Patent Application
20080121131
Embodiments of this invention relate generally to fuzes for explosive devices and, more specifically, to apparatuses and methods for improved timing used in a controlled warhead initiation application or a setter calibration application.
Explosive projectiles must be capable of detonating at the proper time for maximum desired effect in destroying a target. Depending on the application, the proper time may be before impact, at a specific point during flight, during impact, or at some time delay after impact. To control the detonation time and, in some instances to determine that time, these explosive projectiles are frequently equipped with fuzes. Fuzes are commonly configured with the capability of receiving external information from a remote setter located outside the projectile. As used herein, the terms “warhead,” “explosive device,” and “explosive projectile” are generally used to refer to a variety of projectile type explosives, such as, for example, artillery shells, rockets, bombs, and other weapon warheads. In addition, these explosive projectiles may be launched from a variety of platforms, including, for example, fixed wing aircraft, rotary wing aircraft (e.g., helicopters), ground vehicles, and stationary ground locations.
Conventionally, a fuze may be used to activate the explosive projectile for detonation in the vicinity of the target. In addition, the faze maintains the explosive projectile in a safe condition during logistical and operational phases prior to launch and during the first phase of the launch until the explosive projectile has reached a safe distance from the point of launch. In summary, significant functions that a faze performs include keeping the weapon safe during handling and prelaunch transport, arming the weapon when it is a safe distance from the point of launch, controlling time to detonation of the warhead and/or detecting the target, and initiating detonation of the warhead at some definable point after target detection.
The first two functions performed by a fuze which include keeping the weapon safe and arming the weapon are conventionally referred to as Safing and Arming (S&A). Safing and Arming devices isolate a detonator from a booster charge of the warhead used to initiate detonation of the primary explosive until the explosive projectile has been launched and a safe distance from the launch vehicle is achieved. At that point, the S&A device removes a physical barrier from, or moves the detonator in line with, the explosive train. In doing so, the S&A device effectively arms the warhead so that it can initiate detonation at the appropriate time.
The other two functions performed by a fuze, which include detecting the target and initiating detonation, may depend on target type, explosive projectile type, and tactical operational decisions. Target detection may occur using sensors to detect proximity to a target, or using sensors to detect impact with a target. Explosives of other projectiles may be detonated without regard to target detection, using a simple timing device. Still other projectiles may use a timer to activate sensors for proximity and/or impact at an appropriate time. Conventionally, impact fuzes, as opposed to proximity fazes, are designed to detect the target by sensing one or more impacts or contacts with a target.
In an impact fuze the final function of a fuze, initiating detonation of the warhead, may occur as temporally close to impact as possible or may be delayed for a certain period of time allowing the warhead to penetrate the target prior to detonation. Traditionally, delayed detonation has been performed by defining a fixed delay after impact to initiate detonation. Conventional fuze timing devices using a fixed delay may use RC or crystal-based timing devices. Although RC-based devices are robust during setback accelerations and impact decelerations, they are inherently inaccurate. Conversely, crystal-based timing devices are far more accurate but lack durability and require more components, thus resulting in an overall increase in implementation costs.
There is a need for methods and apparatuses that provide increased accuracy of fuze timing while providing a high level of strength for post-setback and impact munition functionality. Specifically, there is a need for an inexpensive, impact resistant timing device which can maintain a high level of accuracy.
An embodiment of the present invention includes an RC timing apparatus for use within an explosive projectile. The RC timing apparatus comprises a fuze that includes a microcontroller comprising an RC-based clock generator. The microcontroller is configured for receiving a timing event from an accurate external time-based source, wherein the timing event has a time duration between a first timing edge and a second timing edge. The microcontroller is also configured for calibrating an internal timing loop of the microcontroller with the timing event.
Another embodiment of the present invention includes an explosive projectile system comprising an accurate time-based source, an encasement, and an explosive material disposed within the encasement and configured for detonation. The explosive projectile also includes a fuze disposed within the encasement and operably associated with the explosive material. The fuze comprises a housing and an RC timing apparatus disposed within the housing. The RC timing apparatus comprises a microcontroller that includes an RC-based clock generator and is configured for receiving a timing event from an accurate internal time-based source, wherein the timing event has a time duration between a first timing edge and a second timing edge. The microcontroller is also configured for calibrating an internal timing loop of the microcontroller with the timing event.
Another embodiment of the present invention comprises a method of using an RC timing apparatus within an explosive projectile. The method comprises receiving a timing event from an accurate time-based source, wherein the timing event has a time duration between a first timing edge and a second timing edge. The method further includes calibrating an internal timing loop of a microcontroller with the time duration.
In the drawings:
The present invention provides apparatuses and methods of operation for an RC timing device to address accuracy issues concerning conventional RC timing devices and durability issues regarding conventional crystal-based timing devices.
In the following description, circuits and functions may be shown in block diagram form in order not to obscure the present invention in unnecessary detail. Conversely, specific circuit implementations shown and described are examples only and should not be construed as the only way to implement the present invention unless specified otherwise herein. Additionally, block definitions and partitioning of logic between various blocks is exemplary of a specific implementation. It will be readily apparent to one of ordinary skill in the art that the present invention may be practiced by numerous other partitioning solutions. For the most part, details concerning timing considerations and the like have been omitted where such details are not necessary to obtain a complete understanding of the present invention and are within the abilities of persons of ordinary skill in the relevant art.
In this description, some drawings may illustrate signals as a single signal for clarity of presentation and description. It will be understood by a person of ordinary skill in the art that the signal may represent a bus of signals, wherein the bus may have a variety of bit widths and the present invention may be implemented on any number of data signals including a single data signal.
The terms “assert” and “negate” are used respectively when referring to the rendering of a signal, status bit, or similar apparatus into its logically true or logically false state. Accordingly, if a logic level one or a high voltage represents an asserted state (i.e., logically true), a logic level zero or a low voltage represents the negated state (i.e., logically false). Conversely, if a logic level zero or a low voltage represents the asserted state, a logic level one or a high voltage represents the negated state.
In describing embodiments of the present invention, the systems and elements surrounding the invention are first described to better understand the function of embodiments of the invention as it may be implemented within these systems and elements.
Warhead initiation module (WIM) 820 may include a microcontroller (not shown) that includes an RC-based clock generator. Referring to
Implementations of the microcontroller may include, but are not limited to, a setter calibration or a detonation delay application. In both implementations, the microcontroller is capable of sampling a timing event and employing results in a manner appropriate for the intended function. In the case of a setter calibration application, the timing event may consist of an oscillating carrier signal, while in the case of a detonation delay application, the timing event may be a single, accurate time pulse. By way of example only, the calibration process of both implementations will be described with values assigned for ease of description, and by no means do these assigned values limit any embodiment of the invention.
If the microcontroller receives a carrier signal 18 with a frequency of 10 KHz, the microcontroller phase-locks the internal sampling loop by determining how many loop iterations can be completed during a time period from first leading edge 18a to a second leading edge 15b of carrier signal 18. The internal timing loop will start at the first leading edge 18a and will iterate through the loop until the second leading edge 18b of carrier signal 18 is located. In this case, because the time period of the carrier signal is equal to 0.1 ms, the second leading edge 15b will be located after one hundred and five (105) loop iterations. Therefore, once the internal sampling loop is phase-locked to the carrier signal frequency, the 10 KHz frequency is represented by 106 loop iterations. Because the 10 KHz frequency is represented by completed loop iterations, a small error may exist if the second leading 18b is present earlier in the loop iteration. In other words, if the second leading edge 15b is present after one hundred four and one-half loop iterations (104.5), the second leading edge 15b will not be located until one hundred and five (105) loop iterations have been completed. Consequently, the accuracy of the calibration may be off by no more than a complete iteration. In order to increase the accuracy, one complete loop iteration can be completed in less time by increasing the clock frequency or shortening the internal sampling loop.
With a calibrated time base, the microcontroller can set frequency boundary limits for subsequent data bit transfers to a projectile fuze using a frequency shift keying communication protocol. For example, future signals sent to the microcontroller on the carrier signal may be referenced to the 10 KHz time base. Signals with frequencies more than 10 KHz may be represented by digital 1's and signals with a frequencies less than 10 KHz may be represented by digital 0's.
Filtering networks 342 and bit decode and store device 344 extract the fuze setting parameters sent to the fuze 200 from data transmitter 326. Subsequently, the transmitted data is passed to the microcontroller 346. In some embodiments, filtering networks 342 and bit decode and store devices 344 may be incorporated into data transceiver 311. Microcontroller 346 includes an RC-based clock generator 322 and is configured to receive a carrier signal from crystal controlled device 345. Microcontroller 346 may use an embedded software program to self-adjust an internal sampling loop until the sampling loop is phase-locked to the frequency of the received carrier signal. As described above, microcontroller 346 measures a number of completed iterations of an internal timing loop during a timing measurement from a leading edge to a next leading edge of the carrier signal. The sampling loop is then phase-locked by representing the carrier signal frequency by the number of completed iterations. Frequency boundary limits can then be set for subsequent data bit transfers to the fuze 200.
The operation of the apparatus depicted in
FIGS. 3 and 6-9 illustrate a detonation delay application of an RC-based microcontroller according to an embodiment of the present invention. In the detonation delay application, the microcontroller may be configured to receive a timing event comprising a time pulse 16. Calibration of the microcontroller may then take place by determining the number of completed iterations through an internal timing loop for the duration of the received timing event. Referring to
In a delayed point detonation (PD) mode, which may be selected by a user prior to launch, the explosive projectile 100 is triggered to detonate at a fixed time period after impact (detonation delay). As part of the fixed delay after impact, various delays may be used from “super quick,” or almost instantaneous, to any desired delay value. This fixed delay may be pre-programmed in the firmware of fuze 200, possibly based on target lethality studies.
During projectile flight, main controller 320 may power up under its own power, and make flight decisions including sending the detonation delay value, in the form of a time pulse, to the microcontroller 346. By way of example, and not limitation, if a user desires a 10 ms detonation delay, data including the desired 10 ms detonation time delay may be sent to the main controller 320 before projectile launch. Subsequently, after projectile launch, a time pulse with a 10 ms width may be sent from the crystal controlled device 800 of the main controller 320 to the microcontroller 346. Microcontroller 346 samples the time pulse width and calibrates itself, as described above, by recording the number of completed iterations of an internal timing loop during a measurement from a leading edge to a trailing edge of the time pulse. After calibration, microcontroller 346 records the measurement as a detonation delay and stores the data for future reference. Upon sensing an impact of the explosive projectile 100 (
Calibrating a microcontroller with an accurate timing event from an accurate timing source eliminates RC timing errors associated with conventional RC devices. Because the delay times and the sampling rates may be calibrated at the final real-time operating temperature and the final real-time power supply voltage, problems associated with operating temperature effects and power supply changes may be eliminated. Additionally, RC timing concerns regarding component variations may be eliminated while the microcontroller remains more shock resistant due to RC durability. Therefore, the microcontroller is robust during setback accelerations and impact decelerations and, at the same time maintains a high level of accuracy.
The timeline illustrated in
A launch may be triggered after completion of the initialization and message processes. The launch event (also referred to as the initiation event 410) is shown in
Although this invention has been described with reference to particular embodiments, the invention is not limited to these described embodiments. Rather, the invention is limited only by the appended claims, which include within their scope all equivalent devices or methods that operate according to the principles of the invention as described.
