DETECTING OBJECTS IN SHIPPING CONTAINERS BY VIBRATION SPECTRAL ANALYSIS

• US 20100161254A1
• Filed: 07/10/2009
• Published: 06/24/2010
• Est. Priority Date: 07/11/2008
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: McVittie, Patrick, Atlas, Les
• Granted Patent: US 8,571,829 B2
• Time in Patent Office: Days
• US Class Current: 702/56
• CPC Class Codes: B66C 13/16 Applications of indicating, registering, or weighing devices in crane hooks B66C1/40; in safety gear B66C15/00; weighing-apparatus G01G; remote indicating in general G08
• CPC Class Codes: G01H 1/00 Measuring characteristics of vibrations in solids by using direct conduction to the detector G01H9/00, G01H11/00 take precedence
• CPC Class Codes: G01H 13/00 Measuring resonant frequency
• CPC Class Codes: G01V 1/001 Acoustic presence detection

Abstract

Objects in a cargo shipping container are detected by measuring vibration resonant frequency peaks of the container. The mass of an object on the floor of the container effects the vibration resonance of the container, enabling the object to be detected. A vibration source and a plurality of accelerometers are either attached to the steel structure of the container, or are disposed on a supporting structure, such as a cargo crane or lift, so that they contact the container. The vibration source causes the container to vibrate, and the accelerometers detect the vibration resonance of the container. A mismatch between a cargo manifest and an observed cargo, or detection of an object having relatively high mass, e.g., due to lead shielding, can justify a manual inspection. The process uses synchronous processing to achieve the sensitivity needed, is unobtrusive, and does not slow the flow of cargo through a facility.

Claims

1. A method for using a vibration analysis to detect an object within a freight shipping container, based on a mass of the object, comprising the steps of:

(a) while the container is being supported, using a vibration source for exciting the container to vibrate;

(b) sensing resonant vibrations of the container in response to the excitation of the container by the vibration source, at a plurality of spaced-apart locations that are coupled with the container; and

(c) using a computing device, analyzing the resonant vibrations of the container that were sensed, to detect an effect caused by any object disposed within the container, wherein any such object alters a resonant vibration response of the container as a function of its mass, so that the object is detected by its effect on the resonant vibration response of the container.

2. The method of claim 1, further comprising the steps of supporting the container with a container handling mechanism;

and deploying a plurality of vibration sensors at the plurality of spaced-apart locations to sense the resonant vibration of the container, wherein the vibration source and the plurality of vibration sensors are either supported by the container handling mechanism so that they contact the container, or are coupled to the container, while the container is being supported by the container handling mechanism.

3. The method of claim 2, further comprising the step of empirically determining the plurality of spaced-apart locations on a class of containers for monitoring the resonant vibration response of a container that is a member of the class of containers, by determining maximum sensitivity positions on the container where maximum differences are detected in the resonant vibration response of the container, for a comparison of when the container is empty and when loaded with a distributed mass.

4. The method of claim 3, further comprising the step of repositioning the plurality of vibration sensors as required to sense vibration at least at a subset of the maximum sensitivity positions determined for a specific class of the container that is currently being supported by the container handling mechanism and which is different than a class of container previously lifted by the container handling mechanism.

5. The method of claim 3, further comprising the step of determining locations for coupling the plurality of vibration sensors to the container as a function of the maximum sensitivity positions for all classes of containers that pass through a facility, so that the locations are generally optimized for the plurality of vibration sensors on the container handling mechanism when sensing the resonant vibrations of a container being handled by the container handling mechanism, regardless of the class of containers of which the container is a member.

6. The method of claim 1, further comprising the step of enabling a comparison of a cargo manifest that indicates contents expected to be within the container, with one or more objects detected in the container, to determine whether the one or more objects detected were expected to be within the container.

7. The method of claim 6, further comprising the step of enabling a comparison of the cargo manifest with a distribution of objects detected within the container, to determine if the distribution of the objects is consistent with the cargo manifest for the container.

8. The method of claim 1, further comprising the step of comparing a position where an increased level of radiation was detected within a container to a position where an object having a relatively high mass density was detected, to evaluate whether said object may include a radioactive material and high mass density radiation shielding.

9. The method of claim 1, further comprising the step of modeling an interaction of the container, one or more objects included in the container, and the plurality of vibration sensors, to create a vibration model used for characterizing contents of the container, as a function of a mass of the contents.

10. The method of claim 1, further comprising the step of using the resonant vibrations of the container that are sensed at the plurality of spaced-apart locations for localizing a mass distribution of objects comprising a cargo disposed within the container.

11. A memory medium on which a plurality of machine readable and executable software instructions are stored, wherein execution of the machine readable and executable instructions by a computing device enables detection of an object within a freight shipping container that is being supported by a container handling mechanism, as a function of the mass of the object, by carrying out an automated analysis of resonant vibrations of the container that are sensed at a plurality of spaced-apart locations on the container, wherein a presence of the object in the container affects the resonant frequency of the container compared to the container when said object is not disposed in the container, enabling the object to be detected.

12. A system for using vibration analysis to detect an object within a freight shipping container, based on a mass of the object, comprising:

(a) a plurality of vibration sensors that are positioned to couple with the container at a plurality of spaced-apart locations;

(b) a vibration source that is configured to be coupled to the container; and

(c) a computing device that is coupled to the vibration source and to the plurality of vibration sensors, the computing device including;

(i) a memory in which machine readable and executable software instructions are stored; and

(ii) a processor that is coupled to the memory, the processor executing the software instructions to carry out a plurality of functions, including;

(A) controlling the vibration source to excite the container to vibrate;

(B) receiving vibration sensor output signals from the plurality of vibration sensors;

(C) analyzing the vibration sensor output signals to evaluate resonant vibrations of the container and to detect an object disposed in the container as a function of a mass of the object, based upon an effect of the object on the resonant vibrations of the container; and

(D) providing an indication of an object detected in the container.

13. The system of claim 12, further comprising a container handling mechanism that is configured to lift and support a container, wherein the vibration source and the plurality of vibration sensors are automatically coupled with the container at the plurality of spaced-apart locations, when the container is being lifted by the container handling mechanism.

14. The system of claim 13, wherein the plurality of spaced-apart locations on each of a plurality of different classes of containers is empirically determined and corresponds to at least a subset of maximum sensitivity positions where a difference between a resonant vibration response of the container when empty and when loaded with a uniformly distributed mass, is a peak, and wherein the software instructions cause the container handling mechanism to deploy the plurality of vibration sensors at the plurality of spaced-apart locations corresponding to at least the subset of maximum sensitivity positions determined for the class of which the container currently being lifted is a member.

15. The system of claim 14, wherein the plurality of vibration sensors are repositionable to new positions as required to couple with the container at least at the subset of the maximum sensitivity positions determined for a different class of container, when lifting a container that is a member of the different class of container than was previously lifted by the container handling mechanism.

16. The system of claim 14, wherein the plurality of vibration sensors are disposed on the container handling mechanism at positions determined as a function of the maximum sensitivity locations for classes of containers passing through a facility, so that the positions for the plurality of vibration sensors on the container handling mechanism are generally optimized for sensing the resonant vibrations of any container being handled by the container handling mechanism.

17. The system of claim 12, wherein the software instructions further enable a comparison of a cargo manifest that indicates one or more objects expected to be disposed within the container, with one or more objects detected in the container, to determine whether there is a mismatch.

18. The system of claim 17, wherein the software instructions further cause the processor to enable a comparison of the cargo manifest with a distribution of objects detected within the container, to determine if the distribution of the objects detected is consistent with the cargo manifest for the container.

19. The system of claim 12, wherein the software instructions further cause the processor to respond to an indication that a position where an increased level of radiation was detected within a container corresponds to a position where an object having a relatively high mass density was detected, by evaluating whether said object may include a radioactive material and radiation shielding for the radioactive material.

20. The system of claim 12, wherein the software instructions further cause the processor to create a model of an interaction of the container, one or more objects included in the container, and the plurality of vibration sensors, for use in characterizing contents of the container, as a function of a mass of each of the one or more objects comprising the contents.

21. The system of claim 12, wherein the software instructions further cause the processor to use the resonant vibrations of the container that are sensed by the vibration sensors at the plurality of spaced-apart locations to be used for localizing a mass distribution of one or more objects comprising the cargo that are included within the container.

22. A method for using a vibration analysis to determine a vibration signature of a freight shipping container, comprising the steps of:

(a) while the container is being supported, using a vibration source for exciting the container to vibrate;

(b) sensing resonant vibrations of the container in response to the excitation of the container by the vibration source, at a plurality of spaced-apart locations that are coupled with the container; and

(c) using a computing device for determining a vibration signature for the container based upon the resonant vibrations of the container that were sensed.

23. The method of claim 22, further comprising the step of using the computing device for comparing the vibration signature determined for the container with reference vibration signature data determined for a similar empty container, to determine at least one of a plurality of conditions of the container, including:

(a) that the container is empty;

(b) that the container contains homogeneous objects;

(c) that the container contains heterogeneous objects; and

(d) a distribution of one or more objects within the container.

24. The method of claim 23, wherein the reference vibration signature data is part of a database of reference vibration signature data, further comprising the step of compiling the database of reference vibration signature data for a plurality of different types of containers, by measuring a reference vibration signature for each of the plurality of different types of containers while said containers are empty.

25. The method of claim 22, further comprising the step of using the computing device for comparing the vibration signature determined for the container with historical vibration signature data previously collected for a plurality of similar containers and contents thereof, to determine a match to the historical vibration signature data for one or more of the similar containers by the vibration signature data for the container, to determine possible contents of the container, wherein the possible contents correspond to contents of the one or more similar containers.

26. A system for using vibration analysis to determine a vibration signature of a freight shipping container, comprising:

(a) a plurality of vibration sensors that are positioned to couple with the container at a plurality of spaced-apart locations;

(b) a vibration source that is configured to be coupled to the container; and

(c) a computing device that is coupled to the vibration source and to the plurality of vibration sensors, the computing device including;

(i) a memory in which machine readable and executable software instructions are stored; and

(ii) a processor that is coupled to the memory, the processor executing the software instructions to carry out a plurality of functions, including;

(A) controlling the vibration source to excite the container to vibrate;

(B) receiving vibration sensor output signals from the plurality of vibration sensors; and

(C) analyzing the vibration sensor output signals to determine a vibration signature for the container.

27. The system of claim 26, wherein the software instructions further cause the processor to compare the vibration signature determined for the container with reference vibration signature data determined for a similar empty container, to determine at least one of a plurality of conditions of the container, including:

(a) that the container is empty;

(b) that the container contains homogeneous objects;

(c) that the container contains heterogeneous objects; and

(d) a distribution of one or more objects within the container.

28. The system of claim 27, wherein the reference vibration signature data is part of a database of reference vibration signature data that is accessible by the processor, the database of reference vibration signature data having been compiled for a plurality of different types of containers, by measuring a reference vibration signature for each of the plurality of different types of containers while said containers are empty.

29. The system of claim 26, wherein the software instructions further cause the processor to compare the vibration signature determined for the container with historical vibration signature data previously collected for a plurality of similar containers and contents thereof, to determine a match to the historical vibration signature data for one or more of the similar containers by the vibration signature data for the container, to determine possible contents of the container, wherein the possible contents correspond to contents of the one or more similar containers.