EP0347968B1

EP0347968B1 - Device and method for control of a weapon system

Info

Publication number: EP0347968B1
Application number: EP89201478A
Authority: EP
Inventors: Bertil Jan Hijink; Johannes Martinus Keller
Original assignee: Thales Nederland BV
Current assignee: Thales Nederland BV
Priority date: 1988-06-21
Filing date: 1989-06-08
Publication date: 1996-10-30
Anticipated expiration: 2009-06-08
Also published as: EP0347968A1; DE68927395D1; NO892538D0; NO892538L; DE68927395T2; JPH0244197A; ES2094727T3; NL8801576A

Description

The invention relates to an assessment device for assessment of the hitting probability of a gun system comprising a control device suitable for application with the gun system, for generating control signals with which at least one projectile can be manoeuvred towards a target by aiming the gun in a certain direction and where, for the purpose of generating the said control signals, the control device is provided with present target position signals obtained with a first sensor.
The invention also relates to a method for assessment of the hitting probability of a gun system wherein control signals are generated with which at least one projectile can be manoeuvred towards a target by aiming the gun in a certain direction and where the said control signals are generated on the basis of present target position signals obtained with a first sensor.
An example of an embodiment of such a weapon control system is known from patent specification WO 81/00149. In this specification the gun system, is controlled by the control device, in this case a weapon control computer, which for that purpose is provided with target data from a radar tracking device suitable for tracking a moving target.
The control device computes an optimal gun aiming point for the gun to achieve that the projectile, in this case a missile, fired by the gun is directed towards the vicinity of the moving target.
To determine the availability of the gun system against certain targets and the operation of the entire chain in the weapon control system as part of a test procedure or exercise it is necessary to be able to assess the system's operation under operational conditions.
In the case of the above-mentioned embodiment, a measure for the operational quality of the system may be the hitting probability with respect to the projectile hitting the target. Actually, under operational conditions the hitting probability is not only determined by the operation of a target tracking sensor, the control device and the weapon system, but also by the target. The effectiveness of the control device is strongly determined by the quality of target measurements by the target tracking sensor and by the behaviour of the target. An unexpected change in the target trajectory after a non-or partly correctable projectile has been fired by the weapon system may result in the projectile missing the target. This will occur especially in case of projectile times of flight which are long when compared to the intervals between the unexpected target manoeuvres.
A well-known test procedure to specify the hitting probability of a weapon control system is to fire projectiles at a towed target. Although in this procedure all factors determining the hitting probability are included in the assessment, the procedure remains limited to a non-realistic target and target trajectory. Another disadvantage of this test procedure is that real ammunition is used, leading to high costs.
Another well-known test procedure for a weapon system provided with a gun, in which no firing takes place, is to aim the gun, which is provided with well-known video registration equipment including a barrel camera, at a hitting point of projectile with target calculated by the control device, while a zero projectile time of flight is assumed. A disadvantage of this test procedure is that it does not include the influence of unexpected target manoeuvres occurring during the projectile time of flight.
The present invention has for its object to provide a device and method for assessment of the hitting probability of a control system, suitable for application with a weapon system, for generating control signals such as described in the opening paragraph, offering a possibility for a test procedure under operational conditions against realistic targets, while the above-mentioned objections are obviated.
According to the invention, the assessment device is characterised in that an electro-optic sensor is mounted on the gun, that signals representing a predicted hitting point between the at least one projectile and the target, presently valid and calculated in the past from present target position signals, are used for calculating the said control signals such that the electro-optic sensor is substantially pointed onto the said predicted hitting point, and that actual target position signals provided by the electro-optic sensor are made available for indicating the actual target position relative to the predicted hitting point at each time the target should arrive at the said predicted hitting point.
The method according to the invention is characterised in that an electro-optic sensor is mounted on the gun, that signals representing a predicted hitting point between the at least one projectile and the target, presently valid and calculated in the past present target position signals, are used for calculating the said control signals such that the electro-optic sensor is substantially pointed onto the said predicted hitting point, and that actual target position signals provided by the electro-optic sensor are made available for indicating the actual target position relative to the said predicted hitting point at each time the target should arrive at the said predicted hitting point.
The advantage of the present invention is that the influence of target manoeuvres occurring during the said time span on the control device is taken into account in the test procedure.
In an embodiment where the control device is suitable for mounting on a moving platform and where the control device is provided with platform signals containing information on the orientation, velocity and position of the platform with respect to a reference coordinate system, a further advantage is obtained because the control device by means of the platform signals continuously calculates the displacement of the platform and stores these displacement values during at least a certain time span in a memory. Thus a parallax occurring as a result of displacement of the platform may be corrected. Moreover, a way is provided to assess whether the platform signals are processed correctly and in the proper manner.
The device and method for control according to the invention may be applied in various weapon systems.
In an application where the projectile is a projectile correctable by the control device, an embodiment is obtained by the control device calculating a future maximum interception area of the projectile with the target and the control device is provided with signals representing the present interception area calculated a certain time span ago and relating to the present.
The system and method according to the invention will now be described with reference to the accompanying figures of which:

Fig. 1: is a first embodiment of a control device according to the invention applied in a weapon control system provided with a gun, a target tracking sensor and an electro-optic sensor using the same aiming means as the gun;
Fig. 2: is a second embodiment of a control device in a similar weapon control system in an application where the electro-optic sensor is provided with its own aiming means;
Fig. 3: is a third embodiment of a control device in a similar weapon control system suitable for mounting on a moving platform.

Fig. 1 represents a first embodiment of a control device according to the invention applied in a weapon control system which is provided with a target sensor 1, the control device 2 and a weapon system 3. This figure shows a platform sensor unit 4 which is provided with suitable sensors for measuring the orientation S_p and position P_p of the platform on which the weapon control system is fitted.
Target sensor 1 is fitted with a pulse radar apparatus 5 supplying bearing and range information of a target with respect to a line of sight of an antenna of the pulse radar apparatus. Target sensor 1 can also be an electro-optic sensor such as an IR or a TV camera, possibly provided with a laser range finder. The antenna is provided with aiming means 6, placing the antenna in the desired orientation by means of orientation readers recording the orientation S_s of the antenna with respect to the platform. For this purpose, aiming means 6 are provided with servos and so-called synchros. The bearing and range information of the target, the information relating to the orientation S_s of the antenna, the information with respect to the orientation S_p of the platform and the data relating to the position P_p of the platform are supplied to control device 2. The measured target data are, by means of data relating to the orientation S_s of the antenna, the orientation S_p and position P_p of the platform, preferably converted (block 7) to a first reference coordinate system, which is preferably earth-orientated. Moreover, the measured target data are filtered ("target track filtering", block 7) for the purpose of control signals for aiming means 6. The converted target data P_d(t₁), indicated at regular intervals at a first point in time with t₁ (block 8), are used to calculate a gun aiming point SP_R(t₁) for weapon system 3 (block 9). For this purpose, by means of a target trajectory model and an initial estimation of a time of flight TS(t₁) of a projectile to be fired from weapon system 3, a future target position after this time of flight is calculated (block 10). This future hitting point TP(t₁) calculated at a first point in time t₁ is converted by means of data concerning the position P_p of the platform to a relative future hitting point TP_R(t₁) with respect for the platform (block 11). Subsequently, a model of the projectile trajectory is used to make a new calculation (block 12) of the projectile time of flight TS(t₁), which calculation is used as an improved estimation of the projectile time of flight in the new calculation of the future hitting point TP(t₁). If, after this reiteration, the relative future hitting point TP_R(t₁) is calculated sufficiently accurately, a relative gun aiming point SP_R(t₁) for weapon system 3 is calculated (block 12) by means of the projectile trajectory model. The projectile trajectory model uses stored ballistic and meteorological data B and M (blocks 12a and 12b).
When using the control device in a normal weapon control mode, indicated by control signal $\bar{S}$
₁, the calculated relative gun aiming point SP_R(t₁) is converted to platform coordinates by means of data concerning the orientation S_p of the platform (block 13). On the basis of the converted gun aiming point, control signals are generated (block 13) for aiming means 14a which aim a launching system 14b.
Use of the control device in a mode suitable for assessment of the aiming of the weapon system at the target according to the invention is indicated with control signal S₁. In this mode, at time t₁, weapon system 3 is not controlled on the basis of gun aiming point SP_R(t₁), but on the basis of a previously calculated and stored (block 19) hitting point TP_R(t₂), which is valid at the present time t₁. Time t₂ relates to the point in time at which this hitting point was calculated.
For this purpose, at certain intervals, the calculated future hitting points TP(t₁), a time validity TTP(t₁) corresponding with this hitting point and the point in time t₁ at which these data were calculated, are stored in a memory (block 15) during a certain period of time. The time validity TTP(t₁) is obtained by adding to t₁ the corresponding projectile time of flight TS(t₁). This memory consists of a cyclic buffer whose cycle time is longer than the longest expected projectile time of flight. In order to find the present hitting point TP(t₂) valid at time t₁, two hitting points TP(t′) and TP(t˝) are taken from the memory in which the future hitting points are stored, together with the corresponding time validity TTP(t′) and TTP(t˝) for which t′ < t₁ ≤ t˝ (blocks 15 and 16). The present hitting point TP(t₂), together with the time validity of t₁, is calculated by means of a linear interpolation between hitting points TP(t′) and TP(t˝) (block 16).
The above-described method of interpolation is simple and hence requires less computing time than extensive methods of interpolation. If a higher accuracy is required, it is also possible to use non-linear interpolation between more than two hitting points.
Instead of storing the calculated hitting points TP(t₁), an embodiment may also store, during a particular time, the target trajectory data P_d(t₁) or data derived thereof. The present hitting point calculation will then have to be carried out at a time t₁, on the basis of the stored target trajectory data which were valid at an earlier time t₂.
The present hitting points TP(t₂) are converted by means of data P_p, relating to the position of the platform (block 16a), to present hitting points TF_R(t₂) relative to the position of the platform. These relative present hitting points TP_R(t₂) are subsequently converted (block 13) by means of data S_p, relating to the orientation of the platform, to a coordinate system connected to the platform for the purpose of generating control signals for continuous aiming of weapon system 3 at these present hitting points.
A launching system 14b in the form of a gun has, for the purpose of the use of the control device in mode S₁, been provided with a well-known barrel camera 17 for aligning the gun. Equipment 18, processing the barrel camera video to check the alignment with a target sensor in the form of radar apparatus, is used in mode S₁ to assess the aiming of the gun.
A difference between the present hitting point and the present target position as visible on video 18 from barrel camera 17 may subsequently be further processed in various ways. In the embodiment described, the video information is continuously supplied to a user for assessment, which user is able to obtain an impression of the operation of the weapon control system.
Another embodiment is obtained when assessment is automated by the calculation of quality values, such as hitting probability, by means of data concerning dispersion relating to the trajectory, effectiveness of the projectile and target dimensions. An embodiment including a barrel camera 17 is, strictly speaking, not required if the orientation of the gun has been calculated accurately enough. This orientation can be measured by the said readers, such as synchros, and compared by the control device with the stale hitting points.
Fig. 2 shows an embodiment of a control device in an application in a similar weapon control system which, for the purpose of aiming at the present hitting points, has been fitted with a second target sensor 22 provided with its own aiming means 20. The control device 2 is executed in such a way that, besides conversion of gun aiming points (block 13), simultaneous conversion of present hitting points is executed (block 21). In this embodiment, the second target sensor is coupled in mode S₁ to the control device and continuously aimed at the present hitting points. In mode $\bar{S}$
₁, the second target sensor is available for another weapon control channel 23.
The weapon control systems according to Figs. 1 and 2 are intended for mounting on a fixed platform. In the most simple embodiment, platform sensors 4 consist of means for once-only determination of the platform data relating to orientation S_p and position P_p. In a simpler embodiment, a distinction between earth-oriented coordinates and coordinates determined by the platform is not required. Conversion from and to relative coordinates is therefore no longer necessary.
Fig. 3 shows an embodiment of a control device applied in a weapon control system suitable for mounting on a moving platform. Platform sensors 4 continuously supply data relating to orientation S_p, data relating to position P_p, but also data relating to the own velocity V_p of the platform. The platform sensors 4 may consist of well-known gyro's, acceleration and velocity meters. The control device 2, by means of data relating to position P_p and velocity V_p of the platform, calculates the displacement of the platform at certain intervals at points in time indicated with t₁ (block 24). Position P_p(t₁) at this time, velocity V_p(t₁) at this time and the time t₁ are stored in a memory (block 25) during a certain period of time. This memory is executed as cyclic memory of which the cycle time exceeds the maximum expected projectile time of flight. Subsequently, the present hitting point TP(t₂) (block 19) corresponding with a time t₁ is corrected (block 16a) for own displacement ΔP_p(t₂) of the platform from time t₂ till time t₁. To determine this own displacement, two stored platform positions P_p(t′) and P_p(t˝) are retrieved from memory 25, with t′ < t₂ < t˝ (block 26). Subsequently, the platform displacement ΔP_p(t₂) as from time t₂ is found by linear interpolation between these platform positions (block 26).
It should finally be stated that this description does not include the processing times required for data processing and measurement in order to avoid unnecessarily complicating the description.

Claims

Assessment device for assessment of the hitting probability of a gun system (14b) comprising a control device (2) suitable for application with the gun system (14b), for generating control signals with which at least one projectile can be manoeuvred towards a target by aiming the gun (14b) in a certain direction and where, for the purpose of generating the said control signals, the control device (2) is provided with present target position signals obtained with a first sensor (1), characterised in that the assessment device comprises an electro-optic sensor (17) mounted on the gun (14b), that signals representing a predicted hitting point between the at least one projectile and the target, presently valid and calculated in the past from the said present target position signals, are used by the control device (2) for continuously pointing the gun by means of the said control signals such that the electro-optic sensor (17) is substantially pointed onto the said predicted hitting point, and that actual target position signals provided by the electro-optic sensor (17) are made available for indicating the actual target position relative to the said predicted hitting point at each time the target should arrive at the said predicted hitting point.
Assessment device as claimed in claim 1, where the control device (2) is suitable for mounting on a moving platform (4) and where the control device is provided with platform signals containing information on the orientation, velocity and position of the platform with respect to a reference coordinate system, characterised in that the control device (2) by means of the platform signals continuously calculates the displacement of the platform and stores these displacement values during at least a certain time span in a memory (25).
Assessment device as claimed in claim 2, characterised in that the control device continuously corrects the predicted position signals for the present orientation and the displacement of the platform during a certain time span with respect to the reference coordinate system.
Assessment device as claimed in one of the above claims, where the projectile is executed as a projectile correctable by the control device, characterised in that the control device calculates a future maximum interception area of the projectile with the target and the control device is provided with signals representing the present interception area calculated a certain time span ago and relating to the present.
Method for assessment of the hitting probability of a gun system (14b) wherein control signals are generated with which at least one projectile can be manoeuvred towards a target by aiming the gun (14b) in a certain direction and where the said control signals are generated on the basis of present target position signals obtained with a first sensor (1), characterised in that an electro-optic sensor (17) is mounted on the gun (14b), that signals representing a predicted hitting point between the at least one projectile and the target, presently valid and calculated in the past from the said present target position signals, are used for calculating the said control signals such that the electro-optic sensor (17) is substantially pointed onto the said predicted hitting point, and that actual target position signals provided by the electro-optic sensor (17) are made available for indicating the actual target position relative to the said predicted hitting point at each time the target should arrive at the said predicted hitting point.
Method as claimed in claim 5 for application on a moving platform, where use is made of platform signals containing information on orientation, velocity and position of the platform with respect to a reference coordinate system, characterised in that the displacement of the platform is continuously calculated on the basis of the platform signals, and the displacement values are stored at least during a time span needed for a projectile to reach the predicted hitting point.