Patent Publication Number: US-2006000276-A1

Title: Method of measuring amount of substances

Description:
TECHNICAL FIELD  
      The present invention relates generally to techniques to determine amounts of substances in containers.  
     SUMMARY  
      In one aspect, a method for determining a volume of a substance in a container includes: generating an excitation signal that creates an acoustic signal in the container, receiving the acoustic signal, and determining a volume of a substance in the container based at least in part on a signature of the acoustic signal.  
      In another aspect, a system for determining a volume of a substance in a container includes at least one excitation generator, at least one acoustic receiver, and an analytical instrument. The excitation generator is operable to generate an excitation signal that creates an acoustic signal in the container. The acoustic receiver is operable to receive the acoustic signal. The analytical instrument is operable to determine a volume of a substance in the container based at least in part on a signature of the acoustic signal.  
      In another aspect, an apparatus includes a container, an excitation generator, an acoustic receiver, and an analytical instrument. The excitation generator is operably coupled with the container. The acoustic receiver is operably coupled with the container and is operable to receive an acoustic signal. The analytical instrument is operably coupled with the acoustic receiver. The analytical instrument has a memory containing at least one signature of the acoustic signal in association with at least one corresponding volume of the substance in the container.  
      In another aspect, a differential method for determining a volume of a substance in a container includes the following steps. A first excitation signal is generated in a substance in a container. The first excitation signal creates a first acoustic signal in the container. The first acoustic signal is received, for example, with an acoustic receiver. A second excitation signal is generated either in a gas in the container or on a wall of the container. The second excitation signal creates a second acoustic signal in the container. The second acoustic signal is received, for example, with an acoustic receiver. A signature of the first acoustic signal is compared with a signature of the second acoustic signal to determine a volume of the substance in the container.  
      Implementations may include the following features. The acoustic receiver can be inside the container. The acoustic receiver can be coupled to a wall of the container. The acoustic receiver can be outside the container. The signature of the acoustic signal can include a spectrum of the acoustic signal. The signature of the acoustic signal can include one or more resonant frequencies in a spectrum of the acoustic signal.  
      In addition to the foregoing, various other method and/or system aspects are set forth and described in the text (e.g., claims and/or detailed description) and/or drawings of the present application.  
      The foregoing is a summary and thus contains, by necessity, simplifications, generalizations and omissions of detail; consequently, those skilled in the art will appreciate that the summary is illustrative only and is NOT intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined by the claims, will become apparent in the detailed description set forth herein.  
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       FIG. 1  and  FIG. 2  show a system for determining an amount of liquid in a container.  
       FIG. 3  shows a method for determining an amount of liquid in a container.  
       FIG. 4  shows a differential method for determining a volume of a substance in a container. 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  shows a system  100  for determining an amount of liquid  155  in a container  150 . Container  150  can have substantially any shape, such as solid rectangular, hollow ellipsoid sphere, or other kinds of regular shapes. Container  150  can also be irregular in shape. In one implementation, container  150  is a fuel tank. Container  150  can also include an inlet  152  or an outlet  158 . Although the term “container” is used herein for sake of clarity, those skilled in the art will appreciate that the container  150  is meant to be representative of substantially any structure that may contain some volume of a substance. The container  150  can be, for example, an open container or an enclosed container. Some examples of container  150  include fuel tanks and/or coolant tanks and/or lubricant tanks of planes, automobiles, trains, ships, submarines, or other kinds of vehicles. Other specific examples of container  150  include fluid reservoirs and/or gel reservoirs and or other material (e.g., sand) reservoirs of industrial equipment (e.g., reservoirs used in refineries, chemical plants, and/or glass plants, etc.). Other specific examples of container  150  include rooms or other building storage areas wherein materials are kept (e.g., wafer storage facilities of semiconductor manufacturing plants). The general term “system” is used herein for sake of clarity, and those skilled in the art will appreciate that system  100  is meant to be representative of substantially any type system wherein container  150  may be utilized, such as planes, automobiles, trains, ships, submarines, military conveyances (e.g., tanks and/or helicopters), industrial facilities (e.g., petro-chemical refineries, chemical plants, nano-technology plants, and/or glass plants, etc.), and/or other systems wherein container  150  may be utilized.  
      System  100  generally includes an excitation generator  110 , an acoustic receiver  120 , and an analytical instrument  130 . Excitation generator  110  can generate an excitation signal for creating an acoustic signal in container  150 . Excitation generator  110  can be an acoustic generator (e.g., a speaker, or a spark generator), an accelerometer (e.g., a piezoelectric accelerometer, an electrodynamic accelerometer, a magnetostrictive accelerometer, or a capacitive accelerometer), or substantially any of other kinds of transducers consistent with the teachings herein. The acoustic signal in container  150  generally is received by acoustic receiver  120 . The acoustic signal received by acoustic receiver  120  generally is sent to analytical instrument  130  for further signal processing. Analytical instrument  130  can use a signature of the acoustic signal to determine an amount of liquid  155  in container  150 . Although the term “liquid” is used herein for sake of clarity, those skilled in the art will appreciate that liquid  155  is meant to be representative of substantially any substance that may be enclosed within a volume of space, such as fluids, gels, particulates (e.g., sand, or grains), solids (e.g., semiconductor wafers), etc. Liquid  155  is also meant to be representative of foods, plants, people, or other living stocks.  
      In one implementation, analytical instrument  130  is operable to compare a spectrum of the received acoustic signal with a list of spectra in a spectra look up table to determine the amount of liquid in container  150 .  
      In another implementation, analytical instrument  130  is operable to find at least one resonant frequency in a spectrum of the received acoustic signal, and analytical instrument analytical instrument  130  is also operable to compare at least one resonant frequency in the spectrum of the received acoustic signal with a list of resonant frequencies in a frequency look up table to determine the amount of liquid in container  150 . As an example of how to find the resonant frequencies, analytical instrument  130  can detect a frequency having a maximum strength in the spectrum of the acoustic signal, and designate the frequency having the maximum strength as one of the resonant frequencies.  
      Some of the implementations for determining the spectrum of the received acoustic signal and the resonant frequencies in the spectrum are described in the following.  
      In one implementation, excitation generator  110  generates a pulse excitation signal for creating the acoustic signal in container  150 . Excitation generator  110  can also generate a chirp waveform signal. For determining the spectrum of the received acoustic signal or the resonant frequencies in that spectrum, analytical instrument  130  can transform the received acoustic signal into Fourier space. For example, analytical instrument  130  can digitize the acoustic signal received by the acoustic receiver and conduct a Fourier Transform on the digitized acoustic signal. Analytical instrument  130  can conduct a conventional Discrete Fourier Transform on the digitized acoustic signal or a Fast Fourier Transform on the digitized acoustic signal.  
      In another implementation, excitation generator  110  generates a substantially white noise excitation signal for creating the acoustic signal in container  150 . Analytical instrument  130  can determine the resonant frequencies of container  150  from the received acoustic signal. A substantially white noise excitation signal includes excitation signals having spectra that are almost nearly flat in a frequency domain. A substantially white noise excitation signal can also include excitation signals having spectra that are not quite flat in a frequency domain.  
      In yet another implementation, excitation generator  110  generates a single frequency excitation signal for creating the acoustic signal in container  150  and sweeps the single frequency excitation from a first frequency to a second frequency. The resonant frequencies of container  150  between the first frequency and the second frequency can be determined by analytical instrument  130  using the received acoustic signal.  
      In an implementation as shown in  FIG. 1 , excitation generator  110  can generate an excitation signal interior to container  150  directly (e.g., by injecting energy into an interior of the container with an acoustic generator). In another implementation as shown in  FIG. 2 , excitation generator  110  can generate an excitation signal in container  150  by exciting a wall of container  150 . Excitation generator  110  can include a transducer that makes contact on the outer wall of container  150  (as shown in  FIG. 2 ). Excitation generator  110  can also include a transducer that makes contact on the inner wall of container  150 . Excitation generator  110  can also include a transducer that injects energy directly into the interior of the container, where the transducer is not in contact with a wall of container  150 . While the embodiment is described with the transducer in contact with the wall or interior, one skilled in the art will recognize that the transducer may couple energy to the inner wall, outer wall, or the interior indirectly. For example, the transducer may launch an acoustic wave a short distance from the inner wall, outer wall, or interior rather than through direct contact. Similarly, the transducer may couple energy indirectly, for example, by generating an acoustic wave in a material coupled directly or indirectly to the inner wall, outer wall, or interior.  
      In an implementation as shown in  FIG. 1 , acoustic receiver  120  is positioned interior to container  150 . In other implementations, acoustic receiver  120  is positioned outside container  150 . In other implementations, acoustic receiver  120  is positioned on or proximate to a wall of container  150 .  
      Excitation generator  110  can receive an electrical signal from an electrical signal generator  112 . Electrical signal generator  112  can generate a pulse electrical signal, a chirp waveform signal, a substantially white noise electrical signal, a substantially single frequency electrical signal, or other kinds of electrical signals.  
      Analytical instrument  130  can include an amplifier to amplify signals received from acoustic receiver  120 . Analytical instrument  130  can also include an analog to digital converter for digitizing signals received from an output of the amplifier. The digitized signals can be sent to a Digital Signal Processor (DSP) for further processing. The Digital Signal Processor can perform filtering, windowing, Fourier transform, comparison, or other kinds of operations on the digitized signals.  
      Analytical instrument  130  can include a memory to store a signature of the acoustic signal in association with a corresponding volume of liquid  155  in container  150 . In some implementations, a signature of an acoustic signal in association with a corresponding volume includes a frequency (e.g., 500 Hz) paired with a corresponding volume of a substance in container  150  (e.g., 30 cubic centimeters). The signature of the acoustic signal can include a spectrum of the acoustic signal, a resonant frequency in a spectrum of the acoustic signal, a collection of multiple resonant frequencies in a spectrum of the acoustic signal, or other detectable characteristics in the acoustic signal.  
      In some implementations, a display device can be used to display the volume of liquid  155  in container  150 . One example of such a display device would include a fuel gauge of a vehicle. Other implementations may include displaying information graphical or textually at monitoring facility or on a portable device.  
      In an implementation as shown in  FIG. 1 , the volume of liquid  155  in container  150  may be determined with devices including excitation generator  110 , acoustic receiver  120 , and analytical instrument  130 . In other implementations, other kinds of substances (e.g., gels, sands or other kinds of sand like materials) can be determined with similar techniques.  
      As specific examples, container  150  can be a fuel tank in a plane, an automobile, a train, a ship, a submarine, or other kind of vehicles.  
      Analytical instrument  130  can be implemented as a stand alone device. Analytical instrument  130  can also be implemented to include software and/or firmware and/or hardware on another computer system. For example, when container  150  is a fuel tank on an automobile and the automobile has an on-board computer, part of analytical instrument  130  can be implemented as software or firmware on the on-board computer.  
      In an implementation as shown in  FIG. 1 , excitation generator  110  is used to generate the excitation signal, and acoustic receiver  120  is used for receiving the acoustic signal induced by the excitation signal. In another implementation, excitation generator  110  and acoustic receiver  120  can be implemented as a single device (e.g., the same device can both excite and receive). In still another implementation, multiple acoustic receivers can be used for receiving the acoustic signal induced by the excitation signal. For example, in one implementation, multiple acoustic receivers are used to reject common mode background noise.  
       FIG. 3  generally shows a method  300  for determining a volume of a substance in a container. Method  300  includes steps  310 ,  320 , and  330 .  
      Step  310  illustrates generating an excitation signal that creates an acoustic signal in a container. In one implementation of step  310 , such as shown and/or described in relation to  FIG. 1 , the excitation signal is generated with excitation generator  110 . Excitation generator  110  can generate a pulse excitation signal, a substantially white noise excitation signal, a substantially single frequency excitation signal, or other kinds of excitation signals. Excitation generator  110  can generate an excitation signal in a gas in container  150 , in liquid  155  in container  150 , or on a wall of container  150 . When a tube is connected to container  150 , excitation generator  110  can also inject excitation energy into the tube connected to container  150 .  
      Step  320  shows receiving the acoustic signal. In some implementations of step  320 , such as shown and/or described in relation to  FIG. 1 , the acoustic signal is received with an acoustic receiver  120 . In some implementations of step  330 , a transducer of acoustic receiver  120  converts the acoustic signal to an electrical representation of the acoustic signal. In some implementations of step  330 , an amplifier of acoustic receiver  120  amplifies the electrical representation of the acoustic signal to an electrical signal. In some implementations of step  330 , an analog-to-digital converter of acoustic receiver  120  digitizes the electrical representation of the acoustic signal and delivers the digitized signal to analytical instrument  130 .  
      Step  330  includes determining a volume of a substance in the container based at least in part on a signature of the acoustic signal. In one implementation, the amount of the substance in the container can be determined by comparing a spectrum of the received acoustic signal with one or more spectra in a spectra look up table. In another implementation, at least one resonant frequency in a spectrum of the received acoustic signal is determined, and amount of the substance in the container can be determined by comparing at least one resonant frequency in the spectrum of the received acoustic signal with one or more resonant frequencies in a frequency look up table. A resonant frequency in a spectrum of the received acoustic signal can be determined by detecting a frequency that has a maximum strength in the spectrum of the acoustic signal.  
      In some implementations of step  330 , analytical instrument  130  receives a digitized version of an acoustic signal from the analog-to-digital converter of analytical instrument  130 . In some implementations of step  330 , upon receipt of the digitized version of the acoustic signal, logic of analytical instrument  130  executes a Fourier analysis to determine what frequency of the digitized signal has maximum strength (e.g., via program executing a Fast Fourier Transform on a processor of analytical instrument  130 ). In some implementations of step  330 , logic of analytical instrument  130  designates the determined frequency of maximum strength as the resonant frequency. In some implementations of step  330 , logic of analytical instrument  130  then compares the determined resonant frequency against a look up table that contains a list of frequencies in association with volumes of substance in container  150  to select a frequency of the table deemed most proximate to the determined resonant frequency (e.g., via comparison hardware and/or firmware). In some implementations of step  330 , logic of analytical instrument  130  designates the volume associated with the selected frequency of the table (e.g., that most proximate to the resonant frequency) to be the volume of the substance in container  150 .  
      Method  300  can also include additional steps. For example, method  300  can include recording a background acoustic signal. In one implementation, the recorded background acoustic signal is first subtracted from the acoustic signal received by the acoustic receiver to obtain a compensated acoustic signal. Then, the compensated acoustic signal is further processed to determine some signatures that can be used for determining a volume of a substance in a container.  
       FIG. 4  generally shows a differential method  400  for determining a volume of a substance in a container. Method  400  includes steps  410 ,  420 ,  430 ,  440 , and  450 .  
      In step  410 , a first excitation signal is generated in a substance in a container. The first excitation signal creates a first acoustic signal in the container. In step  420 , the first acoustic signal is received, for example, with an acoustic receiver. In step  430 , a second excitation signal is generated either in a gas in the container or on a wall of the container. The second excitation signal creates a second acoustic signal in the container. In step  440 , the second acoustic signal is received, for example, with an acoustic receiver.  
      In step  450 , a signature of the first acoustic signal is compared with a signature of the second acoustic signal to determine a volume of the substance in the container. The signature of the first acoustic signal can be a spectrum of the first acoustic signal, or one or more resonant frequencies in a spectrum of the first acoustic signal. Similarly, the signature of the second acoustic signal can be a spectrum of the second acoustic signal, or one or more resonant frequencies in a spectrum of the second acoustic signal.  
      In the above, methods and systems for determining a volume of a substance in a container are disclosed. The methods and systems disclosed herein can be implemented or modified to have one or more of the following applications. In one application, methods and systems disclosed herein can be used to determine how much diesel fuel is stored in a tank car, for example, under the condition that the diesel fuel may exhibit foaming or gas entrainment behavior. In another application, number of persons in a room can be determined based at least in part on a resonant frequency of the room, or other signatures of an acoustic signal. In another application, methods and systems disclosed herein can be used to determine a specific condition, such as, whether a volume of a substance stored in a container is above a threshold volume. In the implementation of  FIG. 1 , a specific condition can be determined by including a conditional filter in analytical instrument  130 , and passing the acoustic signal received by acoustic receiver  120  through the conditional filter.  
      Those having skill in the art will recognize that the state of the art has progressed to the point where there is little distinction left between hardware and software implementations of aspects of systems; the use of hardware or software is generally (but not always, in that in certain contexts the choice between hardware and software can become significant) a design choice representing cost vs. efficiency tradeoffs. Those having skill in the art will appreciate that there are various vehicles by which processes and/or systems described herein can be effected (e.g., hardware, software, and/or firmware), and that the preferred vehicle will vary with the context in which the processes are deployed. For example, if an implementer determines that speed and accuracy are paramount, the implementer may opt for a hardware and/or firmware vehicle; alternatively, if flexibility is paramount, the implementer may opt for a solely software implementation; or, yet again alternatively, the implementer may opt for some combination of hardware, software, and/or firmware. Hence, there are several possible vehicles by which the processes described herein may be effected, none of which is inherently superior to the other in that any vehicle to be utilized is a choice dependent upon the context in which the vehicle will be deployed and the specific concerns (e.g., speed, flexibility, or predictability) of the implementer, any of which may vary. Those skilled in the art will recognize that optical aspects of implementations will require optically-oriented hardware, software, and or firmware.  
      The foregoing detailed description has set forth various embodiments of the devices and/or processes via the use of block diagrams, flowcharts, and examples. Insofar as such block diagrams, flowcharts, and examples contain one or more functions and/or operations, it will be understood as notorious by those within the art that each function and/or operation within such block diagrams, flowcharts, or examples can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. In one embodiment, the subject matter described herein may be implemented via Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), or other integrated formats. However, those skilled in the art will recognize that the embodiments disclosed herein, in whole or in part, can be equivalently implemented in standard integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and or firmware would be well within the skill of one of skill in the art in light of this disclosure. In addition, those skilled in the art will appreciate that the mechanisms of the subject matter subject matter described herein are capable of being distributed as a program product in a variety of forms, and that an illustrative embodiment of the subject matter subject matter described herein applies equally regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of a signal bearing media include, but are not limited to, the following: recordable type media such as floppy disks, hard disk drives, CD ROMs, digital tape, and computer memory; and transmission type media such as digital and analog communication links using TDM or IP based communication links (e.g., packet links).  
      The foregoing described aspects depict different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled”, to each other to achieve the desired functionality.  
      While particular aspects of the present subject matter described herein have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from this subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of this subject matter described herein. Furthermore, it is to be understood that the invention is solely defined by the appended claims. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense of one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense of one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together).