WO2008108802A2

WO2008108802A2 - Penetration detection device

Info

Publication number: WO2008108802A2
Application number: PCT/US2007/015621
Authority: WO
Inventors: Jay Lipeles; Martin E. Tanenhaus
Original assignee: Jay Lipeles; Tanenhaus Martin E
Priority date: 2006-07-10
Filing date: 2007-07-09
Publication date: 2008-09-12
Also published as: WO2008108802A3

Abstract

A penetration detection device earned by an earth penetrating bomb includes an inertial measurement unit and a penetrator processor and logic circuit contained in a shock isolated package which can withstand the transmitted environment encountered during earth penetration The inertial measurement unit derives information relative to the attitude of the bomb and the penetrator processor and logic circuit is responsive to the outputs of the inertial measurement unit as well as the outputs of external accelerometers to not only detect the transitions of adjoining layers but count the layers penetrated and also to determine the material of each layer This is compared with a stored layer characterization and if the stored and computed values are in correlation, a signal will be sent to start the arming initiation process A second layer characteπzation may also be stored for comparison if the first layer does not correlate

Description

PENETRATION DETECTION DEVICE

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority of U.S. provisional patent application serial number 60/806,805 filed on July 10, 2006, which is hereby expressly incorporated by reference.

FIELD OF THE INVENTION

The invention in general relates to munitions, and more particularly to an earth penetrating vehicle such as a bomb.

BACKGROUND OF THE INVENTION

Many military targets around the world are impervious to conventional attack. For example, hardened facilities in caves or underground concrete bunkers may house command centers, ammunition stores, or illegal research laboratories. In order to destroy such facilities, earth penetrating bombs, also known as "bunker busters", have been developed whereby the combination of speed and weight drives the bomb through the earth and through hardened concrete bunkers.

Current earth penetrating bombs do not have any circuitry for providing information relative to attitude of the bomb as it penetrates the earth. Lacking such circuitry, the bomb cannot sense if it is turning back to the surface, a condition known as J-ing.

Further, these bombs have a single accelerometer, axially oriented, for determining changes in layers so that they may be counted. If the bomb should hit concrete reinforcing bars the axial accelerometer becomes saturated and can't immediately recover. Accordingly, the layer count would be erroneous.

It is an object of the present invention to provide an arrangement for an earth penetrating vehicle which obviates the deficiencies of the prior art earth penetrating bombs. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 is a block diagram of an earth penetrating monitoring arrangement of the present invention.

FIG. 2 illustrates one type of mounting arrangement for the apparatus of FIG. 1.

FIG. 3 is a view along the line 3-3 of FIG. 2

FIG. 4 illustrates another type of mounting that may be used for the apparatus of FIG. 1 FIG. 5 is a view along the line 5-5 of FIG. 4

DETAILED DESCRIPTION OF THE INVENTION

Although the present invention is applicable to a variety of vehicles, such as those for gathering data, or munitions such as artillery shells, it will be described, by way of example with respect to an earth penetrating bomb.

Referring now to FIG. 1 , there is illustrated an earth penetrator detection device 10 which is carried in the casing of an earth penetrating bomb. The earth penetrator detection device 10 includes a rugged IMU (inertial measurement unit) 12 which has a built in array of three orthogonally positioned low G MEMS (micro electromechanical system) accelerometers 14 each positioned on a respective X, Y and Z axis to provide the inertial measurement unit 12 with information needed for inertial measurement unit calculations of all of the forces associated with the bomb as it penetrates the earth. These low G accelerometers may have a rating from around ±3.6 to ±4.9 Gs.

The IMU 12 also contains an array of gyros 16 each positioned on a respective X, Y and Z axis using an inner alignment structure to provide angular rate information. In a preferred embodiment eight such gyros are located on each of the axes. By using eight gyros better performance for drift and noise is obtained. The outputs of the eight gyros are combined to cancel out noise effects resulting in a more stable and accurate output which does not drift over a temperature range nearly as much as would a single gyro for each axis.

Other 3-D accelerometers with higher G ratings may be used as well. The same performance advantages for the array of accelerometers rather than a single device can be obtained in the same way as used for gyro arrays. In fact all sensors are aligned with one another on orthogonal axes using the combination of the inner alignment structure and software algorithms to align all the axes precisely.

When going through the earth MEMS inertial sensors produce objectionable noise. Accordingly, to improve the quality of the output signals from these sensors the signals are subject to a signal processing operation such as the well-known cascade algorithm to remove the noise thereby resulting in more accurate and precise computations by the IMU 12. The IMU 12 functions to obtain measurements of parameters such as velocity, acceleration and change in acceleration, angular rate (rotation) and distance with respect to time.

The IMU 12 reports the status of the bomb as it launches, accelerates and first penetrates the earth, and its trajectory through the earth. The term earth is used herein to include both natural and man-made structures as may be encountered in a bombing target. At initial penetration the velocity and angular orientation of the bomb will be recorded. After penetration the IMU 12 continues to measure the trajectory characteristics and reports bomb movement as it penetrates through each material.

The IMU 12 can tell if the bomb is turning around, that is, J-ing, in which case the bomb is detonated at its lowest point of penetration. The IMU 12 is a device well-known to those skilled in the art and is used, for example, in UAVs (unmanned aerial vehicles) but has never been used for a fusing function in a bomb. An example of a typical IMU is described and claimed in Patent Application Publication US 2007/0032951 A1 , which is hereby incorporated by reference.

While penetrating through the earth a condition may occur whereby the acceleration and vibration may exceed certain maximum limits. If this occurs, the IMU 12 may not perform to design expectations. In order to detect the occurrence of this condition, a High G monitor 18 is provided. This high G monitor 18 includes high G accelerometers, for example in the range of around ±500 to ±10,000 Gs, on three mutually perpendicular axes and if preset limits are not encountered, the high G monitor will enable the IMU 12 to perform its function. If such high G limits are encountered, the high G monitor may shut down the IMU 12 or instruct it to ignore data which may be suspect. The previously mentioned denoising operation is also performed on the output of the high G accelerometers of the high G monitor 18. The parameters calculated by the IMU 12 are provided as inertial measurement unit signals 19 to a penetrator processor and logic circuit 20 having logic executable to compute not only the number of earth layers penetrated, as well as the change of material between layers and the composition of each layer, such as sand, dirt, void or concrete, etc. The computation of layer penetration is carried out using the information from the signals from high G X, Y and Z accelerometers 22, 24 and 26 positioned on mutually orthogonal axes, and the outputs of which may also be denoised. These accelerometers, which may be in the range of around ±500 to ±10,000 Gs, as well as those in the IMU 12 are of sufficient response bandwidth and dynamic range to avoid saturation or limiting.

As the bomb penetrates different layers, it is subject to different vibrations. The accelerometers 22, 24 and 26 detect these vibrations and the accelerometer signals are provided to the penetrator processor and logic circuit 20 where they are processed by a vibration spectral difference analysis to obtain the layer information by comparison with known values. The derived layer information is compared with a layer pattern of the target area which is stored in the penetrator processor and logic circuit 20 based on known information, intelligence or best estimate.

They also measure the difference between adjacent materials to designate a new layer. The algorithm processes multiple accelerometer outputs to detect changes in the material transitions as the bomb passes from one into the other.

If the computed layer information compares with the stored information, the penetrator processor and logic circuits 20 will, after entering a target region such as a target void, send an arming initiation signal 29 to the safe and arm circuit 28 to initiate the explosive by sending a corresponding signal 30 to an initiator 31. In a preferred embodiment at least a second and different stored pattern is stored in the penetrator processor and logic circuit 20 so that if there is no correlation with the first pattern, the second pattern may be selected for comparison. If there is no correlation with this second pattern the penetrator processor and logic circuits 20 may be programmed to send a signal to the safe and arm circuit 28 to initiate detonation after a predetermined number of layers are detected or a preset time delay is completed following initial impact with the target area. In the prior art, if the bomb hits a concrete reinforcing bar during earth penetration, the axial accelerometer may be blinded, that is, its output signal would saturate at some maximum value. When this occurred, the layer counting function would cease until a recovery at some later point in time, if at all. In the present invention if the bomb hits a concrete reinforcing bar during earth penetration the layer counting function continues, as well as layer composition characterization. This is due to the fact that the present arrangement includes radial accelerometers 22 and 24 in addition to the axial accelerometer 26. The radial accelerometers sense the relatively lower magnitude of the radial components of the impact shock, which are primarily in the mid and high frequency environments. The output signals from these radial accelerometers 22 and 24 continue to be processed by the penetrator processor and logic circuit 20 to derive the desired information.

In FIG. 1 , the high G monitor 18, IMU 12, and penetrator processor and logic circuit 20 are all contained in a package 32 that may be shock isolated, to be subsequently described. The three accelerometers 22, 24 and 26 used to determine the number of layers and their composition are located outside of the package 32 and are purposefully not isolated from the shock loading. The safe and arm circuit 28 and initiator 30 may also be shock isolated. Also located outside of package 32 is an external setter 34. This external setter 34 is a panel that can be programmed to enter certain conditions into the penetrator processor and logic circuit 20. More particularly, the external setter 34 is operable to select the time delay before a detonation occurs, if the layer matching operation is unsuccessful. The external setter 34 is also operable to dictate how many layers are to be counted and can select which stored layer pattern is to be initially compared with computed values, or when a specific material or void transition is detected.

There are two dominating aspects to the structural design of package 32. The first is that loads are very large. The second is that a high speed impact of the bomb on its target is a true shock, regardless of the target properties. High speed impact imposes a load that is severe in respect of being very large and very fast. The package 32 of the present invention protects the high G monitor 18, IMU 12 and penetrator processor and logic circuit 20 against such shock. With the use of tiny MEMS accelerometers and gyros, and integrated circuits, the package 32 may be made extremely small.

By selecting a relatively high isolation frequency and with the package weight being small, the sway space required can be limited, a convenient feature considering the small space available in the bomb. An additional important effect of isolation is that the sensors become more precise by attenuating the high frequency motion. This is a consequence of the fact that high frequency motion is essentially noise to the void sensing logic. Isolation will eliminate much of the ringing and the signal-to-noise ratio of the sensors will therefore be improved. One example of a package which will meet the isolation requirements is illustrated in FIG. 2 in side view, and in FIG. 3 in end view. The package 32A includes a protective housing 40 having an end wall 42 to which is connected a power source for the electronics. The power source is constituted by batteries 44. Internal to the housing 40 is the IMU 12, as well as a plurality of circuit boards 46 interconnected with the IMU 12 and to each other by leads 48. These circuit boards 46 carry the integrated circuits constituting the high G monitor 18 and the penetrator processor and logic circuit 20.

Brackets 50 and 52 are secured to the housing 40 and carry respective isolators 54 and 56 which are secured to a mounting surface (not illustrated) in the bomb casing. The isolators 54 and 56 provide both axial and radial isolation and are strong enough to sustain the penetration loads and flexible enough to provide the required isolation, yet stiff enough so that the package 32A behaves essentially as a rigid body. Selection of the isolation frequency requires a careful balance. On the one hand the isolation frequency must be relatively high so as to limit the accompanying sway space. On the other hand if the isolators are too stiff, the environment transmitted to the circuitry within the package 32A will be excessive.

The X, Y and Z accelerometers 22, 24 and 26 are external to the housing 40 and are mounted at some convenient place outside of package 32A. In one embodiment, as illustrated in FIGS. 2 and 3, is seen that they are carried by the isolators 54 and 56. More particularly, X and Y accelerometers 22 and 24 are mounted on isolator 56 while the Z accelerometer 26 is mounted on isolator 54. It is to be understood that although three accelerometers are illustrated, redundant accelerometers could be provided. The output signals from accelerometers 22, 24 and 26 are provided to the electronics within the housing 40, via respective leads 58, 60 and 62, connected to a terminal board 64, seen in FIG. 3. The output of the external setter 34 (FIG. 1 ) may also be provided via lead 66, and an output to the safe and arm circuit 28 may be provided via lead 68. In one embodiment, the interior of the housing 40 is potted in a rigid encapsulate

70 so as to restrict movement of the electronics within the housing 40. The encapsulate should be one that does not allow expansion and contraction, one example being epoxy.

FIGS. 4 and 5 illustrate another package 32B which is smaller and lighter in weight than the package 32A of FIGS. 3 and 4. The primary difference between the two packages is the absence of a protective housing in the embodiment of FIGS. 4 and 5. The IMU 12 is potted in an encapsulate 80 and is surrounded by circuit boards 82 on all four sides and on the back, and interconnected by leads, one of which, 84 is illustrated. A series of frames 86 each in the shape of a thin angle iron and made, for example of aluminum, extend along the length of the package 32B and are are positioned at the corners of encapsulate 80 surrounding the IMU 12, and where the circuit boards 82 meet, with the frames 86 being held in position such as by bonding. Isolators 88, 90, 92 and 94 are secured to these frames 86 by fasteners 96 and are secured to a structural member 98 of the bomb. Isolator 88 carries the Z accelerometer 26, isolator 92 carries the X accelerometer 22 and isolator 90 carries the Y accelerometer 24. As before, redundant accelerometers may be provided.

All of the accelerometer outputs are connected to the electronics within the package 32B and FIG. 4 illustrates the connection of accelerometers 22 and 26. An output lead 100 from accelerometer 22 is connected to an input terminal 102, and an output lead 104 from accelerometer 26 is connected to an input terminal 106. A power supply in the form of batteries 108 contained within a case 110 supplies power to input terminal 112 via lead 114. Terminals 116 and 118 are also provided to receive the input from external setter 34 and to provide an output signal to the safe and arm circuit 28. Thus the structure of FIGS. 4 and 5 illustrate an arrangement which can operate as a fuzing device for a bomb and is contained in a small package 32B which may have dimensions of 3.03 inches in length, 1.61 inches in height and 1.39 inches in width in one embodiment, resulting in a volume which is no more than half the volume of current designs. The electronics is supported by a frame which has less mass and volume than a complete housing. The arrangement, even without a housing, is strong enough to sustain the transmitted environment and stiff enough to behave as a rigid body and it is believed that the package (as well as that of FIGS. 2 and 3) would be able to withstand forces in excess of 20,000 Gs.

Thus, there has been described an earth penetration detection device which measures the bomb's trajectory before and after earth penetration. Logic executable by the electronics will provide the characteristics of the trajectory from bomb release through free flight to and after earth penetration. At initial penetration the velocity and angular orientation is measured. After penetration the apparatus continues to measure the trajectory and reports bomb movement as it penetrates through each layer. It also reports if and when J- ing occurs so that the bomb can be immediately detonated. High G accelerometers measure vibration and shock associated with each layer penetrated to obtain a characterization the material, and the transitions between layers. Logic executable by the penetrator processor and logic circuit compares the real time occurrences with the preprogrammed layer pattern and when they correlate, or when the bomb reaches its deepest penetration, or after a selected time of penetration, a signal for detonation is generated.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.

Claims

CLAIMSThe invention claimed is:

1. A penetration detection device, comprising: an inertial measurement unit including a plurality of accelerometers on mutually orthogonal axes and a plurality of gyros on mutually orthogonal axes, the inertial measurement unit operable in response to signals from the accelerometers and gyros to provide inertial measurement unit signals indicative of travel of a vehicle prior to and after penetration into a target area; a penetrator processor and logic circuit receiving the inertial measurement unit signals; the inertial measurement unit and penetrator processor and logic circuit being contained in a package shock isolated from a structural member of the vehicle; a plurality of external accelerometers located outside the package and operable to provide output signals to the penetrator processor and logic circuit in response to the munition passing through layers of the target area; the penetrator processor and logic circuit including at least one stored layer characterization of an intended target area; the penetrator processor and logic circuit being responsive to the inertial measurement unit signals and the outputs of the external accelerometers to determine a characterization of layers penetrated and to compare it with the at least one stored layer characterization.

2. A penetration detection device in accordance with claim 1 wherein: the vehicle comprises a munition; and wherein the penetrator processor and logic circuit is responsive to the inertial measurement unit signals and the outputs of the external accelerometers to determine a characterization of each layer penetrated and to compare it with the at least one stored layer characterization for selective generation of an arming initiation signal for the munition.

3. A penetration detection device in accordance with claim 2 wherein: the penetrator processor and logic circuit includes at least a first and a second stored layer characterization of the intended target area.

4. A penetration detection device in accordance with claim 3 wherein: the penetrator processor and logic circuit is operable to compare the determined characterization of the penetrated layers with the second stored layer characterization if if there is no correlation between the determined characterization of the penetrated layers and the first stored layer characterization.

5. A penetration detection device in accordance with claim 4 wherein: if there is no correlation between the determined characterization of the penetrated layers and either the first or the second stored layer characterization, the penetrator processor and logic circuit is operable to provide a signal to start initiation of the munition after a predetermined time period.

6. A penetration detection device in accordance with claim 5 further comprising: an external setter outside the package operable to set the predetermined time period.

7. A penetration detection device in accordance with claim 6 wherein: the external setter is additionally operable to select which of the first or second stored layer characterization is initially to be compared with the derived characterization.

8. A penetration detection device in accordance with claim 1 which includes: a high G monitor contained in the package and including a plurality of accelerometers on three orthogonal axes and operable to control operation of the inertial measurement unit as a function of acceleration exceeding a predetermined value.

9. A penetration detection device in accordance with claim 1 wherein: each of the accelerometers and gyros comprises a MEMS device.

10. A penetration detection device in accordance with claim 1 wherein: the package includes a housing which contains the inertial measurement unit and a plurality of interconnected circuit boards constituting the penetrator processor and logic circuit; a power supply carried by the housing; the inertial measurement unit and the plurality of interconnected circuit boards being surrounded by an encapsulate.

11. A penetration detection device in accordance with claim 10 wherein: the encapsulate is a rigid encapsulate.

12. A penetration detection device in accordance with claim 10 further comprises: first and second isolators attached to the housing for connection to a structural member of the vehicle; the external accelerometers being carried by the isolators.

13. A penetration detection device in accordance with claim 1 wherein: the package is devoid of any housing; the penetrator processor and logic circuit comprises a plurality of interconnected circuit boards; a plurality of frame members extending along a length of the package at edges where the circuit boards meet; a plurality of isolators connected to the frame members for attachment to a structural member of the vehicle; the external accelerometers being carried by selected ones of the isolators; and the inertial measurement unit being surrounded by an encapsulate.

14. A penetration detection device in accordance with claim 2 wherein: the munition is an earth penetrating bomb.

15. A penetration detection device for a munition comprising: a package supported from a housing of the munition by a shock isolation apparatus; an inertial measurement unit supported in the package and producing inertial measurement unit signals responsive to movement of the munition; axial and radial accelerometers external to the housing and producing axial and radial accelerometer signals; a processor supported in the package and receiving the inertial measurement unit signals and the axial and radial accelerometer signals; and logic executable in the processor for selectively producing an arming initiation signal in response to the inertial measurement unit signals and the axial and radial accelerometer signals.

16. A penetration detection device in accordance with claim 15 further comprising logic executable by the processor for producing the arming initiation signal when a layer characterization produced by the processor in response to the axial and radial accelerometer signals corresponds to a first stored layer characterization.

17. A penetration detection device in accordance with claim 16 further comprising logic executable by the processor for producing the layer characterization in response to the radial accelerometer signals when the axial accelerometer signal exceeds a predetermined value.

18. A penetration detection device in accordance with claim 16 further comprising logic executable by the processor for comparing the layer characterization produced by the processor to a second stored layer characterization when the layer characterization produced by the processor does not correspond to the first stored layer characterization, and for producing the arming initiation signal when the layer characterization produced by the processor corresponds to the second stored layer characterization.

19. A penetration detection device in accordance with claim 16 further comprising logic executable by the processor for producing the arming initiation signal in response to a timing signal when the layer characterization produced by the processor does not correspond to the stored layer characterization.

20. A penetration detection device in accordance with claim 15 further comprising logic executable by the processor for producing the arming initiation signal in response to the inertial measurement unit signals when a path of motion of the munition is a J-ing.