EP0844457A2 - Improvements in weapons systems - Google Patents
Improvements in weapons systems Download PDFInfo
- Publication number
- EP0844457A2 EP0844457A2 EP98102311A EP98102311A EP0844457A2 EP 0844457 A2 EP0844457 A2 EP 0844457A2 EP 98102311 A EP98102311 A EP 98102311A EP 98102311 A EP98102311 A EP 98102311A EP 0844457 A2 EP0844457 A2 EP 0844457A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- muzzle velocity
- weapon
- kalman filter
- prediction
- muzzle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F41—WEAPONS
- F41G—WEAPON SIGHTS; AIMING
- F41G3/00—Aiming or laying means
- F41G3/12—Aiming or laying means with means for compensating for muzzle velocity or powder temperature with means for compensating for gun vibrations
Definitions
- the present invention relates to improvements in weapons systems and in particular, to devices and methods for predicting parameters useful for determining the aim of projectiles. It is especially, although not exclusively, suited to applications concerning the aiming of a shell fired from a gun.
- the invention extends to prediction and aiming methods and devices per se and to weapons systems incorporating such devices.
- One important aspect of the invention entails prediction of muzzle velocity.
- the present invention can achieve this through measuring the muzzle velocity and using the result to aim the gun appropriately. In general the measured muzzle velocity is used to predict a new muzzle velocity for the next firing and takes this into account in determining the appropriate alevation setting of the next firing. Of particular significance is that modern guns perform a small number of firings in each series. The invention can be particularly effective at improving accuracy in these first few firings.
- the present invention provides an aiming system for an indirect fire weapon, the system comprising a muzzle velocity measuring device, and prediction means responsive to an output of the muzzle velocity measuring device for determining a new elevation setting from the weapon.
- the aiming system is integrated with the weapon itself, most preferably directly co-operating with the weapon's gun (barrel) laying system.
- the first aspect of the present invention also includes a method of determining an elevation setting for an indirect fire weapon, the method comprising firing the weapon and measuring the resultant muzzle velocity, and using the result of the measurement to make a prediction and thus determine a new elevation setting for the weapon.
- the predictor means utilizes previous measured muzzle velocities to predict new muzzle velocity under the conditions for the next firing and uses the predicted muzzle velocity to determine the elevation setting.
- prediction of other parameters useful in determining elevation is also within the ambit of the present invention.
- the muzzle velocity measuring device may for example be a Doppler radar device attached to the barrel of the weapon for measuring the velocity of a projectile as it leaves the barrel.
- an interface is also provided between the predictor means and the gun laying system used for setting the barrel, so that the quadrant elevation can be reset automatically according to the new muzzle velocity predicted by the predictor means.
- the predictor may predict a new muzzle velocity based on the measured muzzle velocities from previous firings, it is also responsive to initial values to enable the first firing to be effected with reasonable accuracy.
- a convenient way of realising the predictor means is in the form of an electronic computer programmed in a way to be described in more detail hereinbelow. It is very much preferred for the computer to be electronically connected to the muzzle velocity measuring device, for example via an appropriate interface, to receive output signals from the latter for use in the prediction method. As indicated above, it is also preferred for the computer to be connected direct to the gun laying system via an appropriate interface.
- the electronic computer should consist of:
- Some of the memory for storing parameters and data is preferably used to retain information even when the device is switched off.
- This part of the memory is non-volatile and is implemented as a battery-backed Random Access Memory or as magnetic tape, magnetic disc or optical storage medium etcetera.
- the prediction means and method utilizes an adaptive empirical prediction method (AEPM), that is a method which is capable of 'learning' from a comparison of its prediction and the subsequent-real life result and adapting the way in which it makes the next prediction accordingly.
- AEPM adaptive empirical prediction method
- the AEPM is used to estimate the various effects which influence muzzle velocity, in order to derive an improved RMV for input to the gun laying system. This is achieved by estimating the primary errors present in RMV calculations, ie the difference between the nominal (calibrated and corrected) RMV and the true muzzle velocity.
- the AEPM combines measurements taken at each firing to estimate the major errors present in the nominal estimate of RMV.
- the analysis of the available measurements permits the following major errors to be estimated separately. In statistical terms, the following errors are separable:-
- a second aspect of the present invention comprises a device for predicting a future muzzle velocity of an indirect fire weapon, the device comprising means responsive to a measurement of muzzle velocity and adapted to implement an adaptive empirical prediction method to predict the future muzzle velocity.
- the second aspect of the invention also includes a method of predicting a future muzzle velocity of an indirect fire weapon, the method comprising measuring a muzzle velocity and using an adaptive empirical prediction method to predict the future muzzle velocity.
- the device includes means responsive to (means for inputting) relevant environmental, projectile and other calibration data.
- appropriate means utilize future muzzle velocity to determine an elevation setting for the weapon.
- the AEPM is implemented as a Kalman Filter, most preferably in combination with a first round prediction algorithm (FRPA), or it is implemented as a neural network, which incorporates the FRPA.
- FRPA first round prediction algorithm
- the FRPA specifically estimates the combination of Barrel Effect and Within Series Effect for the first round of a series.
- the AEPM uses at least the following measurements:-
- Kalman filter was first developed during the 1960's.
- a Kalman filter contains a dynamic model of system errors, characterised as a set of first order linear differential equations.
- the Kalman filter comprises equations in which the variables (state-variables) correspond to respective error sources and the equations express the dynamic relationship between these error sources. Weighting factors are applied to take account of the relative contributions of the errors.
- the weighting factors are optimised at values depending on the calculated simultaneous minimum variance in the distributions of the errors.
- the filter constantly reassesses the values of the state-variables as it receives new measured values, simultaneously taking all past measurements into account. Therefore, the Kalman filter is able to predict a value of one or more chosen parameters based on a set of state-variables which are updated recursively from the respective inputs.
- the FRPA Whilst it is possible to initialise the prediction by the Kalman filter of the muzzle velocity for a first round, eg. using firing tables, it is much preferred to use a first round prediction algorithm.
- the FRPA utilises a weighted average of previous first round errors for similar charge/projectile combinations.
- the present invention may use a neural network (sometimes abbreviated to neural net), in particular, a recurrent multi-layer neural network.
- a neural net can be regarded either as a 'second order' Kalman Filter or as a separate entitity in its own right.
- a neural network is essentially an electronic or software equivalent of the network of neurons in the human brain. It consists of 'artificial neurons' which receive various inputs and apply weighting factors to each before combining them into a function to produce a required output result.
- a recurrent multi-layer neural network consists of at least an input layer and an output layer of artificial neurons, separated by hidden layers. The neural network compares errors and uses these to continuously adjust the weighting factors and/or the operative functions to minimise the errors and optimise the result. Therefore, unlike the Kalman Filter, it 'decides' for itself which inputs to use and what significance to attach to them and it continuously improves this model based on result.
- the theory and implementation of neural nets are well documented, for example in 'Neural Computing: An Introduction', R. Beale and T. Jackson, Adam Hilger 1990.
- the neural net does not require initialisation.
- the neural net receives all available inputs and through its internal 'learning process', applies appropriate weighting factors so that it takes as much or as little (including zero) account of each to find an optimum estimate of the parameter to be predicted, in the present case muzzle velocity.
- the neural net then computes an estimate of the correction to be applied to the nominal muzzle velocity. Like the Kalman Filter, the neural net continually updates the relative weighting it allocates to each variable, based on a comparison of its prediction of muzzle velocity and the subsequently measured real-time muzzle velocities.
- a weapons system 1 comprises a gun barrel 3 on which is mounted a Doppler radar muzzle velocity detection device 5.
- the elevation ⁇ of the barrel is set by the gun laying system 7.
- Electronic circuitry includes means 9 for making an initial RMV calculation based on initial calibration values and projectile data.
- An adaptive empirical prediction device 11 also forming part of the circuitry, implements on AEPM. It utilises the initial RMV value and the measured muzzle velocity to predict the next muzzle velocity.
- the gun laying system utilises predicted muzzle velocity, together with environmental and positional information, to perform the ballistics calculations necessary to select the appropriate charge and shell type and determine the appropriate azimuth and elevation for the gun.
- the improved muzzle velocity prediction supplied by the AEPM permits the gun laying system to determine an improved elevation for the next firing.
- FIG. 3 shows the configuration of the circuitry which comprises a (microprocessor) processing unit CPU.
- the CPU is connected to a non-volatile memory MEN for back-up memory storage.
- the CPU is connected via a first interface INT1 to receive the output of a Doppler radar muzzle velocity measuring device MVMD (5) which in use is attached to a gun barrel to measure the muzzle velocity of shells as they are fired.
- MVMD Doppler radar muzzle velocity measuring device
- the CPU is also connected via second interface INT2 to an interactive display terminal TEM and to an automatic barrel laying system BLS.
- the CPU receives values of the available measurements such as projectile mass and type, charge type and temperature, estimated barrel wear, shell seating depth and the like. These may be programmed into the terminal by the operator.
- the muzzle velocity measurement is provided by the Doppler radar and time is derived from the internal clock of the CPU. Alternatively, measurements of some variables such as barrel temperature may be provided direct to the CPU by appropriate sensors (not shown).
- Initialisation parameters are resident in non-volatile memory together with the Computer program.
- the inputs are categorised as muzzle velocity and AEP measurements, which are state-variable measurements to be incorporated within the AEP device, projectile measurements, which are required for the RMV Calculation, and positional and environmental measurements, which are required for Gun Laying.
- Examples of environmental measurements are air temperature and pressure, and wind speed and direction.
- positional information examples include target position, gun position and terrain information.
- a multi-state Kalman Filter is used to estimate the major sources of error in muzzle velocity prediction, ie the difference between nominal Muzzle Velocity and measured muzzle velocity.
- the Kalman Filter embodies:
- Barrel Effect is modelled as a time series with a time constant and variation chosen to reflect the persistence of the effect over a number of series.
- the variable a 1 represents a white noise process with a specified variance v 1 (z), ie v 1 is a function of z.
- Occasion to Occasion Effect is modelled as a time series with a time constant and variation chosen to reflect the persistence of the effect over one series.
- w(t) W w(this round) +a 3 , where W is a factor reflecting the variation of w from round to round (note that 0 ⁇ W ⁇ 1). Also a 3 represents a white noise process with a specified variance v 3 (z).
- the state variable is modelled as a time series with a time constant and variation chosen to reflect the persistence of the effect over more than one series.
- the variables b, s, w and d are the state-variables.
- the above formulae represent the state variables in a way which completely defines the Kalman Filter propagation equation.
- the state variables are initialised at the beginning of each series. Those variable which are persistent over a single series, ie Occasion to Occasion Effects, are initialised to zero. Barrel and Seating Depth Effects are initialised with the estimates derived during the previous series, as described below. Within Series Effects are initialised so that Barrel Effects plus Within Series Effects sum to the First Round Prediction, which is also described below.
- the AEP measurements may be divided into Initialisation and Parametric Measurements and described in terms of their relationship to the state variables. This specifies the details necessary to implement the Kalman formulation.
- the following initialisation measurements indicate when the start of a series occurs, and the Kalman Filter is to be initialised with state estimates derived from the First Round Prediction Algorithm. They have the significance hereinbefore described and are: Time; Change in Projectile Type; Change in Charge Identifier; and Barrel Temperature.
- the following measurements are input to the Kalman Filter as standard measurements.
- the relationship between each measurement and the state variables is specified, which defines the information necessary to carry out the Kalman Filter measurement update.
- Delta Muzzle Velocity is the computed difference between the Measured Muzzle Velocity, output from the Muzzle Velocity Measuring Device, and the nominal Muzzle Velocity.
- the term including SSD which denotes the measurement of Shell Seating Depth (as indicated below), is included only if this measurement is available.
- the measurement of depth of the seating of the shell may be input to the device if such data is available.
- the relationship described in the above equation incorporates the state variable s which estimates the correlation between SSD and RMV.
- a major benefit of the AEPM is that it can retain information about the significant characteristics of the gun between firings. For the Kalman filter this is achieved by retaining estimates of the state variables which persist longer than a single firing, ie Barrel Effect and Seating Depth Effect. At the end of each series, these variables, together with the associated co-variances (as computed in the Kalman filter), are stored in non-volatile memory. At the start of a new series, these variables are then restored.
- a Recurrent Multi-Layered Neural Network can also be configured to implement the AEPM and generate corrections to nominal muzzle velocities and to predict muzzle velocities for subsequent rounds.
- the benefit of the neural network approach over any other is that it is 'self tuning' and does not require the derivation of Initialisation Parameters.
- the neural Network self organises in the general manner hereinbefore described.
- the preferred mechanism offers the benefit that it modifies its weights, by back propagation, at every firing.
- the neural network further extends the concept of calibration of every gun by removing the need to carry out this initial data analysis. If the AEPM is implemented as a neural network, then the implementation effectively conducts this analysis for each gun. This reduces the effect of variations within guns and simplifies the calibration process.
- the specific implementation is a multilayered feed forward network, as represented diagrammatically in Figure 4. All nodes in one layer are connected to all nodes of the next layer. Associated with each link is a weight which is updated, by back propagation, following each measurement of muzzle velocity.
- Each input measurement has a set of nodes on which the input values are encoded.
- the output of the network is the correction to be applied to the nominal muzzle velocity for the prescribed projectile at the prescribed time.
- the input data In a neural network the input data must be encoded in an efficient and effective way.
- the appropriate mode applied to many of the measurements is called spread encoding.
- an input value is encoded on a number of input nodes, m say. This is achieved by dividing the range [a to b], over which the variable is encoded, into m-1 parts.
- the variable takes the value f, which lies in the range [a to b].
- i 1 + integer part of ( (m-1) x (f-a)/(b-a)).
- nodes i and i+1 All input nodes are set to zero, except nodes i and i+1. These nodes take values defined as follows.
- n j 1,2, .., m
- n j denote the value input to node j.
- the measurements input to the AEP device are those previously described under the heading Data Input. Each measurement is input to its designated input nodes in the way described below.
- the neural network achieves muzzle velocity prediction by outputting the correction to be applied to the nominal muzzle velocity at each firing.
- the network is updated following each firing by performing back propagation.
- the actual muzzle velocity measurement is spread encoded onto the output nodes, and the procedure modifies the weights to reduce the difference between the predicted and the actual muzzle velocities.
- the new weights are then applied at the next prediction.
- the predicted muzzle velocity is generated on the output nodes in a spread encoded form.
- a benefit of the AEP is that it can be arranged to retain information about the significant characteristics of the gun between firings.
- the statistical behaviour of the gun are represented in the weights which are derived in the network. Therefore these weights should be retained between firings, even if the equipment is powered down. Retention of the weights permits effective First Round Prediction.
- the AEP Device maintains a table of First Round Corrections. These corrections are applied to the nominal RMV in order to predict the first round muzzle velocity.
- the table contains a correction appropriate to: previous charge type/current charge type pairs.
- the table is updated as follows.
- the measurements input to the FRPA are:
Abstract
Description
Retention of the weights permits effective First Round Prediction.
- Previous First Round Prediction Table
- Previous Charge Type,
- Current Charge Type,
- Measured First Round Muzzle Velocity,
- Nominal Muzzle Velocity for the Previous/Current Charge Type pair.
Claims (16)
- A device for predicting a future muzzle velocity of an indirect fire weapon, the device comprising means responsive to a measurement of muzzle velocity and adapted to implement an adaptive empirical prediction method as a Kalman filter, for predicting a future muzzle velocity.
- An aiming system for an indirect fire weapon, the system comprising a muzzle velocity measuring device, and predictor means responsive to an output of the muzzle velocity measuring device for determining a new elevation setting from the weapon by implementing an adaptive empirical prediction method as a Kalman filter.
- A device according to claim 1 or a system according to claim 2, further comprising means for utilizing future muzzle velocity to determine an elevation setting for the weapon.
- A device according to claim 1 or a device or system according to claim 2 or claim 3, further comprising means responsive to relevant environmental, projectile and other calibration data.
- A device according to claim 1 or a device or system according to any of claims 2-4, wherein the Kalman filter is implemented in combination with a first round prediction algorithm.
- An aiming system according to any of claims 2-5, which aiming system is integrated with a weapon.
- An aiming system according to claim 6, arranged to cooperate directly with a gun laying system of the weapon.
- An aiming system according to claim 7, wherein the predictor means is adapted to utilize previous measured muzzle velocities to predict new muzzle velocity under the conditions for the next firing and is also adapted to use the predicted muzzle velocity to determine the elevation setting.
- An aiming system according to any of claims 4-8, wherein the muzzle velocity measuring device is a Doppler radar device attached to the barrel of the weapon for measuring the velocity of a projectile as it leaves the barrel.
- An aiming system according to any of claims 4-9, wherein an interface is also provided between the predictor means and the gun laying system used for setting the barrel, so that the quadrant elevation can be re-set automatically according to the new muzzle velocity predicted by the predictor means.
- An aiming system according to any of claims 4-10, wherein the predictor means is responsive to initial values to enable the first firing to be effected with acceptable accuracy.
- An aiming system according to any of the preceding claims, wherein the Kalman filter self organises to represent:(a) a definition of errors and their stochastic behaviour in time;(b) the relationship between the errors and the muzzle velocity measured by the muzzle velocity measuring means; and(c) how the errors influence the prediction of muzzle velocity.
- A method of predicting a future muzzle velocity of an indirect fire weapon, the method comprising measuring a muzzle velocity and using an adaptive empirical prediction method implemented as a Kalman filter for predicting a future muzzle velocity.
- A method of determining an elevation setting for an indirect fire weapon, the method comprising firing the weapon and measuring the resultant muzzle velocity, and using the result of the measurement to make a prediction of the future muzzle velocity by using an adaptive emperical prediction method implemented as a Kalman filter and thus determine a new elevation setting for the weapon.
- A method according to claim 13 or claim 14, wherein the Kalman filter is implemented in combination with a first round prediction algorithm.
- A method according to any of claims 11 to 15, wherein the Kalman filter self-organises to represent:(a) a definition of errors and their stochastic behaviour in time;(b) the relationship between the errors and the muzzle velocity measured by the muzzle velocity measuring means; and(c) how the errors influence the prediction of muzzle velocity.
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB919109954A GB9109954D0 (en) | 1991-05-08 | 1991-05-08 | Method and device for predicting the muzzle velocity of projectiles |
GB9109954 | 1991-05-08 | ||
GB9112793 | 1991-06-13 | ||
GB919112793A GB9112793D0 (en) | 1991-05-08 | 1991-06-13 | Improvements in weapons systems |
EP92304165A EP0512856B1 (en) | 1991-05-08 | 1992-05-08 | Weapon system |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP92304165A Division EP0512856B1 (en) | 1991-05-08 | 1992-05-08 | Weapon system |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0844457A2 true EP0844457A2 (en) | 1998-05-27 |
EP0844457A3 EP0844457A3 (en) | 2001-07-25 |
Family
ID=10694647
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP98102311A Withdrawn EP0844457A3 (en) | 1991-05-08 | 1992-05-08 | Improvements in weapons systems |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0844457A3 (en) |
GB (2) | GB9109954D0 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10907934B2 (en) | 2017-10-11 | 2021-02-02 | Sig Sauer, Inc. | Ballistic aiming system with digital reticle |
US11060816B2 (en) | 2017-12-20 | 2021-07-13 | Sig Sauer, Inc. | Digital turret ballistic aiming system |
US11454473B2 (en) | 2020-01-17 | 2022-09-27 | Sig Sauer, Inc. | Telescopic sight having ballistic group storage |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4457206A (en) | 1979-07-31 | 1984-07-03 | Ares, Inc. | Microwave-type projectile communication apparatus for guns |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3591772A (en) * | 1968-06-24 | 1971-07-06 | Hughes Aircraft Co | Computer circuit |
US3538318A (en) * | 1968-08-21 | 1970-11-03 | Hughes Aircraft Co | Wear weighting function generator for the determination of the proper aiming of a gun |
GB2094950B (en) * | 1981-03-12 | 1984-08-30 | Barr & Stroud Ltd | Gun fire control systems |
DE3225395A1 (en) * | 1982-07-07 | 1984-01-12 | Fried. Krupp Gmbh, 4300 Essen | DIGITAL BALLISTICS CALCULATOR FOR A FIRE CONTROL SYSTEM FOR A PIPE ARM |
-
1991
- 1991-05-08 GB GB919109954A patent/GB9109954D0/en active Pending
- 1991-06-13 GB GB919112793A patent/GB9112793D0/en active Pending
-
1992
- 1992-05-08 EP EP98102311A patent/EP0844457A3/en not_active Withdrawn
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4457206A (en) | 1979-07-31 | 1984-07-03 | Ares, Inc. | Microwave-type projectile communication apparatus for guns |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US10907934B2 (en) | 2017-10-11 | 2021-02-02 | Sig Sauer, Inc. | Ballistic aiming system with digital reticle |
US11287218B2 (en) | 2017-10-11 | 2022-03-29 | Sig Sauer, Inc. | Digital reticle aiming method |
US11725908B2 (en) | 2017-10-11 | 2023-08-15 | Sig Sauer, Inc. | Digital reticle system |
US11060816B2 (en) | 2017-12-20 | 2021-07-13 | Sig Sauer, Inc. | Digital turret ballistic aiming system |
US11454473B2 (en) | 2020-01-17 | 2022-09-27 | Sig Sauer, Inc. | Telescopic sight having ballistic group storage |
Also Published As
Publication number | Publication date |
---|---|
EP0844457A3 (en) | 2001-07-25 |
GB9109954D0 (en) | 1991-08-21 |
GB9112793D0 (en) | 1991-08-07 |
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