l) providing output corresponding to the calculated position.
[0026] Such a method will be described below with the understanding
that it may have a plurality of uses. Indeed, while various uses
are contemplated, the method is rather suitable for use in
association with a fuel tank, to, in turn, accurately measure the
fuel within the tank. Such accurate measurements are rather useful
and important for, for example, racing cars and pit crews.
[0027] A system capable of executing the foregoing method is shown
in FIG. 1 and the system is identified generally as 10. More
specifically, system 10 comprises ultrasonic transducer 11
associated with hardware 12 (i.e. proper IC base circuitry equipped
with software), output device 14, and input device 16. Transducer
11 is capable of transmitting and receiving signals having a pulse
width and an amplitude. Hardware 12 is capable of directing
transducer 11 to transmit particular pulses, and to process
information received by input device 16 and transducer 11, toward
eventual display to output device 14. Output device 14 may comprise
a monitor, printer, an analog and/or digital gauge, among others.
Input device 16 may comprise a keyboard (specialized or
conventional), keypad, and/or a series of toggle switches, among
others. Of course, it will be understood that the invention
described herein is not limited to any particular IC based
circuitry, software, output device and/or input device.
[0028] To operate system 10, system 10 is first activated.
Generally, system 10 will first undergo a system diagnostic
operation. If a failure condition is detected with any of the
system diagnostics (i.e. faulty transducer, other hardware failure
or software glitch) an output is directed to output device 14 to
alert the operator that a failure condition has been detected. In
certain embodiments, the failure detection may be enhanced such
that the output directed to output device 14 identifies not only a
failure condition but the particular component or subcomponent that
is the cause of the failure condition. Of course, other embodiments
will omit entirely a system diagnostic operation.
[0029] Upon successful diagnostic testing, system 10 is prepared to
acquire a target. In certain embodiments, the acquiring process is
initiated by first searching to see if a previous target position
has been stored in the system for a previous operation. For
example, if system 10 had previously been used to track the level
of fuel in a tank, system 10 can retain this information so that
during subsequent operations, system 10 will have a smaller
sampling window in which to execute the below described
target/object position acquisition procedure. If no such prior
position is stored in system 10, then system 10 will assign a
default sampling window which, for example, encompasses the entire
possible range for the target. For example, where the target is the
surface of fuel or other fluid in a tank, where no previous range
exists in the system, system 10 will assign a default total
sampling window which extends from the approximate base of the tank
to the upper end of the tank.
[0030] After determining a total sampling window of search, system
10 first divides the entire range into a plurality of sampling
windows, such that each sampling window is searched sequentially to
identify targets within each of the sampling windows. For example,
and certainly not so as to be limited thereto, the contemplated
total sampling window in the present invention is divided into
three sampling windows. The range division facilitates the accurate
and quick acquisition of possible objects which may comprise
desired targets for tracking. In particular, as the sampling window
extends further and further away from transducer 11, the pulse
width, amplitude, and gain are increased so as to maximize signal
to noise ratios. At shorter distances, the pulse width, amplitude,
and gain are reduced to minimize false echoes which can occur at
generally closer ranges. Additionally, as will be explained, system
10 tracks the echo width, the noise, the echo amplitude, among
other readings which are fed back into system 10 to fine tune the
pulse width, amplitude, and amplifier gain of transducer 11.
[0031] Each sampling window is sampled a preset desired quantity of
times. In the contemplated system, transducer 11 is directed by
hardware 12 to execute ten samples. Sampling ten times provides a
more accurate target acquisition procedure. Indeed, by limiting the
sampling window, it is possible to execute the foregoing sampling
in a temporally efficient manner.
[0032] For each sampling, the waveform is transmitted by transducer
11. Presumably, as shown in FIG. 1, at least a portion of pulse 110
is reflected (i.e, echo 120) from the upper surface of the fluid.
Echo 120 is received by transducer 11 for filtering and processing.
Once processed, any points that are above predetermined "noise
threshold" levels are stored in the system. One such received pulse
is shown graphically in FIG. 2. The positive and negative peaks of
the acquired points that are outside the threshold levels are
compared relative to each other to determine if the frequency is
within a narrow band that corresponds to the outgoing signal. If
the frequency is within a narrow band that corresponds to the
outgoing signal, then the received waveform is deemed an echo.
System 10 continues to receive and store the waveform until the
waveform subsides and no further points outside of the threshold
levels are received. The time from the first to the last point is
determined and stored as the echo width. This echo width can be
used in a feedback mechanism to facilitate calculation of the
sample window duration, outgoing pulse width, pulse amplitude, and
amplifier gain settings, and, for varying sampling windows.
[0033] As shown graphically in FIG. 2, to determine the actual time
of echo 120, system 10 identifies the points which correspond to,
for example the first five maxima and minima. Once this has been
established, the values are interpolated to determine the leading
edge. In other embodiments, a different quantity of minima and
maxima can be utilized to facilitate the determination of the time
of occurrence of the echo. Using such a system to determine echo
time of occurrence leads to increased accuracy over systems which
utilize the peak amplitude as the echo occurrence.
[0034] In addition to determining peaks, system 10 likewise tracks
noise (or other interference). If system 10 detects excess noise,
then system 10 can deem the particular sample tainted and unusable.
One manner in which to track noise is to detect points which are
deemed to be unrelated to the determined echo (i.e. points which
exceed the threshold levels but do not correspond in frequency). If
the number of points that exceed the threshold levels which are
deemed to not be related to the determined echo exceeds a
predetermined level (for example, the quantity of such points
exceeds ten for a particular echo), then system 10 rejects the
previously determined echo as being possibly tainted due to
excessive noise. System 10 further tracks the noise level and from
this data determines an average noise level. The average noise
level is used in the feedback portion of the system and can aid in
the determination of the pulse width, amplitude, and gain for
future samplings.
[0035] System 10 repeats the sampling process and continues to
receive signals within the particular sampling window. For each
received signal, a determination is made as to whether the received
signal comprises an echo. If the received signal is determined to
be a valid echo, the echo is compared with previous echoes. If the
echo time of occurrence substantially matches the relative time of
previously determined echoes, or a time multiple of any one of the
previously determined echoes, then system 10 recognizes that the
two echoes represent the same target. However, if the different
determined echoes do not have such a relative time relationship,
then each determined echo is stored as representative of a separate
target.
[0036] Once each of the sampling windows have been sampled a
predetermined number of times (i.e. ten times or more, while not
limited thereto), and the signals that have been determined to be
valid echoes have been stored, system 10 is prepared to analyze
these echoes. In particular, the echoes are placed in order by time
between the respective transmission of the pulse and the receipt of
the echo (and echoes which correspond temporally are grouped into
an echo group). It will be understood that repeated sampling during
the acquisition process should yield an echo at substantially the
same time during each sampling. For example, if ten samplings are
taken, a given target should have produced an echo to transducer 11
for a majority of the samplings at approximately the same time.
Thus, to determine if the stored echoes are valid, system 10 checks
each echo to determine if any other echoes were received within a
narrow predetermined time band of the echo under consideration. If
any echo group has, for example, fewer than ten or another
predetermined number, then the echo group is dismissed as being
noise or other interference as opposed to possibly corresponding to
a target or group. Of course, system 10 can be modified to be more
or less inclusive, (i.e. echoes that did not occur during each
sampling can be dismissed, or echoes that occurred in less than a
predetermined number of samples can be dismissed). This is repeated
for each of the received echoes. After such a comparative analysis,
the echoes that remain are designated as objects, and comprise
potentially valid targets that have been acquired during the
acquisition process.
[0037] If no objects (possible targets) have been acquired, it is
possible that the targets were moving at such a rate that the
acquiring process is unable to deem any one of the echoes as
representative of a valid target. In such an instance, system 10
can alert the user to take steps to stabilize the potential targets
before attempting to proceed with the steps related to acquiring
the target.
[0038] Once the potentially valid targets have been identified,
system 10 can follow two different selection procedures, namely an
auto target select method or a manual select process. In the auto
target select mode, system 10 automatically selects the desired
target to track from the determined potentially valid targets. For
example, this can be accomplished by identifying the target which
was the first valid target found (i.e. the echo with the earliest
time of occurrence). In the manual select mode, system 10 provides
the operator (through the output device) identification of all of
the potentially valid targets. The operator then selects which, if
any, of the valid targets the operator wishes to track.
[0039] In either mode, once the target has been identified, system
10 proceeds to lock onto this target and to track this target. To
lock onto the selected target, the sampling window is first set to
a time period which envelopes the time of the echo, the time period
extends beyond the time of the actual echo (both before and after)
a predetermined time period. For example, if the echo was received
after 10 ms, the window may be set to extend from 9 ms to 11 ms.
The size of the window depends on the quantity of contemplated
movement of the target as well as the type of material that is
measured, among other issues. System 10 likewise fine tunes the
pulse width, amplitude, and amplifier gain parameters for use
during tracking (all of which are based on the amplitude of the
locked echo waveform).
[0040] To track the target that has been selected for tracking,
system 10 directs transducer 11 to generate a pulse. The echo that
is returned during the time period which is encompassed by the
sampling window is then amplified, filtered, and digitized, then
followed by a peak-finding procedure identified above. Once
received, the echo is compared to the echo received during
tracking. If the echoes correspond temporally to a predetermined
valid time separation, the new occurrence is then stored and the
process is repeated for a predetermined period of samples (i.e. ten
samples, twenty samples, etc). Also, the amplitude of the echo from
the most recent sampling is used in the feedback mechanism to
calculate pulse width and amplitude and gain settings.
[0041] If the echo is compared to the echo received during tracking
and the echoes do not correspond to a particular valid time
separation, then the new echo must be analyzed to determine the
cause of the time separation. For example, the target may have been
displaced or an obstruction may have entered the path which has
obstructed the actual target. For example, the echo may be greater
than the maxima of the predetermined window. System 10, in turn,
first reviews as to whether previous signals showed a trend of
movement that would be consistent with the echo being greater than
the maxima. If the previous signals did show such a trend, then the
new echo is deemed a valid echo. On the other hand, if the previous
sampled echoes showed an opposite trend (i.e. an obstruction), then
system 10 will track the alternate echo and continue the sampling
procedure until an echo is received that did correspond to the
previous established trend. At such time that an echo is sampled
that does correspond to the previous trend, then the echo is deemed
a valid echo. The tracking and storing of echoes until a valid echo
is determined can continue as long as obstructions block the
target. As such, in certain circumstances, system 10 will track
multiple echoes (i.e. greater than one echo, such as two, three,
four or more) simultaneously until the valid echo is determined. As
such, the target is not only tracked, it is not lost in the event
that multiple obstructions are present. In addition, if trends
upward or downward are detected, then the system will reset the
sampling window maxima and minima accordingly so that the sampling
window accurately corresponds to the window in which the
appropriate echo is to be received. For example, an obstruction
would be between the sensor and the target. The target then moves
towards the sensor and the obstruction until the target overlaps
the obstruction. Finally, the target moves away from the
obstruction, either toward or away from the sensor. The invention
facilitates the detection and tracking and discerning of the target
even with the presence of the obstruction.
[0042] As with the acquiring step, the tracking procedure executes
the foregoing tracking sampling procedure multiples of times to
insure accurate tracking (i.e. ten samples). System 10 can utilize
statistical functions to minimize errors which can occur from
outside disturbances such as, for example, turbulence or
temperature variations in the medium. Once the signals are
statistically improved, they are converted into operator readable
measurements and output is provided to the user. Once completed,
system 10 will check if any particular output type is requested or
if a new target for tracking is desired. For example, where two
fluids that do not mix are contained within a container, system 10
can be changed to track the interface between the two fluids or on
the top surface of the upper fluid. If no particular output type is
requested and if no new target is selected, then the tracking
procedure is repeated with system 10 taking the necessary
samples.
[0043] If at any time the target being tracked becomes lost, system
10 will continue to sample for a predetermined number of cycles in
an attempt to locate the target. If the target cannot be located
within a predetermined number of cycles, system 10 can enter into a
quick acquire mode. The quick acquire mode differs from the steps
associated with the above-identified acquire mode in that the quick
acquire mode designates a particular window for sampling that is
expanded over the narrow tracking window but which is less than the
various sampling windows used during a full acquire procedure
identified above. As such, if a target is lost, system 10 can
quickly sample from an appropriately sized sampling window to
reacquire the target. It will be understood that if the target
cannot be relocated, then it may become necessary to execute a full
acquiring step.
[0044] The foregoing description merely explains and illustrates
the invention and the invention is not limited thereto except
insofar as the appended claims are so limited, as those skilled in
the art who have the disclosure before them will be able to make
modifications without departing from the scope of the
invention.
* * * * *