DRAWINGS
Various aspects and attendant advantages of one or more exemplary embodiments and modifications thereto will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is an exemplary schematic top plan view of an interior of a shipping container showing the ultrasound signal paths between door-mounted ultrasonic transducers/receivers and corner reflectors that are disposed along the sides of the shipping container;
FIG. 2 is an exemplary schematic top plan view of an interior of a shipping container showing the multiple ultrasound signal paths followed by multiple ultrasound signals emitted by door-mounted ultrasonic transducers, which are reflected back to ultrasonic receivers by side-mounted corner reflectors;
FIG. 3 is a schematic diagram of a shipping container door and the various parameters that relate to determining that the door has been opened and the extent of the door opening;
FIG. 4 is an isometric view of an exemplary corner reflector illustrating how an ultrasound beam is reflected back along a path that is generally parallel and in the opposite direction relative to the path of an ultrasound signal transmitted toward the corner reflector;
FIGS. 5A and 5B illustrate the relative distances and recorded responses for different degrees of a shipping container door being opened, for door mounted and wall facing ultrasonic transducers/receivers with two wall mounted corner reflectors;
FIGS. 6A and 6B illustrate the relative distances and recorded responses for different degrees of a shipping container door being opened, for door mounted and ceiling facing ultrasonic transducers/receivers with three ceiling mounted corner reflectors;
FIGS. 7, 8, and 9 respectively illustrate bit values for exemplary waveforms in a complex environment, in regard to: (a) single capture raw ultrasonic receiver output data, (b) averaged data, and (c) single capture with match filter data—all based on an ultrasound signal at a frequency of 100 kHz, and a data length of 6,975;
FIG. 10 is an exemplary schematic block diagram and ultrasound signal propagating in a shipping container without interaction with any contents of the shipping container;
FIG. 11 is similar to the FIG. 10, but illustrates the result of the ultrasound signal interacting with contents in the shipping container, to show the change in the ultrasound signal that is received by an ultrasonic receiver;
FIG. 12 is an exemplary schematic plan view of an interior of a shipping container showing the propagation of ultrasound signals between a plurality of ultrasonic transducers/receivers and a plurality of corner reflectors, to detect changes in a configuration of contents of the shipping container;
FIG. 13 is an exemplary functional block diagram showing the components of an ultrasound system that is used to monitor a door open position and/or detect changes in a configuration of the contents of a shipping container;
FIG. 14 is a flowchart illustrating exemplary logical steps for detecting an open door of a shipping container;
FIG. 15 is a flowchart illustrating exemplary logical steps for detecting a change in a configuration of the contents of a shipping container;
FIG. 16 is a schematic cross-sectional side elevational view of a shipping container that includes a liquid, showing how ultrasound is propagated between an ultrasonic transducer/receiver and a corner reflector to detect a change in the amount of liquid in the shipping container; and
FIG. 17 is a side-elevational view of a portion of a shipping container door and top, illustrating an alternative approach for mounting an ultrasonic transducer/receiver to detect when the door is opened based upon a change in an ultrasound signal reflected from the upper doorframe member.
DESCRIPTION
Figures and Disclosed Embodiments are Not Limiting
Exemplary embodiments are illustrated in referenced Figures of the drawings. It is intended that the embodiments and Figures disclosed herein are to be considered illustrative rather than restrictive. No limitation on the scope of the technology and of the claims that follow is to be imputed to the examples shown in the drawings and discussed herein.
Exemplary Ultrasound Systems for Monitoring Door of Shipping Container
Two exemplary embodiments for using ultrasound to detect that a door of a shipping container has been opened, and even detect the extent that the door was opened are illustrated in FIGS. 1 and 2. In each of these Figures, the portion of a shipping container 20 is illustrated in plan view to indicate how ultrasound signals are propagated between ultrasonic transducers/receivers 34 and corner reflectors 36 within an interior 22 of the shipping container. Shipping container 20 is constructed to include corrugated sheet metal walls 24. A door 26 and a door 28 are included in one end of the shipping container as shown in each of these Figures and are pivotally connected to the sides of the shipping container by hinges 30. Door 26 is first swung outwardly, enabling door 28 to then be opened. The doors are locked in their closed position by engaging latches 32.
As illustrated in FIG. 1, ultrasonic transducers/receivers 34 are mounted on the interior surfaces of each door 26 and 28, and are intended to be left there during the remaining usable life of the shipping container. A suitable adhesive, such as epoxy, or appropriate threaded fasteners that pass through flanges (not shown) of the ultrasonic transducer/receiver and into the underlying surface of the shipping container doors can alternatively be used to mount the devices in place.
Similarly, ultrasonic transducers/receivers 40 are mounted on door 26 and 28 in FIG. 2. Although not separately shown, each of ultrasonic transducers/receivers 34 and 40 includes batteries that are capable of powering the ultrasonic transducers and receivers for periods of up to seven years, depending upon the rate at which the ultrasonic transducers are selectively caused to transmit ultrasound pulses. Also not shown in either of these Figures is the logic unit or processor that controls the ultrasonic transducers/receivers and processes the signal output from the ultrasonic receivers so that door open events can be detected and stored as data that can subsequently be accessed by a user.
As illustrated in FIG. 1, one of the ultrasonic transducers/receivers that is mounted on the interior surface of door 26 (typically near the ceiling to avoid interference caused by the contents of shipping container 20) transmits ultrasonic signals toward corner reflectors 36, which are mounted within valleys 38 of corrugated sheet metal walls 24. The corner reflectors are mounted in the valleys to avoid or minimize the risk of damage that might be caused when loading or unloading the contents of the shipping container. However, corner reflectors 36 that are mounted on the wall adjacent to the hinge for each door are not so well protected, but will be more evident and therefore, less likely to be inadvertently damaged when the contents of the shipping container are loaded or unloaded. The ultrasonic transducers can be set to produce ultrasound pulse signals at a desired repetition rate, which will likely be at least 20 pulses per minute to insure that federal guidelines specifying a three second maximum time interval for detecting that a door is opened are met. However, it should be apparent that other pulse repetition rates can instead be used, as appropriate for a particular application of this technology. Clearly, when a faster pulse repetition rate is selectively set, the battery life for ultrasonic transducers/receivers 34 will be reduced, compared to a slower pulse repetition rate.
As will be evident by inspecting FIG. 1, as door 26 is opened, the length of the path followed by the ultrasound signals between ultrasonic transducer/receiver 34 and corner reflectors 36 will increase, which will be evident in a longer time for the reflected ultrasound signal to be received back by the ultrasonic receiver. The greater the extent to which door 26 is opened, the longer will be the time interval between the transmission and receipt of the ultrasound pulse. Thus, based upon the duration of this delay, it is readily possible to determine the extent that door 26 was opened. It will be understood that the opening of door 28 can also be detected, as well as a determination of the extent to which door 28 is opened. The initial opening of either door can be detected as a result of an increase in the time between the transmission of ultrasound pulses toward each of the corner reflectors and the receipt of the reflected pulses by the ultrasonic receiver.
FIG. 17 illustrates an alternative exemplary embodiment for mounting ultrasonic transducer/receiver 34 so that the ultrasound signal that is produced by the ultrasonic transducer is directed toward a top doorframe member 25, which also supports a top 27 of a shipping container 21. The ultrasound signal is directed through an orifice 23 in the upper portion of the door, but so that it is reflected back from the top doorframe member to the ultrasonic receiver. However, when door 26 is opened, the ultrasound signal is no longer reflected by the top doorframe member, so the output signal of the ultrasonic receiver changes to indicate that the door has been opened. The characteristics of the reflected ultrasound signal can also be used to detect if an attempt is made to employ a different reflective surface after the door is opened to attempt to “spoof” the ultrasound detection system. It will be apparent that many other configurations for mounting ultrasonic transducer/receiver 34 within a shipping container can be employed to detect when a door of the shipping container has been opened, and the disclosed exemplary embodiments are merely intended to show a few examples of how this may be done.
In FIG. 2, ultrasonic transducers/receivers 40 produce and receive a plurality of ultrasound signals that are directed in a plurality of different directions. These signals are reflected back by corner reflectors 36, which are again disposed along the sides of shipping container 20. The greater area coverage provided by ultrasonic transducers/receivers 40 enables them to also detect changes in the configuration of the contents of shipping container 20, as well as detecting the opening of the door. Since the plurality of ultrasound pulses disperse over a wide area within the volume of the shipping container and thereby cover a substantially larger portion of the interior than those produced by ultrasonic transducers/receivers 34 (in FIG. 1), the ultrasound pulse field can readily detect changes in the configuration of the contents of the shipping container if the changes affect the interaction of the ultrasound signals with the contents or change the ultrasound signals that are reflected back to the ultrasonic receivers. Further details describing the use of ultrasound signals for detecting changes in the contents, including changes in the configuration, or the addition or deletion of contents within a shipping container are discussed below.
Two exemplary experimental setups to evaluate this approach were constructed, including one with wall mounted corner reflectors, and one with ceiling mounted corner reflectors. FIG. 3 illustrates the two setups and includes identifying reference letters indicating the pertinent geometry of the container and the relationship between the ultrasonic transducers/receivers and corner reflectors mounted therein for each of these two configurations. Wall mounted corner reflectors 34, which are shown in the upper portion of FIG. 3, are generally like those shown in FIGS. 1 and 2 and serve to reflect back the ultrasound signal produced by the ultrasonic transducer, as discussed above. The wall mounted corner reflectors were mounted about 11 inches from the ceiling in this empirical test to minimize the chance that cargo would block the reflections. The ultrasonic transducer/receiver was placed on a door cross beam and angled towards the closest corner reflector 36, so that as the door was opened, the corner reflectors would remain in the beam cone produced by the ultrasonic transducer.
The ceiling mounted corner reflectors (shown in the lower portion of this Figure) were mounted in the valleys on the ceiling corrugation, also tending to protect them from damage during loading and unloading of the contents of the shipping container. The ultrasonic transducer/receiver in this second setup was mounted near the top corner of the door and angled to face the most distant corner reflector so that the corner reflectors would remain in the beam cone as the door was opened. Due to a large lip on the top of the door opening (about 8 inches wide), the closest corner reflector was blocked as the door opened more then a few inches.
In order to understand and evaluate the performance of the door position estimation in this empirical test, it was necessary to develop a model for predicting the response. To this end, a predictive model relating the door position to the echo (reflection) distance was generated from the shipping container door diagram shown in FIG. 3. For example, in regard to the distance parameters indicated in FIG. 3, the predicted echo distance for corner reflector R2 in the wall mounted corner reflector setup configuration was estimated to be:
d
R
2
=√{square root over ((b+c cos θ)2+c2 sin2 θ)}
where, dR2 is the distance to the R2 reflector, θ is the angle of door 26, c is the distance from hinge 30 to the ultrasonic transducer/receiver, and b is the distance from corner reflector R2 to the door.
In the ceiling mounted corner reflector case, the distance to reflector R3 is given by:
d
R
3
=√{square root over (hR32+(e+d cos θ)2+(d−d sin θ)2 )}{square root over (hR32+(e+d cos θ)2+(d−d sin θ)2 )}
where, hR3 is the height difference between the reflector and the door mounted transducer, e is the distance between corner reflector R3 and the closed door, and d is the distance between the door hinge and the ultrasonic transducer/receiver.
Since the size of the door opening is a more intuitive metric of door position, an estimate relating it to the door angle was approximated by:
θ≈cos−1(dOpen/wDoor)
where, dOpen is the distance between the two edges of the doors, with one in a closed position, wDoor is the width of the door, and θ is the angle of the door relative to its closed position. With this approximation, the distance to corner reflector R2 can be simplified to:
dR2≈√{square root over (2bcdOpen/wDoor+b2+c2 )}
The following table illustrates exemplary measured distances for the parameters used in connection with the illustration of FIG. 3.
|
Parameter
[in]
|
|
|
a
24
|
b
14
|
c
11
|
d
45
|
e
6
|
f
14
|
g
24
|
|
While other types of reflectors can be used inside a shipping container to reflect ultrasound signals, when the ultrasonic transducer that emits an ultrasound signal is located immediately next to the ultrasonic receiver that is intended to receive the ultrasound signal back after it is reflected, it will generally be desirable to use a corner reflector. FIG. 4 illustrates an exemplary corner reflector 50. Corner reflector 50 includes three orthogonally oriented and conjoined surfaces 52, 54, and 56. A simple example shown in this Figure illustrates how an incoming ultrasound signal 58 that is incident on surface 52 is reflected along a path 60 toward the underside of surface 54, and reflected from the underside surface along a path 62, before again being reflected from surface 56 along a path 64. Path 64 is generally parallel to, but directed in the opposite direction from that of ultrasound signal 58. Because each reflection of the ultrasound signal is at an angle to the surface equal to the angle of incidence of the ultrasound signal impinging on the surface, the net result is that the reflected ultrasound signal will always be generally parallel to and traveling in the opposite direction from the incoming or incident ultrasound signal, regardless of whether the incoming signal is reflected off two or three of the surfaces of corner reflector 50.
FIGS. 5A and 5B illustrate the recorded responses for different door openings distances for the first case illustrated in FIG. 3, where a door mounted, wall facing ultrasonic transducer is used in connection with two wall mounted corner reflectors. In FIG. 5A, recorded responses 70 illustrate the reflected pulse packets received as reflections from the two wall-mounted corner reflectors as the door is open by different degrees ranging between 6.3 cm and 16.5 cm. Similarly, in FIG. 5B, recorded responses 74 show the reflected pulse packets for door openings in different amounts ranging between 6.3 cm and 97.8 cm. Using the relative distances indicated for the start of each distinctive pulse packet, it is possible to compute the distance that the door was opened for each recorded response, using the equations set forth above.
FIGS. 6A and 6B similarly respectively illustrate recorded responses 76 and 78, showing the pulse packets received at different door opening distances in connection with the door mounted, ceiling facing ultrasonic transducers, and using three ceiling mounted corner reflectors. Recorded responses 76 illustrate pulse packets at door opening extents ranging from 6.3 cm through 16.5 cm, while recorded responses 78 indicate pulse packets for door opening extents ranging between 6.3 cm and 97.8 cm.
Using Ultrasound Signals to Detect Changes in the Contents of Shipping Container
While potential terrorist threats can be detected simply by detecting that the door of a shipping container has been opened, it is desirable to also determine if the contents of a shipping container have been changed in some way. Changes that might be detected with ultrasound signals include the addition of an item to the contents, or the removal of an item, or a change in the configuration of the contents. If the door of a shipping container has been opened while it is in transit from its originating port, and if the contents of the shipping container have changed in some manner, then there is a much higher justification for investigating the shipping container before it is allowed to enter this country and offloaded from the ship in which it enters a port. The combined indications of an opened door and a change in the contents of a shipping container are clearly of greater concern than the determination alone that the door was opened, or only determining that the contents have changed in some manner. It is possible for the configuration of contents to shift due to the ship being exposed to rough weather, or due to improper handling, but not as a result of a potential terrorist threat. However, if the door was opened and the contents appear to have changed at about that point in time, there is a very strong justification to investigate the shipping container more thoroughly.
FIGS. 7, 8, and 9 illustrate different forms of the ultrasound signal that is received by an ultrasonic receiver after ultrasound signals have propagated through a relatively complex environment inside a shipping container and have interacted with one or more objects included in the contents. In FIG. 7, an exemplary raw output signal 80 from an ultrasonic receiver is illustrated. This raw output signal can be averaged to produce an averaged signal 84, which is shown in FIG. 8. Finally, the averaged signal can be further processed using a match filter, resulting in a match filtered signal 86, as shown in FIG. 9.
Clearly, either the raw, the averaged, or the match filtered signals can be used as a baseline signal pattern that is detected and saved immediately after the shipping container has been loaded with its contents and the doors closed. Subsequently, any change in the signal pattern that is detected, by comparison with the baseline signal pattern, can be used to detect that the contents of the shipping container have been changed, either by adding one or more items, removing one or more items, or changing the configuration of the items included therein. If such a change is detected shortly after an opening of the door of the shipping container has been detected, the combined evidence can provide a strong justification for further investigation.
To better illustrate the concept of how ultrasound signals can be employed to detect changes in the content of a shipping container, FIG. 10 shows a schematic diagram of a portion of shipping container 22 where there is no carton interacting with ultrasound signals 98 that are transmitted from an ultrasonic transducer 90. These ultrasound signals are reflected by surfaces 94 and 96 of the shipping container, producing reflected ultrasound signals 100 that are received by an ultrasonic receiver 92. In addition, reflected ultrasound signals 102 in the shipping container are not received because their return path does not reach the ultrasound receiver. A baseline signal pattern 108 results from the return ultrasound signals that are detected by the ultrasound receiver, which correspond to the energy pulses 104 and 106 shown to the side of the FIGURE.
In FIG. 11, interior 22 of the shipping container now includes a box 110, which interacts with ultrasound signals 98, for example, producing reflected ultrasound signals 100′ and 112, and thus, producing a new or current signal pattern 108′ that clearly differs from the baseline signal pattern 108 that was stored when box 110 was not interacting with the ultrasound signals. The clear difference in the current signal pattern is the result of the blocked reflection shown at the right of the FIGURE, since energy pulse 104 is no longer detected. By comparing the current signal pattern with the baseline signal pattern and detecting that a significant change (e.g., greater than a predefined minimum) has occurred, it is possible to detect that a change in the contents of the shipping container has occurred. The time at which this change in the contents or configuration occurred can also be determined and included with the data that are stored and can subsequently be accessed. Optionally, when a change in the contents is detected, an audible, visual, radio signal transmission, and/or some other form of alert can be provided. Thus, if only a few individuals aboard a ship were involved in opening a shipping container to insert a terrorist weapon, the alarm being activated would alert the other persons on the ship to investigate the cause of the alarm.
As discussed above, it is possible to use the same ultrasonic transducers and receivers to both detect the opening of a door of a shipping container, and to detect a change to the contents of the shipping container. However, a separate ultrasound system can be employed just to detect changes in the contents of the shipping container, independent of the door being opened. FIG. 12 illustrates an exemplary embodiment of such an ultrasound system. In this exemplary embodiment, two ultrasonic transducers/receivers 34 are disposed at spaced apart location near the ceiling, along one side (i.e., a first side) of the shipping container, one transducer/receiver 34 is disposed near the ceiling along the opposite side (a second side) to provide ultrasound path coverage between that provided by the other two ultrasonic transducers/receivers on the first side, and two additional ultrasonic transducers/receivers 34 are disposed at spaced apart locations near the ceiling on the end wall, i.e., on the wall opposite from where doors 26 and 28 are disposed. The ultrasound signals produced by the ultrasonic transducers are directed through interior 22 of the shipping container toward corner reflectors 36 disposed at spaced apart locations near the ceiling on the side walls of the shipping container. All of ultrasonic transducers/receivers 34 and corner reflectors 36 are mounted within valleys 38 of the corrugated sheet metal comprising the walls and end of the shipping container, to provide protection against damage that might occur when the contents of the shipping container are loaded or unloaded. The ultrasound signals produced by the ultrasonic transducers thus cover virtually the entire area of the shipping container and are reflected back to the corresponding ultrasonic receiver by the corner reflector as shown, unless a container or other object within the path interferes with the ultrasound signal.
Most shipping containers are packed with cartons or other objects very efficiently, leaving only a small region at the top that may be free of the contents. It is this region that can readily be monitored by the arrangement shown in FIG. 12, since the ultrasound signals are propagating within interior 22 of the shipping container near the ceiling. The actual depth covered below the ceiling can be selectively determined by the elevations at which the ultrasonic transducers/receivers and corner reflectors are mounted.
It should be understood that the numbers and locations of ultrasonic transducers/receivers 34 and corner reflectors 36 that are employed in a shipping container can be very different than the exemplary embodiment illustrated in FIG. 12, and the configuration of this system is only intended to be one example of many different configurations for such a system. For example, it may be desirable to monitor the lower portion of a shipping container that is supposed to be empty, to detect when something has been added to the shipping container. This function can readily be achieved by providing one or more additional ultrasonic transducers/receivers and corner reflectors at a lower elevation in the shipping container or by angling the paths of the ultrasound signals so that they cover the lower portions of the shipping container.
Hardware Components of Exemplary Ultrasound System
FIG. 13 illustrates an exemplary functional block diagram of at least a portion of an ultrasound system that can be used to detect a door of a shipping container 120 being opened and/or to detect a change in the contents of the shipping container. A control signal 122 is provided by a logic unit 136 to an ultrasonic transducer 124 each time that an ultrasound pulse signal 126 is to be transmitted within the interior of the shipping container. Alternatively, the control signal may not be required if the ultrasonic transducer is instead designed to produce ultrasound pulses at a set or selectable predefined interval. As a further alternative, the control signal might only initiate the start of consecutive ultrasound pulses that continue until commanded to stop by another control signal.
Ultrasound signal 126 is reflected either by a surface, an object, or a reflector (e.g., a corner reflector) 128, producing a reflected ultrasound signal 130 that is propagated back to an ultrasonic receiver 132. In response to receiving the reflected ultrasound signal, ultrasonic receiver 132 produces a corresponding output signal 134, which is input to logic unit 136 for processing. A temperature sensor 150 produces a temperature signal 152 that is also input to the logic unit, so that the output signal from the ultrasonic receiver can be compensated for the temperature inside the shipping container, since this temperature affects the speed of sound in air, which will thus affect the distance or range determined for a reflected ultrasound signal. The logic unit can be any type of a variety of different logic devices, including for example, a single or multi-chip microcomputer integrated circuit, an applications specific integrated circuit (ASIC), a programmable logic array, etc. If the logic unit processes the output signal and determines that the output signal represents an event of interest, such as an opening of the door of the shipping container, or a change of the ultrasound pattern from the baseline signal pattern indicating a change in the contents of the shipping container, it records an event 138 as stored data 140 and optionally, also records the time/date of the event as part of the stored data (assuming that the logic unit has the capability to determine the time/date and is caused to do so). As a further option, detecting such an event of interest can cause an alarm signal 142, which cause an alarm 144 such as an audible alarm, a visual alarm (blinking light), a radio transmission, and/or other alert signal to be produced, to indicate that the event has been detected. The stored data can be recorded in non-volatile memory, or other suitable memory storage.
A combined device that includes an ultrasonic transducer and receiver in one integral package is available and is known as the X-Coupler™. This device is available for just a few dollars each. Other similar devices are available for even less cost. It should also be understood that the ultrasonic transducer that emits ultrasound can be disposed at a different location from the ultrasonic receiver that receives the ultrasound signal after it has been reflected from a reflector, a surface, or an object.
At an appropriate time (typically before the shipping container is offloaded from the ship in which it is transported), a user can query the stored data over a line 146, to access any data that might be stored indicating that an event of interest was detected. This data can indicate whether, and when, and to what extent a door of the shipping container was opened, and can indicate that a change in the contents of the shipping container was detected and the date/time it was detected. A user can access the stored data either wirelessly, e.g., over a Bluetooth or other type of radio frequency data connection, or by directly electronically connecting to the stored data and downloading any such data that are included therein.
Exemplary Logical Steps for Implementing Procedures
FIG. 14 illustrates exemplary logical steps 160 for carrying out the process of detecting whether a door of a shipping container has been opened. After the process starts, for example, after the door is closed at the time the shipping container is sealed for shipment, a step 162 commands the ultrasonic transducer to transmit (or at least initiate transmission of) ultrasound pulses at a desired repetition rate, e.g., at a repetition rate greater than about 20 pulses per minute so that there is less than three seconds between successive ultrasound pulses. A step 164 provides for receiving the output signal from an ultrasonic receiver that has received a reflected ultrasound pulse within the shipping container. The output signal is processed, e.g., by compensating it for the temperature inside the shipping container, averaging the output signal, and applying a match filter to the averaged signal.
For an initial output signal detected shortly after the shipping container was sealed at its point of origin, a step 166 provides for determining a baseline range for the door in its closed state, or this baseline data can be determined using a minimum range between the door and the reflector. A decision step 168 subsequently determines if the difference between current range or distance to the door (i.e., relative to the distance between the ultrasonic transducer and the reflector that reflects the ultrasound signal) and the baseline range is greater than a predefined limit. Baseline ranges can be determined for each of a plurality of different reflectors, and the differences between the current range and the corresponding baseline range can then be determined for each reflector to reach a determination in decision step 168. If the difference is greater than the predefined limit, which is selected to provide some margin for acceptable variations in the measurement, an affirmative response results in a step 170 detecting and storing the door open event data, as well as the date/time and the extent of door opening, if possible and desired. An optional step 172 can also be provided to initiate an alarm signal, which can comprise any desired form of a human perceptible alert signal. If the result of decision step 168 is negative or following optional alarm initiation step 172, the logic loops back to step 162.
A similar flowchart 180 showing exemplary logical steps for detecting a change in the contents of a shipping container is illustrated in FIG. 15. After the process starts, e.g., following the sealing of the shipping container at its port of origin, a step 182 is carried out to initiate the transmission of ultrasound pulses, just as in step 162 of FIG. 14. Similarly, a step 184 provides for receiving and processing the output signal from an ultrasonic receiver to detect a current signal pattern, generally as in step 164 from FIG. 14. At some time shortly after the shipping container was sealed, a step 186 determines a baseline signal pattern for the initial content configuration of the shipping container and records this baseline signal pattern in a non-volatile memory. Thereafter, a decision step 188 determines if any subsequent new current signal pattern has changed from the baseline signal pattern by more than a predefined limit and if so, a step 190 stores data to record the event, including the date/time, if possible and desired. An optional alarm signal is produced in a step 192, generally as discussed above. After step 192, or if the result of decision step 188 is negative, the logic loops back to step 182. It will be understood that either the logic of FIG. 14, or the logic of FIG. 15 can be implemented, or both.
Detecting Changes in Fluid Level
FIG. 16 illustrates yet another way in which ultrasound signals can be employed to detect changes in the contents of a shipping container. In this example, a shipping container 200 comprising a fluid housing 202 is shown holding a fluid 204 (likely a liquid—but not necessarily) within the fluid housing. An ultrasonic transducer/receiver 206 is mounted in the interior at one end of the fluid housing, while a reflector 208 (e.g., a corner reflector) is mounted in the interior of the housing at the opposite end. A current level 210 of the fluid serves to reflect an ultrasound signal 214 that is transmitted by the ultrasonic transducer toward reflector 208, which reflects the ultrasound signal back from the surface of the fluid toward the ultrasonic receiver, as a return ultrasound signal 216. Furthermore, a different baseline fluid level 212 may previously have been detected when the shipping container was originally filled with a fluid. When the baseline fluid level was determined, an ultrasound signal 214′ was reflected from the surface of the fluid toward the reflector and then received after being reflected by the reflector and then from the surface of the liquid at level 212 to form a return signal 216′.
If a substantial change in depth, AD, is subsequently detected between the baseline fluid level and the current fluid level, then the detected change can be noted and recorded as event data, along with a date/time of the event, if possible and desired. The change in the depth of the fluid in the shipping container might be an indication that a relatively innocuous fluid originally pumped into the shipping container has been removed and replaced with a dangerous fluid that might be used in a terrorist attack. For example, a biological or chemical threat might have been loaded into the shipping container as a fluid to subsequently be dispersed in high population areas once the shipping container enters the U.S. at a port of call and is off loaded from a ship. By detecting the change in depth, authorities can be alerted to investigate the contents of the shipping container before the threat can be deployed in this country.
The level of fluids other than a liquid (such as gases) can also be detected by ultrasound. For example, if the fluid is relatively dense compared to another fluid above it, the interface between a dense fluid and the overlying layer of air or other type of lower density gas can reflect ultrasound so that the depth of a gaseous fluid and changes in the depth can be detected with the ultrasound signal, as generally shown in FIG. 16.
Although the concepts disclosed herein have been described in connection with the preferred form of practicing them and modifications thereto, those of ordinary skill in the art will understand that many other modifications can be made thereto within the scope of the claims that follow. Accordingly, it is not intended that the scope of these concepts in any way be limited by the above description, but instead be determined entirely by reference to the claims that follow.
Patent Application
20080047350
