GB2107833A

GB2107833A - Target-tracking interception control systems

Info

Publication number: GB2107833A
Application number: GB07943941A
Authority: GB
Inventors: Reindhard Weisbrich
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1979-02-28
Filing date: 1979-12-31
Publication date: 1983-05-05
Also published as: DE2907543C1; IT7928228A0; FR2518248B1; NL8001201A; IT1126617B; FR2518248A1; GB2107833B; NL184130C

Abstract

In a target-tracking interception control system, such as a fire control device for an anti-aircraft defence system, the lead-angle for anti-aircraft defence, is calculated in accordance with a path sampling principle using a digital computer to which target object position data is supplied from sensors, and a delay time DELTA t is introduced to obtain a theoretical position for a future impact time T1 at which the target object and projectile positions will coincide. The hypothetical impact time is composed of the sum of the projectile flight time and the delay time. <IMAGE>

Description

SPECIFICATION Target-tracking interception control systems The invention relates to a target-tracking interception control systems, for example for use as a fire control device in anti-aircraft defence, using a digital computer which is supplied with target object position data obtained from sensors forming part of the system.

In known launch or fire control devices for use in anti-aircraft defence systems, the predictor or lead-angle computer is of special significance. The problem of calculating the lead-angle consists in directing the launched weapon in such a manner that both the target object and the projectile can be expected to arrive at a common interception point at the same time.

Reference will now be made to the explanatory graph shown in Figure 1, which schematically represents the calculation of the impact point vector, using target data supplied by a sensor, together with the ballistics of the particular projectile from a launch point 0, in order to determine the required impact point vector rT. The following two equations can be used to determine the lead-angle by the predictor computer: =AA +.Tf (1); and Tf=fba, (rT), or rT=fba" (Tf) (2) In equation (1 ) rM=measuring point vector; VT=the target object velocity: and Tf=the projectile flight time, which is the unknown factor.

Equation (2) represents an empirically determined, non-algebraic function. Therefore-the combination of equations (1) and (2) can only be solved mathematically by iteration calculation.

Analogue and digital computers can be used in the lead-angle computer to solve the combinations of equations (1) and (2), and if an analogue computer is used, then generally a comparator circuit withe servo system is employed, and one wave of the computer simulates the projectile flight time. A signal derived from the difference between the impact point vectors corresponding to equation (1) drives the wave until the correct projectile flight time, and thus the correct impact point has been determined.

If a digital computer is used, the solution is generally obtained in accordance with the iteration method. However, this presents difficulty, as there is necessarily only a short calculation time available, which results from the need for real-time operation.

As a consequence of the continuously growing demands on fire control devices, including adequate matching facilities, accuracy, and reliability, the requirements are now such that electromechanical analogue computers are generally unable to satisfy these demands.

One object of the present invention is to provide means enabling a target-tracking interception control system of the type described in the introduction to effect a simple determination of the requisite lead-angle, avoiding the use of the iteration method.

The invention consists in a target-tracking interception control system in which a digital computer is supplied with target object position data from system sensors, and means are provided to determine the lead-angle for launch control using the sensor detection data of the target object by determining an impact point vector using a hypothetical impact time which is composed of the sum of the projectile flight time and a delay time.

The introduction of a delay time tw serves to avoid a time consuming solution of the above mentioned combination of equations, 1 and 2, for the calculation of the lead-angle when using a digital computer. The lead-angle can be determined by one single equation, in which the time to of the target measurement and the given impact time t1 are defined by: rT(t1}=rM(to}+vT(to} ' (tttosv This equation can be solved immediately as all the values on the right-hand side are known. For this purpose, when a flying object is detected by the measuring sensor, an approximated projectile time is calculated from the target data, and to this there is added a time At whose value is such that the sum of the approximated projectile flight time and At is equal to or greater than the projectile flight time to the impact point.When the impact point vector rT(t11 is known, as determined in the lead-angle computer, the weapons can be positioned and the exact projectile flight time to this impact point and the delay time can be determined in a simple manner. The first launch is then triggered following the delay time tw, which is given by: tW=(t1to)Tf In all the following calculating steps, the exact projectile flight time calculated in the preceding step is used as an approximation value of the projectile flight time. The value of At, and thus of the delay time tw then become considerably reduced.

The selection of the impact times t, must be made in accordance with the following criteria A) The time period ti-to between the impact time and the measuring time must exceed the duration of the projectile flight time Tf to the impact point B) The difference between two consecutive impact times must be small; that is to say that the distance between two consecutive impact points must be small.

The difference to previously used lead-angle prediction methods consists in that no plot of a continuous impact point path is produced, as in the case of the analogue computer (or a quasicontinuous impact point path plot in the case of a digital computer using the interation method), but the impact point path is sampled.

In addition to the advantage of simplified lead-angle calculation, a favourable regulating algorithm is achieved for the weapon control.

The result of the iteration process is the theoretical position of the weapon at the present time. In a path sampling method of the type now proposed in accordance with the invention, the theoretical position for a time in the future is supplied, so that fundamentally, follow-up can take place without any deviation. The time tolerance results from the difference between the given time (t1-t0) and the projectile flight time T0 which can be in the order of milliseconds.

Further details of the Invention will now be described with reference to Figures 2 to 4, in which.

Figure 2 shows a simplified vector diagram for determining the lead-angle with the introduction of a delay time; Figure 3 is a block schematic circuit diagram of one exemplary embodiment of a fire control computer operating in accordance with the proposed delay time principle; and Figure 4 is an explanatory illustration of the simulation of the impact point path from a number of sample points.

At the time to the sensor of a deft naive device A (Figure 2), eg. a tank equipped with an antiaircraft gun locates a flying object M on a measuring point vector rM. During the flight time of a projectile fired by the defensive device A, the target object covers the path VT.T,, and at the time to+t, the target object reaches the target location T. The introduction of a delay time tw determines an impact time T, which is described by an impact point vector rT(t,}.

The fundamental mode of functioning of the fire control computer which serves to determine the lead-angle in accordance with the delay principle will be explained in detail making reference to the embodiment shown in Figure 3. Commencing from the target data rM, t M supplied by the systems sensor at the time t0,the determination of the impact time t, is carried out. This impact time must be selected to be such that the time t, always exceeds the projectile flight time To to the impact point.The target data supplied from the sensor is fed from the input of the remote control computer to a stage 1 for coordinate transformation and for purposes of speed and acceleration calculation, to a lead computer 2, and to a stage 3 in which an approximated projectile flight time Tfo is calculated from the target data. In a following stage 4, there is added to the approximated projectile flight time Tfo a time At whose value is such that (Tfo+At)=T,.

The impact time t, obtained at the output of the stage 4 is fed into the lead-angle computer 2 together with the co-ordinate data from stage 1, and this computer 2 then determines the impact point vector rT(t,) in accordance with the equation (3).

On this basis the required gun angles are calculated in a stage 5 and, following new coordinate transformation, are fed to the directional control equipment of the weapon. Simultaneously the projectile flight time T, and the delay time tw are determined from the impact point vector in respective stages 6 and 8.

In the next calculating cycle the projectile flight time T1 obtained from the output of the projectile flight time computer 6 is used as an approximation value for achieving an improved determination of the impact time in the stage 7. By actuation of a change-over switch S, the lead-angle computer 2 receives the impact time T, from the output of the stage 7. In this way it is possible to reduce the time At to approximately 0.01 s.

Figure 4 illustrates the mode of operation of the delay time process as regards the determination of sample points of an impact point path TB. At the times tM/1X, to 2} to tM(i), which correspond to points a, b and c of a flight path F of the target, target data is input into the lead-angle computer, at intervals of 20 ms, for example. The time of the beginning of the lead calculation is that. Commencing from the first measurement of the target at the time to(1?, the first impact point T, is determined at the time tut(1}.

For this first impact time the delay has been selected to be relatively long (approximately 0.05 to 0.5s).

The time curves ZL of all the impact times are represented by concentric arcs around the path point a at the beginning of the lead-angle calculation. The first impact time tT(1 is maintained until the delay time tw falls below a specific minimum value (e.g. 0.05s in Figure 4). The impact points T1 to Ti are located on the first time curve ZL, which corresponds to the impact times tTI " to ttii. In spite of the fact that the impact time is retained, the deviation of the impact points from the flight path F changes during this time from T, via T2 to T1 on account of the continously changing target measurement data in the exemplary 20 ms cycle.

Not until the delay time tw has fallen below the minimum time, is the next impact time ttl,+" determined from tT(I and a time advance (e.g. 0.02s). As a result the impact point path TB is repeatedly sampled, at intervals of 0.02s for example, which, at a target speed of 300 m/s, results in section spacings of 6 m. The deviations of the impact points T1 to Ti from the flight path F characterise the build-up process in the calculation of the lead-angle. In the built-up state the impact point path is virtually identical to the flight path of the target.

Claims

1. A target-tracking interception control system in which a digital computer is supplied with target object position data from system sensors, and means are provided to determine the lead-angle for launch control using the sensor detection data of the target object by determining an impact point vector using a hypothetical impact time which is composed of the sum of the projectile flight time and a delay time.

2. A system as claimed in Claim 1, in which said lead-angle determining means calculate an approximated projectile flight time from the target data and add a supplemental time-period whose magnitude is such that the sum of the projectile flight time and the supplemental time period is equal to or greater than the duration of the projectile flight time to the impact point, and following the determination of the impact point vector in the lead-angle computer the projectile flight time, the delay time and the required gun angles are then determined.

3. A system as claimed in Claim 1 or Claim 2, in which successive calculating cycles are then effected, in each of which the previous projectile flight time used as an approximation value for determining the impact point

4. A system as claimed in any preceding Claim, in which a simulation of an impact point path is produced from successively obtained sample points.

5. A system as claimed in any preceding Claim, in which calculation of the launch control is predetermined by virtue of the fact that a theoretical position and the time at which this position must be reached are predetermined.

6. A system as claimed in any preceding Claim, in which the triggering of a first'launch by an operating fire control unit is actually delayed by said delay time so that the target object and launched projectile can be assumed to arrive at the same location at the hypothetical impact time.

7. A target-tracking interception control system substantially as described with reference to Figure 3.

New claims or amendments to claims filed on 3 12 81.

Superseded claims 1-7.

New or amended claims:

1. A target-tracking interception control system in which a digital computer is supplied with target object position data from system sensors, and the lead-angle for launch control is calculated using the sensor detection data of the target object, together with an impact vector calculated for an estimation impact time which is obtained by computing a predicted projectile flight time and adding to this a delay time to give a calculation time for which said lead-angle is then calculated.

2. A system as claimed in claim 1, in which said lead-angle determining means calculate predicted projectile flight time from the target data and add said delay, which constitutes a supplemental time-period whose magnitude is such that the sum of the projectile flight time and the supplemental time period is equal to or greater than the duration of the projectile flight time to the impact point, and following the calculation of the impact point vector in the lead-angle computer the results is used to recalcuiate a projectile flight time, delay time and required gun angles.

3. A system as clamed in claim 1 or claim 2, in which successive calculating cycles are then effected, in each of which the previous projectile flight time is used as an approximation value for determining the impact point.

5. A system as claimed in any preceding claim, in which calculation of the launch control is effected by selection of an impact point and of the time at which this impact point is to be reached.

6. A system as claimed in any preceding claim, in which said delay is used to postpone the triggering of a first launch by an operating fire control unit so that the target object and launched projectile can arrive at the same location at the impact time.