Abstract:
A system for locating impacts comprises at least one array of a plurality of carbon nanotubes, each carbon nanotube operable to emit electrical activity when compressed. The system also comprises at least one sensor coupled to the at least one array configured to detect emitted electrical activity from the plurality of carbon nanotubes. Furthermore, a computer is configured to determine the location of an impact on the at least one array in response to the detected emitted electrical activity from the plurality of carbon nanotubes.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates generally to locator systems and more particularly to a passive hit locator system. 
       BACKGROUND 
       [0002]    In combat situations, it may be advantageous to know the location of damage from projectiles on equipment. Such functionality would give insight to the personnel being fired upon in that they may be able to determine from which direction the fire was originating as well as what equipment may have been damaged by the projectiles. Similar functionality may be built in to body armor which may increase the probability of saving a life by providing instant wound information. 
         [0003]    One solution for providing this functionality uses an active sensor system to detect the hits. A powered circuit is connected to the equipment, and when a hit occurs, parts of the circuit are broken. Detecting the location of the broken part of the circuit indicates where a hit took place. However, this requires that the circuit be continually powered. This leads to increased cost and complexity as batteries may have to be integrated into the system as well. The increased weight is also problematic, especially in body armor applications. 
       SUMMARY 
       [0004]    According to one embodiment, a system for locating impacts includes at least one array of a plurality of carbon nanotubes. Each carbon nanotube is operable to emit electrical activity when compressed. The system also includes at least one sensor coupled to the at least one array that is configured to detect emitted electrical activity from the plurality of carbon nanotubes. A computer is configured to determine the location of an impact on the at least one array in response to the detected emitted electrical activity from the plurality of carbon nanotubes. 
         [0005]    The system may include situating the at least one array of carbon nanotubes in a garment. The at least one array of carbon nanotubes may also be situated in a vehicle. Also, the plurality of carbon nanotubes may include single walled carbon nanotubes. In addition, the at least one array of carbon nanotubes may include two arrays of a plurality of carbon nanotubes. These two arrays of a plurality of carbon nanotubes may also be configured into a grid. 
         [0006]    According to another embodiment, a method for locating impacts includes aligning a plurality of carbon nanotubes into at least one array and detecting electrical emissions from at least one of the plurality of carbon nanotubes of the at least one array in response to application of pressure on the at least one array. The method also includes computing the location of impact upon the at least one array based on which of the plurality of carbon nanotubes emitted electrical activity. 
         [0007]    Depending on the specific features implemented, particular embodiments may exhibit some, none, or all of the following technical advantages. According to one embodiment, a system for locating impacts may be provided that adds almost no weight to equipment it is placed on, making it inexpensive to deploy. Further, the use of carbon nanotubes reduces the need for external power, such as through batteries, which causes the system to be less expensive and facilitates deployment. Other technical advantages will be readily apparent to one skilled in the art from the following figures, description, and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numbers represent like parts and which: 
           [0009]      FIG. 1A  illustrates one embodiment of a hit locator system according to the teachings of the disclosure; 
           [0010]      FIG. 1B  illustrates one embodiment of a computer that may be used with the hit locator system of  FIG. 1A ; 
           [0011]      FIG. 2A  illustrates the hit sensor of  FIG. 1A  with the cover removed; 
           [0012]      FIG. 2B  illustrates one embodiment of the operation of the hit sensor of  FIG. 2A ; 
           [0013]      FIG. 3  is a flowchart describing the operation of one embodiment of a hit locator system according to the teachings of the disclosure; 
           [0014]      FIG. 4A  illustrates one example of the placement of a hit sensor such as in  FIG. 1A ; and 
           [0015]      FIG. 4B  illustrates another example of the placement of a hit sensor such as in  FIG. 1A . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1A  illustrates one embodiment of hit locator system  1  according to the teachings of the disclosure. Hit locator system  1  includes hit sensor  10  coupled to computer  14  via connections  12 . Hit sensor  10  further includes cover  11 , under which lie tubes  30 . Tubes  30  are coupled to sensors  28 . Sensors  28  are coupled to computer  14  via connections  12 . In some embodiments, hit sensor  10  may be impacted causing tubes  30  to be compressed. When compressed, tubes  30  emit electrical activity. Sensors  28  may be configured to send signals to computer  14  via connections  12  in response to the electrical activity. Some of the signals transferred to computer  14  may be processed to determine if and where hit sensor  10  has been impacted. 
         [0017]    Tubes  30 , in some embodiments, are carbon nanotubes as discussed further below. In some embodiments, sensors  28  are electrodes. Connections  12  may be any configuration of components that allows for electrical transmission. In one example, connections  12  include at least one wire. In other examples, connections  12  include at least one bus. In still other examples, connections  12  may include wireless communication, such as IR, RF communication, or any other form of electromagnetic transmission. As examples only, other types of electromagnetic transmission include using Bluetooth technology and/or the IEEE 802.11 technology family. 
         [0018]      FIG. 1B  illustrates one embodiment of computer  14 . In this embodiment, computer  14  includes display  16 , processor  18 , hit graphing application  19 , memory  20 , storage  21  and input  22 . In particular embodiments, computer  14  may be configured to receive signals from hit sensor  10  and utilize hit graphing application  19  to indicate the location of an impact upon hit sensor  10 . Some embodiments of this process are discussed further below with respect to  FIG. 3 . In certain embodiments, computer  14  may include some or none of those components. In other embodiments, computer  14  may be a handheld device, such as a Personal Digital Assistant (PDA) or mobile telephone. Computer  14  may be capable of producing sounds instead of, or in addition to, a visual display. Computer  14  may also include a database containing information about equipment co-located with hit sensor  10 . In particular embodiments, this database is stored in storage  21 . 
         [0019]    Display  16 , in some embodiments, may include projectors, OLED screens, LCDs, CRT monitors, LED monitors, or any other suitable device or devices for displaying sensed hit information. In various embodiments, display  16  may include devices suitable for tactile feedback, such as haptic displays or surfaces. Display  16  may also include printers or plotters. In still other embodiments, display  16  may include devices suitable for providing audible feedback, such as speakers. 
         [0020]    Memory  20  stores hit graphing application  19 . Hit graphing application  19  processes signals delivered to computer  14  via connections  12  and utilizes display  16  to indicate the presence of impacts upon hit sensor  10 . In some embodiments, hit graphing application  19  further determines the location of impacts upon hit sensor  10 , as discussed below with respect to  FIG. 3 . 
         [0021]    Memory  20  and storage  21  may include files, stacks, databases, or other suitable forms of data. Memory  20  and storage  18  may be random access memory, read-only memory, CD-ROM, removable memory devices or other suitable devices that allow storage and/or retrieval of data. Memory  20  and storage  18  may be interchangeable and may perform the same functions. However, in the below examples, memory  20  will be used for storage and retrieval of data conventionally stored in random access memory, and storage  21  will perform the functions associated with data conventionally stored in read-only memory. 
         [0022]    Processor  18  is operable to execute the logic of programs stored in memory  20  or storage  21 . Examples of processor  12  are the Pentium series processors available from Intel Corporation; however, any type of processor may be used without departing from the teachings of the invention. 
         [0023]    Input  22 , in some embodiments, may include keyboards, mice, touchpads, touch screens, microphones, optical receivers, or any other device suitable for inputting information into computer  14 . 
         [0024]      FIG. 2A  shows one embodiment of hit sensor  10 . Here, cover  11  is not shown. In this embodiment, hit sensor  10  includes an array of tubes  30  which are arranged in a grid configuration and electrically coupled to sensors  28 . Sensors  28  may be composed of any suitable metallic conducting material, such as copper, silver, or gold. Further, sensors  28  may be composed of non-metallic conducting material, such as graphite. In other embodiments, tubes  30  may be arranged in a different configuration, such as a hexagonal configuration. When tubes  30  are compressed, they emit electrical activity. 
         [0025]      FIG. 2B  illustrates one embodiment of the operation of hit sensor  10 . In certain embodiments, when hit sensor  10  has been impacted at impact area  32 , tubes  30  underneath impact area  32  are compressed. The compressed tubes  30  emit electrical activity which is transmitted by sensors  28  to computer  14 . In this example, sensors  28   a  and  2   8   b  correspond to the Y-axis of impact area  32  while sensors  28   c  and  28   d  correspond to the X-axis of impact area  32 . In some embodiments, computer  14  may process the received signals from sensors  28  and display a graph corresponding to the location of the impact on hit sensor  10 . 
         [0026]    Tubes  30  may be single walled carbon nanotubes (SWCNT). When aligned and in composite material, SWCNT will emit electrons when compressed. One way of achieving a grid configuration of SWCNT is to take two layers of composite material in which the SWCNT have been aligned and put one on top of another such that one layer has its SWCNT aligned perpendicularly to the other layer&#39;s SWCNT. In order to obtain aligned SWCNT in composites across sufficient lengths a variety of options are available. One option involves extrusion. Mechanical extruders disperse the SWCNT across large composite materials. The extrusion process may lead to the breaking up of the nanotubes. As a result, a microwave field is applied to the composite materials and causes the nanotubes to link up. Another option is to mix the SWCNT with an uncured composite host. During and after the physical mixing an electric field is applied to the composite as it cures; a magnetic field may also be used instead of an electric field though the following discussion focuses on the use of an electric field. This passing of electricity through the material serves to physically move the nanotubes to a point where they will be aligned and dispersed with the electric field lines. This dispersion/alignment will be maintained and in some cases continually improved until either the composite cures or the electric field is removed. It is most advantageous to wait for the composite to cure. A modification to the SWCNT may make this process more effective. This modification involves placing the SWCNT in a liquid and then evaporating the liquid; one example of a suitable liquid is water. Evaporating water in the presence of CNTs has the effect of caused the resulting hydrogen and oxygen atoms of being adsorbed or absorbed by the SWCNT allowing easier dispersion and alignment along the electric field lines. 
         [0027]    Another option for disbursement and alignment in the composite material involves using yarn made from SWCNT. It is possible to use nanotube-based yarn along with traditional textile techniques to produce a woven cloth of nanostructures suitable for a hit locator system. 
         [0028]    Disbursing and aligning the carbon nanotubes may also affect properties of the composite material, including its hardness. The following table illustrates how the hardness of the composite material may be affected by the nanotubes: 
         [0000]                                            Material   Hardness (Durometer D Scale)                           Original Material (without   55           the nanotubes)           Material with unaligned   45           nanotubes           Material with partially   70           aligned nanotubes           Material with well aligned   90           nanotubes                        
An advantage to the system is illustrated in the table above. For nearly zero additional weight, a harder material may be realized. This is especially advantageous in armor applications where a harder material may increase the armor&#39;s effectiveness against projectiles.
 
         [0029]      FIG. 3  is a flowchart describing the operation of one embodiment of a hit locator system. In step  300  of this embodiment, the output of sensors  28  of hit locator  10  are monitored. In some embodiments, the monitoring may be done by computer  14  through hit graphing application  19 . In step  302 , the voltage across sensors  28  is compared to a threshold voltage. In some embodiments, the threshold voltage is in the microvolt range. If the voltages associated with sensors  28  are lower than the threshold, the leads continue to be monitored. However, if any of the sensors  28  have a voltage higher than the threshold, then the system proceeds to step  304 . In step  304 , sensors  28  corresponding to the X-axis of hit locator  10  which had a voltage higher than the threshold are mapped to a set of X-coordinates. In step  306 , sensors  28  corresponding to the Y-axis of hit locator  10  which had a voltage higher than the threshold are mapped to a set of Y-coordinates. The mapping in steps  304  and  306  may be accomplished, in some embodiments, by hit graphing application  19  of  FIG. 1B  using suitable logic to compute the incoming signals into location information. Steps  304  and  306  may be completed in any order; further, in other embodiments, steps  304  and  306  may be completed simultaneously. In step  308 , display  16  is updated to reflect the X and Y coordinates of the sensors  28  having voltages higher than the threshold. The system continues to step  300  where it monitors the leads. 
         [0030]    In certain embodiments, when hit locator  10  has not been impacted, tubes  30  are not emitting electrical activity and the results of step  300  are that sensors  28  have a very low voltage. Thus, when these voltage levels are compared to the threshold in step  302 , the system returns to step  300  and continues to monitor the leads because the voltages are lower than the threshold. 
         [0031]    However, in some embodiments, when hit locator  10  has been impacted by a projectile certain tubes  30  may have been compressed and emit electrical activity which is transmitted to sensors  28   a - d.  In step  302 , the voltage from sensors  28   a - d  are higher than the threshold. Thus, in step  304 , an X-coordinate is generated based on the fact that sensors  28   c  and  28   d  are emitting voltages higher than the threshold. Further, in step  306 , a Y-coordinate is generated based on the fact that sensors  28   a  and  28   b  are emitting voltages higher than the threshold. These generated coordinates are used in step  308  to update display  16  such that in indication of the location of impact area  32  is communicated. After this first impact, tubes  30  remain compressed so that the voltages on sensors  28   a - d  remain higher than the threshold; thus, the indication of the location of impact area  32  remains displayed. 
         [0032]    In particular embodiments, hit locator  10  is impacted twice by a first and second projectile creating a first and second impact area  32 . As a result, in certain embodiments, two sets of tubes  30  are compressed, causing a voltage higher than the threshold to appear on two sets of sensors  28 . In some embodiments, a further result of the second impact is that two sets of X and Y coordinates are generated in steps  304  and  306  since there are now two sets of sensors  28  emitting voltages higher than the threshold. In step  308 , display  16  is updated now showing two locations of impact, corresponding with the two sets of X and Y coordinates generated in steps  304  and  306 . 
         [0033]      FIG. 4A  illustrates one embodiment of a hit locator system  1 . In this embodiment, person  400  wears body armor  402 . Body armor  402  includes layers  404 . In some embodiments, there may be only one layer  404 . In this embodiment, hit sensor  10  is embedded into layer  404   a.  Layers  404   b  and  404   c  provide further protection from projectiles. Layers  404   a - c  are present all around body armor  402 . Each of the layers  404  may be used for ballistic protection. Layers  404  may be composed of metallic or composite materials. In this manner, hit sensor  10  may also be present all around body armor  402 . In the depicted embodiment, hit sensor  10  is coupled to computer  14  via connections  12 . In operation, if body armor  402  was impacted by a projectile, hit sensor  10  may send signals to computer  14  via connections  12 ; computer  14  may process these signals and provide information regarding the location of the impact on body armor  402 . The transmitted information may be advantageous in that it could increase the probability of saving lives since it may communicate valuable information about the location of the wound. In other examples, hit sensor  10  may be embedded into other articles of clothing or worn equipment. 
         [0034]    In some embodiments, hit sensor  10  and computer  14  need not remain constantly connected. In certain embodiments, connections  12  are established when information about impacts on body armor  402  is desired. 
         [0035]      FIG. 4B  illustrates another embodiment of hit locator system  1 . In this example, armored vehicle  450  includes layers  452 . Layers  452  may be made of metallic or composite material. Layers  452  may be situated all around armored vehicle  450 . In this example, layer  452   a  is the outermost layer made of metallic material while layer  452   b  is situated behind metallic layer  452   a  and includes composite material. Further, hit sensor  10  is placed within layer  452   b.  In this manner, hit sensor  10  may also be situated all around armored vehicle  450 . In some embodiments, armored vehicle  450  is in a combat situation. In certain embodiments, when armored vehicle has been impacted by a projectile, hit sensor  10  communicates the location on the armored vehicle of the impact as described with respect to  FIGS. 2A and 2B . As another example, computer  14  may be configured to receive the location information transmitted by hit sensor  10  and display the location of the impact on display  16 . Further, computer  14  may correlate the impact information with a database of equipment on armored vehicle  450  stored in memory  20  or storage  21  and provide a list of potentially damaged equipment. In other examples, hit sensor  10  may be placed anywhere on the vehicle. Hit sensor  10  may also be placed within any number and types of layers on the vehicle. 
         [0036]    Particular embodiments of a hit locator system have been described. Use of the hit locator system will add virtually no weight while, in some cases, improving ballistic performance of armor systems. Further, the hit locator system may provide insight into potentially damaged equipment in some embodiments. It may also give vital medical information if, for example, it is used on body armor. 
         [0037]    Although several embodiments have been illustrated and described in detail, it will be recognized that modifications and substitutions are possible without departing from the spirit and scope of the appended claims.