Patent Application
20120210858
The present invention relates generally to a new and improved fuze design to simplify the interface between the fuze electronics and the fire control system.
In an embodiment of the present invention, a self contained fuze apparatus is disclosed. This embodiment includes a power supply, a power conditioner electrically connected to the power supply, a microprocessor connected to the power conditioner, an oscillator connected to the microprocessor, a reference oscillator connected to the microprocessor, and a detonation circuit connected to the microprocessor and the power conditioner. In this embodiment, the reference oscillator directly calibrates the oscillator.
In another embodiment of the present invention, a projectile detonation system is disclosed. This embodiment includes a ballistic computer, a projectile, and a microcontroller located on the projectile. In this embodiment, the microcontroller includes a microprocessor, a low frequency oscillator, a reference oscillator, and a detonation circuit. In this embodiment, the Microprocessor is capable of receiving detonation timing data from the ballistic computer and is connected to the low frequency oscillator and the detonation circuit. In this embodiment, the reference oscillator is capable of calibrating the low frequency oscillator.
In yet another embodiment of the present invention, a method includes: receiving data by an internal microprocessor from an external ballistic computer, where the microprocessor is located in said projectile and the ballistic computer is located external to the projectile in a Fire Control System (FCS); calibrating an internal low frequency oscillator coupled to the microprocessor via an internal reference oscillator located in the projectile, where the low frequency oscillator can withstand launch accelerations of tens of thousands of g's; powering off the reference oscillator on completion of calibration; and transmitting from the microprocessor a detonation signal to a detonation circuit.
An illustrative embodiment of the invention is discussed in detail below. While specific illustrative embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention.
An illustrative embodiment of the invention relates generally to a new and improved fuze design used to detonate munitions. The fuze circuit may be disposed in a projectile that requires accurate detonation timing. In one embodiment, an internal fuze (i.e., internal to the projectile) may be used in, for example, 50 caliber and larger (e.g., but not limited to, up to 155 mm) projectiles. External to the projectile, a Fire Control System (FCS) may be used to determine the desired range for the fuze to optimally detonate the projectile. Once the desired range is determined, the time to detonation from launch may be calculated. The required data may be transferred from the external FCS to the internal fuze of the projectile. The data can be of a variety of types depending on the weapon it is installed in. The data type can be, for example, Mode, Target Range, Event Time, diagnostics, or Ballistic Data.
The internal fuze may utilize an internal microprocessor which may process data and, based on the data, detonate the accompanying projectile at the appropriate time and distance from launch.
Thus, any oscillators internal to the fuze and projectile must be calibrated from a source external to the fuze and projectile and are therefore, not directly calibrated. As a result of the need to convey or preprogram the exact frequency from the FCS 445 to the microprocessor 410, there is a one-to-one relationship between the fuze electronics 485 and the FCS 450. In other words, a particular internal fuze electronics 485 only works with a particular FCS 450.
An illustrative embodiment of the internal oscillator calibration of the current invention may eliminate the dependence on having to convey or preprogram the precise frequency of the external FCS oscillator parameters into the internal fuze.
In an exemplary embodiment, DC power from power source 105, is initially routed to power conditioner and storage component 160. The DC power source 105 may be attained, for example, via a piezo power source, a battery, an external circuit, or other means to supply electric current. The DC power source 105 may vary in current and voltage and the power conditioner and storage component 160 may be used to supply a constant and steady source of power even after the power source 105 stops supplying power. For example, the power conditioner and storage component 160 may store and condition a charge from the power source 105 (e.g., but not limited to a piezoid power source) at the time of projectile launch and acceleration. Alternatively, power may be obtained when a projectile containing the fuze is initially placed in a weapon breech or gun barrel (not shown). The particular storage capacitor 160 used, is a function of the DC Power Voltage (Vcc) being supplied, how long the projectile has to operate, and the volume available.
Conditioned power may be supplied to the microprocessor 110, the power switch 155, and the detonator 145. In one embodiment, the microprocessor 110, via a control port 130, may enable and/or disable power to the precision reference oscillator 115 through the use of the power switch 155.
In one embodiment of the current invention, a sacrificial reference oscillator such as the precision reference oscillator 115 is used for calibration. The sacrificial reference oscillator may be considered internal as it is part of the fuze and may be launched with the projectile. The precision reference oscillator 115 may calibrate either the high frequency oscillator 120 or the low frequency oscillator 125, the oscillators 120, 125 may, for example, be of a resistor-capacitor (RC) type oscillator. The oscillators 120, 125 may be of any type, for example, that can survive the high launch g's, be stable for a matter of several seconds and draw low power. Thus, the microprocessor 110 and/or oscillators 125, 120 may be directly calibrated (i.e., calibrated internally to the fuze) via the precision reference oscillator 115. Precision reference oscillator 115 could be the only oscillator required if it could meet the criteria listed above, but such an oscillator has not yet been developed.
The precision reference oscillator 115 may only be powered on for a short time (e.g., but not limited to, 1 to 200 milliseconds), if the precision reference oscillator 115 current draw exceeds the available power (e.g., when the precision reference oscillator 115 operates at a high frequency). A sufficiently accurate, for example, +/−0.05% or better, oscillator may be required for proper calibration. In one embodiment, the precision reference oscillator 115 may not need to survive a high g-force environment since the calibration may take place prior to projectile acceleration and a common crystal oscillator may be sufficient for the precision reference oscillator 115.
However, in another embodiment, the precision reference oscillator 115 may be required to survive in a high g-force environment. Although commonly used crystal oscillators may have sufficient accuracy, it may be impractical for a crystal oscillator to be used as the precision reference oscillator 115. Crystal oscillators may not survive launch accelerations of tens of thousands of g's. High speed projectiles, especially those with a piezo power source 105, may require the precision reference oscillator 115 to remain operational during accelerations of tens of thousands of g's. With a piezo powered projectile, there may be no voltage available until the projectile begins accelerating. Further, the precision reference oscillator 115 may require operation within milliseconds (e.g., but not limited to, 1 to 200 milliseconds) so that the microprocessor 110 can be programmed early in the firing cycle. Small size and weight may also be important for the precision reference oscillator 115 because of limitations imposed by the size of the projectile and the attendant fuze cavity.
A table illustrating an exemplary Event vs. Time is shown below:
Recently available silicon reference oscillators can survive tens of thousands of g's and the calibration may be concluded before the oscillator fails, mechanically, even if levels above tens of thousands of g's are reached. Several exemplary silicon oscillators that may be used include the CWX813-16.0M oscillator manufactured by Connor Winfield Corp., the FXO-HC735-16MHz oscillator manufactured by Fox Electronics, the KC2520B25.0000C2GE00 oscillator manufactured by AVX Corp., DSC1030 oscillator manufactured by Discera, Inc., the C3392-16.0000 oscillator manufactured by Crystek Corp., and the EMK22H2H-20.000M oscillator manufactured by Ecliptek Corp.
Calibration information from the precision reference oscillator 115 may travel from the precision reference oscillator 115 via an output port 140 to an input port 135 on the microprocessor 110. In one embodiment, the precision reference oscillator 115 calibrates the high frequency oscillator 120, the high frequency oscillator 120 may then calibrate the low frequency oscillator 125. In another embodiment, the precision reference oscillator 115 directly calibrates the low frequency oscillator 125. In another embodiment, the high frequency oscillator 120 and the low frequency oscillator 125 may be one element.
For precise fuze detonation, the low frequency oscillator 125 may require accurate calibration to +/−0.1% or better. The low frequency oscillator 125 typically operates at a low enough frequency to enable the circuit to draw low enough current so that it may operate from the power stored in the power conditioner and storage component 160 even after no power is supplied from DC power source 105. On the other hand, the high frequency oscillator 120 may operate at a frequency in the MHz region.
The microprocessor, 110 may calculate the appropriate time to detonate, at which point, the microprocessor 110 may send a detonation command from, for example, port 3 150 to the detonation circuit 145.
When the appropriate length of time has expired, microprocessor 510 issues a detonation signal to the detonation circuit 145. The detonation circuit 145 detonates explosive 560 causing the projectile 590 to explode. Various actions can take place such as a warhead exploding, release of a payload, etc. HE is normally activated because its action is rapid. The projectile may also have a default mechanism (not shown) for triggering detonator 145 in the event of a malfunction within the fuze electronics 585.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. The sizes and ranges may change depending on the various embodiments of the invention. For example, the rate of oscillation of the reference oscillator 115 may change depending on the weapon and type of projectile used (e.g., the fuze electronics used for a 50 caliber round may be different from a 155 mm round). Thus, the breadth and scope of the present invention should not be limited by any of the above-described illustrative embodiments, but should instead be defined only in accordance with the following claims and their equivalents
This application is related to U.S. Pat. No. 5,942,714, to Richard Oberlin and Robert Soranno, titled Accurate Ultra Low Power Fuze Electronics, assigned to the AAI Corporation, Hunt Valley Md., the contents of U.S. Pat. No. 5,942,714 are hereby incorporated herein in their entirety by reference.
